Help diagnose an engine stall problem that has vexed me for almost 4 years now

[TimQ]

I'm about ready to run my truck off a cliff...but before I do that I'm hoping the collective wisdom on the board can give me some ideas to address a stalling problem I've been wrestling with off and on for about 4-years. Here's the symptons and the run down of what has been done so far:

- four years ago when I moved into my current house, the truck died twice enroute to the new home (with trailer). Shop replace plugs, wire, and distributor cap.
- For the next 2 1/2 or 3 years, she didn't get tons of use...maybe once every month or two, but she ran fine.
- Sometimes the the truck was sometimes rough to start but I chalked that up to age and sitting for so long. Eventually, starting about a year ago, sometimes she wouldn't start, and sometimes would start and run just fun
- I had it into the shop and they put new plugs in. Problems still occured.
- the truck eventually started stalling out at speed. For example, I could be going down the highway at 60 miles an hour and the engine would just quit. No roughness or sputtering...it would just quit and I'd coast to a stop. Most of the times it would start back up after just a few seconds. Sometimes not.
- one time it stalled, wouldn't start and I had to be towed. Waited 45 minutes for the tow, and my truck still wouldn't start. After it was towed home I jumped in and she started right up. Good thing I have AAA.
- After that the shop told me my carb was shot and suggested a replacement. I got a rebuilt q-jet, installed it myself, she started right up and sounded better than ever. Later that day, she died twice. Was able to get her started both times...the first time right away, the second after 10 minutes or so. I got her home and my wide swore she'd never get in the truck again with me.
- Replaced the PCV valve and fixed the hose that goes from the drivers side valve cover back to the air filter (it had come out of the valve cover so I got a new gromet that held it in place better). She ran OK for a few weeks.
- Then, in December, she died again. Could not get it started and had it towed. Was so annoyed I told the tow truck driver to just take it and see what he could find. He got to it after a few weeks and she started just fine. Given everything else that was done, he figured maybe it was the ignition controller. He replaced that and she ran great from January to March. There was only one time where she sort of quit for a split second but the engine fired back up without me even stopping.
- In March she went to the painter and I got her back two weeks ago.
- She ran great to/from the painter (more than an hour drive). She ran great the first week I had her back (I used her as my daily driver for the whole week). Yesterday I drove more than 3 hours round trip with no problems (the wife even came with me).
- Tonight I went to the store and she died as I pulled into the lot. I manged to coast into a space, tried to restart he but nothing. Went in, did my shoping and came out and she started with a bit of pumping on the gas pedal. On the 10 mile trip home, she died with a mile to go. I waited 2 or 3 minutes and she started back up and got me home.
- when running, the truck is fine. Engine runs smooth, I just clocked her at about 14 mpg (86 c-10, V6, 4.3, automatic engine with about 87,000 miles) and she seems to have decent power (as decent as you might expect in a V6). Sometimes she is tough to start and it seems pumping the had pedal helps. Other times she starts right up. There doesn't seem to be a pattern with hot vs. cold starts or anything like that. Norm does there seem to be a pattern with regard to when she will sputter and stall out.

I've done some poking around here and some other message boards and I'm now thinking maybe the fuel filter and/or fuel pump. One other outside idea is water in the tank??? I'm going to do the fuel filter tomorrow, but, before I go and buy a new pump and figure out how to replace it and/or try and drain the tank, I figured I'd see if there are any other ideas on what it might be. All suggestions welcome.

Sorry for the long post but figured more details are better.

Thanks,
Tim Q

[1LowToy]

Sounds electrical to me. Check connections for your ignition system. Tou may have a bad connection at the distributor or a bad ignition module (located in the distributor). May still be fuel but just son't sond like it. I have found where someone threw a parking ticket in the fuel tank and it wraped around the pickup screen in the tank and stopped the truck intermittently. (That just served up more parking tickets for the owner lol).

[gchemist]

Replace ignition module and FUEL PUMP!!

[amodedude1]

Do the fuel filter first, if not the problem try the pump. If it's the original filter/pump, you're destined for problems anyway, and its just a good idea. IMO

If that doesn't do it, it's probably electrical, in which case, good luck.... haha

[Copytech]

My truck acted very similar, turned out one of the rubber lines, connecting the fuel tank sending unit to the steel fuel lines, had a pin hole in it. Funny thing is it never leaked. The truck would just stall and after sitting ,sometimes for days, it would start up and run fine.
Replaced the line and 0 problems since ( five+ years)

[grinch4om]

diagnosis time...when this happens you need to see what has gone away, fuel or spark...methods vary but if you catch this and do test while it is in no start mode, you will be onto the area of failure and then can diagnose properly. could be fuel delivery which encompases tank to intake...could be ignition which goes from battery to ignition switch to distributor..I know this is vague but determine which area is at fault and I believe you can isolate the problem with logic. Is this an injected truck?

[motornut]

pump and lines,i've had the same with a car only to find a break as soon as it bends coming out,do you smell gas in the back area,being a carb the fuel pump siphones from the tank may not see a leak,have you tried to pour gas down the carb when it dies and won't start?

[primetime]

does your truck have the egr and smog related stuff on it?

[tucsonjwt]

Caution: Long Post Below:
I have two thoughts:
1) The normal response is "fuel or spark". But often overlooked is "vacuum". If you have a vacuum leak it can be very hard to track down. I have one in my truck and nobody can find it. This gets to the real problem:
2) Can you find a mechanic who will diagnose and guarantee to fix this problem, and will he keep fixing if for free if he guesses wrong? Or, will you be paying for "guesses" like you have been? Unfortunately, you are not likely to find that mechanic - just like you won't find a doctor to "guarantee" to fix that stomach pain you have, with no charge if he/she guesses wrong (could be ulcers, could be acid reflux, could be bad diet, could be food allergy, - so let's try different things until we find something that works and you can help pay for my kid's college education.)
I, like you, am not a mechanic - but I have done simple repairs (tune ups, carb swap outs, minor electrical, etc.) but left the rest to the "professionals." I have come to the conclusion that there are no real professionals when it comes to fixing old vehicles - there are just too many possible reasons for one symptom, so the pros guess just like us - only they have more experience and tools to guess with.
You won't like this suggestion:
1) Ask around and try to find a mechanic who will guarantee to fix your truck once, and fix it for free thereafter if he guesses wrong. Tell him you will pay for a fix and not a guess. (Good luck with this one.)
2) If you can't find this mechanic, sell the vehicle. If you must have a pickup truck for occasional hauling, then rent one for those occasions. Buy a new or newer modern fuel injected economy car if you need a commuter vehicle (one still under factory warranty - I could make some suggestions.) This is heresy for this website, but I don't think you are a good candidate for dealing with the frustration of the unfixable truck, as is evidenced by your initial post.
BTW - rebuilt carburetors, unless done by a specialized Qjet guy, are all junk.
Also, carburetor vehicles with are not driven daily or see only city driving will always carbon up/get varnished up and cause trouble. Your driving use of this truck does not sound conducive to an old carbureted vehicle.
I hope you and others don't take any offense to what I am posting - just trying to face reality, and speaking from decades of old truck and new truck consumer experience.

[tucsonjwt]

Sorry, duplicate post

[Hottrucks]

Originally Posted by gchemist

Replace ignition module and FUEL PUMP!!

I have to agree I was fighting the same problem for about 3 months...I replaced the mod..and its all better now...

I think alot has to due with how hot the body if the dizzy gets then tranfers the heat inside..once it cools it seems to be better..??

[Jonboy]

Sounds a lot like the ignition module to me, too. I would make sure you get a good (Delco) part, and make sure you use the dielectric grease under it.

[chevymotocross]

Fellow board members here helped me out on an intermitten problem I had with my 92' S10 blazer with the 4.3 tbi. I feel your pain. I was driving this blazer while I worked on my c10. The problems started in route to the scrap yard WITH my trailer attached and my old c10 bed and scrap metal. Blazer died in the middle of a busy intersection, Friday afternoon rush hour, during a nice HOT sunny day..... couldn't get any worse.

Spray fuel in the TBI and it would start and run fine.

Problem got more frequent. I checked fuel pressure, all was fine, replaced fuel filter, no luck. Ended up being the Ignition Module. Pump was putting out pressure, working correctly, but the injectors weren't firing. The module senses pulses from the engine to allow the injectors to squirt. All is good now!

On a carbureted truck, I'm not sure how it would affect running but instead of fuel injector problems like I had, maybe you will have the ignition issues.

[TimQ]

Thanks all for some great tips. Guess I have some more sluething to do.

Several have mentioned the ignition module. I believe that is what was replaced back in January. Receipt from the shop says "ignition control module" so I guess this is what people are suggesting? Is there something I should look for that might be causing that unit to fail that I ought to check?

Primetime asked about the egr and smog stuff...yeah, I still have all that, best I can tell.

Hottrucks mentioned maybe something with too much heat from the dizzy. If it only happened after a long drive, I'd think maybe that or some other heat related issue, but it has only ever happened on short drives. Might be luck, but other than the first time is happened on the move 4 years ago, it has not happened again more than a few miles from the house.
I haven't tried pouring some fuel down into the carb when it won't start. Always happens on the road, but maybe I'll carry some tools from here on out till I figure it out.

And tuscon...I hear ya on the mechanics. The last guy I had like what you describe was near my old house. I may just call that guy up and drive the truck the 3 hours. Might save me time in the end.

Anyhow, I'm still leaning towards the fuel pump and filter and plan to attack that tonight. That or some random loose connection but I shudder at trying to find that.

Now that leaves one question to really expose my lack of mecanical skills. Can anyone tell me where the darned fuel pump is on this engine (V6, 4.3)??? The pictures in my Haynes guide aren't the best and I just can't seem to find the damn thing.

Thanks all.

TimQ

[Hottrucks]

make sure your Dizzy is getting 12V if there hasn't been a new wire run from the fuse box its NOT!!

[tucsonjwt]

Like I was saying, you could go the "try this, try that, it has to be this" route, but you are taking the same crap shoot (no offense meant to anyone posting here.) I would invest your time and trouble in asking friends/relatives if they know a mechanic who will absolutely guarantee to fix the problem, and continue fixing it for free if he is wrong. Try AAA recommended shops, Click and Clack "mechanix files" for your neighborhood, etc. But I would not spend another dime on that truck until you found that rare mechanic who will guarantee his diagnosis and stand behind his work. And ask that mechanic point blank if he will guarantee his diagnosis and put in in writing in advance. They all say they will, but when the fix does not work they tell you to fork over your credit card again. Not maligning mechanics - just stating my experience - good folks, just not infallible. Would you pay a plumber to fix your faucet, and pay him again to fix it if it still leaked two weeks later? If you go the guessing route, then by all means take the various items of advice given here - I do that all the time, only because I have not found the infallible mechanic.

[dan76]

Fuel pump on this engine is mechanical and is located on the pass side of the block at the front...just above the oil pan.

[TimQ]

Thanks dan76...guess I need to get at it from the underside then?

[tucsonjwt]

If you have never changed a fuel pump before, please check out the instructions before you begin. Lots of gas can come out at you, it is easy to not re-tighten the fuel lines correctly (cross thread hard line fittings, if involved, radiator style clamps left too loose, fuel pump can be under some stress when reinstalled - causing improper bolt-to threaded hole lineup -potential cross thread.) I say this because you often don't have a lot of space to work in on that job - so check out the territory first. Why do I say this? Well, let's just say the voice of experience - I usually find every way to do a job wrong before I do it right. You don't need a fire or cross-threaded fuel pump bolt on top of your other issue Not saying you can't do it - just do some research first. Also, this is one of the cheaper auto mechanic jobs to get done - should not take a pro more than 30 minutes with the truck on a lift - and he is probably dogging it at that.

[87chevy.com]

Originally Posted by tucsonjwt

2) Can you find a mechanic who will diagnose and guarantee to fix this problem, and will he keep fixing if for free if he guesses wrong? Or, will you be paying for "guesses" like you have been? Unfortunately, you are not likely to find that mechanic -

you will NOT find that mechanic at jiffy lube, however you will find your technician at the dealership. you just have to pay for the diag time. I'm sure a lot of you guys will get your panties in a wad but its proven time and time again at my dealership (BMW). a brief run down how it seems at my job. 1st visit - verify concern/complaint, hopefully advisor secured 1 hour of diagnoisis on non warrantee items. Get as much diagnosis as possible without going over the 1 hr guarranteed diag time. If it requires further diag, I would stop and write a estimate with more time requested... the customer would then have the option to pay or not to pay.
There are people who pay the 1 hr check out time and dont buy the service/further diagnosis, the advisor will ask us whats wrong with the car, and I would say I havent finished diagnosis it. Well of course they want me to tell them how to fix the car so the customer can go to jiffy lube and pay 60$ /hr v.s. our 129$ /hr labor and fix it.. it almost never works out that way.

long and short of it, if they pay the diag, pay for a repair that I said would fix it and say it didnt fix it, yes I (they) would have to work on the vehicle a second time for no charge unless I (they) can prove (within reason of course) that its not in for the same problem. When you go to the dealership, you have lots of players that you can argue to and get your point across. Try that at a mom and pop store. You only have mom and pop to gripe to. Dealership you have the advisor, service manager, service director, general manager and maybe even someone higher than that. Im sure everyone knew that but throwing it out there.

[TimQ]

Thanks again, all. New fuel filter is in. Old one didn't look bad...turns out it was new with the rebuilt carb I put in back in November, so I'm doubtful that was it. But you never know.

Hottrucks..checked the ignition wire. Appears to be a nice new pink wire coming off the main fuse panel (in the slot marked ignition) heading through the firewall. Was too dark to trace any further, but I think I'm good there.

Tuscon...thanks for the tip on the install of the pump. I'm thinking I may pass that job off to a pro. It's look to be the original pump so it ought to be replaced anyhow and it looks to be tight quarters and I've had enough of that the last few days. As for finding a mechanic...pretty much anyone I talk to is hesitant to do major work on this truck for the exact reasons you note. Given the age, two things might break in the process of fixing the first. Or, two things might be broken but disguised by the thing you know is broken...just the nature of the game when we play with these old broads. And besides, if it was only about efficient use of cash, I'd have never bought the thing!

[tucsonjwt]

Tim - good call on the fuel pump - you can probably get one installed for $50 labor at a local shop - buy a good Delco pump and take it to the shop yourself.
87 chevy - I have not yet found a dealership who would guarantee to fix an intermittent driveability problem - which is what Tim has. Even the best mechanic cannot find a problem that does not exist when the vehicle is in the shop. If the vehicle is under warranty, then the manufacturer can assist to keep the dealership looking for the source of the problem. However, I have seen "cannot duplicate problem" on many dealership bills for vehicles I have owned. Like Tim says, old vehicles can have many problems affecting the same symptom, so it is not likely a mechanic will stick his neck out to guarantee a fix. I'll bet that confident mechanic exists somewhere. (Hint: it ain't Mr. Goodwrench

[cableguy0]

OK chances are the distributor is worn. Ignition parts tend to wear at about the same rate. A bad coil will kill a module and vice versa. Everything in the ignition is dependant on one another. I would vote to start with a fresh coil and module. They should be replaced together anyhow because as I said the parts are dependant on each other. If its shutting off like you turned the key off chances are its an ignition problem. Usually a fuel issue will cause the engine to sputter out and die. A carbureted gm vehicle is about as simple as it gets to actually have a running engine. The next time it dies you need to pull an ignition wire and have someone crank the engine to check for spark. If no spark either get a new distributor because im sure yours is sloppy after 25+ years or replace the coil and module together. I would also replace the cap and rotor at the same time. Bad spark plugs are not going to cause an engine to randomly stop running. A bad plug will cause a miss or rough running but its going to be gradual and get worse. It will also constantly run bad. A coil and module can both cause intermittent running problems. They will short out when they get hot and then function again once cooled down.

[73chevyman]

the coil is on the starter replace the starter and your problem should be fixed if the module been changed i'm with cable guy here...... i was thinking coil all along or a bad wire from the battery to the starter..... if this were my truck i would 1 replace all power wires and ground wires to the starter and make sure the body ground is attached then change the starter...... bad cables and starter will cause this too....

[cableguy0]

??? The ignition coil is in the distributor cap. Replacing a starter will have nothing to do with the truck stalling while the engine is running. Though checking all the connections is a good idea the starter has nothing to do with this issue.Once the engine is running the starter and battery are out of the picture.