Engine Stall and Transmission issue-85c10

[Read]

1985 C10 350 engine, 700R4 Transmission, Holley Carb

I am having two issues and unsure if they are related or completely separate. Both appear to be triggered by heat. I purchased the truck last year and as temps increased over the summer I began having stalling issues as well the truck would lunge at cruising speed. I wasn't able to determine/fix issue last year and now it is happening again as temps increase. Yesterday after driving for 30 mins the engine stalled(however radio and fan still had power)--pulled over and noticed there was no fuel in the fuel filter. After a few minutes it started up and was able to get it home. Also during drive it lunged on numerous occasions as if the lock up was trying to engage. Shifted down to 3rd and no lunging issue. Also last summer I temporarily unhooked the electrical connector on driver side of transmission and couldn't recreate the lunging issue.

I do not have much experience with these trucks and unsure exactly where to begin. Are these related issues or completely separate but both being caused by heat. I had no issues during winter months. Fuel filter is new and was thinking of replacing fuel pump to see if it solves stalling issue. On a side note the truck gets horrible gas mileage, ~8mpg, so maybe fuel pump??

What tests can I do before I just throw parts at it or would it be best to just take to a shop, who definitely have more experience than I do, with hopes they can easily diagnose the issue.

Any and all suggestions are appreciated.

 

[Dutch Rutter]

I'm no expert but, I'm willing to bet those are seperate issues all together.

The lunging sounds like it is converter lock up related as putting it in 3rd or removing the lock up wiring solves it. I'd start by adjusting the Lock up cable and make sure that's good. Don't want to burn up a transmission. Then go with the other easy things, check for vac leaks.

As for the stalling seems as though you already narrowed it down to a fuel delivery issue. Could be a bad line somewhere. Cracked and leaking possibly. Visually check them out. Or it could be heat soak related. I'm not sure about Holleys but Edelbrocks recommend to have a fuel pressure regator and a plate or spacer between carb and intake to run better and not have similar issues.

I'm sure others will chime in shortly.

 

[Jethro224]

Vapor lock?
If the fuel line that runs up the front of the engine is too close to the block it can cause that.

 

[Read]

Just noticed my fuel pump has 2 lines but truck has 3 coming from tank. 3rd line is not hooked up to fuel pump which I assume is a return line. Wonder if I replace with 3 line fuel pump that could fix issue???


Sent from my iPhone using Tapatalk

 

[JoeR Jr]

On an 85, the 3rd line goes to the charcoal canister. Did someone plug it? If so, you just diagnosed it. Plugging that line will make it develop a vacuum in the tank as you drive it. That sure would explain the empty fuel filter, surging and no-start.
Joe

 

[Read]

The charcoal canister line is hooked up. The 2nd line to fuel pump is not hooked up which I believe is a return line back to tank.

 

[Dutch Rutter]

The charcoal canister line is hooked up. The 2nd line to fuel pump is not hooked up which I believe is a return line back to tank.

This is correct. One to the can, one to the pump and one from the pump to the tank. Could be that someone put on a two port pump instead of the 3 port and plugged the return.

Edit: I don't know if that would cause this symptom but it can't be very good for things.

 

[Matt69olds]

Lock up cable??? If your referring to the TV cable, DONT MESS WITH IT! The converter is controlled electrically, the tv cable has no influence on lockup. Loosening the cable will affect shift quality, and could create other problems.

There is a electrical thermal switch in the transmission pan. It’s designed to close and lock the converter if trans temps get too high. It’s possible it’s doing exactly what it’s suppose to do, or it’s possible it’s out of calibration and closing too soon.

How long do you have to drive it before this happens? How hot does the engine run? Inspect the trans cooler lines, any kinks or restrictions? What does the trans fluid look like? Is it smell burnt?

 

[Read]

The time it takes for it to happen really depends on outside temps. On a warm day it can occur in 10 mins, the other day it took 30-40 mins before it starting acting up. Engine runs about 210. Cooler lines look fine as well as the fluid. During winter months no issue.

What do you suggest I do?

 

[Matt69olds]

You must be registered for see images attach

I don’t have a transmission wiring diagram near me to be sure, but I’m pretty sure you can unplug the connector to the thermal switch. All the switch does is provide a ground for the solenoid if the temps get too high. The idea is to lock the converter under high heat conditions to eliminate any converter slip to cool things down.

You must be registered for see images attach

I circled the switch, good luck

 

[75gmck25]

A three port pump has a feed line in from tank, return line to tank, and the line running to the carburetor. The vapor line is completely separate and it comes from the tank and runs to the vapor canister.

The return line to the tank allows fuel to keep flowing when the pump dead-heads against the float, and that keeps the fuel cooler. The missing line may be part of your problem.

A new fuel pump is a cheap and relatively easy solution. You need a flare nut wrench to remove the metal line from the pump to the carburetor, and you need to read about how to keep the pump rod up so you can install the new pump. I’ve had good luck using an old hack saw blade with a bend in it to hold up the pump rod while I get the pump arm under the rod. If you are lucky it’s about a 15 minute job.

Bruce

 

[dustyduds]

My 77 K5 also acts up when it's hot outside. It will run great for 20-30 minutes, then shuts down. After a few minutes it will refire. Took 3 restarts to get home from the store. The lunging and jerking also seem to be heat related but I don't think it has anything to do with the trans or lock-up. Check your thermostat and radiator. A new thermostat and a radiator flush seem to have solved the lunging issue.

I've been asking around about it shutting down. Was told to replace my mechanical fuel pump (2 lines from the tank to the pump, 1 line from the pump to the carb) with an electrical one mounted near the gas tank or that my distributor is bad. Would she run like a wild child if the distributor is bad? Then I said something about the boiling point of ethanol vs gas and was almost laughed at.

Just before it got so hot, I had the timing, carb, electric choke and anything else I could think of either adjusted, repaired, or whatever. I know I'm stubborn but do I just need to get a manual fuel pump with a return line? What about fuel line? I insulated the aluminum lines within a foot or more of the block. A rubber line goes to the carb. 2 aluminum lines run from the tank along the frame rails to near the right front wheel and into the pump.

I really need to get Ol' Blu running good; my daily driver (02 GMC Sierra) needs to spend about 2 weeks in the shop.

Thanks all!

 

[Ricko1966]

A three port pump has a feed line in from tank, return line to tank, and the line running to the carburetor. The vapor line is completely separate and it comes from the tank and runs to the vapor canister.

The return line to the tank allows fuel to keep flowing when the pump dead-heads against the float, and that keeps the fuel cooler. The missing line may be part of your problem.

A new fuel pump is a cheap and relatively easy solution. You need a flare nut wrench to remove the metal line from the pump to the carburetor, and you need to read about how to keep the pump rod up so you can install the new pump. I’ve had good luck using an old hack saw blade with a bend in it to hold up the pump rod while I get the pump arm under the rod. If you are lucky it’s about a 15 minute job.

Bruce

I'd about guarantee that's the problem.Since you"'ve got a Holley I doubt your running a hard line from pump to carb a fuel filter for like a 71 impala would have a 2 line pump a 3 line filter return line from filter would be the line with the restrictor in it.. The fuel keeps moving and returning to tank and taking bubbles with it preventing vapor lock.