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1987 Chevy Truck injectors not firing

Tiny
JASONLEWIS
  • MEMBER
  • 1987 CHEVROLET TRUCK
Engine Performance problem
1987 Chevy Truck 6 cyl Four Wheel Drive Manual

I have a 1987 chevy truck throttle body injected 4x4 manual. The injectors are not firing.I have checked with a noid light, no pulse.I have replaced pickup coil in distributor, no pulse.I have replaced ecm, no pulse.I have replaced tps, no pulse.I have unplugged tps to see if in flood mode, no pulse.I have replaced map sensor, no pulse. Check oil -correct amount, pressure is 30psi on dash gauge. Fuel pump comes on and is getting fuel to injector just no pulse. The battery also has been replaced and has 12.22 vlts also on charge while cranking and trying to get truck running.I have also checked voltage at injectors which is 10volts on the power side. Please help what else do I need to do to get injectors to fire. Also truck will run when fuel is poored in throttle body.
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Wednesday, August 27th, 2008 AT 1:13 PM

7 Replies

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
What about control module in dist? The ECM grounds inj. To fire but first it needs signal from module.
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Wednesday, August 27th, 2008 AT 1:31 PM
Tiny
JASONLEWIS
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  • 5 POSTS
No I have not checked control module. Can I do this with a ohm meter and volt meter or does it need to be removed to check at a local parts store?
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Wednesday, August 27th, 2008 AT 1:47 PM
Tiny
PEAR69
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  • 1,482 POSTS
If you have 10 volts at the injector then there is a problem with the ecm ground. The ecm controls the injector by pulsing the ground not the voltage.
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Wednesday, August 27th, 2008 AT 1:47 PM
Tiny
JASONLEWIS
  • MEMBER
  • 5 POSTS
Thank you I will check all grounds and control module.
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Wednesday, August 27th, 2008 AT 1:49 PM
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Uto Zone can check mod. If good check wiring to ECM.
Good luck
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Wednesday, August 27th, 2008 AT 2:00 PM
Tiny
JASONLEWIS
  • MEMBER
  • 5 POSTS
I checked control module at oreilly parts store, it passed. Then I checked wiring and there might be some grounding issues. Battery shows 13.44 on charge at the injector wiring power side it shows 8-10 volts. Also main negative battery cable has corrison on both ends.
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Wednesday, August 27th, 2008 AT 3:53 PM
Tiny
PEAR69
  • MECHANIC
  • 1,482 POSTS
You should have around 12 volts at the injectors. 10 volts is a little low but the injector will fire if the ground is good. It seems that you indeed have some corrosion issues with the wiring to the injectors. Corrosion can cause a voltage drop on both the "positive" side of a circuit and the "negitive"or the ground. A corroded or overloaded ground will fail just like an overloaded positive wire.
Hope this helps.
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Friday, August 29th, 2008 AT 8:22 PM

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