I am still trying to find someone who knows the solution to my truck's problem. I have a 1995 Ford f-150 straight six cylinder truck. It does not show any codes on the computer. Using the paper clip method, it does not show any codes, either. It will crank up and run fine for about 5 minutes during which time you can depress the accelerator and it runs fine. After about 5 minutes it starts skipping on one cylinder, then two cylinders, then 3 cylinders (all during a few seconds' time) and then dies.
It will immediately crank back up and idle all day, but if you press the accelerator it dies. will crank back up immediately and then if depress accelerator, it dies again. Does not flood. My mechanic said fuel pressure is about 40. He put a new box of some kind on the fender well and it did make it run better, but did not solve the problem. The truck does not have any relays that would cause this problem. He has used parts from a donor truck that was running fine. He has put a new pickup in the distributor, computer, map sensor,coolant temp sensor, 2 ignition control modules, throttle position sensor, checked yellow wire in harness, fuel injectors are fine, does not have vacuum leak, 2 different coils, Map sensor, ECM, fuel filter is clean, has disconnected the exhaust system above the catalytic converters so there is no back pressure. Thank you. Floyd Edmondson.

 

Have your mechanic put a vacuum gauge on it after it warms up. If he's losing vacuum, it's most likely a cracked manifold which the 4.9 is prone to having. You may end with having to buy a new one as junkyards pretty much have been picked clean of them.

 

This thread is a repost.

https://www.f150online.com/forums/pr...ruck-dies.html

Might want to look at the responses there.

 

My mechanic said it does not have a vacuum leak. Any other suggestions? Thanks.

 

Just out of curiosity, I'd check the compression.

 

My mechanic did a compression check and found 125-128 pounds on all cylinders except #3. #3 ran 97-98 dry and 125-128 wet (after spraying oil ). All of the spark plugs looked good and were clean--no sign of fouling.---including on # 3. Any thoughts and/or suggestions?---please refer to previous posts for history. Thanks, Floyd.

 

Check the fuel pressure cold and hot.
Check the vacuum line to the regulator for a fuel smell.