Four pressure tests can be made with this tester:
- Cold Control Pressure engine cold, valve open
- Warm Control Pressure engine warm, valve open
- Primary Pressure engine cold or warm, valve closed
(closed valve eliminates control pressure)
- Rest Pressure engine warm, valve open
The CIS pressures shown in this book are for the warm
control pressures. For pressures for tests A & C, consult the vehicle
service manual, a Mitchell Fuel Injection manual, of Robert Bosch Service
Guide booklet for Fuel Injection.
To make tests:
- For test A (above), the engine should be cold,
standing several hours or overnight.
- Relieve fuel system pressure.
- Make sure fuel filter is not clogged. Replace if
- Clean dirt off the fuel distributor cap.
- Referring to the typical CIS hookup diagram, hook up
the tester between the fuel distributor and the control pressure
regulator. The hose without the flow control valve should be connected to
the center of the fuel distributor. The hose with the valve should be
connected to the hose removed from the fuel distributor or connected
directly to the control pressure regulator.
- CAUTION: hand tighten any adapters with the
O-rings to avoid damage to O-rings.
- In a few cases, to get the right combination of
threads to connect, the adapters may have to be piggy-backed.
- Reactivate fuel pump, start the engine and check for
- When the tester is connected, remove the air from
- If your tester has a release valve under the
gauge, wrap a rag over the valve and depress button until the air is
released. Do not do this over a hot engine or manifold.
- If your tester has a bleed-off valve, put the end
of the bleed-off valve tubing in a fuel container and with fuel pump
operating, bleed until air is removed.
- If your tester has none of the above, position the
gauge downward as far as the hoses will allow with the gauge below the
hoses and control valve. Operate fuel pump with the engine off. Open and
close the control valve at least 5 times with the valve in the off and
on position at least 12 seconds.
- When pressure stabilizes, read the gauge. If the
Cold Control Pressure is not correct, the warm-up regulator may be at
- If pressure is okay, run the pressure checks
- Warm Control Pressure and Rest Pressure must be
measured with engine warm.
- Primary Pressure can be measured with engine cold
- Pressure range
- If pressures are not within the normal range on
the control Pressure Warm test, try adjusting the fuel pressure
regulator. If it cannot be adjusted to normal pressures, replace it
unless the problem is as below (b)
- If the pressure is low with engine running and at
idle, check to see if the voltage is at least 11.5V at the warm-up
regulator plug contacts. If full voltage is available at the plug, then
the warm-up regulator may need replacing.
- If the pressure is too low, test the fuel pump
volume. Also, there may be a blockage in the supply line or leakage in the
return line. If the system has none of these, the fuel system pressure
needs adjustment. Consult the factory manual or fuel injection manual for
- If Rest Pressure drops too quickly, check for leaks
at O-rings and fuel line connections. If no external leaks, check for a
leaking cold start valve of fuel injectors. If still no leaks there,
leakage may be at the fuel pump check valve or at the O-ring on the relief
valve in the fuel distributor. Repair or replace.
- If no problems can be found in the fuel injection
system through pressure testing, fuel pump should be checked. For this,
your tester should have a bleed-off valve and tubing. If you do not have
one, it can be purchased from your tool supplier. With gauge hooked up to
pressure test, put bleed-off tube into a fuel container of at least 2
quarts or 2 liters. Fuel flow in 30 seconds should be 1.5 - 2.0 pints or Ύ
- 1 liter. Turbo cars may have a volume of 20 25% more than non-turbo.
- Deactivate fuel pump and relieve fuel system
pressure. With key off, put bleed-off tubing in a fuel can and press
bleed-off valve. If your tester has no bleed-off valve assembly, wrap rags
around connection and release slowly. A bleed-off assembly can be
purchased from your tool supplier.
- Remove tester and reconnect all lines.
- Start engine and check for leaks.
- Remove fuel from all hoses. If fuel remains in gauge
hose assembly, connect the smallest banjo bolt adapter into the quick
coupler over a fuel container. Hold gauge above hose and fuel will flow
into the fuel can.
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