Truck dies at high speeds

[CheemsK1500]

My 84 K1500 has a strange habit of running fine at low speeds, but stalls out in higher speeds. On the road, the the first three gears seem fine, but when I shift into fourth, the truck acts as if it is flooded and stalls out. after it sits for a while, it starts back up with ease. The truck in question currently has a 305 with a new Edelbrock 1406 sitting on top, and a SM465 transmission. Any help is appreciated, thanks.

 

[WP29P4A]

Is it possible it's not getting enough gas at higher speeds? (lack of flow) Is it possible that the choke is not adjusted and fully opening when up to temp? How sure are you that it's a gas issue and not spark? Is "a while" close to 5 minutes or closer to 30 minutes? Does it smell like gas when it stalls?

 

[CheemsK1500]

Is it possible it's not getting enough gas at higher speeds? (lack of flow) Is it possible that the choke is not adjusted and fully opening when up to temp? How sure are you that it's a gas issue and not spark? Is "a while" close to 5 minutes or closer to 30 minutes? Does it smell like gas when it stalls?

I unplugged the choke wire on the last run to see what would happen, and nothing changed. As for fuel flow, the see-through fuel filter seems to be full enough when the truck dies.

I've thought about a spark issue, but I don't understand why it would only be an issue at higher speeds. Vacuum related perhaps?

 

[StickyLifter]

You mentioned it starts right up if you let it sit for a while. What happens if you try to start it right away? Does it always happen in 4th gear or only at higher RPMs in 4th gear?

 

[CheemsK1500]

You mentioned it starts right up if you let it sit for a while. What happens if you try to start it right away? Does it always happen in 4th gear or only at higher RPMs in 4th gear?

Mainly just higher rpms in general. Sometimes it'll start acting up third, if I leave it there long enough.

 

[CheemsK1500]

I had a second person turn the key, while I examined the see-through fuel filter yesterday. It turns out, the truck isn't flooding, but rather it gets leaner the more that it's ran. The fuel in the fuel filter gets below the the carb inlet line, and when the engine is cranked, the fuel comes in spurts, rather than a steady steam.

 

[Mr Clean]

Do you have a filter inline down on the frame? The reason I ask that, when I had my 82 LWB I replaced a little steal looking inline fuel filter I didn't know was there. I'm guessing the previous owner put it there. After replacing it, my truck started doing the same thing, dying at higher RPMs. I thought got a crap new filter so I replaced it...same thing. So I just removed it, and Bobs your uncle it started running like it should. The filter was close to one of the exhaust pipes, with no heat shield. It was vapor locking is all I could come up with.

 

[CheemsK1500]

Do you have a filter inline down on the frame? The reason I ask that, when I had my 82 LWB I replaced a little steal looking inline fuel filter I didn't know was there. I'm guessing the previous owner put it there. After replacing it, my truck started doing the same thing, dying at higher RPMs. I thought got a crap new filter so I replaced it...same thing. So I just removed it, and Bobs your uncle it started running like it should. The filter was close to one of the exhaust pipes, with no heat shield. It was vapor locking is all I could come up with.

I did not see such a device coming from either tank (this is a dual tank truck.). I've thought about a potential vapor lock issue as well, but the engine operating temp seems to be good, and the fuel line isn't near the the exhaust or manifold. I'll inspect the routing for the fuel lines just to be sure.

 

[fast 99]

Description sounds like a fuel related issue. Using the fuel filter as a diagnostic tool will lead you down a dirt road. Check the fuel pressure AND volume.

If it turns out to be a fuel pump get a Delphi if possible. Cheap ones are just that cheap.

 

[Grumpy]

As I have said before for others, install a fuel pressure regulator with gauge AFTER the filter. Without knowing the actual fuel pressure that the engine sees, you may end up chasing your tail.

Another thought, considering the numbers of Woke people in the country, it is possible your truck may now have become self-aware and now may have self-identified as a Ford, and is now scared of higher speeds.
Have you decided to set aside your prejudice and asked it?

 

[CheemsK1500]

As I have said before for others, install a fuel pressure regulator with gauge AFTER the filter. Without knowing the actual fuel pressure that the engine sees, you may end up chasing your tail.

Another thought, considering the numbers of Woke people in the country, it is possible your truck may now have become self-aware and now may have self-identified as a Ford, and is now scared of higher speeds.
Have you decided to set aside your prejudice and asked it?

I think it developed an identity crisis when a previous owner put a Cheverolet tailgate on it.

 

[CheemsK1500]

Description sounds like a fuel related issue. Using the fuel filter as a diagnostic tool will lead you down a dirt road. Check the fuel pressure AND volume.

If it turns out to be a fuel pump get a Delphi if possible. Cheap ones are just that cheap.

The fuel pump is not very old, but given the quality of today's replacement parts, it wouldn't surprise me if it's already broken. I'll do a few other tests, and then I'll toy with the fuel pump and perhaps pay a few dollars more for a Delphi.

 

[fast 99]

Found several manufacturers are not installing the return spring on top of the pump arm. Installed 2 pumps without the springs, both would not provide enough volume because the arm did not return completely. Motor ran out of fuel merging on the freeway, not good.

 

[CheemsK1500]

After further inspection of the truck and reading posts here, I have come to the conclusion that it either the fuel pump, or a rubber line going to the fuel tank sending unit. I might temporarily isolate the passenger side tank to make diagnostic a little easier.

 

[CheemsK1500]

Update: Problem solved after replacing both fuel tanks and sending units.