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Where is the 5 amp fuse located???? If it's the fuse I'm thinking about i checked it but idk if it was a 5 amp
IIRC it's in your main box inside the cab next to your hood latch release and on the lower left of the block. It may be a 5A or a 10A who knows after 30 years? Do you have 12VDC at the injectors with key on? A Noid light won't tell you anything if you don't have power to it.

Forgive me if you’ve already checked this, but have you looked over your grounds? Especially the one on the thermostat housing?
A good point, the grounds by the T-Stat are for the ECM. You need both, power and ground to make a circuit.

I'm not one to advocate throwing parts at the problem, especially used parts! All that does is introduce other variables to the equation. I don't care if they came from a well running donor, but that's my opinion.
 

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Discussion Starter #22
I really don't like to use used parts either but that's what I can afford right now lol it sucks only having $$$ to your name.
I'll look over grounds again tomorrow and that fuse in the cab is good it's a 10 amp

Forgot to mention the iac valve was stuck completely compressed and when I first got it the air system was completely plugged no air getting through but it ran like that to drive on and off trailer.

Ever hear the saying every detail helps? Lol

Background story time(may not help but I'm giving it a try sorry for the long paragraphs)

Okay so the doode I got it from said he was using the truck to haul wood one day he drove about a mile to where he gets wood and he loaded up the truck and he went to leave and the truck wouldn't start so he had to get his family member to pull him home atleast that's what he told me. So that brings me to my next question so it did run long enough to scoot around his yard and drive it on the trailer from there I got the thing home I started it up and to keep on the throttle and backed it down off and drove it around my yard died on me took a little while to get it fired up again and then I got it to the spot on the yard I wanted it so it's been sitting there since while I've replaced stuff

So what could cause it to run intermittently like that? The way it acted I was like ok it's gotta be the fuel pump but then I replaced it and didn't change anything so another thought was could it be a ground wire the gets connection from bumps but that didn't make sense so would the ecm do something like that slowly make not work anymore or something?


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Discussion Starter #23
Okay so did the voltage test on the injectors wires it said 11.66-8 both said the same

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Discussion Starter #24
And the left side injectors connect has 2.50 volts going to it were it's supposed to be grounded or whatever


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Discussion Starter #25
Okay so while I was waiting for replies I decided to go elbow deep in wires dug through everything but the three way tie in of wires behind the block the wires are intact from what I can tell

I also just tried something disconnected the ecm and tried testing the injector wires again and the hot wires are good but that one ground still has power of 2.50 and dropping from there I don't know if that means anything or not

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I also just tried something disconnected the ecm and tried testing the injector wires again and the hot wires are good but that one ground still has power of 2.50 and dropping from there I don't know if that means anything or not
Are you testing this with the injectors disconnected? I don't think you should be seeing and voltage on the dark blue and green wires at all. I'd start there and see if you can find where that wire is getting voltage, go point to point. Here's a link to the service manuals, open the wiring manual for your 1990, go to page 40. Your injection system starts there, on page 45/154 (or 41 in the manual) is a schematic of yours.

Here's the one for yours
 

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Discussion Starter #27
I mean I had the key turned and tested

injector 1 wire had 2.50 volts in one and the other had 11.50-12 volts

injector 2 wire had 0 volts in one and the other had 11.50-12volts

And thank you for the links. It shows red and white go to the fuse box and the other two go to the ecm wish it was easier to follow them down to see if theres anything broke or something

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The reason I asked were the injectors disconnected while testing is that one maybe bleeding voltage through it giving you that 2.50VDC?
 

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Well, I don't know if you have a smoking gun but, it's a start.
 

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Discussion Starter #32
Where do I go from here? Just trace wires or is there more to it?

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I would think you need to find out where that phantom voltage is coming from. Yes, trace wires. Do the cut in 1/2 trick - go 1/2 way between the PCM and the injector, disconnect the wire at the nearest place to that and check. Then go 1/2 way between that and disconnect again. Keep going until you find it.
 

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Discussion Starter #34
Hey do you know what this ip engine thing is? Is it the other part of the plug in to the ecm or where is that part located? If you happen to know.


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I just recently purchased a 1990 Chevy 2500 single cab long bed with the 350 tbi that has been D.O.T inspected until 2018 in MN.
The issue - it has a fuel delivery problem and the previous owner was fairly certain that it needed a fuel pump and I wasnt surprised cuz ive had to do that with past 90s gm trucks.

It ran long enough to drive up on the trailer while under its own power and it also drove off the trailer on its own power(not that same day I brought home) but you did have to keep foot on throttle otherwise it would stall out and not start again until the next day.

Just remembered I had realised that the fuel injectors were not spraying they click with a 9v battery but don't spray fuel
So it's been about a week since I got it home and this is what I have replaced so far-
1. New Fuel pump
2. New Fuel filter
3. New Fuel pump relay
4. New Fuel pressure regulator
5. Used fuel injector wire connecters
6. Used fuel injectors (from junkyard may not be in working condition)
7. Used distributor stem with used cap and rotor and pick up coil or whatever the name is of the third part on the distributor
Fuel pressure in line is good

that's what I've done so far in that order
The motor runs on starting fluid or when you dribble fuel in the carb motor runs fine I removed injectors for first time to try cleaning them and didn't install them correctly and fuel bubbled out on top of the injectors and the truck started to fire but didn't get enough fuel from that to start it fully
I've read mixed things on similar issues the forums that we're almost identical were never finished or they got way off track with others jumping in with different year and models

Thanks in advance for any help. I'm no wire wiz hate messing with electrical

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check ignition fuse 3 goes to maf if fuse blown no code
 

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Update: Alrighty so today I went and got the map sensor ignition control module egr solinoid iac valve and the tps from a well running and healthy 350 tbi nothing changed after those were done I also tried swapping the coil pack just for $H!tz and gigs didn't do nothing.

Also went and pulled out the ecm there was some corrosion or some sticky stuff on the main plug on number 14 15 and 16 so I cleaned that out and plugged it back in checked what I could for wires and the all look in tact from what I could see I didn't dig a alot

Question: is it possible to hard wire a hot wire straight to the injectors from the battery because I believe if ive read right the ecm just grounds the wire so the wires should be hot as long as the ignition it turned correct?

And if there not getting power will the ecm still ground wires

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15 amp ignition fuse check em
 

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IIRC it's in your main box inside the cab next to your hood latch release and on the lower left of the block. It may be a 5A or a 10A who knows after 30 years? Do you have 12VDC at the injectors with key on? A Noid light won't tell you anything if you don't have power to it.


A good point, the grounds by the T-Stat are for the ECM. You need both, power and ground to make a circuit.

I'm not one to advocate throwing parts at the problem, especially used parts! All that does is introduce other variables to the equation. I don't care if they came from a well running donor, but that's my opinion.
 
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