Ok, I've read myself stupid(or smarter depending on which way you look at it) and still don't have an answer to my problem. I can't get fuel to pull from the tank. Truck is a 1996 12V auto 4x4.

Here's the situation: First, this truck ran perfect until I replaced the unit on top of the fuel tank because it was only picking up the top 6-7 gallons of fuel... no big deal. Put the tank back in and couldn't get the truck to run longer than 2-3 minutes. Long story short, I can only get it running if I fill the fuel filter with fuel and crack the lines to bleed. Starts up rough just like it should then runs for a few minutes until it has used what it can out of the fuel filter. Here's what I've learned from there:

- Can't seem to get the primer button to get fuel up to the engine. Not hearing the squirt no matter how long I push that **** button.
- I checked the lines on the unit in the tank to make sure there is no plugged lines. All is well.
- I put light air pressure on the feed line back at the tank with the fuel filter off just to see what what would happen. It appears the lines are clear. I was able to get some air noise up at the engine.
- When started, I AM getting fuel returning to the tank. Took the return line off just to see and fuel was flowing back to the tank.
- Pushed on the primer button while the truck was running and killed the engine after a hand full of pumps.
- Can ALWAYS get the engine running again with fuel filter filled and cracking injector lines. Always runs for a couple minutes then starves out.
- Checked the line connections on top of the tank and both seem to be sealing fine.

Like I said, this truck ran perfect before I did the fuel tank work. With that problem it would run out of fuel, I could fill it up, prime it, then it would start every time. It wasn't until I had the tank out that this started.

I'm not an expert on these pumps, but it seems the truck wouldn't run if the pump was bad. I'm very mechanical, so talk to me about specifics and details.

IDEAS?

Thank in advanced

 

Did you happen to replace the lines at the module to the steel lines at the frame? I gotta admit, I ran into much the same issue when i did a buddies 99. Being the resourceful single guy doing a project, I made the new lines longer and looped them. ( made it easy to connect then put the tank up in place. )

Well, I played heck finding out what went wrong, I could blow air thru the line. but no fuel...... Finally I got back under there and found out when I put the tank up, the loop had gotten under the tank support, partially blocking the line.

If that isn't it, you said you had a fuel pickup issue, what did you do to correct it?

 

Sounds like your fuel supply line has a leak and is sucking air.
They can suck air without leaking fuel.
Personally I would totally abandon the entire stock supply and return lines and run quality diesel rated hose all the way from the tank to engine.

 

So is it a consensus from everyone that if it's a leaking fuel line, I will NOT necessarily be able to see it?

The situation with the pick up was the metal plate had rusted away allowing the lines to move and pull out of their proper position. So, the feed line was only reaching down part way into the tank. I fab'd up a new plate for the lines to be secured to, made sure everything sealed correctly, then attached. After the problems presented themselves I pulled the bed off and found the feed line wasn't pushed all the way in at the fitting, and the return line had a cut in the rubber hose being used. Fixed these problems with high hopes but it didn't change a thing.

 

Sounds like a leak to me as well, and no, you won't always be able to see it. If it's upstream of the lift pump, it will suck in air, but no fuel will be pushed out. What you need to do is to pressurize the tank- carefully and slightly- with air. If you have a compressor you can wrap a rag around a blowgun and squirt some air into the tank filler tube, or use a shopvac set to blow. Your leak may show up when the system is under pressure. Two key places to inspect are: 1) the rubber return hose that goes behind the engine, down the bell housing to the steel lines, and 2) the electrical connector at the fuel heater on the side of the block. The element can overheat and melt the plastic, causing a large air leak.

 

One question regarding the leak in the fuel line....

IF the leak existed before I pulled the tank, and assuming everything is the same now with the exception of what I repaired, wouldn't this have shown up before? Like I said earlier, this truck NEVER had any issues starting, running, or even re-starting and re-priming after it would run out of fuel due to the pick up problem.

 

The leak may be something new, from when you put the tank back up. Lifting the bed to see is (IMO) the best way to check and/or fix without disturbing the tank. Remove the front most bolts, loosen the remaining back two and tilt it like a dump truck. I just replaced the one on my 97 http://metalshop.nobucks.net/?truck

 

Yeah, that's where I'm at right now... 3 days going. I've already corrected everything at the tank that I found wrong but still can't get this thing to pull fuel.

I did pressurize the tank a bit and found it leaked air around the plastic ring that holds the tank unit in the tank. Is that enough to cause this problem, guys?

 

Thanks everyone for the input. Found my problem. Upon further investigation, I found an abrasion and small hole in the line dipping down into the tank module. DONE.