My diesel experience pretty much started with 98.5, but due to being the "diesel guy" in our shop most seem I know them all. I have a 92 that was towed in. Customer said he ran it out of fuel and didn't get the tank switched in time. He was running off an aux tank and had 1/4 left in the main tank, and the truck is presently switched to the main tank. I cranked the truck and it turned over fine, but no start. I unplugged the fuel solenoid on the pump and verified there was voltage with the ign switch on. I then ran a jump wire from the solenoid to bat + and the solenoid didn't click. I thought it was a done deal here, and hit the solenoid a few times with a hammer and punch and it came to life. I then removed the solenoid and put in a clean magnet to see if there was debris from a failing pump. Magnet came out clean. I attempted to pump the lift pump lever manually, but there was little to no resistance on the pump lever and only a small amount of fuel came out of the hole in the pump where the solenoid mounts. I then jumped the starter relay and cranked the engine a little and only a few small blurbs of fuel came out. I then re-installed the solenoid and cranked the engine. Still no start. Cracked 1-2-3 injectors loose and cranked. Finally got fuel and tightened lines and it started. Ok, fine truck needs solenoid.....NOT. Truck sat for maybe an hour. Customer came and picked up deciding to risk driving it as it did start. He left the dealer, drove five miles. Stopped to fill the tank, left the fuel stop and pulled onto the highway and the truck died. Had it towed back and I immediately checked the solenoid and it clicked. Cranked and no start. Bleed injectors again and it started. Let it sit 10 min and cranked. It cranked a long time and finally took off. Obviously I'm getting fuel drain back, or air introduced to the system. Does the manual lift pump have a "check valve" to keep fuel above it? Any suggestions are welcome. The diag in the manuals suck for the older trucks.

 

I have a feeling that the lift pump has a perforated diaphram. I would replace the lift pump as you didn't seem to get alot of fuel out of it when you tested. Inspect the lift pump for signs of fuel leakage from the weep hole. If you remove the front drivers tire, the inner fender is cut away (factory) to view the pump.

After that I would trace the fuel lines to the tanks looking for places for air to get in. An old trick was to pressurize the tanks slighly and then watch for fuel leaks and also adding a soapy sollution to all the connectoins looking for air coming out.


Thats all I got..

J-eh

 

I concur. I would even replcae the rubber hoses as long as you already have the pump off. There are also short rubber hoses connecting the steel lines to the tank. Mine were junk and got replaced.

 

Thanks for the tips. I did get a lift pump locally, but before I opened the box I removed the old one and checked it. It does hold vac and when you actuate the manual lever it does have vac on the inlet side. I found the reason the manual lever didn't have resistance is that it was on the stroke of the cam. I re-installed the old lift pump leaving the fuel inlet line un hooked. I then installed my own fuel supply (3gal jug sitting on the bat). I primed the system with the manual lever and watched it pull the fuel through the clear line I use. I then cranked the engine and after some time it fired up. I ran it for a bit and shut it down. No air ever entered the inlet line. After five minutes or so I attempted to start. Long crank time again and it stumbled and started. I removed the banjo fitting from the lift pump outlet and did a volume test. In 30 sec of cranking time I got 500ml of fuel out. Spec is 750. This is a bit low, but I don't think it's the cause of the problem. I removed the fuel return line (where plastic line connects to go to the tank) and installed a clear line on that fitting and ran it back to my makeshift fuel tank. I started the engine and let it run. I noted lots of bubbles in the return line fuel flow. Thats not a good sign on the newer ones so I'm assuming it's no good in this case. I did notice that after I let it sit a bit and went to restart it fired right up. I have the feeling since the return line is running up higher to my fuel supply can it's not allowing the fuel to run out of the lines. I'm letting it sit overnight and I'll call tech tommorow I guess and fly this info by them. Just thought some may be interested in my "old school" quest.

 

You are bleeding the injectors also right?

 

ANTIQUE!!!: I beg your pardon!!!. Gee wiz its only 14 years old. What would you do if I needed help on my d47u cat(ser# 786 year 1947) .
Clark

 

Can you get more info from the customer on the history of this truck, previous symptoms or did this just start before he had it towed in as a result of his 'low fuel' What did the fuel filter look like? ( wondering if the pump is done ).

 

jbody, sometimes when you leave the manual lever in a certain position on these lift pumps, the pump becomes unable to get fuel up there. Try moving the lever around as a check, but it does sound like the lift pump is a goner.

Good luck with it!.