of these are suggestions are copied from various newsgroups. I have removed the names to
protect the innocent. Let me know if you recognize your work and want credit listed here.
MFI Pump part numbers:
911SC/RS 3ltr = ???
??? = ????
??? = 911RS 3ltr
911T = 0408 126 015
911E = 0408 126 014
911S = 0408 126 013 (euro)
911S = 0408 126 012 (US)
911S = 0408 126 021
(911T = Switched to CIS mid year)
911S = 0408 126 009
911E = 0408 126 010
911T = Carbs
911S 0408 126 001
911S 0408 126 005
911E 0408 126 002
911E 0408 126 006
911T = Carbs
911R = ???
??? = ????
906 2ltr. = ???
911 2.7S = 0408 126 019
Pacific Fuel Injection (Gus Pfister)
|Suite B, 153 Utah
South San Francisco, CA
Tel. 650-588 8880
Jerry Fairchild Industries (Robert Turner)
|5242 Westside Rd
Redding, CA 96001
Tel. 530-241 1592
Walz Diesel Fuel Injection (Norbert Schuller)
Tel. 02-9755 1422
Eurometrix (throttle body rebuilder)
228 Boston Rd
|Groton, MA 01450
Tel. 978- 448 2557 (Matt Blast )
Phil Sumich (throttle body rebuilder)
Tel. 07-3390 8133
(throttle body rebuilder)
|Tel. 714-429 1863
I just took the plunge and replaced my MFI pump with
another that I am hoping has an "S" cam in it. The car pulls stronger now, so it
must be something other then "T".
Very important, rotate the engine to TDC of #4 piston (I
full rotation past TDC of #1 piston) then another 40 degrees (there should be a mark on
the main pulley). Then use a mirror to check the MFI pump to ensure the small mark on the
pulley is lined up with the mark on the pump body.
Removing the pump is the easy part, except for 1 bolt that
mounts the pump to the engine. This "devil" bolt is on the left front side and
is covered by injector lines. To make it more fun using a socket extension is difficult
because it doesn't quite fit with the injector stacks. After 2 hours getting that bolt out
the rest followed including the fuel lines and oil tubes in about 30 minutes. Pick up some
1/2" and 1/4" plastic caps from the hardware store to cap the unit (especially
the oil in tube, otherwise a bunch of oil will leak as you tilt the unit to pull it out).
Lift and pull out the unit. Be careful not to let the drive belt fall off the cam pulley.
While unbolting the unit I actually lost a bolt and it fell under the belt down to the cam
pulley. I was able to fish it out using a screwdriver from the outside left hand side of
the car (don't leave it down there).
Installing the new unit is even more fun. Fill the new pump
with 300cc of engine oil (and cap with one of those 1/2" caps until you are ready to
attach the oil hose). Make sure the crank hasn't moved. Compare the two pumps and make
sure the teeth are absolutely identical when the marks a lined up. If not loosen the gear
and rotate. When sliding the unit in place it is easier to make sure the belt is on the
lower part of the pump and pulling it over the top as you complete the installation. Make
sure the pump pulley mark is still lined up with the mark on the pump. Also make sure the
belt fits cleanly in the teeth of the pulley without rotating it from the marks.
Screw everything back on in reverse of the install process. Good luck with the devil
bolt... I have yet to put it back in mine. :)
injection pumps are complex mechanical devices with many intricate and delicate internal
components. Due care should be exercised when handling or working on these pumps as
the internal parts are often very hard to replace and very expensive to buy.
Therefore it is
essential that your Porsches injection pump is well maintained to provide the
excellent performance and durability that came with it from new. A well tuned
injection pump will provide far better fuel delivery to the engine than any carburetor
setup and work well in all conditions and engine specifications. The injection
system was first developed for the Porsche racecars for just this reason. Keeping
your injection pump clean and maintained to original specification will provide years of
trouble-free motoring for you and your Porsche.
There are actually two
distinct parts two the Bosch mechanical injection pump the pump and the
regulator. The pump section contains the camshaft, the fuel galleries and the six
pistons and associated connections and the control rack. The regulator (at the rear,
direction of car motion) contains all the control devices for the thermostat, enrichment,
leaning, idling and power ranges, counterweighted space cam on the end of the camshaft,
and various levers and adjustment screws to control the metering of fuel supply to the
The following points should be noted with respect to the
mechanical injection pumps.
always keep the area around the pump housing free of debris, oil and
moisture. Look regularly for oil leaks from the various oil lines and cover plates
on the pump housing, examining fuel lines and junctions for fuel seepage.
regular oil changes (with filter) will provide your pump with a regular
cleaning of oil in the cam and piston galleries, reducing friction on moving
parts. Less gumming up is also the result.
the same applies for the fuel filter and fuel quality.
does the control rack move freely? Remove the plastic plug and
the driven end of the pump, insert the blunt end of a biro and gently push into the pump
and release pressure. The biro should move back to the original position. If
not, a gummed up pump is what you have. Thermostat not working? Check
the hose from the heat exchanger to the top front of the pump. It must be in good
condition and unobstructed. Thermostat elements may also need
cleaning. Examine the drive belt for wear, and also the drive gears on the
pump and end of camshaft. Seal can also leak. Other components
related to the injection, which may fail, are the rpm transducer, cold start solenoid,
microswitch and fuel pump. The vacuum system from the distributor and lines may also
if your car is not tuned properly, your pump will never work at its full
potential. An out of tune, worn out engine will force the pumps various
elements to overcompensate for the engines shortcomings, resulting in overly rich
running, poor idling, fuel in the oil, poor acceleration etc. Before doing any fuel
injection service, always ensure that your car has proper timing, good compression,
correct fuel pressure, distributor, ignition and vacuum pressure. A worn engine will
allow carbon buildup in the oil to travel throughout the pump. Carbon can also build
up in the air bleed screw shafts, making the task of balancing the throttle valves almost
impossible. Correlation of the throttle bodies (linkages) is essential.
a major source of problems in the pumps is the ingestion of moisture,
particularly in cool, wet climates where the car is not frequently used. This causes
corrosion of the working parts and eventually seizing of the pump. By regularly
spraying around the pump with WD40 or RP7, moisture will be largely eliminated. Also
regular cranking over of the engine or rotation of the pump drive shaft will maintain
lubrication of parts.
pumps which have been removed for the car should be flushed and sealed
prior to storage. Kerosene is suitable for flushing out the pump and regulator
housing. Pour in through the fuel and oil inlets while rotating the drive shaft
(cam) clockwise and turning upside down. You may also remove the side cover and
governor cover to add more kerosene. Wipe down housing with a clean lint-free cloth
when finished. The pump and governor must now be treated with calibration fluid in
order to preserve the delicate internal parts. Calibration fluid (eg. Bosch # 5 701
301 725 or equivalent) is only available from specialist fuel injection shops and is
expensive. About 1/2 litre should be sufficient. Repeat
the sequence as per the kerosene cleaning and drain well. Replace all covers and
ensure a coating of calibration fluid remains on the outer casing as well. All hose
and fuel line vents should be plugged (plugs available from fuel injection shops) and the
pump stored in a sealed plastic bag in a moist free environment at room temperature.
Quarterly inspection and clockwise rotation of the drive shaft cam is advisable.
seizure MFI pumps which have been allowed to stand idle for long periods
with oil and fuel in side them often suffer from binding or sticking control racks and
gumming up of fuel galleries, as well as possible seizing of internal components of the
pump and regulator. To overhaul such pumps, fill fuel inlet with carburetor cleaner
(or methyl alcohol), Remove plastic plug above driving cog (back of pump housing)
and insert the blunt end of a plastic biro or similar non-metallic object into the hole to
contact the control rack. Using slight pressure, gently push against the control
rack while turning the drive cog clockwise. This is best done if the MFI pump is
clamped to a work bench. Push and release the biro as you rotate the cog.
Repeat this procedure until the rack moves freely with the MFI camshaft using very little
pressure on the biro. You may have to add more cleaning fluid and repeat the steps
several times. If, after several attempts, the control rack is still stuck, it is
time to send the pump off for a rebuild.
The above procedure
can also be performed with the MFI pump still mounted on the Porsche. However, prior
to removal of the drive belt for the pump, the injection timing must be set for the end of
delivery stroke (F-E mark on the crankshaft pulley) in relation to the set mark on the
pump drive cog shaft. To do this, bring piston 1 to TDC, rotate fully 360° (1
revolution of the crankshaft pulley), followed by a 40° turn to reach the F-E mark and
the top mark on the fan housing above the crankshaft pulley. Using a mirror and
torch, examine the position of the drive cog and shaft on the back of the injection
pump. There should be a notch mark showing at the top position of this shaft (a
matching 12 oclock mark on the housing).
The drive belt can now
be removed. This is easily done if the pump housing is loosened on its mounting
bolts and gently slid sideways to the left. This releases tension on the bent and it
can be slid off the drive cog. Place a cloth under the fuel inlet banjo joint and
undo. (Caution avoid any sparks or flames, keep a fire extinguisher
handy!!). Once the fuel inlet pipe is exposed, you can now proceed as above with
carburetor cleaner and try to gain movement in the control rack etc. Reinstall the
hoses, belt and pump mounting in reverse of above. Remember to keep the notch mark
on the drive cog shaft at 12 oclock on the pump. Check the belts tension
with finger pressure there should be 68 mm movement in the center of the belt
travel. Check all fuel hoses and lines for leaks prior to starting engine.
any work on the mechanical injection, it is well advised that you obtain a copy of the
Porsche Factory manual on MFI and read it thoroughly before attempting any repairs.
They stress the importance of three words: stop think
repair! Your Porsches engine will need to be well tuned and have good
compression for the pump to perform properly. Only after you have checked all
components of the ignition, timing, fuel system, wiring, vacuum and oil supply should you
proceed with investigation of the MFI pump, the internals of which are best left to the
It is assumed that your throttle bodies
have been cleaned and intakes (throttle plate, air mixture and vacuum) are
surgically clean. Your throttle bushes should also have no significant
wear. Regarding idle mixture tune-up, first turn the air correction screws on the
throttle bodies fully closed, then back out exactly 21/2
turns. Then adjust the throttle stops by removing all the linkages and, one at a
time, loosening each throttle bolt locking nut. Lightly push the throttle plate
towards the fully closed position. Turn the throttle stop bolt to allow the throttle
plate to close completely. When you get to the point where you have almost removed
the bolt, the throttle plate will stick shut. Now screw the throttle bolt back to
the point where the throttle plate no longer sticks shut. (This is rather critical
as the throttle plate can be closed too far and stick, as engine temps increase and alter
clearances). Now that you have the throttle stop bolt set to just keep the throttle
plate from sticking, screw the throttle stop bolt another 3/4 turn
in the direction that opens the plate. Check for free play by pushing lightly toward
the stop. If all is OK, secure with the locking nut and repeat on remaining 5
At this point the engine should
start and run, but idle will be slow. Run for a while (until engine oil temp. is
about 180 degrees +), then shut down and wait 15 mins for heat expansion, then restart
Check each throttle with an air flow
synchronizer to find the throttle with the lowest air flow. Adjust throttle stop
bolt on this throttle to allow more air through throttle plate. Note: NEVER adjust
the throttle plate for less air (closing the plate)!! Then adjust all six throttles
up to identical air flow. Idle speed should now be close to spec. (circa
900rpm). Note that bad plugs, timing, MFI pump adjustment will affect these
settings, so make sure all is well before attempting this balancing.
Next, with engine still running,
adjust and reinstall the four throttle valve connecting levers to just keep the throttle
arms on the stop bolts without changing the idle rpm. L & R throttle valve push
rods should be as close as possible to 149.5mm and reinstalled. Car should now idle
but idle mixture should be now checked.
Normally if the idle speed is low,
you must determine whether the engine needs more fuel or air. There is an easy way
to check this. Remove the injection pump control rod at the cross shaft end (the
large metal tube linking both throttle bodies). Leave the other end attached to the
MFI pump. Check all throttles are still at their idle stops, then very slightly
push the control rod open. This will inject more fuel into the engine.
Does the engine
speed up? This means the pump is set too lean. Does the engine slow down and
puff a little black smoke? This means the pump is set too rich. At
perfect adjustment, pushing slightly on the control rod will cause the engine to initially
increase revs a little the rapidly decrease. The MFI pump is adjusted @ 1000rpm for
basic rich/lean with the main enrichment. Idle speed is adjusted with the idle
enrichment and is only effective below 1000rpm.
Fine tuning can be achieved by
turning all six air correction screws very slightly (1/16 turn for
example) then rechecking with your air synchronizer to be sure they are all the
same. Then recheck all linkages are lightly tight and ball sockets have Bosch
ignition grease in them. Finally, check throttle pedal goes all the way down
together with the MFI pump being at full throttle. <TOP>
Ensure these small hoses are not leaking and in good
condition. Always use the proper FI hose clamps (i.e. do not use the slotted worm
drive clamps as these cut into the hose over time). The tiny plastic T-junctions and
elbows mounted on the sides of the throttle body trumpets should be tight and look for
cracks if bent out of shape. Treat with care as these are not replaceable I
believe!! (Also check your vacuum hoses and junctions periodically).
and what are the adjustments I can make on the good old Bosch MFI? I have a 1972
911T that is running way to rich..Black smoke from the pipe...I'm sure the MFI pump needs
a rebuild..The car sat for 9 years before I took over as caretaker...I've had the pump
apart and have only a really basic understanding of how it works, but I need an even more
basic understanding...such as what are the base lines I should be shooting for...
2.4 Ts never ran all that well to begin
with, tending to be too fat anyway, and getting richer with age. The MFI training I
received from Porsche/Audi Pacific involved a WEEK of classroom work, a full day of which
was on the road performing the adjustment procedures. You MUST have a thorough
understanding of both the operation and the adjustment procedures, as well as a small
assortment of special tools including a gauge for the pump rod, a set of protractors, and
a couple of screw turning tools, as well as a CO/HC tester that you can carry in a moving
You MUST have the engine in a
PERFECT state of tune, with the plugs (either conventional or the special platinum's) at
exactly the correct gap, the valves at EXACTLY .004", the dwell and timing right on
the money, and the correct octane gasoline.
Then, and only then, can the
adjustment be done. The warm up device must be cleaned and adjusted and the air
supply feeding it must be adequate before adjusting the idle CO. After getting the
idle CO right, the part load screw is adjusted. It CANNOT be done correctly without
the portable CO machine, as it is set with the car moving, the properly adjusted hand
throttle pulled up, in 2nd gear, and usually with the brakes lightly on. After the
part load is set, you'll probably have to go back and reset the idle settings, and then
the part load again. It may take several fine adjustments to get it to run right,
and only then if the pump is in good condition.
I've done a lot of these, and I
have a few friends in the business who have done them too, and I think any expert will
tell you that this is not a job to be undertaken by the untrained nor those unfamiliar
with the system. Remember, these things are, at a minimum, 26 years old, and guys
who received the training have reached or are near the end of their careers, and most
haven't touched one in a long time.
There are guys, including myself,
who have put these into a 914-6, and the nightmare is worse. You can't access the
adjusters in the car. I had mine preset by the guy who rebuilt it, and the engine
was fresh. Luck was with us, and it is within tolerances for the moment. Wear
may cause us untold grief. Good luck, and find someone who knows what he's doing,
it'll be the best thing in the long run.
You should have a copy of the
Bosch/Porsche book for this system if you're going to try it yourself. <TOP>
understand it, when the engine goes to idle, the vacuum ports on cyls. 1 and 4 builds up
and "retards" the ignition thru the "vacuum dashpot" (5deg.).
I have a 72T with MFI that I've
spent $1200 on rebuild, and I just found out that the "dashpot" is bad causing
my idle to wander making some very strange noises. The reason I know this is I
changed over the "dashpot" with an old one (had to drill out 1 mounting hole to
get it to fit) and all the "pinging, clunking, stumbling, and ticking" is almost
gone. I noticed that the one I removed was very easy to move the arm back and forth.
> Emissions niceties aside, what
happens if I plug the line and the vacuum pot on the distributor?
What happens on mine is the timing
changes from "5deg.ATDC" to about "5deg.BTDC". I guess this is
where the "advance" comes in, because when the throttle plates open, the
"dashpot" loses vacuum, and the centrifugal" advance takes
over. When the throttle plates close, vacuum builds and the timing is
"retarded" again to "5deg. After TDC".
Hey, I could be all wrong on this,
because there's some confusion as to what some call "retard" and
I'd like to remove the dashpot but I
don't want to start another problem, I'm not an engine designer, it's there for a
reason. Just don't know what it is! <TOP>
I also have seen this problem (MFI running rich over
4,000rpm). I own a 72 911E with MFI, and I found that the thermostat on the rear of
the injection pump can get dirty/carboned up over time, and will hang up forcing the rack
into an over rich condition constantly.
You can remove this unit and disassemble
it and clean it out, maybe some light sanding of the inside of the housing will be
required but you can check the operation by measuring the travel of the actuating rod cold
and then hook up a hair dryer (blower type) to the inlet hose and check to see if the
little expansion disks pull the rod into the thermostat housing (leaner) as it is warmed.
This rod must retract about 3/16" or so to lean out the rack. Also make
sure that the rack is free to move back to idle position it should not bind, otherwise the
rack is defective. I hope this helps - this worked on mine and seems to be common on these
I have a '72 911E Targa with mechanical fuel injection.
It will start right up, but if I try to
give it any gas it will loose power and stall. If I let it idle for 5-10 minutes it
I don't know how you lived with it like
that for more than a season. You should get the Bosch/Porsche MFI book "tune,
test, adjust" or whatever it's called. You need to start at the beginning like
the book says and check your ignition, compression, and other things and make sure they
are right before you mess with the injection.
Then you might want to start with
cleaning out the disks in the warm-up regulator by removing it and BEING VERY CAREFUL not
to change the order of the disks which are not all the same.
You should also clean out the idle
air passages on each intake. You can do it by removing the adjustment screw (count
how many turns it is from closed first so you can re-install it). Then spray some
carb cleaner down the hole and clean it out with a long pipe cleaner. The pipe
cleaner will be REALLY dirty from carbon. Also clean the needle on the adjusting
You can check for vacuum leaks with
the car idling by spraying that carb cleaner around the base of the intake stacks
if you hit a leak the engine RPM will change. Maybe you can check for leaks on the
head this way too by spraying through the ducting.
Also check the pump timing which
will require a mirror to see the timing mark on the back of the pump. I hear it's
not that critical but couldn't hurt.
After fixing all these wear items, if it
still runs bad you can then do the adjustments throttle linkage lengths, butterfly
valve stops, pump vs. butterfly correlation, etc. Then you can set the part throttle
and finally idle mixtures. Bob Spindel built a neat pipe with an O2 sensor which
clamps onto your muffler and you read the voltage with a digital volt meter. It
works good for the part throttle adjustment. I have an article I accumulated about
using an O2 sensor for tuning if anyone is interested. <TOP>
that your thermostat is working correctly:
Start motor and warm to
operating temperature (180°C).
On the MFI housing behind the
thermostat is a small triangular cover plate.
Remove this inspection plate
and observe if the thermostat rod is pushing against the cam-shaped lever. This
lever should not be able to move back further. (Use a small angled screw driver or
similar to gently check the there is no movement). If there is, continue as below.
If you need to clean out the thermostat I would do it
To remove the bottom screw on
the thermostat cap, grab your air cleaner with your fingers while placing your thumb on
the thermostat cap, remove top screw (cap is spring loaded).
Remove cap, set aside, (don't
lose cap gasket, mine was broken so I made another
one this thing will not
work without the gasket, it's also a spacer).
Draw out the rod with elements
I would not take them off if it works!!
(There are 25 pairs of
expansion elements (mounted like cymbals) fitted first, followed by three slightly larger
Clean with carby spray
cleaner, set safely aside.
Remove bottom screw on
thermostat housing (kind of hard to get at), hold on to housing,
remove top screw, remove
You should have a cross shaped
gasket with a hole in the middle, and a metal spacer.
Should also have a small
rubber "o" ring type gasket in the flange on injection pump.
Clean them up using parts
cleaner or carby cleaner.
Next, hold thermostat housing, install rod with
elements, spring seat, spring, and compress cap with your thumb, install screws.
Check for movement on thermostat rod...about 3/16"
(4.75mm) or so..
Now reinstall thermostat.
The reason for installing the whole thing assembled is, if
you install just the housing, and then the rod with elements, it gets warped and doesn't
move right. <TOP>
Also, about adjusting the pump timing... In my
newsgroup wanderings I read two posts at different times. In both posts, they said that
the Porsche factory racers found that they could detect no difference in engine
performance, no matter how the timing was set. I haven't noticed any difference myself in
the adjustment, but I still set it anyway. Just a little tidbit I wanted to pass on. -Hans
From Rennsport (Visit for more great
Bosch Mechanical Fuel Injection is a splendid, if not
inexpensive, performance induction system. It was used on the 911S and 911E from 69 to 73
as well as the 73 Carrera RS. Porsche used various types of MFI on factory racing cars
from 67 to 84. This is a very complicated fuel delivery system that, if set up properly
and in good condition, makes excellent power and throttle response.
The trouble is, few people anymore possess the necessary
knowledge to make these systems run well and Bosch has little documentation available for
the owner. Pacific Fuel Injection and Eurometrix are two of the most reputable re-builders
of injection pumps and throttle bodies.
Injection pumps can be recalibrated to almost any engine
size and camshaft. 2.7 RS-spec engines equipped with these systems continue to be quite
popular since the requisite space cam for the pump is still available. Eurometrix can
enlarge the throttle bodies to 40mm for larger engines as well. The larger plastic intake
stacks as used on the "S" and Carrera RS engines are still available from
Porsche as this is written.
Tall butterfly throttle stacks from the 73 2.8 RSR and 911
SC/RS are one of the good upgrades for engines used for racing purposes. These 50mm
throttles work quite well for 3.0 litre and larger racing engines. Another upgrade to
consider are the RSR throttle slides from the 74 3.0 RSR. These are being re-manufactured
by Andial for racers as well as restorers. Other aftermarket throttle slides and fuel
rails are available for the 3-bolt flanges used on 3.6-3.8 litre engines. You can even fit
excellent quality aircleaners to these throttle assemblies. Typically, FI pumps used for
racing are recalibrated to RSR-spec and the idle-cutoff solenoid is removed.
The early FI pumps are better suited for the RSR
modification and the later pumps used on the 2.4 litre engines are better candidates for
an RS-type upgrade.
Date: Thu, 5 Aug 1999 22:11:1
I have the same car, and have dealt with the MFI quite a bit. Bruce Abbott certainly
has some good advice; it will take some time to get familiar with it.
You might get some help from my experiences:
(When I had the MFI pump rebuilt and reinstalled it,
the engine still ran like trash. There was still spark, and I could get a timing
light to work, so I never suspected the coil. After lots of frustration, I finally
noticed that the timing light would intermittently wink out when I revved the
engine). It's easy to check the coil with a multimeter (see Haynes manual.)
It's "chock full of info" on MFI! He'll
soon be posting the Porsche factory MFI adjustment manual, called the
73 911E Targa
From: Matt Beaubien <email@example.com>
Date: Wed, 11 Aug 1999 01:48:52 -0600
I'd like to thank everyone who sent me suggestions on what
was wrong with the MFI on my '73 911E. A few discoveries have been made and thought
I'd share them with everyone.
My cold start problem was in fact electrical. I ended
up removing the electrical panel in the rear and cleaning every single electrical
connection with contact cleaner and a brass-wire brush. She fired right up after
reinstalling the panel.
Quite a few people suggested that my poor part throttle
running and missing above 6k RPM may be a supply problem due to rust clogging the screen,
lines, filter etc. I didn't really feel that fuel supply was a problem as it was
fine at 5000 rpm at WOT.
I did some more investigating in the thermostat operation
on the regulator. I removed the top access port to get a better idea on how it
worked. It seemed that the thermostat never really moved that much. I levered
the assembly with the engine running, and was able to see black
smoke for the first time. I then operated the
throttle a couple times and noticed much better response than before.
To make a long story short, I started removing pairs of
discs from the thermostat. I removed one or two pair at a time but it didn't make
much of a difference. I then removed a whole bunch (~ half) and it seemed just
right. Took it for a spin and it pulled to 7k+ RPM in the first
three gears, without missing at all. Perfect!
This allowed me to go to a track the next day for a lapping session to get acquainted with
the physics of 911's.
It then started to miss again occasionally at part
throttle. This time it was a rich-miss. I could tell because giving a little
more throttle opening would make it stop. When it was lean, more throttle would just
make it worse. I'm now tinkering with finding the right number of washers to get it
running properly. I'm thinking of threading the thermostat cap to allow me to adjust
the preload quickly and easily.
(It seems that the spring or whatever in the regulator that
presses against the thermostat is not strong enough. Removing discs reduces the load
required to get enrichment happening).
For those of you that have had your MFI systems overhauled,
can you let me know how much to expect money wise? Private or public emails are
FWIW, my engine only pumps 135 psi on a compression gauge
and burns a noticeable amount of oil. However, I was able to hit 6500 RPM in 5th
which equates to 143 MPH (S+ numbers, no?). This was with the sunroof open and it
was still pulling a bit. I have an RS-esque air dam and a duck tail which may reduce
the drag a bit.
What a fun car...
'72 911 E
From: firstname.lastname@example.org (Peter Cowper)
Date: Fri, 20 Aug 1999 23:13:19 -0700 (PDT)
1974 911 . . . (with a fresh 2.4 S engine under the
bench waiting for 2003 when my car drops off the California Smog Roles!)
From: Terri & Marko <email@example.com>
Date: Thu, 21 Oct 1999 17:21:29 -0400
I recently asked listers if they had any luck using
this approach,aparently no one did so I
thought I'd try various techniques/chemicals...after many
failures I won!!!!!
So, here is what worked for me. I used a 1
litre ultrasonic cleaner (large jewelers or graphic type) must be capable of
heating solution to 150º+ F.
The solutions are simple and available at any hardware
store... mix 1/2 turpentine + 1/4paint remover + 1/4 acetone, bring to temp.150º+ .
Soak injectors vertically for 2 hrs. Invert and soak
for 2 hrs. Lie flat (roll back/forth) for 1hr.
The screens will be perfectly clean (there will be a small
amount of residue on bottom of
I cleaned same and repeated process IT RUNS
FANTASTIC!! You will have to lean the mixture on the pump behind the shroud
approx.3-4 turns or to your liking respectfully.
From: Bob Spindel <firstname.lastname@example.org>
Date: Mon, 25 Oct 1999 11:13:45 -0700
The sockets are made to pop off the
balls. Just wedge a large screwdriver blade between the ball and socket and twist,
or use an open-end 10mm spanner in a similar manner.
The length of only one rod is critical:
the rod between the MFI pump and the accelerator linkage. It should be 11.4 cm +/- a
few 1/10th millimeters from balljoint centre to centre. With that one set right, the
lengths of all the others fall into place.
Essentially, you adjust the length of
all the rods so that the butterflies are closed and each is just resting on it's
stop. The "correlation" will then be right. You don't need the
'73 911T (being restored)
Date: Wed, 27 Oct 1999 11:15:07 EDT
That number is the correct pump for a 2.7RS. They are
0408 126 XXX :
>> I also have the part number for the stack
(911.110.312.1R). Does that look consistent with an RS? <<
That # is not in the MFI book, it would be in the factory
parts book but I have that at home so can not check. The S and RS have bigger stacks
than the T and E, they should be the same as your '73S.
My '72S stacks had "S" written on them with
yellow grease pencil at the Factory I think (wonder if the concours guys check for that?).
>> Also, a more basic question, does the
Carrera RS have different stacks than a '73 S, how about throttle plates? There
seems to be a lot in common between the '73S and the '73RS so far. <<
Yes, they are almost the same engines. Only real
difference is space cam in MFI pump, and
pistons/cylinders. However the MFI book says that the
RS features "throttle valve casing with enlarged bypass bores for idling air;
recognizable by Solex part number on front surface".
So I guess the throttle valves are slightly different,
though it should be easy to bore out the S idle air passes a bit if idle is too low.
Good luck, sounds like you are putting MFI back on your
MFI cold start
From: Mike Piera
>> I have a '72 911E Targa with
mechanical fuel injection. It will start right up, but if I try to give it any
gas it will lose power and stall. If I let it idle for 5-10 minutes it runs fine.<<
You can check for vacuum leaks with the
car idling by spraying that carb cleaner around the base of the intake stacks if
you hit a leak the engine RPM will change. Maybe you can check for leaks on the head
this way too by spraying through the ducting.
Also check the pump timing, which
will require a mirror to see the timing mark on the back of the pump. I hear it's not that
critical but couldn't hurt. After fixing all these wear items, if it still runs bad
you can then do the adjustments throttle linkage lengths, butterfly valve stops,
pump vs. butterfly correlation, etc. Then you can set the part throttle and finally
From: Josh Pinkert <email@example.com>
Last night I pulled my heat exchangers so that I could
rotate my motor on the stand and have better access to the underside of my motor (cleaning
time!!!). It was a piece of cake... judiciously used PB Blaster on the bolts and
they came right off (although the muffler bolts were really rusty).
Upon looking at the exhaust ports, all of them were
uniformly caked with a dry soot, except for #2. Before I dropped the motor, I had
replaced the plugs, cap, and rotor and after subsequent test drives (and an examination of
new and old plugs) I concluded that plug #2 was fouling. Now that I have a chance to
look at the exhaust port for #2, I see that its all wet.
My question is... is there an easy way to tell if it's oil
versus fuel? If it is fuel, I'm not worried. Just retune it. If it's
oil, then I'll have some problems to deal with. How difficult is it to pull just one
cylinder? It would require pulling the head from that side, so I'm looking at a good
investment in tools, plus I'll have to re-time the cams, right?
Josh Pinkert - '72 911T
From: Bob Spindel <firstname.lastname@example.org>
Date: Thu, 23 Mar 2000 13:52:25 -0800
The through-the-stack popping at idle is
reduced mostly be getting the throttle linkages adjusted correctly. If you're off
even a teensy bit on one stack pop pop! A good way to go about it is with a
warm engine at idle, start popping (bad word!) off the links, checking to make sure they
are adjusted so as to present no preload to their respective butterflies. This
includes the link to the MFI pump itself (which should be exactly 11.4cm, ball-to-ball,
this is critical) and the main link from each set of stacks to the accelerator
The backfiring-through-the-exhaust can be minimized
by adjusting the MFI pump for part load adjustment. A simple way to do it is lean
the pump out (clockwise, I think) a lot. Get it to the point where it is so lean it
idles poorly, and backfires like a banshee when you let up on the accelerator at
speed. No need for walls here, you'll hear it if it's lean enough. Then start
enrichening it a few clicks at a time until it idles nicely again, and doesn't backfire,
and allows smooth acceleration through the 25003500 rpm range. All three of
these will happen at the same setting. The switch from way too lean to just about
perfect occurs over a very few clicks maybe 3 or so.
you do need something to allow you to determine how much
air is being drawn in. I use a device called a Unisyn, which has been around
forever. I'm not sure what they cost these days, but I'd be surprised if they were
more than $25 or $30 (although they're probably worth $10). There are all sorts of
fancy tools available. I've seen some with gauges on their faces that
cost nearly $100, but they are big time overkill. The
Unisyn just has a tube with a little ball in it that rides higher or lower depending on
the air flow. One just adjusts the bleed screws until the ball rides at the same
level for each cylinder. The bleed screw adjustment is pretty fine in
that it takes a fairly whopping adjustment to make much
change. With them all at 3 turns out you're probably very close, even pretty equal
on most, but usually there will be one or two cylinders that are off enough to start
popping through the stacks.
The procedure of taking a reading in all six and then
finding the mean and adjusting to it will certainly work, and maybe it can be quicker that
way. It's very scientific of course Germanic but overkill. The
object is simply to get all the intakes equal. You can read fancy vacuum gauges, or
look at little balls. Same result. When they are equal, you may wind up with
the idle a bit high or low, in which case you just decrease or increase each screw the
same amount to get the idle where you want it.
I'm sure you have the linkages set correctly, and I'm
probably misinterpreting your words, but to be doubly certain you don't want to set them
to just evenly close the butterflies alone. There are stop screw adjustments on each
of the butterflies to do that. Disconnect the linkages and set the stop screws so
that the butterflies are all just closed when they rest on the stops. Then adjust
the linkages so that when you pop them on they don't move the butterflies off their
stops. The bleed screws then simply allow you to account for very small
differences in each butterfly/stack. If all the intake stacks and butterflies where
accurate, precise devices, you wouldn't need the bleed screws.
One more thing. If you have one cylinder that
consistently fouls, like Josh's #2, double check the linkage/butterfly/air screw on that
one. It's often the probelm.
Hope this helps.
Date: Sun, 26 Mar 2000 23:49:0
The cam in the MFI pump is matched to the cams in the
engine. Changing your cams can cause rough running. But that can be okay for
increased performance. (I had a "T" pump with "Solex" cams,
switched to an "S" pump and found it runs much better).
absolutely no effect no
matter how far I adjust them out/in).
2) Frequent backfiring through the stacks
primarily from cyls 2 & 5.
-- No idea (see Bob Spindels previous
3) Lots of backfiring through the exhaust
mostly when decelerating but not always.
Date: Mon, 27 Mar 2000 09:42:15 EST
PorschePoor@hotmail.com wrote :
> After spending the last 6 months rebuilding my 2.2S
> Question: If adjusting the air screws on the
TB's doesn't change idle
> speed one whit, despite running them out past ten
turns from stops, am I
> correct in assuming that the fuel at idle is too lean?
> If the problem lies in adjusting the pump, is there
any base point to start
> from similar to the TB air mixture screws? (i.e.
screw in until stop is
> reached & back out 5 half turns). <<
Not that I know of. When I got my last pump rebuilt,
it was not even close to a setting that would allow the engine to run, even though Hans
said it would run fine without adjustment.
If your pump's main setting (mid range mixture) is set
extremely rich or lean, the idle air screws will not do much of anything. Also the
pump's idle screw will not do much you need to set the "part load"
(remove allen bolt in front of pump and use a long thin screwdriver) before setting the
"Idle mixture" (this special tool stuck through the fan). You do have the
CHECK/MEASURE/ADJUST manual??? (I can copy if you
> This is all rather frustrating as the fuel system
worked fine before I
> pulled the motor, and I didn't touch the pump other
than to remove and set aside.
That points to something other than the pump. You
must follow the manual and check each component before blaming the pump. As the
manual says :
"Remember, the injection system is not a separate
component, as, for example, the generator. It should be thought of as part of the
engine. No matter how well the injection system is adjusted, it cannot make up for
problems in the operating condition of the engine. Always begin injection work by
checking the engine's basic tune."
The checking sequence is:
1. Air cleaner cartridge (rubber gaskets in place? filter
2. Compression loss (what is your compression? Maybe the
cams are not timed right???)
3. Spark plugs (are they all firing correctly? some new
plugs are DOA)
4. Dwell Angle
5. Timing (are you 180 degrees off, or off a tooth on the
distributor? Check that at TDC your distributor rotor is pointing to the #1 notch on
the distributor case.)
6. Fuel pressure and flow: should be about 10PSI at the
pump, you can TEE in a cheap gauge for a quick reading.
7. Injection nozzles: when you rebuilt the engine you
should have had the injectors tested/ cleaned.
8. Injection timing: not hard to check and adjust close
enough suing a mirror, as per manual.
9. Correlation (lengths of throttle rods etc)
10. Exhaust emission test:
a) part load I could
write a book about ways of doing this
b) idle never seemed to
make much difference on many engines.
NEVER DEVIATE FROM THIS SEQUENCE (or Hans will poke you
with a long cheesehead screwdriver).
MFI problems I
Date: Mon, 27 Mar 2000 10:32:34 EST
throttle rods. I can't believe that 5mm plus or
minus is allowable... get them all as exact as you can. Do not worry to much about
the angles of the throttle cams... getting the rod lengths correct will take care of that
problem. You might also need to time the pump to the camshaft...requiring some
After all adjustment is done, you will need a
very small screwdriver of some length to adjust the idle mixture and lean/rich mixture
control on the pump. (All this is in the manual). It took me a couple tries to
digest the information and make sense of the procedure, but after setting it up, I've had
zero problems with the exception of adjusting the richness depending on seasonal
cold... once in the winter, returning the setting for summer if it gets cold enough in New
From: Bob Spindel <email@example.com>
Date: Mon, 27 Mar 2000 10:34:41 -0800
I also think you're settings way too
lean, but not because of the way your air bleed screws act (or don't act), rather because
of all the backfiring. The bleed screws actually make pretty minor changes in idle
even when everything else is correct.
You can also manually open the throttle by moving the
linkage, thus letting in more air while keeping the gas the same, thereby leaning the
mixture. If the idle smooths out, or speeds up,
you're too rich. When you're close to perfect, the
idle will get worse when you do either of these.
I don't know if there's a rough rule as you
suggest. I do know that the mid-range adjustment is by far the most critical, and if
you have it right the idle adjustment can be way off and things will still be okay.
I also know that the mid-range adjustment is very fine. Each click is 1/6 turn, and
the right setting is within +/- 2 4 clicks or so. That's less than a
full turn. And the screw itself is pretty dang long with a very fine thread,
and you can probably turn it a zillion times from stop to stop.
Doing what I wrote above ought to get you close, then do
what I posted before, which is lean out the mid-range adjustment until you start to
backfire like a banshee sounds like you're already there and then richen it
as I described.
Hope this helps.
P.S. John Hunt suggested if you're in the Pacific NW
you should contact Chris, at Chris' German Auto in Bellevue, WA. I agree, he's
excellent. (Coincidentally, I'm in Bellevue too!)