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92 s10 Bad ECM?


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bigmaac73
New User

Nov 12, 2012, 12:00 AM

Post #1 of 7 (4803 views)
  post locked   92 s10 Bad ECM?  

First off, here are my vital stats...
92 s10; 2.8; 2wd; 285,XXX miles
Ok, a few days ago I was driving home and stopped at a station to fill up. Got back in the truck and would not start. Have never had this issue. Wanted to do a quick check to narrow down spark or fuel and threw some starter fluid in the TBI and she cranked right up but of course died immediately. Started doing some TS and found that the FP relay was not kicking on. Went up and grabbed a new relay and threw it in, and nothing. Had the truck towed home and when I got there I wanted to check and see one more time if I was getting power to the relay and this time it clicked and I heard the primer kick on. Truck started right up. Drove it around the farm all day and went out the next day to crank it up and nothing. No primer and no relay click. I am getting spark, and when I jumper the hot pin on the relay harness the primer kicks on. on the relay harness there should be a 12v hot wire, which is pin 5 i believe. Then the wire to the pump is pin 2. Then between 1 and 3 there should be 12v with key on. I am not getting the 12v key on. Could this be a bad ECM. I really dont think the pump is bad, it is less than 2 years old. So, fairly new fuel pump, new fuel pump relay, had Ignition Control Module in dist. checked and it checked good...Where do I go from here? Sound like and ECM to anyone else?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 12, 2012, 4:13 AM

Post #2 of 7 (4755 views)
  post locked   Re: 92 s10 Bad ECM?  

The relay should receive power with the key on at the ORANGE wire. It should have ground all the time on the BLK/WHT wire. It should receive power for 2 seconds when the key is turned on at the DkGRN/WHT wire. That power should resume during cranking or engine riunning.

Note also, this engine is capable of running without a FP relay once it has oil pressure.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Nov 12, 2012, 4:15 AM)


bigmaac73
New User

Nov 12, 2012, 7:08 AM

Post #3 of 7 (4743 views)
  post locked   Re: 92 s10 Bad ECM?  

Dangerous to rely on wire colors since it is all too easy to splice in a wire of a different color, that is why i actually put in the pins on the plug. I DO have the 12V from the orange wire(pin 5), which is hot all the time from ECMb fuse. What I do NOT have is the 12v key on power across pins 1 and 3. I know how the relay works, the problem is that the relay is not getting the correct power which comes from ECM. It should be getting 12V key on from pin A1 on the ECM. Just wondering if anyone else has come across this yet.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 12, 2012, 7:24 AM

Post #4 of 7 (4739 views)
  post locked   Re: 92 s10 Bad ECM?  

We don't repair from memory. We` systematically troubleshoot and YES, wire color is the way to look at this.
Don't talk to me like you're some kind of expert and I don't know what I'm talking about because you wouldn't be here if you knew how to troubleshoot a circuit and read a wiring diagram.

By the way, the wiring diagram does not designate the pins by 1,2,3 etc so your numbers mean nothing to me.

Choose your next words very carefully.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



bigmaac73
New User

Nov 13, 2012, 5:27 AM

Post #5 of 7 (4696 views)
  post locked   Re: 92 s10 Bad ECM?  

speaking of not knowing what someone is talking about, maybe the little wiring diagrams you all get int he haynes manuals dont have pins on them but the pro diagrams you get from the dealers sure do. And How in Gods name would you ever know that I dont know how to read a wiring diagram. I have BUILT wiring harnesses and been reading wiring diagrams for avionics systems on various aircraft for over 10 years. And for those who rely on wire colors, sure hope no one has EVER spliced in a different wire into ANY of your electrical systems, or you'll be screwed. I can see this was pointless. Thought I would be on here dealing with pros, not overly egoistic Joes.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 13, 2012, 5:33 AM

Post #6 of 7 (4690 views)
  post locked   Re: 92 s10 Bad ECM?  

Look fool, I am looking at the OEM wiring diagram from Alldata, not some Haynes manual and it does not label pins by sequential number in that year but uses alphabetical tagging.

Better luck at some other forum. The shade trees will be right up your alley.

Question closed



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



nickwarner
Veteran / Moderator
nickwarner profile image

Nov 13, 2012, 8:34 PM

Post #7 of 7 (4675 views)
  post locked   Re: 92 s10 Bad ECM?  

Over ten years of advanced electrical work on expensive airplanes and all you have to show for it is a 20 year old beater truck with over a quarter of a million miles? Maybe its not us that are bad at what we do.






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