Fuel Filter Light Comes on & Truck Dies

Hello Again!

I've got an 89 ford f350 7.3 idi. I can get it started just fine. Unfortunately, after I leave the house in a couple blocks to a mile, the fuel filter light comes on, it sputters and dies. I then have to crank several times and it has trouble starting. I have to keep the starter going for a few seconds once the engine starts to turn over or it will die again. I can idle all day long, but when I hit the accelerator and get the tach up to 1500 to 2500 rpm's, she acts like she's not getting enough fuel, the engine stalls and dies within minutes of the higher rpm's. BTW, this behavior is recent.

Here is what I have done...
1. replaced all the fuel injector return lines, hose clamps, injector caps and seals under the caps.
2. Replaced the fuel filter with a fuel filter/water separator from carquest.
3. Replaced the mechanical fuel pump with NAPA mechanical fuel pump.
4. Replaced the fuel tank sending unit 1.5 years ago so I don't think it's related to that.
5. Replaced the fuel tank selector valve 1.75 years ago so I don't think it's related to that either.
6. Changed my oil 30 miles ago. Dipstick reads full, but not over full.
7. I'm not leaking fuel around the injectors or injector caps or hose/cap connection.
8. Replaced the vacuum pump 3 months ago.

I have a dual tank setup, but have been unable to use the rear tank since I got the truck 2 years ago. Therefore, I can't switch tanks to see if she reacts differently.

Thoughts?

I assume you are running some sort of bio diesel from your name?

Thewespaul said:

I assume you are running some sort of bio diesel from your name?

Click to expand...

I run biodiesel off and on. Right now, I've got around a B50 blend in the tank.

You need to start isolating things and go from there. If your fuel filter light comes on, that means you have a vacuum in your filter housing so issue is not in your injectors, fuel return lines or injector pump.
I would start at the lift pump. There is a volume spec out on the internet for how quickly the pump should fill a quart mason jar. I have used it to test a pump, but don't remember it off the top of my head.
If the pump is putting out the volume, look between there and the injection pump for restriction, if not look between pump and tanks.
You definitely have a low fuel volume issue.

Pint in 30 seconds min.

Shadetreemechanic said:

You need to start isolating things and go from there. If your fuel filter light comes on, that means you have a vacuum in your filter housing so issue is not in your injectors, fuel return lines or injector pump.
I would start at the lift pump. There is a volume spec out on the internet for how quickly the pump should fill a quart mason jar. I have used it to test a pump, but don't remember it off the top of my head.
If the pump is putting out the volume, look between there and the injection pump for restriction, if not look between pump and tanks.
You definitely have a low fuel volume issue.

Click to expand...

Thanks Shadetreemechanic. I'll get to work on that, probably next week since I'm working through the weekend.

Might be a dumb ? Do you have the bowl style fuel filter or bowless style, fuel filter light could also be your sensor that connects to the fuel filter. I need to replace mine once my truck starts again.

Sure sounds to me like you have an obstruction in your fuel line somewhere.

I think shade tree mechanic has it nailed, as your IP is actually pulling suction trying to get fuel, can't get any, so has nothing to inject.

My IDI does the same thing as you describe should I turn my electric lift pump off, making the pump itself an obstruction.

I have been using this as yet another frustration to present to thieves... So if they aren't aware of the hidden fuse holder, it'll start, but die on him just the time he thinks he's getting away with it.

I predict you will find a restriction in the suction side of the system. I once had a big fight with an issue like this and it turned out to be the showerhead (suction screen / bell) disintegrated and got sucked into the line.

Yep sounds like a restriction to me, I’m sure it’s related to the bio fuel and/or rust from water

*UPDATE*

I'm still working on finding the restriction. However, I was able to blow air through the fuel line from the lift pump back to the tanks. I heard air bubbling in the forward fuel tank, but nothing in the rear tank. Since I've been meaning to drop the rear fuel tank and look inside at the fuel tank sending unit for about 18 months now, I decided to drop the tank and pull the sending unit for inspection. In the process, I discovered 2 things. 1. The tank is not original to the truck (has a 96 written in crayon on top with no rust on top.) The nylon fuel lines running from the fuel tank selector valve look very new. Whomever hooked up the newer lines and newer tank, installed the main 3/8" fuel line on the return line port and the smaller return line on the fuel sending port. 2. What I saw inside the tank, had me saying ***. There is some kind of thin layer of thick/firm sludge-like stuff coating the bottom of the tank. It's dark in color. I can use a putty knife and scrape it up, but it's too consolidated/congealed to remove with just my hand alone. Here are some photos. Thoughts on what it is or best way to remove it. I'm trying to avoid purchasing a new rear tank. Suggestions please welcomed.







You can see where I scrapped with a putty knife in the photo directly above. I the depression, I found what remained of the rubber foot of the sending unit. It was literally melted into a pile of goo. Advice!?!

That would be old wmo

Thewespaul said:

That would be old wmo

Click to expand...

Thanks Thewespaul. Do I need to worry about it clogging my sending unit or fuel line? Should I clean it out?

I would have it boiled out by a radiator shop or replace it, that gunk is no good

Think you found a good reason the engine is running out of fuel and the fuel filter is plugging up quick.

Drop the tank and take it to a radiator shop to be boiled out. OR, take a sample of what you can scrape up and try disolving it with stoddard solvent in a cup. If the Stoddard solvent works, buy 5 gallons of it and dump it in tank and let it set and work. I would be surprised if it disolves the goop in the bottom of your tank.
Looks like dead motor oil or something.

I would be planning on pulling the front tank for a good look inside that one also. Likely previous owner dumped some crap in it also.