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Truck died after rough bump now no fuel!

RockBottomRacing

RockBottomRacing

1/2 ton status
Joined
Oct 10, 2011
Posts
128
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Location
Simi Valley, CA
1991 TBI 350, ran great, hit a speed bump after a 40 mile drive, instantly died, wouldn’t fire back up. Zero fuel from injectors. Trying to figure out where to start. I do have a bad distributor, been driving it with timing advance bypass unplugged. But this happened randomly and instantly. Any tips?
 
Turn key to run (not start). Does fuel pump run for a couple of seconds? You can only test this once every fifteen seconds or so IIRC. If yes, problem is not the fuel pump/ fuel pump wiring/fuel pump relay.

(If no, run a wire from battery + to the single red wire hanging off the fuel pump relay. If fuel pump does not run, need to check connector/ground near the tank, and fuel pump + wire for continuity from relay to tank connector. If the wire has continuity, ground and connector is good, fuel pump almost certainly is the issue)

FWIW, you can try tapping the bottom of the tank to see if you can get the pump to run while you have 12V to the relay connector. Apparently sometimes this can get a failing pump to work a tiny bit longer. Just for diagnosis, if that "fixes" the issue, then the pump needs replaced.
 
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The fuel pump is brand new, the rough bump was no where near that rough. I can hear the pump prime when I turn the key, then it stops when cranking, zero fuel. I have a previous diagnosed bad distributor but it ran great with the timing advance wire unplugged. No codes. Code 12 flashes as normal so I believe the ecm has power. Because fuel pump primes I don’t suspect a bad pump relay. It won’t even try to fire, just cranks and cranks, so I don’t know that an oil pressure switch failure/wiring issue would be cutting fuel out like that. When it was driving I had consistent oil pressure. I have a cold right now and can barely smell but I could swear I smelled electrical. Tomorrow I will check for spark. Mechanic friend says for it to run fine and then all of the sudden die from a bump in the road like a key off dying, he thinks something came unplugged, or the fusible link failed from the bump, he doesn’t suspect anything mechanical. I will be cracking the fuel line tomorrow to check prime but I’m confident my pump is secure. Does anyone have other ideas for what to check?

I do not believe this truck has an inertia switch. 1991 suburban v2500
 
No inertia switch.

If the pump is new, and you hear it prime, that circuit is good. Unfortunate as its an easier one to diagnose. Doesn't mean you have pressure but you can test that.

If the pump isn't running when cranking (I wouldn't be able to hear mine lol) then it is LIKELY the ECM isn't getting a signal from the distributor. This would be corroborated if there is a no-spark condition, but they can exist independent of each other.

Kind of a crapshoot, but the ~$100 aftermarket distributors are a relatively cheap way to get a new one in there (with theoretically all new parts), and not mess with the individual components that will make you remove the distributor anyway. I'd agree with checking connectors and wiring before anything else. But if there is already a distributor issue, probably best to resolve that before anything else.

Won't hurt to check the fuses/fuse panel as well. I don't recall which would be potentially implicated in all this, but I'd pull all of them just to verify they are good. My panel actually melted in one position.
 
Hey guys, hope y’all had a great thanksgiving!

So My mechanic friend told me not to do the distributor unless I’m doing an ACDelco, but I couldn’t get my hands on one, so I decided to do a new ICM, cap and rotor, all ACDelco and I got them for cost same day. Anyways, I tested spark prior to and after the swap. Spark was and remains weak, orange in color. Still no fuel at the injectors. I also tried the eprom trick to no avail. Rechecked my fuses, my wiring, and my plugs, nothing obvious. Checked resistance at the pick-up coil wiring, around 600 ohms (im told 500-1500 is expected and normal?). Mechanic friend says the ECM doesn’t control spark at start-up cranking so it wouldn’t be ECM related, said the fact that it happened suddenly after a bump could have been a fluke. Had a wire tap at ECMB fuse that had a bare stripped wire on the end under the carpet laying on the floorboard, that fuse had popped, so I replaced it with the fuse for my trans for trouble shooting purposes.

My truck had a problem with super low idle and stalling out and the fix was to disconnect the timing advance bypass wire (tan and black), and it ran fine after. I drove it like that. Then this happened. I figured the distributor needed to be replaced but if still drove so I was gonna wait til I could afford a Delco.

One odd thing to note: with the timing advance bypass wire disconnected I SHOULD be getting a code 42, but, I’m not. I only have codes 81/82 from pulling my trans fuse. Im wondering, is this a sign of a bad pick-up coil? Or yet another symptom. So frustrating! I’m either going to order a $300 ACDelco or im going to buy the in-stock duralast gold distributor and swap my new ACDelco parts on before I drop it in. But I’ve seen nothing but problems from people who went aftermarket instead of OEM for distributors on TBI’s… and I could really use the extra $150 these days…

Anyways, any continued help is much appreciated!!!
 
Perhaps I got super lucky, but when my pickup coil died on me (when I couldn't diagnose, and after wasting the money on an ICM) and I finally got the chance to diagnose the problem, I went with a part store cheapy complete distributor that has been on there for years. Truck sees 1.5-3k miles a year at best, so it's not a lot of use, but regardless, years later, still working. I did break the cap immediately, I felt it was a lot more brittle than the GM version.

I just did a quick search for similar problems to yours (in regards to the EST), apparently people have had pickup coils that were wired backwards, but the more common problem is the typical one...the distributor is not in the correct position.

If you disconnect the bypass, you are "losing" about 20* of timing.
 
Just a long shot, but did you replace the hose that connects the pump to the sending units pickup tube....? And if so, did you replace it with the right kind of tube?
Those have a tendency to break and all your fuel just shoots back into your tank.
I did mine once and inspected the original tube well. All looked good. It broke a week or 2 later.
 
dyeager535 said:
Perhaps I got super lucky, but when my pickup coil died on me (when I couldn't diagnose, and after wasting the money on an ICM) and I finally got the chance to diagnose the problem, I went with a part store cheapy complete distributor that has been on there for years. Truck sees 1.5-3k miles a year at best, so it's not a lot of use, but regardless, years later, still working. I did break the cap immediately, I felt it was a lot more brittle than the GM version.

I just did a quick search for similar problems to yours (in regards to the EST), apparently people have had pickup coils that were wired backwards, but the more common problem is the typical one...the distributor is not in the correct position.

If you disconnect the bypass, you are "losing" about 20* of timing.
Click to expand...

I found a post on another forum talking about weak spark, it’s either the coil itself or the pickup coil in the distributor, and since the ignition coil doesn’t control the injector pulse, I assume it to be the pickup coil. Everything else it could be either has been replaced or checks out according to testing procedures I’ve found, and with the bypass disconnected it ran prior to this, and I had a SES light I assume one of which was code 42 but I never checked. Then the ECMB fuse popped and no more codes. So… now it looks like I’m installing a distributor later today lol
 
Wes Harden said:
pump fall off of pick up ???
Click to expand...

THIS

might be time to cut that access hole in the bed floor now.

ive been there and done that.



Happened out on a trail. one bump too many.
key on, fuel pump running- can hear it running, but truck no worky.
wasnt until I got a look inside that i saw what was going on. yes the fuel pump was broken off the pick up, and was still wired, but spinning round in circles spraying fuel in every direction (except out to the throttle body!). Was not the fuel pump's fault though -the tank itself must have flexed when the truck took the hit, and the plastic baffle assembly that had been bonded to the bottom of the tank came loose and clobbered the fuel pump, breaking it off the pick up tube. I cut the plastic tray into several pieces with tin snips and brought them out of the top of the tank. new fuel pump assembly, and new patch for the floor, and then back on the road.
 
RockBottomRacing said:
Hey guys, hope y’all had a great thanksgiving!

So My mechanic friend told me not to do the distributor unless I’m doing an ACDelco, but I couldn’t get my hands on one, so I decided to do a new ICM, cap and rotor, all ACDelco and I got them for cost same day. Anyways, I tested spark prior to and after the swap. Spark was and remains weak, orange in color. Still no fuel at the injectors. I also tried the eprom trick to no avail. Rechecked my fuses, my wiring, and my plugs, nothing obvious. Checked resistance at the pick-up coil wiring, around 600 ohms (im told 500-1500 is expected and normal?). Mechanic friend says the ECM doesn’t control spark at start-up cranking so it wouldn’t be ECM related, said the fact that it happened suddenly after a bump could have been a fluke. Had a wire tap at ECMB fuse that had a bare stripped wire on the end under the carpet laying on the floorboard, that fuse had popped, so I replaced it with the fuse for my trans for trouble shooting purposes.

My truck had a problem with super low idle and stalling out and the fix was to disconnect the timing advance bypass wire (tan and black), and it ran fine after. I drove it like that. Then this happened. I figured the distributor needed to be replaced but if still drove so I was gonna wait til I could afford a Delco.

One odd thing to note: with the timing advance bypass wire disconnected I SHOULD be getting a code 42, but, I’m not. I only have codes 81/82 from pulling my trans fuse. Im wondering, is this a sign of a bad pick-up coil? Or yet another symptom. So frustrating! I’m either going to order a $300 ACDelco or im going to buy the in-stock duralast gold distributor and swap my new ACDelco parts on before I drop it in. But I’ve seen nothing but problems from people who went aftermarket instead of OEM for distributors on TBI’s… and I could really use the extra $150 these days…

Anyways, any continued help is much appreciated!!!
Click to expand...
im not sure the dizzy is what your truck needs, but im chasing my own problems with my K5... after a lot of looking in the last few weeks, I found Classic industries here in HB CA has rebuilt GM distributors for quite a bit le$$ than Napa. the one from classic May not come with cap and rotor, but I think that would be the way I would go now... in order:
1) refurb GM from classic
2) complete unit from autozone, and carry spare ac/delco ICM and pick up coil (i just ordered those from summit)
3) buy the reman unit from Napa (this would have been #2, but was the most expensive of all options and still had no cap and rotor)
 
UPDATE: new distributor, still no fuel from injectors. Pump primes. Fuel squirts. Injectors click when I hit them with a 9 volt battery. Picking up noid lights after work. Would oil pressure switch cause no fuel while cranking by chance? I thought it was a fail-safe after the fuel pump relay?
 
if you hear the pump priming, i think you have only a few options here. you said you replaced the fuel filter right?

maybe take the fuel filter out and prime the truck- see if it sprays/dumps fuel from the open line into a pan or bucket... if it does, maybe a blockage somewhere closer to the engine. if not... you need to get that fuel sender assembly out of your gas tank, and take a look at it, AND what's going on in your tank

-edit- what did you mean "fuel squirts"? if not from the injectors, then from where?
 
If pump primes the switch isn't your problem.

Use that noid light to make sure the injectors are being fired. I doubt the issue is fuel delivery if hear the pump prime and see fuel flow, but it's still possible if you haven't checked pressure.

But if the noid light doesn't blink on the injector, then fuel system issues are irrelevant.

Just in case you don't know, you test across the injector connector for injector operation during cranking, NOT with one leg of the test light to ground. You first need to see if the injector is seeing 12V with the key in "run" however, and that IS done with the test light grounded to the chassis.
 
Update: no injector pulse. With the key on I’m not getting voltage at the injector connector wiring. I am aware that both wires are 12 volt and the ECM pulls ground from one of them, but I’m getting no voltage at either wire. I went to check the wire at the ECM side but while I was there I noticed that my wiring at the ECM connectors don’t match what I’ve found online. The blue and green wires from the injectors aren’t in D14 and D16, they’re at C15 and C16. Also read that D15 isn’t used, but on mine it is. I went through multiple diagrams online and it doesn’t seem any of them match this. Is it because it’s a 91 with a 4L80e perhaps? Trying to figure this out lol.
 
The 91 with 4L80E is wired differently I believe. That is a true PCM and not an ECM. Are you using the actual GM wiring diagrams for that year? GM makes mistakes in the manuals, not likely something that big though.

You've checked fuses?
 
Yes gm needed to update the tbi computer when the 4l80e trans was offered. The Tbi computer wasn't up to the task of running the trans.
 
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