6.5 TD fuel full of air bubbles!

[6 Door King]

I need help from someone that has been where I am currently. I traded into a 1997 crew cab 4x4 with 6.5 Turbo Diesel. According to the previous owner the tank just had trash in it and it needed a new filter or strainer in the tank. So, I disconnected the line upstream of the lift pump and blew out the line to make sure there was nothing in it, hooked it back and it fired up after a snort of starting fluid and drove around the neighborhood. Got it back in the driveway, cut it off and it would not restart without more starting fluid and there was a huge puddle of fuel under the truck and across the driveway going in and out, and probably down the street as well. So, started looking around under the truck and the drivers frame rail is soaked in fuel, and the back of the block and transmission also. SO then I pulled the fuel filter out and replaced it, still leaked once I got it restarted, so I remembered reading about cracked filter housings and pulled off the whole assembly. No sign of cracks or leaks, but there was rust in the bottom of the housing so I cleaned it out, blew out the ports and rinsed everything out. Put everything back together, poured some diesel in the housing, no drips, put the filter in, no leaks and it fired and ran for maybe a minute and cut off dead. No sputtering, no knocks or bad behavior. Restarted with ether but only for 20-30 seconds at a time. Suspecting the tank filter/sock I dropped the tank and pulled the sending unit and sock out. Everything looked good but while in there I replaced the sock anyways. Put everything back in place and still no dice. I bled out the lines the best I could by cycling the key on and off and opening the vent cap on top of the fuel filter housing to release any air. I have not yet been able to get the system completely clear of air. No matter how many times I cycle the key and bleed the cap there is always air. Truck will fire and run about every 5th time I attempt to start it and even resorted to replacing the lift pump and still no dice. I know that was not the smartest order to check things but was really hoping it was something easy first, then resorted to cheapest first for replacing parts and now I am just stuck. I don't want to replace the injector pump just to rule it out, expensive way to go about troubleshooting this b!tch. Any help would be greatly appreciated, thanks in advance.

[joe231]

Sounds like the lift pump may be sucking air. I'd start by inspecting the fuel line from the tank to the pump.

[6 Door King]

Thanks for the suggestion. Are there o rings on the lines? If that is the case it might be the source of my air, as mine does not have an o ring on either side of the lift pump. Can anyone confirm whether my hard line fittings should have an o ring on them?

[special-K]

Sounds like the fuel lines are rusted out. Stop using starter fluid. It's not starting because it's sucking air. Bleed the air out, then it will start

[6 Door King]

Assuming I find the leak or multiple leaks is my cycling method of allowing the lift pump to run and then opening the bleeder on top of the fuel filter housing to bleed the air the best way to go about it? Is drawing air through the new lift pump going to burn it up and do I need to prime the line(s) somehow? Thanks for the help guys, will be crawling around in the snow to check things out tomorrow.

[joe231]

I don't believe o rings are needed on the fuel lines, but I'm not sure.
And I second the "don't use starting fluid" mantra.
You could prime the fuel filter by pouring diesel in it, but it shouldn't take much cranking to get fuel to the injection pump.
Are you familiar with the PMD problems on these trucks? If the PMD is bad it won't send fuel to the injectors. If it hasn't been done yet you should relocate the PMD. You can google it.

[special-K]

The lift pump can handle the air as long as there's fuel,too. That method is the best way to bleed since it doesn't draw on the battery nearly as much as cranking. But, the pump only runs with oil pressure...or when engine is running. Do you have a jumper wire to the pump from battery or is the oil pressure switch bypassed?
You do know the lift pump is fed power through the oil pressure switch on the rear of the engine, right? If that fails you get no power to the lift pump. I guess you are hearing the pump run, so that's not the problem here, but something to check before replacing the pump when not hearing it run. I was having fuel delivery problems last winter and said screw it and by-passed the oil pressure switch all together. My problem ended up being the replacement float/pickup I put in "while I was at it" a year before when I dropped the tank to check for rust and run new lines. The truck would start right up, then starve out randomly. Tried everything under the sun and nothing worked. Trying to get it home I could blow (at lift pump) into the line back to the tank and it started. The tank looked like new inside and fuel looked great. I cut that sock off and opened up. It looked fine up to the light. Blew 120 psi on it and saw no difference where it blew through, no color change or anything. BUT...I realized a lot of air was coming back on the hand holding the blow tip and the hand on the other side of the screen wasn't feeling all that air. So it was a microscopic issue no eye could see. Was it micro organisms in the fuel or was that Chinese screening just made a bit to tight to allow proper microbe passage? I got Advance to warrant the part and it was fine after that. So, one of those no explanation things. All I know is it worked after that. This was when we were getting these 'Polar Vortexs' last year. But the fuel was certainly treated

[6 Door King]

Originally Posted by special-K

I was having fuel delivery problems last winter and said screw it and by-passed the oil pressure switch all together. My problem ended up being the replacement float/pickup I put in "while I was at it" a year before when I dropped the tank to check for rust and run new lines. The truck would start right up, then starve out randomly. Tried everything under the sun and nothing worked. Trying to get it home I could blow (at lift pump) into the line back to the tank and it started. The tank looked like new inside and fuel looked great. I cut that sock off and opened up. It looked fine up to the light. Blew 120 psi on it and saw no difference where it blew through, no color change or anything. BUT...I realized a lot of air was coming back on the hand holding the blow tip and the hand on the other side of the screen wasn't feeling all that air. So it was a microscopic issue no eye could see. Was it micro organisms in the fuel or was that Chinese screening just made a bit to tight to allow proper microbe passage? I got Advance to warrant the part and it was fine after that. So, one of those no explanation things. All I know is it worked after that. This was when we were getting these 'Polar Vortexs' last year. But the fuel was certainly treated

I seem to remember reading about your woes in an effort to correct my own.

My lift pump was/is running and cycles in about 15 second runs with the key in the on position. When I open the bleed on the fuel filter cap it runs maybe 30 seconds or until the fuel level reaches the sensor I am assuming. The reason I replaced it was because I thought it was making too much noise, it seemed very loud and almost had a ticking to it, so just swapped it out as relatively cheap insurance against killing my injector pump.

Is the pressure switch you mentioned for fuel pressure or oil pressure, the one that controls the lift pump power source?

According to the previous owner the PMD has been replaced also, although I have no paperwork to verify this claim.

I suspect it is something very simple that I have overlooked because when I initially got it running after sitting for a year plus, it ran like a champ, and has gone down hill since. I did look at the feed and return lines when I pulled the tank and didn't see any corrosion or damage but I guess I could have missed it.

Thank you guys again for your help.

[mrolds88]

Pressure switch is pressurized by engine oil and turns on the circuit for the pump. I just went through almost the exact same thing. 96 burb the fuel line between the pump and tank was weeping and sucking air. Replaced the line (Saturday) and runs like an almost new one.