I've got an 1987 f150 with a 4.9L straight 6. It stalled out on me yesterday. It acts like a fuel delivery problem. Discovered that when the key was turned off and on several times (assuming charging the fuel system) it would start up and run for about 2 min then sputter and die. After sitting a couple of hours (while I went to get a fuel pressure gauge), the truck started up and ran fine. I went ahead and hooked up the fuel pressure gauge. It showed a steady pressure of 45psi and would briefly jump to 55 when the engine was goosed. After about 10 min of idleing, the pressure starting fluctuating about 2psi. This model has two fuel pumps an external high pressure pump and a low pressure pump internal to the tank. I replaced the high pressure pump (easy to get to) and drove it nearly 100 miles then it did the same thing again. It sat for about 3 hours while I was making arrangments to tow it home. When I got back to it, I tried to start it and it started up like nothing had happened and I was able to park it at work. My question is, if the low pressure fuel pump is bad, would it be intermident or would it just stop altogether and if it doesn't seem like the fuel pump, what kind of symtons would a bad fuel pressure regulator have. The truck itself has about 175K mi on it but it has a new engine with about 2K mi. I don't know for sure, but I think the fuel pumps are OEM so it probably wouldn't be a bad idea to replace them anyway.

 

How about the ignition system. I am thinking of the primary side in particular. It should be EEC IV and these are known to have problem with intermitent stalling/no start when warm.

 

I think the ignition system is ok because it will try to start and even run for about a min then start to sputter mis then die altogether. It doesn't just cut out completely, it acts like it is getting starved for gas.

 

I checked the vac line going to the pressure regulator and it was dry (no fuel) and also line looked good. Pulled tank (that was a pain in the ***!) and checked wiring. Didn't find anything so replaced the fuel pump in the tank. Won't know if it's fixed until I drive it work next.

 

same thing happened to me on my 93 Tracer. I put a gas cap and a new fuel filter on it and havnt had any probs since. I think i got some water and dust in the tank when it didnt have a cap on it.

Good luck finding the prob.

 

If your FP is good, and it is, my guess would also be ignition. TFI module.

 

When the truck would sit for a couple of hours, it would start up and run normal. I wasn't able to check the fuel pressure while the truck was actually acting up. I wanted to know if a fuel pump could fail intermidently. When the engine would fail, you could turn it over and it would try to run (sputter a bit then die a few seconds later) Also, if you turned the key on and off several times (waiting for the fuel pump to kick off) it would start up and run normal for about a min or two then start to sputter, miss out, and then die. But after a few hours, it would start and run normal. The fuel pressure occilations that I did see where after the truck had sat for 2 hours then idled for about 10 mins. When the truck died initially, the high pressure fuel pump wasn't actually turning on and off but it did have a rattling sound that would come and go. After installing the new pump the rattling sound was constant but at that point the truck had started running normally anyway so I couldn't tell if it had fixed it (obviously it hadn't since it died the next day on the way to work). I'm assuming the rattling sound is normal and the low pressure pump was intermidently starving the high pressure pump. After installing the low pressure pump, I could hear it running in the tank whereas before, I couldn't. Because this problem has actually only occured twice, I don't know yet if it is actually fixed, but the indications I was seeing (at least to me) seemed to point to a fuel delivery problem. Any more comments would be appreciated.

 

Yes a fuel pump can be intermintent. I just had that problem on a Van I was working on. Was a bad conection in the tank. Also change your fuel filter it could be plugged. Sounds like a fuel problem since you said the pressure went to 2lbs.

 

Yeah it sounds like that was the problem... the only purpose of the low pressure pump is to feed the high pressure pump so it doesn't burn up...