I inherited a 99 6.5 Burb from my dad (original owner). He passed away years ago and it sat mostly unused for the last few years at my mother's place. She gave it to me a few months ago.

With that being the case, it isn't a surprise that I have had a few issues.

First problem - The PMD went bad a week after I started driving it. I bought a new one and a relocation cable. It's now in the front bumper.

Second problem - Engine got sluggish and became impossible to start. Checked the filter, black. Changed that. Noticed when I tried to bleed the air out, that the lift pump wasn't strong.

Third problem - Three days after new filter, the lift pump did indeed quit. Replaced it with a new AC Delco. Very strong, works fine.

Fourth problem, I am down to a quarter tank and I am getting very sluggish response and thick fishbiting past 50mph. Very hard to get it to 60mph.

Obviously the entire fuel system with the exception of the injection pump has been a problem. So now I am wondering if this could be a fuel sock clogging issue. When I bought my new lift pump a week ago, I went ahead and bought a new fuel sender which has a sock with it. I was going to wait until my tank was closer to empty to check the tank, but I'm scared to drive it. I think I will just go ahead and siphon the tank down and drop and clean it.

Bottom line, my question is do you all think this is now a dirty tank / dirty fuel sock issue? It has never been dropped and cleaned.

 

diesel fuel in storage for extended periods will grow algae. If you are getting black filters the only thing i can say is get ready for some work. The tank will have to come out and get cleaned completly. you will also have to purge the lines, pumps, filter housing completly of old fuel and replace all screens and filters. You have to manually remove the algae from the system and then put a additive in to kill what you missed and hope it doesnt come back. Sorry, get your wrenches out.

 

Make sure you got the right fuel sock. If you went to the dealer and ordered the factory sending unit you should be okay.

If they sit up it can cause all sorts of problems. You probably will need to clean the fuel tank and do the stuff the last guy recommended.

Look on the bright side, you won't have an $900 a month payment for a new suburban due every month!

 

Check lines as well depending where you are (salt country???) you could have corrosion in steel and rubber lines sucking air, also gnd for lift pump on frame needs to be spotless.

Good way to check for delivery, get "old school" vac/press test gauge about $20 at most auto part stores, and about 6' or so rubber hose, connect 1 end to the FFM drain valve outlet valve (center front of engine) brass valve chrome tee handle, line out the 90 degree side is the drain side.

connect your line there run into the cab routing so you aren't pinching off hose and "dead head the line" then connect to gauge in cab or taped to windshield so you can see while driving.

open valve start engine check pressure 7-10 psi is healthy lift press on new pump and no clogged sock, rev up/dn a little and watch needle should see movement 1-2 psi,.

Close hood rev should still see same movement if not check for pinched hose between hood and body

Go for test drive , stop to full throttle a few times pressure may drop some with new lift pump maybe 1-2 psi and should come back up to 3-7 fairly quickly, if not and it goes to 0-1 and struggles to return to full pressure you have a starvation issue to your new pump.