I've posted recently about my problems with my '86 302 EFI F150. The truck won't start unless I go through a little starting "ritual". I have to touch the ignition 3 or 4 times to pressurize the fuel delivery system. On the 5th try it fires right up and runs real nice. The wise members of this forum tell me that, more than likely, I have a bad fuel pump(s).

1. If one or more of the fuel pumps is bad, why does the truck run fine once I've pressurized the system & the truck has started? Wouldn't you think it wouldn't run at all with a bad fuel pump(s)? Once started, the truck runs fine on either tank.

2. I have 2 low-pressure in-tank pumps, and one frame rail hi-pressure pump. Do all 3 have to be working properly for the system to stay properly pressurized?

3. Why/how is the system losing pressure? Where's the pressure escaping?

4. I've been told that if the hi-pressure pump is working properly and the in-tank pump is not, then I should hear a "whine" from the hi-pressure pump. I do not hear a whine from the frame rail pump. Does that mean the frame rail pump is faulty, and not the in-tank pump(s)?

5. Can the truck run at all if the hi-pressure pump is faulty? Once it's started, the truck runs sweet. So that means the hi-pressure pump must be working properly. No?

Eventually I'll test all 3 pumps, but i'm trying to come to a basic understanding of the system before I get started. Again, thanks in advance for your help. Jimmy

 

While i cant comment on 3 pumps ( do you have dual tanks) i can give you and easy way to try to find the faulty one. Lay and listen while someone turns the switch on. Listen to frame pump first, even put your hand on it to feel it kick in when turning on.

My guess is its the frame pump though. The in tank units are designed to just get the fuel running, like 1st granny gear. The frame pump is the up shift the really get it moving.
The reason as you know it takes so long to start is is doesnt hold pressure. So it has to fill the system again running off the low pressure in tank pumps.

 

Also dont just assume the pump went bad. Check fuses and wiring connections first. If it dont kick in remove it and try using jumper wires straight to the battery to see if it will run.

 

what is happening this the check valve for the fuel pressure is bad in the frame pump allowing the pressure to bleed off after the truck sits...hence why you have to cycle the key a few times

 

djfillmn hit it on the head, I think its the in frame one that has the check valve in it. It could be the FPR too. Allowing it to bleed past it in the return side. Easy to check. Pull the vacuum line off of the regulator and see if you smell fuel or if its wet with fuel. If you see fuel present here the regulator is bad even if it does not bleed down. Carefully pull your return line and block it off. Put a fuel pressure tester on the rail. Cycle the key a couple of times and watch the fuel pressure. It should jump up to ~40-50 psi and hold there very slowly bleeding down to ~15-20 in like 15 minutes. If it bleeds down really fast at this point then its the check valve in the fuel pump. If it holds then its the fuel pressure regulator. Good luck

Frank

 

Your posts were really helpful, guys. I've got a much better understanding of what's going on with my truck. Given that the FPR was just replaced by the PO, I've gotta think my problem is the hi-pressure pump. Will get under there & have a listen, and eventually do a pressure check. Feeling' pretty good about my course of action now. Again, many thanks for the posts. This forum is the scha-dizzle. Jimmy

 

There is no check valve. The DFR may be sticking, probably is sticking. It's behind the frame pump, the fuel filter is inside it.