Fuel Injection problems, please help!
Thread Starter
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Fuel Injection problems, please help!
Alright guys, my friend is still having trouble with the 95 Z-28. We know for a fact that the cam is in time and the opti is on correctly. I can watch with a timing light that the spark is firing at TDC on the compression stroke. This got us back to a fuel injection problem. We don't have a light to test so we had to use a volt meter, a crappy one at that. Anyway the result is that there is voltage to the injectors with the key in the on position, and it doesn't pulse at all when you crank the engine. This makes me think that the injectors are open all the time, flooding the crap out of the engine. Logical since you can crank on it for a while and then pour gas into your hand out of the spark plug.
It could be something as simple as a bad ground, anybody know any specifics?
It could be something as simple as a bad ground, anybody know any specifics?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Fuel Injection problems, please help! (Nathan Plemons)
When you turn the ignition On there should be power to one side of the injector harness, but the other side should be floating and so read about the same voltage. When an injector is fired, the ECM pulls that injector's driver to ground to flow current through the injector and so open it up.
I can't remember if your ECM uses batch fire (one bank at a time) or sequential (one at a time), but in any case with the ignition On but not cranking the motor there should be no current flowing through the injectors.
If your voltmeter has the capability, hook it in series with an injector and measure current flow with the ignition On (of course there sould be none). It should read about zero. Then crank the motor and the current flow should pulse to about 1 Amp or to several hundred mAmps if the voltmeter is slow and reads an average integrated over the pulse width.
I can't remember if your ECM uses batch fire (one bank at a time) or sequential (one at a time), but in any case with the ignition On but not cranking the motor there should be no current flowing through the injectors.
If your voltmeter has the capability, hook it in series with an injector and measure current flow with the ignition On (of course there sould be none). It should read about zero. Then crank the motor and the current flow should pulse to about 1 Amp or to several hundred mAmps if the voltmeter is slow and reads an average integrated over the pulse width.
Instructor
Joined: May 2001
Posts: 140
Likes: 0
From: Connecticut Shoreline CT
Re: Fuel Injection problems, please help! (Nathan Plemons)
if you have no ground or a bad ground your injectors should stay closed. for some reason the ecm is telling the injectors to stay wide open. have you hooked up a scanner? maybe just resetting the ecm will do it.
Safety Car
Joined: Mar 2000
Posts: 3,620
Likes: 2
From: Hillsboro OR
Re: Fuel Injection problems, please help! (Nathan Plemons)
95 ECM is Sequential.
Check the ECT sensor on the front of the waterpump. You may have a very high rich condition because the sensor thinks its very cold. See what the resistance is by measuring it with an ohmmeter.
Its also possible the computer that Ed Wright sent you is bad.
The resistance reading for the ECT are as follows:
Temp Deg F Resistance
23...................12300
32...................9420
41...................7280
50...................5670
59...................4450
68...................3520
77...................2796
86...................2238
95...................1802
[Modified by AquaMetallic94LT1, 6:00 PM 10/20/2001]
Check the ECT sensor on the front of the waterpump. You may have a very high rich condition because the sensor thinks its very cold. See what the resistance is by measuring it with an ohmmeter.
Its also possible the computer that Ed Wright sent you is bad.
The resistance reading for the ECT are as follows:
Temp Deg F Resistance
23...................12300
32...................9420
41...................7280
50...................5670
59...................4450
68...................3520
77...................2796
86...................2238
95...................1802
[Modified by AquaMetallic94LT1, 6:00 PM 10/20/2001]
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Fuel Injection problems, please help! (Nathan Plemons)
If it's just one spark plug, then the injector is probably bad. If all are staying open, then it may be the harness or the ECM. To test the harness, use a test light. With the key on, each side should light. While cranking, each side should blink. If the engine doesn't get reference pulses (from the crank trigger on this car?), then the ECM won't pulse the injectors so it doesn't flood the engine. By the way, if the engine isn't firing, the cylinders are going to flood if you are turning off the key, waiting about 10 seconds, then repeating the test. The ECM, after a brief amount of time following shutdown, doesn't know that the motor didn't fire and when you turn the key and crank it, it's going to pulse the injectors again.
Melting Slicks
Joined: Apr 2001
Posts: 2,116
Likes: 221
From: Ca.
Re: Fuel Injection problems, please help! (Nathan Plemons)
I just want to double check-when you are checking the inj. for voltage; you're placing the red on your voltmeter to the pos. on the inj. and the neg. on your voltmeter to the inj. ground or to body/engine ground? Because the "pulse on" for the inj. that the ecm uses is ground on. It has 5 volts on con't and pulses the ground. So if you have a short to ground in the ground side of the inj. harness that would do it. Try disconnecting the ground feed to the inj. at the ecm-then check both sides of it. Bet you have a shorted to ground somewhere in the harness. Have fun! (I just love electrical problems too!) :smash:
