I'm stumped
Thread Starter
|
5th Wheeling
Joined: Dec 2013
Posts: 35
Likes: 0
I'm stumped
I'm about out of ideas on my '90 F250 5.8L. It keeps dying on me while driving, but idles fine. I have had it sputter and die, but it starts right back up and keeps going. This weekend, it sputtered and died, and I tried to nurse it home, but it came to a point where it would no longer run. After it sat for a bit, it started up and idles fine, but I was afraid to drive it very far. In its recent past, I have replaced the fuel tanks and pumps, fuel pressure regulator, ignition module, and MAP sensor. The engine was rebuilt about 2 years ago, and I have had some sporadic problems, but this one has me stumped. I once again replaced the fuel pressure regulator and fuel filter, did a small test drive (about 3 miles) and it died on me twice. I could start it up and keep going. With the new regulator, I initially measured 34 psi, but now I measure 25. It only goes to 35 with the vacuum pulled. I don't understand how I could lose 10 psi with a 15 minute drive. I'm not entirely trusting my Harbor Freight gauge, but it is suspicious. What am I missing?
Thread Starter
|
5th Wheeling
Joined: Dec 2013
Posts: 35
Likes: 0
Good suggestions! When you get frustrated, it becomes harder to think clearly. I will shortly go and check whether any codes were stored. My rear tank is nearly empty so I when I did switch the engine would barely run.
I am getting suspicious of my tank selector valve. My truck is a late 89 or early 90, and I think they changed the valve in 90. I need to look underneath and see what I have as I have seen some YouTube videos on cleaning that valve. I may even bypass it to eliminate a variable. I feel like I have been chasing this gremlin for a while and the fuel tanks may not have been the root cause -- well, one was leaking so it had to be changed. It seems like when I touch the fuel system things are better for a while, and then the problem comes back. I will now focus on the things that are still 30 years old.
I am getting suspicious of my tank selector valve. My truck is a late 89 or early 90, and I think they changed the valve in 90. I need to look underneath and see what I have as I have seen some YouTube videos on cleaning that valve. I may even bypass it to eliminate a variable. I feel like I have been chasing this gremlin for a while and the fuel tanks may not have been the root cause -- well, one was leaking so it had to be changed. It seems like when I touch the fuel system things are better for a while, and then the problem comes back. I will now focus on the things that are still 30 years old.
Cargo Master
Joined: Jun 2013
Posts: 3,174
Likes: 15
From: Somewhere n North America
1990 MY was the first year with High Pressure pumps in the tanks and no High Pressure Pump on the fuel rail. Also they did away with the switching valve this year in the gasoline models, so yeah, check to see what you have..
Trending Topics
Thread Starter
|
5th Wheeling
Joined: Dec 2013
Posts: 35
Likes: 0
I would almost bet it is water. I do have the "newer" dual tank system that does not have the big reservoir on the frame. I also don't have any fault codes other than my disconnected air system being inoperative. I will get some fresh fuel in the other tank and some additive before I do anything else.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Cargo Master
Joined: Jun 2013
Posts: 3,174
Likes: 15
From: Somewhere n North America
The Octane level of fuel degrades as well over time, so depending how long it's been, the octane level in the tank now could be well below 89.
Same for the Ethanol Phase Separation, the longer it sits without being refreshed, the more the separation.
Other snake oils like SeaFoam do little soaking up of water.
Thread Starter
|
5th Wheeling
Joined: Dec 2013
Posts: 35
Likes: 0
I found this article ( https://cropwatch.unl.edu/ethanol-an...oval-additives) that indicated HEET was 1 of only 2 products tested that actually absorbs water. It may take me till tomorrow to get that plus some fresh gas in the tank.
Cargo Master
Joined: Jun 2013
Posts: 3,174
Likes: 15
From: Somewhere n North America
I found this article ( https://cropwatch.unl.edu/ethanol-an...oval-additives)
see attached, looks like the same crowd;
EDIT; lol, ok, same as the link in your link.....
Thread Starter
|
5th Wheeling
Joined: Dec 2013
Posts: 35
Likes: 0
Update: Getting the rear tank usable was a little more work. I was not using it because after I changed it I noticed a leak from the top of the tank and I just didn't feel like messing with it at the time. (I just use this truck locally, so two tanks is really not needed.) Last night I removed the rear tank and found that I had not properly put the metal seal ring in place -- one of the tabs was not engaged, so the sealing gasket did not have even pressure. I put in some Heat and some fresh 93 octane fuel in each tank and went for a drive. For a couple of miles everything was fine, but then it died on me. I switched to the rear tank and everything was fine. I switched to the front and drove a bit farther. It started bucking on me so I switched to the rear tank and it ran fine. I definitely have some problem with my front tank, which I would not expect for a new tank and new pump that I installed in November.
Thread Starter
|
5th Wheeling
Joined: Dec 2013
Posts: 35
Likes: 0
I measured once and they were both the same -- ~ 32 psi. I think the front one cuts out or acts up occasionally. I'm having trouble catching it when I can see something. Today, I could only get it to act up when driving, and it died at 15 mph when it was really not under load. A fuel pressure gauge in the cab would be handy, but I'm not sure I want to run a fuel line inside.
Cargo Master
Joined: Jun 2013
Posts: 3,174
Likes: 15
From: Somewhere n North America
They are rarely the same, so I'm wondering if you have a restriction somewhere, or a Gauge issue?
When reporting Pressures, post both tanks, with and without vacuum applied to the Fuel Pressure Regulator for a complete picture.
Did you receive the correct parts when you replaced the pumps?
When reporting Pressures, post both tanks, with and without vacuum applied to the Fuel Pressure Regulator for a complete picture.
Did you receive the correct parts when you replaced the pumps?