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

[TimQ]

Again thanks to everyone who pitched in with ideas. As mentioned from the last post, I replaced the fuel filter and ordered a new fuel pump. But, based on feedback, I don't think that is the issue. But, it acted up again today, this time in the driveway and right near the house, so I was able to do some tests. Here's what happened (see top of thread for original details):

I tried starting the truck this morning. It would crank but not start. I gave up when I noticed the battery starting to die. I could smeall gas, which probably means I flooded it suggesting fuel wasn't the problem. Didn'd have time to play then, but. just to be sure I didn't have a weak battery later, I threw the charger on it for a few hours.

After dinner this evening, I tried again and she started right up. Decided to take a test drive and she died after a few hundred yards. I tried to restart countless times over a good 45 minutes. I even tried jumping from another car (thinking maybe the battery wasn't strong enough) but nothing worked.

I then went to my Hanes manual and tried the test for ignition. They suggest pulling a spark plug wire and holding it near a ground to see if you get a consistent spark when someone turns the key. Well, I did that, saw some sparks and the damn engine actually started up on five cylinders.

In typical amateur fashion (and wanting to get the truck out from in front of the neighbor's house) I figured I'd shove the plug wire onto the plug and drive it home before it stalled again. Well, that thought lasted about 2 seconds as I got a nice shock from the wire and yelled to the wife to cut the engine.

I hooked the plug wire back up and had her try again and she started right up. Pulled her into the driveway and since then have started and stopped her 5 or 6 times. Each time she starts right up without even hesitating.

I'm hell bent on trying to fix this myself, but, as you can probably tell, I'm just knowledgable enough to be dangerous. Anyhow, the original tips suggested checking the distributor/ignition and maybe replacing the coil and/or ignition module. So, does this new event rule anything in or out? Any others suggestions?

Thanks in advance.

Tim Q

[tucsonjwt]

One thing for sure - your problem is classic "intermittent no start" condition.
Sounds obvious, but since you are messing with the spark plug wires - do you have a bad spark plug wire/boot? I have learned to start with new plug wires/plugs/dist. cap/coil on every old vehicle I buy. It's small cost, except for the wires. I buy only Belden wires - you can search online for a good price or buy NAPA, which are rebranded Belden on their box. ($30) Don't get any other brand of wires - I have had new spark plug wires of other brands which were bad out of the box - mostly tiny cracks/gaps in the boots.

[87chevy.com]

check your spark plugs, see what they all look like.. if all are ok and gapped correctly check each spark plug wire. set the volt meter to ohm and put one lead to each end and measure the wire (cold) and wiggle the wire in all sorts of ways to see if there is a break in the wire. worth a shot and your not throwing parts at it just yet.
clint

[Rollie396]

This may be a longshot,but is your gas cap venting properly?Is the fuel line from pump to carb resting on or close to the intake manifold?You've verifyed that there is still spark after it stalls so it sounds like a fuel issue to me.If the gas cap isn't venting properly in older vehicles it can cause a vacuum that will starve the engine and cause this problem.If that's the case with a mid eightys carb engine I can't say.I also know that a fuel line resting on or too close to the intake manifold will heat up and cause a lock up which will stall the engine as well.Just another couple of options I guess.Good luck.

[tucsonjwt]

I concur with all suggestions from Rollie and 87 Chevy. However, checking spark plug wires will be difficult, because likely any defect will require simulation the exact bend of the plug wire when it is attached to the spark plug, which is hard to do when the wire is out of the truck. Temperature/humidity can also affect small defects in plug wires and other parts, like a tiny crack in the distributor cap. What year is your truck? If you have not changed plugs/wires/dist. cap,/ignition module, etc. in a few years, why not just go ahead and do that, then take it to a mechanic to put the truck on an engine analyzer and check the ignition/timing that way. I'll bet you can do this for less than $100 to eliminate a lot of the typical electrical issues up front. Just make sure you get AC Delco ignition parts and Belden plug wires. And change the wires one at a time so you don't get them crossed - good to have a firing order chart handy before you start so the distributor to spark plug orientation is known.

[Hottrucks]

Done any welding on your truck?? I smoked a voltage reg after weldiing a muffler bracket...yea I know...but I clmaped the tail pipe welded the hanger back up and then figured I better hit the other side as a safety thing.....got in the truck..crank it up to head to 4th fireworks half way there it radio stopped working....let foot off the gas radio back on??? bad wire right...nope chased it to the voltage reg replaced it truck is fine again.....all I did was wel the muffler hanger??

[TimQ]

Damn...I'd love to know how you managed to do that trace back to the voltage reg.

Anyhow, I think I may have found an issue...hopefully it is "the" issue. I took apart the distributor this afternoon and did all the tests called for in various manuals I have. When testing the ignition coil, at first one reading was OK and one was wrong. Then, later, both seemed OK. Then, a while later, both readings were bad. I thiought I was going mad, but I actually had a printout of the steps and wrote down the ohms I was getting for each step. I went on to test the stuff still in the truck and it all came back OK. So, I went back to the ign. coil and the tests all came bad.

So, perhaps the intermittant test is akin to the intermittant stalling I was getting.

My other clue...the date code stamped on the ignition coil was 1986...another original part that doesn't owe me anything. Cap and ignition controller mod are both new.

So, tomorrow I'm off to the parts store to see if I can track down a coil on a sunday.

Fingers crossed. In the mean time, thanks all who helped with tips. I'll report back and let you know what I find.

TQ

[Hottrucks]

when I pulled over to check for a loose wire getting cought on the linkage I heard the alt running hard..so I unplugged it rev'd the engine a couple times and the radio stayed on..plugged it back in rev'd it and the radio went out..I unplugged it and drove home..I grabbed the volt meter and it was charging to 16V.....I was lucky it didn't smoke anything else...I guess when you been around them you can just hear things going funny

[tucsonjwt]

Get the best brand you can, since you have all this energy invested in the project. I see the price ranges from $10 to $60. If correct Delco coil is not available, I'm pretty sure the rest are made in China. My next step down would be Standard Motor Products.

[mooseknuckles]

Originally Posted by 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.

ya.... what he said.

[crashwrench1]

Hello,
I had the same Problem It lasted for over a year with 1978 C-10 Long bed. W/ ' 400 CID Stroker - 4-bolt main eng. 800 CFM Q-Jet (modded ) , HEI /MSD Ignition Upgraded, Edelbrock Intake, headers, Flow masters exhaust system, A480LE OD Auto Trans. Full Set Of Gauges . All Emmissions parts and CAT. Convertors ( 2 ).
It would run when cold, get it up to temp , QUIT....
Checked , Changed Everything, IE: Dual Fuel Pumps ( One Electric , One High Volume mechnical w/ Regulator , Dual tanks , Fuel selector ,All steel and rubber Lines , New Fuel Tanks and Pickups , All Electrical Componets New.

Did not THINK to check the """" Fuel Tank GAS CAPS (2) ....
I had bought ( 2 ) Locking Gas Caps ,I Did Not Look to See IF They Were """ VENTED CAPS """"" .

The truck would lose fuel pressure, Did not matter if tanks were full or Empty.
The Fuel Gauge would start to Flutter , Then Drop to ZERO.

A Friend Was Helping me Pull the ' Tanks ' for third time , he twisted off one of those ""CAPS """ and a rush of air into the tank, also seen the tank move ( Thump ) !!!!
We started the Truck ,,, Ran fine,(( Eng. cold )) Waited for Water temp to come up, ( 195* DEG . )
Ran fine ,, installed THAT Fuel CAP - 20 Mins. Later ><?"}{ QUIT !!!!
Removed " Fuel Cap " Started - Ran Fine !!!!!
Checked Right side tank --- Same Thing !!!!!
Also Found the Charcol Canister Was Plugged ( due to paint ) .
Changed fuel caps , Charcol Canister ( Both Fuel tanks Are Vented to this Canister. )
problem Solved !!!!!!!!!!!!!!!!!!!!!!!!!!!!
Those little things will Screw with me All the time .
hope this Help,
Later,
Mark K.

[TimQ]

I think I am declaring victory!!! Tracked down a new coil this morning, put her back together and threw some new plugs in for good measure then went for a spin. Probably 45 miles without even a hiccup. Best of all was that she seemed to have some kick back when I hit the gas (yeah, it's only a V6 but still) and didn't have the hesitation like it used to when I floor it. The best test was coming up the final hill by my house. Yesterday I was barely able to get above 40 or so. Today, I shut her down as she creeped past 60.

So, thanks again to all the great ideas...especially all those who pushed me to look more at the ignition and related components.

Now its on to the various oil drips....