<--Thatguy

So I've noticed a bunch of threads about problems that are like this but none seemed to work for me, so I figured I would add one more too the pile. I've been having a weird problem with my truck when trying to start it in the morning or after it has sat for an extended period of time. Mainly I have to prime the gas quite a bit by turning the key on and off, but even then, it's still a hassle to get the truck to stay running. This is a dual tank truck and it seems to happen on both tanks. I recently (yesterday) replaced the front fuel pump with a newer delphi one since it would allow gas to bleed into the tank. I don't see any types of leaks where it could be leaking and I don't notice any gas in the vacuum line for the Fuel Pressure Regulator- When I unhook the vacuum line, the rpms drop so I don't believe that is the culprit. I have heard multiple suspects to be causing this problem and I don't want to go blindly buying parts that are not going to help. Any help would be appreciated. Further information: 92 F150 XLT dual tank with 5.0 motor and automatic. About 141 thousand miles. Thanks guys.

joshtowal

Check the fuel pressure. Do a key on, engine off and key on, engine running test. Also, after you shut the engine off, watch for a quick pressure drop.

joshtowal

Also, if the check engine light is on, pull the codes.

<--Thatguy

I actually do not have a fuel pressure gauge. Is there anyway to check pressure without it? I heard Autozone sometimes checks, but are there any other places that will let me use one?

fltdriver

x2

Also grab a vacuum gauge and test the engine vac, easiest from the brake booster line. You can learn a lot about how an engine is running just by vac. If it remains steady 17-22hg you are good. Also pull the lines one by one from the tree and test them with the vacuum to ensure you don't have any vac leaks-which will cause running problems.

fltdriver

You can borrow one from any auto parts store, pay with a credit card and when you return it they credit the full amount back. They usually come with a multimeter so that would also be a good time to check voltage on your components.

<--Thatguy

Thanks. I'll be sure to stop by and grab one to do some test. Any other self test I can perform to further narrow down the problem? Or is it mostly based off of what the fuel pressure and vacuum lines say?

joshtowal

From what you're saying, the fuel system sounds like the problem. F150's love fuel problems. Since the test is this easy, at the very least ruling out the fuel system is a great place to start.

<--Thatguy

Will do. I was hoping the new pump would help fix the problem. I doubt it's faulty since it runs great when actually running. It seems as if it is losing pressure while it sits, but I'll wait til i perform the test before I can make that conclusion. Thanks for the quick replies by the way, really helps.

<--Thatguy

Sorry for the long wait guys. I have yet to use the fuel pressure tester but plan to after work today. But this morning I noticed something that seemed odd. I cycled the key about 8 or so times and she wouldn't start. I had to do this about 4 separate times before she actually started up (with help from the gas peddle). This makes me think it might not be a pressure problem, but something else. I'm going to test the pressure today just to make sure, but are there any other possibilities on what it could be or any test I can perform to narrow it down? Thanks in advance.