Hey all,

I could use some help with this problem on my 1992 F150 with 4.9L I6. It has a single fuel tank. It's a 4x4 with a 4 speed (3 speed with granny gear...no overdrive).

On long trips, the truck (after driving fine for, say, an hour) will start to sputter at highway speeds and eventually die. It seems to initially start the problem when "coasting" downhill with the transmission in gear (compression braking situation, though we're not really trying to slow down with the engine...we just don't need throttle to maintain speed down the hill).

Once the truck dies, we have to let it sit for 20-30 minutes and it will eventually start back up and run again. One time, after starting it back up, it ran fine for an hour plus. Today, it would only run for 20-30 minutes before acting up again.

When it won't start during these episodes, it will fire for a few revolutions, but not enough to start. Sometimes it will run VERY poorly if you pump on the throttle a lot...but it won't clear up and run right unless you let it sit quite a bit longer.

I noticed today that when it started sputtering, I could keep it going indefinitely if I was willing to keep my foot in the throttle. Obviously, I can't drive around all day with the throttle on the floor...but it didn't die unless I got off the throttle.

This last part leads me to believe that it's "loading up" on fuel for some reason (problem with the return line? Problem with the fuel pressure regulator?)...

One thing is that my engine temperature guage does not read correctly (and hasn't since I bought the truck). I see this mentioned as the culprit in other queries about this type of problem...However, I understand this truck has 2 temp sensors. One that the computer uses for input and one that controls only the gauge on the dash. I replaced the one for the computer (mistakenly, before I realized there were two, some months back).

I've seen mention that sometimes trucks with dual tanks exhibit similar symptoms...but I don't have dual tanks.

I do feel that it's a fuel problem. My experience makes me feel it's not a fuel starvation issue (clogged fuel filter, bad fuel pump(s))...but rather a problem of too much fuel. But I'm sure it coule be any number of other problems.

The old truck is pretty neglected and could use attention to lots of deferred maintenance, to be sure.

I'd appreciate any input from folks who have seen similar issues. I'll provide any other info that might be necessary...I'm sure I've forgotten or not realized a detail or two that might help.

Thanks!

 

1st thing I would do is check for codes.

2nd thing would be to test fuel pressure cold and then when it won't start.

 

Thanks, neighbor.

I'll go by and see if the parts store can pull any codes. However, it has not lit the check engine light for me during these episodes. My wife mentioned it came on once yesterday while it was doing it for her...so we'll see what it says.

For #2, I sure wish I didn't have to drive an hour or so at highway speed to make it happen, lol. But...that probably is going to be about the best way to narrow it down.