I have a 92 F`50, with a 4.9 six cylinder. I use it for plowing snow, and general maintenance at our farm. The original motor was replaced with a low mileage 4.9 and it runs good, and it doesn't,
I deleted the smog pump, but left everything else alone. I had removed the rear fuel tank, and plugged the lines to it, so just running on the main tank.
Since the motor swap, I have been having issues with starting, and recently running.
When I go to start, I have to cycle the key switch at least 10 times, before it will even try to fire up. I have replaced the fuel pump and fuel filter, but it still hard starts.
Lately when using, after about 10 minutes or so, it will lose power. It still runs, but hardly power to even move. I found out if I shut the truck off, and re start, it will fire up, and act normal, for another 10 minutes.
I'm pretty sure I checked the fuel pressure at the fuel rail,and believe it's in normal range. I wouldn't think it would be injectors, or a vacuum leak, ,which I did find and repair, I
It's been a damn good old truck, but I'm at my wit's end, trying to fix what's wrong.
The fuel pump is an aftermarket one, and makes me wonder if it's not strong enough to hold fuel up to the fuel rail? I'm pretty good with mechanics, but understanding fuel injection is touchy with me. Has anyone out there had problems with cheaper fuel pumps? Should I buy an OEM one
Hoping someone out there can steer me the right direction, and help me with a permanent fix.

 

I would start by pulling codes and check actual pressure at fuel rail.

 

You should check fuel pressure before you start and after one key cycle and report the numbers. Also check ignition timing, retarded timing will cause hard starts as well.

Yes the aftermarket pumps are very sketchy. The Motorcraft ones are not available anymore AFAIK unless you can find an NOS one on eBay.

 

Sounds like you are repeatedly cycling the key to build fuel enough pressure to start which indicates a weak pump and/or leaking injector(s) or bad regulator.

What is the normal range you saw?


The specs are the same for your year.

 

If you have to turn the key muliple times to start it there's a check ball in the fuel pump that keeps pressure from bleeding back or you could have a sticky return valve. Check fuel pressures and timing if it cranks hard you could have bad battery connections and wiring to the starter.

 

I've had this issue for a while, but I think I checked the fuel pressure a while back, but will do so again this weekend. As far as the timing, it is spot on. It does not, crank hard while starting.
I would have to lean toward the check ball in the fuel pump? As I had just recently changed it out. Where would be a darn good place to get a different fuel pump? I even think I had replaced the fuel regulator too. Like I said, it may be cranky, but it's a good old truck.

 

Try cycling the key twice to on, and then start it
Also try a flood clear start
Both can give you clues as to what's happening
I'd drive it around with a fuel pressure gauge taped to the windshield for a day or 2 and watch what happens to the pressure as you turn it off and let it sit
Here is my Snap-On gauge with a long enough hose to reach the windshield

 

Thinking about this overnight, made me think of a check valve to keep the fuel in the lines. When I replaced the fuel pump, there was a short extension on one of the lines. Always wondered what that was. Could that be, a check valve? Just watched a video showing a person installing a new fuel pump on the front tank. He was wondering what the extension was for and decided to not install it. He later in the video mentioned that it might be a check valve, because there was one on his rear tank also. Read an article, that Ford had a problem right around 92, about a check valve problem with their fuel pumps. So, they installed an in-line check valve to fix the problem. Hard to believe, but even if this is true, the "installed" external check valve shouldn't cause a problem. Apparently, Ford doesn't offer them, at least online. Does anyone know of these things, and shed some light on the subject? Maybe know where to get one, besides a salvage yard?

 

Yes, the short metal "extension" is the check valve. You will lose your fuel pressure if it isn't installed. If you are running two tanks, your fuel may return to the wrong tank causing it to overflow also.

 

Well, here's my results from today. I hooked up a fuel pressure gauge, on the fuel line. Key on, engine off. Gauge went up to 15 psi, and then dropped to zero.
When I cranked the motor over, the gauge went up to 20 psi.
When I got engine running, the gauge fluctuated between 25 and 30 psi.
I checked the to see if there was gas in the vacuum hose at the fuel regulator. No gas in the hose.
I am thinking the fuel pump I installed is faulty, and hoping that's what you all who answered my post, will agree.
Unless someone else has another thought.
Kinda ticks me off, that a new pump, would fail.

 

Before replacing the pump, verify 12 volts is getting to the pump. If you have that, I would replace it. Very frustrating for sure!

 

A 1992 with a 4.9 needs 45-60 lbs of fuel pressure to run right
A V8 that needs 30-35 will run on 18-20
Your 6 pop should barely run at 30
I'd replace the pump
The new pump might be failing due to a contaminated fuel tank
Did you inspect the inside of the tank?

 

Correct. There were problems with the check valves on the FDM so instead of replacing the FDM, Ford had a TSB to install check valves between the lines and the pump.

Picture stolen from manicmechanic


I put the pressure specs in post #4.

 

The fuel tank is clean. I had it out and checked the inside. No problems there.

 

I wouldn't mind finding one of those check valves, but I checked the ford site, and they are not available anymore through them.