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Discussion Starter #1
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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Howdy and Welcome.
What exactly does good fuel pressure mean? Did you check it with a gauge?
 

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Another thing to check - your TPS (Throttle Position Sensor) - if it's bad your ECM will think it's in flooded mode and won't fire the injectors. This link shows how to calibrate the throttle body which includes the TPS. Maybe try this before you spend the money for new injectors. If you do buy injectors get flow matched ones.

TBI tuning-website - Tuning the TBI.pdf
 

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Discussion Starter #6
Thanks guys I'll be sure to give that a try today and I'll let you know what happens

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Discussion Starter #7
So I didnt get to switch the tps. I had a spare laying around but it was a bit different with a different plug in so I wasn't able to do that I did however try putting the peddle to the floor to try starting it and nothing happened I read that on a different form that it would clear the flood thing but I have no idea if that was something that actually worked.

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Got a scan tool (not a code reader)? You can see TPS voltage among other things (ie. injector BPW and duty cycle) that can help you diagnose your issue.
 

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Discussion Starter #9
No I do not but I have one of those electrical wire test things don't really know how to use but could probably figure it out. What should it get for voltage or ohms? and to test it do I just need the key on and to step on the peddle?

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Did you read the PDF I linked for you? It explains how to test the TPS. I find it hard to believe both injectors went bad at the same time (did you shine a flashlight behind them to see if they are spraying when cranking the engine), I would lean more towards a sensor or ground issue (not likely but possibly the ECM). A scanner will save you a bunch of money instead of just shooting the parts cannon at it, just saying. If you don't have access to a scanner, buy one or, take your truck to someone who has one.
 

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Discussion Starter #11
I did skim through it at first but must have missed the voltage part but I read that now. I'll dig in tomorrow morning on that.
And for injectors is it possible to only run on one injector poorly and not missfire?
Just had a thought that maybe it was always running on one that was about to go out and the other one may already was bad but I thought it would probably be missfireing if only one side was getting fuel
Also just watched a video on youtubs and they said if it's been sitting for a while or injectors are just old to run 12volts straight from the battery and it might wake them up or do something that the 9 volts can't I don't know just want other opinions but I will try that voltage test on the tps in the morning thank you for pointing that out again!

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And for injectors is it possible to only run on one injector poorly and not missfire?
Yes, they are designed to fire synchronously, meaning every other intake event one fires then the other fires for the other intake stroke, the intake manifold has crossover ports to help balance AFR (Air Fuel Ratio). There's other times that they will fire asynchronously but that's a different discussion.

they said if it's been sitting for a while or injectors are just old to run 12volts straight from the battery
Yes, I've heard of some guys actually hitting them while cranking to free them up. Doesn't sound like a very good procedure to me, ha ha.

I will try that voltage test on the tps in the morning thank you for pointing that out again!
It probably won't be the TPS since you sprayed ether and it fired but died after. Usually if the TPS is bad after it fires with ether, it'll keep running because it's no longer in "flooded mode", when RPMs go above 400, it'll switch to choke or normal fuel trims depending on CTS (Coolant Temperature Sensor) feedback, but it's something that won't cost you anything to confirm, HTH!
 

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Discussion Starter #13
So I'm messing with stuff right now I got a noid light and tested the plug in things to injectors and they are not getting power so now I know it's that and not the injectors. As for testing the tps I haven't done that yet in about to but I did find something that I don't think is right on the coil pack I'll post pics of it just looks like there's a wire missing or something. It's that black box like thing that I'm wondering about

What would cause the ecm to not send power to injectors? The tps which I'm about to check out and what else?


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Discussion Starter #14
Okay so I don't know if I did this right but I followed a video on YouTube I spliced the blue wire that goes to the tps sensor and and used the voltage meter thing set the voltage to 200 and found a good ground then had my gf turn key and slowly pump the peddle and the highest number was 2.1 with the peddle to the floor.

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I'll post pics of it just looks like there's a wire missing or something.
That white wire on the coil is the feed for the tach in the dash, if your truck didn't come with one it's left unhooked.
and found a good ground then had my gf turn key and slowly pump the peddle and the highest number was 2.1 with the peddle to the floor.
The TPS should go from >0 to ~4.8 VDC (IIRC), for example mine goes from 0.45 - 4.39VDC at WOT. I know they say it should be ~ 0.58 - 0.59VCD but, that's close enough for me. You did have the meter set on DC Volts right? If so, I'd look into getting a new TPS. Even if that's not the cause for not starting, it'll effect your performance anyway.
 

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Discussion Starter #16
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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Did you check the 5 Amp fuse that feeds the injectors (fuse A)? If so, then follow wire #481 (red) from fuse block to the injectors. Here's a snip for my 88 but it should be the same for your 90.

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Discussion Starter #18
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
yeah the one I checked was next to the fuel pump relay and that ones good. But where the 5 amp your talking about??

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Forgive me if you’ve already checked this, but have you looked over your grounds? Especially the one on the thermostat housing?
 

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Discussion Starter #20
Yes there's 2 black wires that go into one connection and I've cleaned it with brake clean as for other grounds I have not as I don't really like to dig in to following nor messing with wires but I have looked at the majority of what's bolted to the block or the body all look clean and good.

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