Bad coil? Module? OR?

[bobs409]

I'm gonna run this one by you guys. My 69 Chevy pickup has a 350 w/HEI. A few months ago, the truck would occasionally die out and not start for a few minutes. It acted like it was electrical as it just shut off, no sputter.

I tried many things back then like swapping in a different control module, a different coil. I put on a new cap & rotor at that time although I'm sure it wasn't that. The problem stopped so I figured I hit it on one of those.

A few months went by and in that time, no problems. Today, it died out 3 times on me. First time it started right back up and went a block and died again. Then started right back up and went about 1/2 mile and died as I was driving (on the gas), like someone turned the key off. This time, it wouldn't start and the engine even turned over slowly. I got out and checked under the hood to make sure the wiring looked ok and the choke was open and it fired right up like nothing ever happened.

So I'm right back to where I was a few months ago. Scratchin' my head on what the heck is wrong?

I can fix it once I know what is wrong but this is something you can "make happen" so you can test things.


I'm thinking of getting a new coil and module from NAPA (hopefully made in the USA) and starting with that.


Thoughts??

 

[oldskydog]

Bob,
A common problem on the 60's Corvettes was the bulkhead connector on the firewall from the main harness to the engine harness with the same symptoms. I would assume the truck uses a similar type connector. The problem seemed to be corrosion buildup on one of the spade connectors to the point that continuity could be broken randomly, just by vibration or a bump. I also had a problem with the ignition switch on one exhibiting the same symptoms. You might try wiggling the firewall connector while running to see if it causes the prob- or just clean the contacts just on general principles.
One other prob I had was the nut on the lead to the starter solenoid had worked loose.
Like you though, I would have suspected the hei initially. My only experience with a non-HEI coil failure was that it acted more like a fuel problem when hot rather than a total shutdown as you describe.

 

[dq409]

When you changed the module did you use the electro grease that goes between the moduale and dist body?
If not it will over heat and fail.
Or, the moduale is just that aftermarket crap they sell now,,,

My guess is the moduale failed again,,

 

[k9hotrodder409]

Hi Bob, I had the same problem with my '61 bubbletop when I bought it. The motor would start right up and run great for a few miles and then crap out on me. It would start right up and then crap out again. I bought the car any way because the old tired 283 was getting tossed for a truck 348 "W" motor .When I trailered the car home I went to start it up and it would barely crank. I giggled the bulkhead connector because it looked loose and it started right up. When it wouldn't start I would giggle the bulkhead connector and it would start right up. I took the connector off the bulkhead and discovered that the terminals were a bright green.:? I soaked the plug with WD-40 and plugged and unplugged a few times and it has worked every time since. Just a suggestion. Try the WD-40 and see what happens. Good Luck.

 

[bobs409]

I hadn't thought of the trucks wiring. :? I'll check that out tomorrow. That just might be it! After all, the truck is 40 years old.

DQ, The module I put in was an older one that I think was an original GM part. I did use the grease so I'm good there. I always thought a module either worked or didn't but I guess anything can happen.

I too have had either a module or coil go bad and act like the truck was flooded when hot. I put up with that for about 6 months thinking it was the carb flooding and all along it was one of those two. (still not sure which as I replaced both at the same time)

Thanks, glad I asked.

 

[raymar58409]

Bob, Does it have vacuum advance which can break pick-up coil wire. Also have had pick-up coil act that way. Also many green wire deals at plug as others have mentioned.

Ray

 

[bobs409]

Ray, I was thinking of a possible break in one of the distibutor wires too. I'll add that to the list if the bulk head connector theory doesn't work out.


Thanks,

Bob

 

[PAINTJOHN1]

Bob,check the pick up sensor.I've had problems years ago with a 79' Olds 88.The car would run great and all of a sudden just die.Let it sit for 30 seconds and would start right up.Because the distributer shaft goes thru the pick up sensor you must remove the distributor to repalace it.You would knock the shaft pin out.Then you pull the entire shaft out from the body of the distributor.Once that is out the pick up comes out with a few screws. John

 

[bobs409]

Thanks John. Sounds possible. I have another distributor just sitting here so I could swap the whole thing.


Bob

 

[rstreet]

now you're talking Bob. a distributor switch should get you closer. Let's hope it's the same type of distributor. We will expect a full report tomorrow
robert

 

[62impala409]

BOB, Ray and the others are right about the pick-up coil wires breaking inside of the rubber insulation. I found this quite a few times on dist. with vacume advance. The wires are constantly being moved back and forth. Easy check is to unplug the wire pair from the module and pull on each wire. The broken wire will feel like a rubber band. The repairs I did were on motors with exactly the same symtoms. GOOD LUCK. LEO

 

[bobs409]

My report isn't quite ready yet. These are all really great ideas!

Yesterday I drove the truck all over and it ran perfect. I tried wiggling the bulk head connector around with it running but it's tight and didn't cause it to die.

The other distributor is an exact match for this one. I'll get that in today and check those wires over better once the old one is out. We'll see...


Bob

 

[raymar58409]

Another thing you can do is put a vacuum pump on the vacuum can and with it running pump it up and release a few times , sometimes this will make it die if it is a broken wire.

Ray

 

[rstreet]

These are all great trouble shooting guides. There is a large amount of knowledge here. With all of these suggestions I got an idea we won't hear from Bob for a few days as he will be busy
robert

 

[bobs409]

Busy but I work fast.

I pulled the distributor and if those wires are broken, they sure aren't showing it. I tried tugging on them and they feel ok. I swapped the other distributor in and will be road testing soon.

I think for the heck of it, I better pull that bulk head connector and see what that looks like. That turning over slow thing that happens might point more towards this being the problem.

And if all this fails, I will look like this---> But I'm hoping to look like this--->

 

[bobs409]

Ok, I'm doing the banana dance.

You guys were all wrong. (well, somewhat wrong)

I swapped the distributor, started it up and backed out of my yard and it died! Checked for spark at #1 and nothing. I tested for power going into the coil and that was good. Tried again and it started, then died again.

When I got it going again, I found I could kill the engine by moving the power wire around going into the cap. Since adding the HEI, I have a wire going from the fuse box out to the BATT terminal on the cap. So I replaced that and all is good again.

So it was a bad connection where the wire goes into a solderless connector. That one sure had me chasing my tail.

Thanks to all who replied. They were all great ideas and it could have been any one of them.

 

[rstreet]

Bob: Glad you found it. I learned from rigging boats to avoid solderless connections whenever possible but still use 'em also myself. Good to hear that you can now find time to do other things.
robert

 

[bobs409]

Yes, there's nothing more frustrating than a problem you can't figure out!

I think I can trust my truck again.

Can you solder a solderless connection? I got a new handy dandy Harbor Freight soldering gun I've been wanting to try out...

 

[jwhotrod]

soldering solderless connectors

you shurely can solder them, in fact I do NOT crimp anything without soldring it also. When the insulation is in the way, I strip it off and then replace it with heat shink tubing. Amperage running thru those connectors heats them, so they expand and contract constantly untill they fail. Solder everything including weather paks, you wont be sorry!!!!!!


Big jim

 

[oldskydog]

Depends on where it is and how much vibration it experiences. In aircraft, soldered connections are not common due to vibration issues . An in line soldered connection of a broken wire is Ok since the two parts are not subject to the work hardening and breaking due to vibration that can occur between a flexible wire and a fixed point like an end connector to a wire terminal. Not such a big deal on a car, since you can pull off the road and shut it down when the fire from the short starts.....a little more problematic in the air.