Please help, My 1991 f-150 will sometimes act as if its running out of gas? After it sits for a while it will start again and run just fine? I've had the fuel pump checked and it appears to be o.k. this problem seems to happen on warmer days when the engine is at operating temp. Any ideas? Thanks. J.

 

when was the last time you changed the fuel filter?

 

give more info on condition of truck.

last tuneup, air filter condition, mileage, etc.

 

The truck has approx. 124,000 miles and has had new plugs and wires within the last 5,000 miles. Fuel filter was replaced approx. 2 months ago or about 1,000 miles. A compression check was done on the fuel pump and it is working fine. I keep the oil changed and haven't had any other real problems. I thought it might be vaporlocking as it does it on warm days but after adding a new heavyduty rad and fresh antifreeze it still occurs. Sometimes my check engine light comes on and goes off again but not at the same time the truck stalls. i am wondering if it might be a sensor or something? J.

 

my 94 was doing that, it was an old(read: original) O2 sensor, with cracks in the cap, and i think water got in it, screwed it up

 

Thanks, I will try the 02 sensor. I love this truck and hate the thought of having to get something else. I really want in the 200,000 mile club.

 

Try to pull the codes first, then list them here.

Upstream 02 sensors, can create a code and pour running conditions.
I am not sure if your truck has

1. an EGR valve.
2. IAC = idel air control.

02 sensors are "supposed" to be looked at/replaced in the 100,000 mile range.

 

recheck plugs, 5000 plenty of time to foul out

compression check on fuel pump???

check codes

check temp sensor not the dash gauge temp sensor, the one that gives info to computer.

 

Food for thought...I had another pickup (not a ford) that gave me similar problems. We tested the fuel pump and it seemed to be working fine. After replacing most everything and still getting the same problems, I replaced the fuel pump as there was nothing left to replace. That fixed it. Talked with a mechanic friend and he suggested the fuel pump was most likely overheating and failing during long periods of use.