Misbehaving diesel

[thedrip]

I have a 1985 E350 with a 6.9L. I'm posting here, because the 6.9 uses the same Injection Pump as the 6.2L (DB2), and diagnostics wise, they're virtually identical. Diagnose as you would for a 6.2, and it'll be close enough =) The van is new to me (less than 1 month ownership). I have fixed a number of minor issues with the van and a couple scary ones. The current issue I'm working on has been getting progressively worse as I drive the van more and more.

Hard cold starts. Starts on the first try, runs for 1/2 second, dies. takes 30+ seconds of cranking to fire again. Glowplugs all work, and I have a manual switch to burn them. It seems to be having issues with losing prime.

I fixed a couple of minor fuel leaks in the return lines, minor drips. No change in behavior.

The van has always 'surged' a little bit while driving, sometimes having lots of power, sometimes having very little power, as if the fuel supply was hit and miss.

Starting this morning, any time you go full throttle for more than 2 seconds, the van takes off running great, then the engine quits. 10 seconds of cranking, and it fires again.

All of these symptoms combined, I am now theorizing that the lift pump is Either working very poorly, or not working at all. This would explain the long time to prime in the morning, the loss of power while driving, and the stalling after full throttle.

Any other suggestions? I have not found any fuel leaks on the supply side.

 

[Russell]

My first thought was a clogged fuel system, be it a filter, or the sock in your fuel tank. My old K25 did that once when my in-tank fuel pump sucked up a bunch of crap off the bottom of my fuel tank and caused very similar issues to what you've described here. It eventually sucked up enough that it stalled the truck right out, and the injection pump created a vaccum on the fuel system.

If the filtration system is alright, and everything flows freely, I'd be suspecting a combination of a weak / non-op lift pump with a fuel leak somewhere that is allowing air into the fuel lines as the truck sits.

 

[smalltruckbigcid]

I think Russell has you pointed in the right direction

 

[thedrip]

I double checked with the previous owner. I had asked him specifically about the fuel filter, and he said he had changed it about a month ago... I smartened up and asked him where it was. Under the engine he said. New filter fixed the WOT problem, and all the driveability issues, we'll see how the cold start is in the morning.

 

[thedrip]

Got up this morning, started, but with the immediate start, die, crank 30 seconds, then start problem again. Definitely a fuel leak somewhere. Got crawling around underneath, identified 8 leaks. 7 were trans fluid lines, 1 was the fuel supply line from the tank to lift pump. That was definitely the largest fuel leak on the truck, now its fixed, we'll see how it starts tomorrow morning now. Maybe I can drive it to work, and have heat! .... if not, well, I'll drive the Trazer to work, with no heat and a broken window in sub freezing temps.

 

[Russell]

Betcha she'll fire right up! It takes a bit of cranking to get the IP bled out again after running it dry. If the fuel system remains full overnight it should fire up immediately, and remain running

 

[thedrip]

I've fixed 3 more noticeable leaks. Today I replaced about half of the soft lines in the fuel supply system. They were all getting spongy from having the outside covered in fuel/oil for so long. Also replaced the worst tranny cooler line. We'll see if it starts in the morning. Theres still a leak coming from somewhere, but its not even 10% of how bad it was before. At this point I'm pretty sure the fuel pump itself is leaking diesel. New hose, new hose clamps, cleaned & retightened hardline fitting, and the fuel STILL shows up dripping from the bottom of the fuel supply line.