87 S-10 no inj Pulse

Tiny
IMPRESSIONS141
  • MEMBER
  • 1987 CHEVROLET S-10
  • 4 CYL
  • 2WD
  • MANUAL
  • 187,000 MILES
I have a 87 chevy s-10 with the 4-tech 2.5 engine I have spark but no injector pulse I have changed the hall effect switch, ignition module and ecm to no avail, I have also checked my wires going from injector to the ecm and all checked out. Also I have power at injector and plenty of fuel pressure. The only problem I have found is I dont have 10 volts at the p term on the module, but as far as I know that should just not get spark but I am. At this point I am getting frustrated the only thing I can think left to check is for a tach signal getting to the ecm can any one tell me which wire I am looking for and what I should be getting when I check? PLEASE SOMBODY HELP ME!
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Tuesday, March 8th, 2011 AT 11:06 PM

5 Replies

Tiny
HMAC300
  • EXPERT
The 2.5 engines had a problem with teh reluctor inside the distributor. They would crack and sometimes run other times not. Check for that, the cure is another distributor. It can also be a problem with a ecm ground. You might try a jumper wire from the negative battery to pcm ground and see if that does anything. If it starts and you get pulses, then it's probably a bad ground.
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Tuesday, March 8th, 2011 AT 11:51 PM
Tiny
IMPRESSIONS141
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Actually that was one of my thoughts on the subject and I did supply a good ground to the ecm to no avail.
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Wednesday, March 9th, 2011 AT 3:18 PM
Tiny
IMPRESSIONS141
  • MEMBER
Well I replaced the distributor and the truck still refuses to start, the only thing I can think of is the new distributor did not come with all new wiring so I had to reuse the few wires inside the distributor as well as what I would call a diode (a small black plastic box with a wire soldered to a ground strap, when I tested this with my dvom I got zero continuity in either direction. I can get a new wire loom with said (diode) but it is almost 250 dollars and am reluctant to replace without confirmation. What are your thoughts on the subject? Also I rechecked the ecm grounds and all three seem to be fine. Do you know which wire at the pcm gets the tach signal and what I should I be reading when I turn over the engine? Please help
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Wednesday, March 9th, 2011 AT 8:30 PM
Tiny
HMAC300
  • EXPERT
If you knew what type of diode was supposed tobe there you could just go to a place like radio shack and replace the diode. I am sending along pictures and info on how to physically check this system including coil. Hopefully this iwll help find yoru problem. Sometimes the diode should be checked with voltage not ohms.
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Thursday, March 10th, 2011 AT 12:14 AM
Tiny
HMAC300
  • EXPERT
One other thing, here is the only diagram i've found of your system due to age of vehicle. Also make sure when the module is put in the distributor that you use dielectric compound on the metal part that touchs the dist.
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Thursday, March 10th, 2011 AT 12:19 AM

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