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SmokinVette.com Forums : Corvette Forums : C4 Corvette Forums : C4 Corvette General Discussion : 1988 no injector pulse
C4 Corvette General Discussion
1984 - 1996 Corvettes

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Old 11-29-2009, 11:51 AM   #1
dave5950
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Default 1988 no injector pulse

I changed the intake manifold gasket and now have no injector pulse.I have checked everything and can not find the problem.
Used noid lamp and no pulse
Have VATS bypass, tried with and without
Tried spare key,checked reading of keys
and VATS bypass
Oil pressure switch works,and tried a jumper
Fuel pump runs and pressure at rails
Have power at both injector harness wires
Changed distributor
Changed ECM
Need help,Thanks
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Old 11-29-2009, 01:49 PM   #2
Bob Perry
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Default Same Problem

Quote:
Originally Posted by dave5950 View Post
I changed the intake manifold gasket and now have no injector pulse.I have checked everything and can not find the problem.
Used noid lamp and no pulse
Have VATS bypass, tried with and without
Tried spare key,checked reading of keys
and VATS bypass
Oil pressure switch works,and tried a jumper
Fuel pump runs and pressure at rails
Have power at both injector harness wires
Changed distributor
Changed ECM
Need help,Thanks
I have the similiar problem, although am not sure about "injector Pulse" How did you check this? I unplugged an injector wire at the plug, with the key on I have battery power (12v )at the plug. The injectors have to trigger with the rotation of the engine, so are the injectors adding gas when they are powered with electricity or with no power? I don't know what a "noid lamp" is if that is what is needed to check pulse. I will monitor your post in hopes that your fix is also my fix.
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Old 11-29-2009, 02:31 PM   #3
95vette
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Quote:
Originally Posted by Bob Perry View Post
I have the similiar problem, although am not sure about "injector Pulse" How did you check this? I unplugged an injector wire at the plug, with the key on I have battery power (12v )at the plug. The injectors have to trigger with the rotation of the engine, so are the injectors adding gas when they are powered with electricity or with no power? I don't know what a "noid lamp" is if that is what is needed to check pulse. I will monitor your post in hopes that your fix is also my fix.
You can buy or even borrow a noid light set from Autozone. The set costs $25 or they rent them for free. Unplug the wire from the injector and plug the light in instead. When you try to start the light should pulse rapidly indicating the ECM is supplying the ground to the injector. Since the positive power is constant it is the ground that activates the injector, which in turn injects gas into the intake. A proper test is to do all 8 injectors one at a time. Hope this helps you.
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Old 11-29-2009, 02:47 PM   #4
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Default

Quote:
Originally Posted by dave5950 View Post
I changed the intake manifold gasket and now have no injector pulse.

Changed distributor

Need help,Thanks
The ECM only pulses the injectors when it receives the pulses from the distributor, that are generated once the engine begins to turn, much as it re energizes the fuel pump relay when the engine is cranking.

If the engine cranks, it is not a VATs problem.

The oil pressure switch has zero, zip, nada , to do with the pulsing of the injectors.

Depending on when you observed the fuel pump running it may or may not indicate the distributor is sending pulses.

Was the distributor replaced as an adjunct to the gasket job, or was it done in hopes of getting it running again?

RACE ON!!!
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Old 11-29-2009, 03:50 PM   #5
dave5950
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The distributor in the car was new,the one I put now was my old one that worked when I took out a month ago.I did this a check to see if this was the problem.
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Old 11-29-2009, 03:58 PM   #6
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I did use the noid lamps and they did not light with key on or cranking over.There is power to both injector harness wires with key on.
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Old 11-29-2009, 04:11 PM   #7
dave5950
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Originally Posted by 95vette View Post
You can buy or even borrow a noid light set from Autozone. The set costs $25 or they rent them for free. Unplug the wire from the injector and plug the light in instead. When you try to start the light should pulse rapidly indicating the ECM is supplying the ground to the injector. Since the positive power is constant it is the ground that activates the injector, which in turn injects gas into the intake. A proper test is to do all 8 injectors one at a time. Hope this helps you.
I did use the noid lamps and they did not light with key on or cranking over. There is power to both wires on the injector harness with key on
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Old 11-29-2009, 04:17 PM   #8
dave5950
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Quote:
Originally Posted by CFI-EFI View Post
The ECM only pulses the injectors when it receives the pulses from the distributor, that are generated once the engine begins to turn, much as it re energizes the fuel pump relay when the engine is cranking.

If the engine cranks, it is not a VATs problem.

The oil pressure switch has zero, zip, nada , to do with the pulsing of the injectors.

Depending on when you observed the fuel pump running it may or may not indicate the distributor is sending pulses.

Was the distributor replaced as an adjunct to the gasket job, or was it done in hopes of getting it running again?

RACE ON!!!
The distributor in car was new and the one I have in now was the the one I took out a month ago that was working.I did this for a test to see if it was the problem
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Old 11-29-2009, 04:26 PM   #9
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Default Same Problem Different Car

Quote:
Originally Posted by dave5950 View Post
I did use the noid lamps and they did not light with key on or cranking over. There is power to both wires on the injector harness with key on
I have power to both wires on mine too with the key on.
If the injectors inject fuel when the power is off and shut off when the power is on, can I unplug four of the injectors and get the thing to run?
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Old 11-29-2009, 04:37 PM   #10
vetteoz
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Originally Posted by Bob Perry View Post
If the injectors inject fuel when the power is off and shut off when the power is on, can I unplug four of the injectors and get the thing to run?
No
Like many other items in your car, the injectors have 12V supplied to them when the key is on.
The injectors spray fuel by the computer putting the other wire to ground completing the circuit (power ON )

Last edited by vetteoz; 11-29-2009 at 04:40 PM.
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