I did not check the pressure while trying to go above idle. The whole reason I went fi was so I didn't have to worry about a carb lol

 

I am not the expert on fuel injection by any means, but I have done a buttload of research all winter on my EFI project. In regards to the EFI fuel pump(the one that creates the 39 psi for EFI) it doesn't have enough pulling ability to maintain fuel volume, it either has to be in the fuel tank or have a secondary low pressure fuel pump between it and the tank also a fuel reservoir between the two pumps. thats what alot of earlier EEC IV vehicles used. that system was done away with when the high pressure pump was put directly in the tank. Now I think you could still use the inline high pressure pump if it is below the tank being gravity fed. That would be easy to accomplish if using an original behind-the-seat tank because the fuel line is in the bottom of the tank(at least on the bonus builts). you simply put a filter down there and then to the pump. but it HAS to be below the tank, like on the frame rail. you can find the two pump system in most late 80's to early 90's f-series or e-series vehicles. I think that setup would be a PIA to install and you got another pump to go bad as well.
Again I have read it over and over, the high pressure pumps are not going to pull fuel well they will push fuel well.
I have a fuel tank from a jeep grand cherokee hangin between my frame rails with the pump in the tank to avoid the two pump system, also to get the original tank out of the cab.
there are guys that have modified the tank behind the seat to accept an in tank high pressure pump, but they are noisy as heck in the cab. so thats not a great solution either.
Seems to me,at this point, you should get that pump down on the frame rail, but its still hard to troubleshoot from the dining room table! LOL

Yes life does get in the way sometimes! Keep us posted!
As Sam mentioned...check that pressure gauge when it starts to stumble. before anything else.

 

Yeah sometimes I think the same thing!

But if we never experiment we never learn! heck we would still be ridin horses! which, with the price of fuel, might not be a bad deal! but I prefer the technology route!

 

Joe I sent ya a private message but you got to have 25 posts, i think, to be able to reply. you only got 13 so... let's get those posts out there buddy!

 

I have the opposite problem, high idle. I have to clean the throttle body and IAC, hopefully this will help.

I bought a fault reader and it helps with troubleshooting, not that expensive. You can check codes using multi-meter but reader is goof proof.

Tom

 

I had an 89 ford f250 that idled too high and i cleaned the IAC then replaced it with another after no change, it still did the same thing and eventually found out that the TPS was not set right. I adjusted it myself and it idled great. finally!

 

It might also be a vacuum leak???

 

yeah could be that too!

 

I'm no expert but you can do a TPS test using multi-meter, with TPS connected look for steady voltage range between idle and full throttle. should be from 0.6 - 4.0 VDC or so.

I've done the TPS test so vacuum test is next.

 

How high is it idling? I was looking through your engine pics and couldn't tell, but are you using the speed density efi without a MAF sensor or the SEFI injection with the MAF? just curious.

 

TPS voltage readings were taken manually

 

Sorry for the confusion, how many RPM's at idle?
And I was asking about your EFI setup. Is yours the speed density without a MAF sensor or is it sequential fuel injection with a MAF sensor?
Oh duh! its in the title sorry again!

 

while FUEL PRESSURE is my first thought, VACUUM LEAK is also a good possibility.. on your upper intake manifold there is a vac tree on the underside that you may have forgotten to hook your BRAKE BOOSTER HOSE to or any one of the 3 or 4 hoses that connect under there. ALSO, check to be sure you have everything properly grounded (EFI FORDS are very sensitive to open grounds) and be sure that you have the correct 302 firing order set. Standard 80's TBirds and such have a different firing order than the 5.0L-HO found in Mustangs and Lincoln Mark VIIs (which use a 5.8L/351W firing order)

 

I'm going over to my buddies tonight to work on the truck. How many grounds should I have for the whole system? I think I only have two right now. One is a block ground and the other is part of the harness. I'll check the fuel pressure issues tonight, with key on, not running, idling and under throttle.

I'm still running stock brakes so there isn't a brake booster, should I try and find the brake booster hose and cap it? Or is it part of that little four opening black plastic vacuum bracket?

I'll keep you guys updated.

 

So I'm over at my buddy's house right now. We put in a low pressure fuel pump (4-7psi) before the hi pressure. You said there needs to be a resevoir between the two. How big does it need to be, or will a small length of hose work?

We wired it up with the new pump with just a small length of hose and it still acts the same way. Starts and idles great, but as soon as we give it any throttle at all it dies. We are completely at a loss here, and I really just want my truck back. I know it's hard to diagnose anything from behind a computer, but if anyone else has any ideas that would be awesome. Thanks.

Joe