wont stay running

Asked by Mar 09, 2015 at 11:17 AM about the 1991 Ford F-150 XL 4WD LB

Question type: General

i have a 91 ford f150 with a 302 5.0 litter engine. filled up tank and wouldnt start, got a test ignition module and it fired up but had to put foot on the gas pettel. so put a used module on it and it ran fine for anout a week and then started doin the same thing after i filled the tank back up. so i put a new one on and drove it and during test drive it died obn me three times. So i put a new stater in it and made sure timing was good and it started but ran horrible could barly get out of its own way. So made it home and went to drive it morning after and made it to the end of my road and it died and would start but had to put foot on gas and when i put it in gear would die like it was running out of gas. Put new iac and made it about two miles and it did same thing. So i puit gas in my rear tank and it would run fine for about two minutes and started running ough. Almost made it home and it died. Got it home and now on both tanks itll run ok fo a couple minutes but then starts running rough and when put it under a load it acts like it wonts to die. Checked fuel preassure and it is great and i am getting plenty of fuel at the rail, so im thinking i have a spark issue.

2 Answers

16,120

Not sure with the 91 F150, but my 2010 was doing the same thing. It threw a code indicating there was a problem with the EVAP system. Visually check the gas tank and make sure you did not pull a vacuum on it while driving causing it to collapse. Hard starting after fillups indicates you overfilled the tank causing liquid gas to flow into the charcoal canister. It's easy to check. Remove the canister and look for fuel, there should be none. Then check hoses for leaks or kinks. If there is a code you are going to have to have it removed. Disconnecting the battery will not erase it from the memory, you'll need a scanner. Additionally, upon checking, there were two updates to my 2010 f 150's PCM which had to be installed.

16,120

Forgot. If small charcoal pellets fall out of the canister when you check it you got raw fuel in there at one time of another. Replace it. Make sure none got sucked up in the line toward the engine.

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