|Editor's Note: This is a collection of
notes from Jimm Thorusen on
the relocation of the 914 fuel pump to the front of the car.
I will send you what I have, Dave. Unfortunately, it isn't quite
complete. To reduce the possibility of fuel leaks under the tank, I was
forced to make up two "stacks" of adapters to replace the original Porsche
special fuel hose.... you know, the one that ends up a different diameter
from what it started with? Anyway, I don't have the data about the
adapters in place and correct in the article, and I am not perfectly
satisfied with the layout, anyhow. The ideal solution would be a fuel
filter with 9 mm inlet and 7 mm outlet hose barbs, rated for FI pressure,
and no larger in diameter than the pump itself. Such a fuel filter does
So.... you will need to read between the lines a bit about the under-tank
portion of the fuel line hookup. If Pelican wanted to have some dual hose
barbs made up that are 7 mm on one side and 9 mm on the other, such an item
would be very helpful. As my pump is now configured, I have two stacks of
three parts each of adapters, 6 clamps, and two extra short pieces of hose
to interconnect the adapters, all jammed under the tank.
The rest of the procedure worked out well, however. I did use a fuel
pump blister from a '75 car.... these are in somewhat short supply, and
Pelican may want to lay in a stock of them or see about having some made.
With those provisos, however, here is the procedure:
This is a more elaborate way than most, but it is how I did mine. It may
give you some ideas, anyway.
>From my files:
There are several ways to go about it. I opted to get as close
to the factory idea of how to do it as possible.
Therefore, this is the way that I did it:
1 Fuel pump mounting blister from a '75 or '76 car...
.....available used... ask on the mailing list or inquire
of various Porsche junk yards.
1 6" length (approximately) slotted shelf bracket
4 #10-32 Nutserts (install in 9/32" hole)
4 #10-32 pan head machine screws
4 #10 star washers
4 #10 flat washers
2 Large hose clamps (sufficient to go around pump body and
shelf bracket piece; I forget exact size.
1 Can Rustoleum metal primer
1 Can Rustoleum finish coat... as close to current color of
inside of front trunk as possible.
1 Can silicone spray lube
10-32 Nutsert installation tool
"Super-Champ" or equivalent electrical crimp tool
1/8" or similar size small pilot hole twist drill
9/32" twist drill
Appropriate size twist drill for rubber mounts used...
in my case, 9/32" also
Scrolling type Sabre saw with at least two metal cutting blades.
Mini tubing cutter
8-1/2 x 11" sheet of stiff white paper.
Black flow pen
1 Set rubber mounts... C&H Sales stock # M19303 @ $3.95
C&H Sales Co. 2176 E. Colorado Blvd. Pasadena, CA.
(800) 325-9465 (note: their minimum order is $30.
Note: Any similar mounts will do...
[ M19303 does not appear in their latest catalog... M19404 may be a
substitute, but the studs are a lot bigger, and may necessitate a
modification in the pump mounting scheme; wider shelf bracket
stock to accomodate larger nuts.]
1 5/16" Hose barb, brass, with 1/8 NPT
1 3/8" Hose barb, brass, with 1/8 NPT
1 1/8 NPT elbow, brass
1 Fuel filter, rated for FI use, with 5/16" hose barbs
10' 5/16" fuel injection hose
8' 3/8" fuel injection hose
NOTE: Lengths are approximate... depends on how many mistakes
you make, and how generous you are with service loops...
7mm and 9mm hose would be better, but I have not found it to be
available in the U.S. at reasonable prices.
Note 2: I used 1/4" hose and 1/4" small hose barb, and had a devil
of a time getting the stuff to fit over the plastic fuel lines. 1/4" is
good for re-building the fuel injection rail system, but I think 5/16'
would be better for this project. Buy a few inches and try it for fit over
the plastic lines (small ones).
1 Roll teflon tape
16 Hose clamps (sized for 5/16" and 3/8" FI hose)
4 Blue crimp-type butt splices
2 Ring terminals (crimp-on) suitable for M8 bolts.
1 Bottle insulating varnish (red glyptol) or equivalent
(The rubber dip for tool handles that can be purchased
in the paint section of your local home improvement
store is an acceptable substitute for Glyptol
in this application.)
1 Bag medium ty-wraps
15 feet #16 stranded automotive wire, black
15 feet #16 stranded automotive wire... different color than above
First, remove the gas tank. You will need the access to see what
you are doing, especially when sawing out your mounting hole, and
you need to renew the hoses on the bottom of the tank anyway, so
go ahead and do it.
Next, place the sheet of paper over the flange side of the blister
and do a "rubbing" with the crayon which will allow you to see an
image of the blister flange and the mounting holes. Cut out the
outline of the blister flange on the paper so as to make a drilling
and cutting template.
Next, take a look at the Haynes book, page 45, fig. 2.19. This
shows you about where to cut out your hole. The location is the
bulkhead between the fuel tank bay and the luggage area, just
above the spare tire well on the driver's side. There is a flat spot
here big enough to accomodate the blister. The pump will protrude
into the space beneath the tank; the hole you are going to cut out
should be such that the pump will be just forward of the brake fluid
reservoir lines that go down through grommets to the master cylinder
Place your template in the correct position (glue it on is good) and
center punch through it to mark the locations for the mounting screws.
I can't overemphasize accuracy here! The #10-32 screws just
barely fit through the factory holes in the blister; if you are not right on
the money, you will not get the thing to line up. Finish with the
template by marking the outline of the large hole with the felt pen on
Next, drill the center punched mounting holes with the small pilot
drill. Again, for accuracy's sake, you must drill in two steps.
Next, punch the holes out to 9/32". Don't forget to debur the holes, but
don't enlarge them, or the nutserts will not work!
Now, install the Nutserts. You can check the blister for fit at this
point if you wish by installing it with the 10-32 screws.
Finish the metal work by cutting out the large center hole with the
sabre saw. You will probably have to drill one other large hole to
provide a starting point for the blade. When you have finished, the
hole should be just large enough for the pump to fit through with a bit
of jockeying. Debur the large hole, too. If you glued the template
on, now is a good time to remove it.
Next, apply the Rustoleum primer to the area, being sure to get a
good coat on both sides and on the cut edge. Put some matchsticks
into the Nutserts to keep paint out of their threads.
While the paint is drying, you can think about electrics. Here's how
I did mine. There are two wires to the pump; on the '74 they are
brown and black with red. I think that they are the same on the '73,
but you can check. At any rate, the standard Porsche color for
ground is brown; the other one is +12 volts.
Locate the existing wiring to the pump. It terminates in a special
connector that plugs onto the pump. BE SURE that in the next step,
you leave the leads from this plug good and long!
Cut these wires and save the plug with it's pigtails for future use.
Pull the wires out of the harness that they are in back to the common
point at the center of the front of the engine shelf. Cut the brown
wire off short where it exits the harness.
To facilitate the next steps, remove the center tray, the carpet, and
the wooden floorboard from under the pedals in the interior of the car.
Next, fish the remaining wire (probably black with red) down through
the rubber goose neck and into the inside of the car. My goose
neck had a hole in it near the bottom which made this easier; if yours
does not, and you don't wish to make one, remove the gooseneck
from the lower firewall and fish the wire through in two steps. Then
re-install the gooseneck. (Be careful; the goosenecks are old and
fragile... it might be better to make a small hole near the bottom and
patch it up later with RTV than risk tearing the whole thing up by
trying to remove and reinstall it through the firewall.
Once you have the wire inside the car, you can splice onto it fairly
easily inside. The original length will only go as far as the back plane
of the seats, so splice on a bunch more with a butt splice crimp
connector. Glyptol insulating varnish is a good idea here, too.
Water inside crimp connectors ruins the connection rather quickly.
Route the wire along the existing harness on top of the tunnel.
Use ty-wraps as required to get the wire to follow the harness closely.
Route the wire along the branch of the harness near the front that
arches up and over the pedals along the metal front bulkhead.
Ty-wraps will be necessary here to keep the wire from drooping down
into the pedal mechanism. Follow this harness with the wire,
ty-wrapping the two together at frequent intervals until you encounter
a gromet that is inserted in a hole that is punched through the
horizontal piece of sheet metal above and behind the dashboard.
This comes out right below and behind the brake master cylinder fluid
From inside the trunk, fish down through this grommet and pull your
new wire up through. You will see more wiring harness running down
into the space below the fuel tank. Run your wire down along this
harness until a convenient jumping-off point near the hole that you
cut earlier, but do not ty-wrap it yet.
Time to stop and paint; spray on the finish coat around the hole you
cut (assuming that the primer is dry by this time). Don't forget to get
the cut edge as well as the surrounding area.
While this is drying, you can make up the rear fuel lines.
Assemble the two hose barbs into the elbow using teflon tape as a sealant.
Get 'em good and tight; fuel leaks and air-cooled engines equate to fire.
Remove any old flexible rubber fuel lines from the plastic lines under
the engine shelf. Locate the brass assembly that you just made up in
the lower right corner of the underside of the engine shelf. (There is
a cubby there formed by the various chassis members.) Cut a length
of 3/8" hose suitable to connect the large rigid plastic tube coming
out of the firewall to the 3/8" hose barb, which should be facing it.
You will probably have to cut off a length of the rigid plastic line with
the tubing cutter in order to get room to make the connection. Lube
both the rigid plastic tube and the hose barb with silicone lube; ditto
the inside of the cut-to-length piece of hose. Put two hose clamps
on the hose, being careful to orient the screws so that they can be
accessed later with the engine installed, and install the hose, being
sure that you are connecting to the LARGER of the two rigid plastic
tubes. Tighten the clamps.
Cut a length of 5/16" hose suitable to connect the smaller hose
barb to the rigid plastic supply tube going up through the engine
shelf. Install two clamps, lube as before, and fit the hose.
Cut an additional length of 5/16" hose suitable to go around the
corner from the smaller rigid plastic line coming through the firewall to
the equal size line that is the fuel return line through the engine shelf.
Fit clamps, lube, and install as before.
Note: The supply line is the one that connects to the fuel injector
rail. The return line connects to the fuel pressure regulator.
Up in the engine bay, connect a temporary length of 5/16" hose
between the rigid plastic supply and return lines. This will be used
later to purge the fuel system.
Next mount the pump to the blister. Measure the distance between
the two large holes in the blister bulge, and mark and drill two holes
an equivalent distance apart in the bottom of the "U" formed by the
shelf bracket material. Cut the bracket material so that it extends
about 1/4" or so (not critical) beyond the holes just mentioned above
on each end.
Mount the bracket stock to the pump blister with the rubber mounts
and their associated hardware. The rubber mounts should be on the
hollow side (partially down inside) the blister. Mount the bracket
stock to the rubber mounts so that the open end of the "U" faces
away from the blister. Cut off the studs inside the bracket stock so
that they are as far below the top of the "U" as possible. Cut the
other studs off so that they do not protrude an excessive distance beyond
the blister into the luggage area, or you will bark your hands on them
sooner or later.
Mount the pump to the assembly by using the large hose clamps
around the shelf bracket stock and the pump body. It will be
necessary to position the clamp screw mechanisms so that they do
not chaffe against the brake lines from the reservoir, and yet are not
so sideways that they prevent getting the pump through the hole. A
bit of cut and try is necessary here, and is one of the reasons that the
fuel tank is out; you can see what is hitting what. In addition, the
pump should be mounted so that no part of it chaffes against those
same brake lines.
At this point, since you have been trying the pump assembly for fit,
we assume that the last of the paint is dry.
Run the supply wire that you added before down the existing
harness to a convenient jumping-off point, and then run it out through
the large hole. Leave a foot or two and cut off the rest. Add an
additional length of wire (preferably of a different color) to be the
Leave a foot or so of this wire hanging out the large hole for the
pump, and then route it along with the other (supply) wire back to the
existing harness. Now ty-wrap both wires to the harness, backing up
towards the brake fluid reservoir as you go. When you get near the
grommet that the supply wire comes through, stop ty-wrapping and
lead the ground wire off toward the center of the car. Find a
convenient nut to remove, cut the ground wire to a suitable length,
crimp on a ring terminal, and secure it to ground.
Next, take the supply wire and butt-splice it to the black with red
wire from the fuel pump connector. Then butt-splice the ground wire
to the brown wire from the connector. Again, seal the butt splices
with glyptol, and put the completed wiring aside until later.
Last, the hose routing: This is most easily done with the pump and
blister assembly not mounted to the bulkhead. Run a length of 3/8"
hose from the "D" port on the pump to the large plastic line coming
through the firewall. be sure to run the hose through the service hole
that you cut, and to leave a service loop so that the pump can be
removed for service. Lube the line and install with clamps.
Next, run a short length of 5/16" line from the outlet side of the
filter to the "S" port on the pump. Lube with silicone and secure with
clamps. Run a longer length of 3/8" line from the inlet side of the
filter over to the access hole below the fuel tank. Connect and
clamp to the filter, but leave the other end loose. Leave enough to
work with. This will be connected later.
Run a length of 5/16" hose from the smaller rigid line coming
through the firewall to the "Y" connector. Lube, install, and clamp.
Run another length of 5/16" hose from another leg of the "Y"
connector to the "R" port on the pump Leave a service loop. Lube,
install, and clamp.
Run a length of 5/16" hose from the third leg of the "Y" to the
access hole beneath the tank. Lube, install, and clamp the "Y" end,
but leave the other end loose. Be sure you leave enough to work
Install the electrical connector on the pump, and stuff first the fuel
filter and then the pump into the hole. Secure the blister with the
10-32 screws and washers.
Take a last look at the hoses that will be under the tank, to see if
there are any obvious trouble spots. Be sure that the loose hose ends
refered to earlier are hanging out of the under-tank access hole.
Re-install the fuel tank.
From underneath the car, and working through the under-tank
access hole, lube, install, and clamp the 3/8" hose to the larger of
the two tank stubs.
Lube, install, and clamp the 5/16" hose to the smaller of the two
This completes the conversion.
When the car is almost ready to run, remove the pump and blister
assembly, so that it's hose connections may be observed. Put some
fuel in the tank, and short pins 30 and 87 of the fuel pump relay
socket with a suitable jumper (relay removed).
The pump should run, and fuel should be observed to circulate in
the plastic lines in the engine bay. (At least at first, when some
bubbles and dirt should be in evidence.) Allow the pump to run for 2
or 3 minutes, to purge all dirt from the lines. While it is running,
inspect the pump itself and all other fuel line connections for leaks.
When the purge is complete, remove the temporary jumper from the
relay socket, and re-install the relay. Remove the temporary hose
connecting the supply and return lines in the engine bay and
connect them to their correct points on the engine.
When the car is first run, re-inspect the fuel pump connections, as
the pressure will be higher than in purge mode. If all OK,
re-install the pump and blister assembly to the bulkhead.
YOU ARE DONE!
This is pretty verbose, but was written for someone who asked for
"detailed" instructions... I hope that some of it will be useful.