Intermittent stall 1988 Suburban V20 350 TBI

[Silverbullet555]

I have a 1988 Suburban V20 with a 250TBI motor. About 175K miles on the clock. I do the regular maintenance and have owned it for 10 years or so. Fuel pump was replaced about 6 years ago, cap, rotor, wires, plugs, etc about 2 years ago. Doesn't get a lot of miles normally, but for the last 3 months, it has been a daily driver.

Driving today, filled it with gas and was heading to my next place. It just up and quit. No warning, no stutter, no nothing. I coasted to a stop and tried to get it to start. I got it to grab a time or two, but it immediately died. As I sat there pondering the issue, I beat on the fuel tank (worked when the last one went out), checked for loose wires, checked fuses, etc.

Pulled the air cleaner and noticed I was getting fuel when I tried to start it, but I could not for the life of me hear the fuel pump. A good samaritan and I tried to figure it out. He laid down next to the fuel tank when I put the key in run and shut it off and he could hear nothing. I found that odd. It seemed that I was getting fuel, but no spark.

90 minutes later and the tow truck had not arrived I got an idea. Wiggle the single wire connector on the sender (I think oil pressure), on the drivers side of the block between cylinders 1 and 3. It fired right up. It was fine all the way home.

I parked it in the garage and shut it off. I could hear the fuel pump. I tried disconnecting that wire before starting, disconnecting it after starting, wiggling it, etc, but could not replicate the stall. To my knowledge, that sender would cut off fuel pressure and not spark.

I'm going to do a tuneup because it's due. Cap, rotor, etc. I'm also changing the fuel pump relay as a prevention measure. I'll change the plug out to a clean one and likely change the oil pressure switch.

Anyone else have any ideas on what I should be looking it or why wiggling that wire would fix it if the engine was already getting fuel?

I know it's a shot in the dark to ask, but I thought I would throw it out.

[Silverbullet555]

Correction. That is not an oil switch. It's a water temp sender. But, that couldn't be related, could it? Coincidence that I wiggled the wire and something else fixed itself at the same time?

[Silverbullet555]

Replaced one of the two fuel pump relays. They both rattle when shaken. Not sure if that was GM design or they are going out. Either way they are getting replaced but the parts store only had one in stock today.

I wish it wouldn't have started. Then at least I could trouble shoot a known issue.

[Silverbullet555]

No issues today to or from work. 40 miles total.

I did replace the other fuel pump relay and wired in an emergency bypass for the pump. If it stops working I can power up the bypass and see if the pump is the issue for sure. At least that is something.

I cut open both solenoids and they looked good. One did have a little piece of solder rolling around inside. Not sure if that cause or coincidence. I'll never know.

[68Timber]

That there is a conundrum. I was hoping someone that knows TBI's would see this. I bought a 94 GMC Sierra once that came with the factory temp sender wire disconnected. It had an aftermarket temp gauge mounted under the dash and was wired direct to the sender, truck ran fine before and after I removed it and hooked the factory gauge back up. Odd. Keep us posted.

[Silverbullet555]

Thanks Bruiser.

Nothing new today. Truck ran fine. I did check the ECU to see if it was storing any codes and it wasn't. I do plan to change out the oil pressure switch as a precaution. I hope to have my wife's car done this week so we will be back to a 3 car stable. Then I can work more on this one.

[swissarmychainsaw]

"It's a water temp sender."

If the temp senors gets too hot does it not shut off the vehicle? (sounds like it would interrupt the fuel pump).

Seems logical if you wiggled that wire and it came on. Can you unplug that wire (to the fuel pump at the water temp) and see if it shuts off?

[Silverbullet555]

Originally Posted by swissarmychainsaw

"It's a water temp sender."

If the temp senors gets too hot does it not shut off the vehicle? (sounds like it would interrupt the fuel pump).

Seems logical if you wiggled that wire and it came on. Can you unplug that wire (to the fuel pump at the water temp) and see if it shuts off?

I don't think the gauge temp sender will do anything to regulate the engine but I will look into it.

I did try to replicate the issue by starting the engine with the wire connected and then unplugging it. I also tried starting it unplugged, plugging it in and then unplugging it. All to no avail.

I have had no more issues. I did wire in an emergency jumper for the fuel pump and haven't needed that. I am still reluctant to drive it on the freeway during rush hour as they are doing construction and there are areas with no shoulder.
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[swissarmychainsaw]

Agreed, you want to have confidence in your rig, so track it down!

One thing I'll share from my 84 PU, I had the "Electronic Control Module" go bad on me one time (it's under the distributor cap and looks like this
Sometimes called a HEI Module
https://www.google.com/search?q=ecu+...ml%3B728%3B530


The symptom for this though is NO SPARK. so it won't go bump-ity-bump-bump-bump at all. Will just crank over.

You can have yours tested at a parts dealer like Napa. Might be worth looking at while you are doing the cap/wires, etc.

Just be scientific about it all and you'll track it down.
As you described it caught a *little bit, I'm going to guess you have spark though, I'd start with the fuel system. Maybe just a fuel pressure gauge on the line, that way if it does conk out again, you have that system monitored.

By the way, my Dad worked for GM and brought home a brand new 88 suburban with the "Fuel Injection" ( I was in high school ) and thought it was the baddest thing on god's green earth!
(I now own a '73!)

[Silverbullet555]

Thanks for the tip. I'll check into that as well.

[68c10airstream]

AS a past ase dealer mechanic working at a gmc dealer from 89-97 i will say this; the fact you had injector spray says you are getting a good rpm signal. First test to a spin over but no start is to check for spark, then check for injector spray. I would check for a corroded ground on the driver's side frame rail near the left rear tire on top of the rail. Remove it and the star washer, sand down frame till shiny, clean bolt and star washer, reinstall and when done put grease all over the bolt and forget it ever happening again from a corroded ground. Now about the oil pressure sender; this is a back up power source for the scenario if your fuel pump relay quit working you would have extended crank times until oil pressure built up enough to close the contacts and start the truck. These senders will usually have 3 wires, 2 wires related to the fuel pump circuit, one wire for the dash gauge. I believe (from memory ) the defective relay will set a fault code but a quick dirty check to see if you fuel pump relay has quit is once the truck is running disconnect the sender and if the truck dies you need to investigate the fuel pump relay circuit. Just thought i would throw my 2 cents worth in before going to bed, as this is all from memory but a trip through a friend's alldata later can verify this if needed. Good luck, Brian F.

[Silverbullet555]

So it did it again today. Been fine for the last couple of weeks, but stalled this morning. Bypassed the fuel pump relays and it wouldn't fire. Seems to be a spark issue.

I did send it to the mechanic as I simply don't have the time to take this one on. I am hoping it did not "fix" itself again after sitting at the mechanic for a while.

[68Timber]

Originally Posted by Silverbullet555

Thanks for the tip. I'll check into that as well.

Just curious, did you ever get the HEI module tested?

[Silverbullet555]

Originally Posted by BRUISER

Just curious, did you ever get the HEI module tested?

The shop did and that is what was wrong. Ingnition module is bad. I never got a chance due to schedule and other car torn apart. I couldn't afford two cars down at once so I paid a shop to fix the truck. Getting raked over the coals but it is what it is. I'm only one person and can only do so much.
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[87Skier]

Just throwing this out there, but I had a similar issue one time in my boat. It has a Chevy 350 in it and would die occasionally. It would always start right back up. Spent hours troubleshooting that. Turned out to be a failing distributor cap.

[junour11]

i had a brand new control module which came in a brand new distributor go bad. pulled the old control module out and put it in the new distributor. it has been over a year since i had this problem occure. the control module controls when the fuel pump turns on. it senses crank rotation and arms the fuel pump relay. so no crank no fuel pump.

[Hoods69BadBowTie]

That sucks you had to take it in. I was thinking a bad ignition module myself I see I am a bit late on the reply though. Hope it doesn't cause you any more headaches any time soon.

[Silverbullet555]

Originally Posted by 87Skier

Just throwing this out there, but I had a similar issue one time in my boat. It has a Chevy 350 in it and would die occasionally. It would always start right back up. Spent hours troubleshooting that. Turned out to be a failing distributor cap.

I could see that. Those things that happen when vibrating or heat are the worst.

Originally Posted by junour11

i had a brand new control module which came in a brand new distributor go bad. pulled the old control module out and put it in the new distributor. it has been over a year since i had this problem occure. the control module controls when the fuel pump turns on. it senses crank rotation and arms the fuel pump relay. so no crank no fuel pump.

I had fuel, but the ignition module was not sending the signal for spark. So, now spark to the plugs, hence no fire. Same kind of thing though. Stuff like that can last 5 minutes or 5 decades. I have to remember that about this truck. Everything is getting old. The brake pedal switch went out a couple weeks ago. Seriously? Fortunately, it was an easyfix and autozone (eek) had the part.

Originally Posted by Hoods69BadBowTie

That sucks you had to take it in. I was thinking a bad ignition module myself I see I am a bit late on the reply though. Hope it doesn't cause you any more headaches any time soon.

It is what it is. It has been to the shop only 3 times in the last 10 years so I can't really complain. It has it's issues now and then, but usually I can fix them.

It needs some other stuff done. I think I have a rear wheel bearing going out as I can hear a tick when I rotate the wheel. Of course, I just did a drain and refill on the rear diff. That will teach me to not check other stuff first. I also need to reseal the Tcase, transmission, pan shift selector and maybe drop down solenoid. Nothing earth shattering, but all time consuming.