"Tricked" Fuel Pump To Stay On - Pressure 40psi?

James, interesting issue.

It can be normal for FP to be up a little when first started (alt output can be higher than normal to recharge battery from starting, etc) and this higher voltage allows the pump to flow more fuel (same idea as running a pump-regulator/booster type product).

Other than that, I cant really think of a reason why this occurs. Do you still have a one wire alt? Now if this occurs before the alt kicks in, there goes my idea.

So if you run the pump normally, the pressure drops right back to normal?

grounding the wire in the STC is the same thing the puter does with the wire (sends the ground pulse to the FP relay), so I dont see how there is any way for a change to occur.

Interesting - let's see what the smart folks say.

If the engine isn't running (no vacuum for the FPR) , 40 PSI is good.

As for starting problems that require you to press the throttle, there are three possiblities:

1.) Failed IAB (no airflow to start engine). Press the throttle ¼ way down and try to start the car.
2.) No start when hot - Press the throttle to the floor & try starting it. If it starts, replace the ECT.
3.) leaking injectors -
Fuel pressure OK, the injectors are not firing, OR one or more injectors stuck open

The red wire on each injector is powered up whenever the ignition switch is in the Run position. The computer provides a ground to complete the circuit and fire the injector. The injector must have a ground to squirt fuel on command. A short to ground in the injector return wiring can cause one or more injectors to be continually open or triggered


A.) A Noid light available from Autozone, is one way to test the injector wiring. If the light stays on constantly, either the wiring has a short to ground or the computer has failed
B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles An injector stuck open will release a continual stream of bubbles. Cheap if you have the stuff laying around, and works good too. The same trick works great to find leaking injectors too.


The wiring for the injectors may have some bare spots in it causing the injector to computer control wire to ground out. This would cause the injector to remain on anytime the key was in the Run position. Remove the injector wiring connectors from the injector. Note that each injector has one red wire for power and a non red wire (wire some color other than red) for computer controlled ground. With the key off, use an Ohmmeter between the non red wire and ground. You should see more than 100 ohms resistance.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. You’ll need it to do the cylinder balance test

See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

Second method is the cylinder balance test. Warm the car's engine up to normal operating temperature. With the Engine Off, Key OFF, use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 99 or the number of the failing cylinder such as 22 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure