fuel issues

[masonbytrade]

Im new to the site and looking for advice. I've got an '84 M1008 that seems like its had a long life. The issue is that 10-15 minutes after start-up, she'll start to stumble and surge with some whitish smoke while it's happening. It does return to idle and only dies time to time. It drive perfect up until the first sputter. It's got a new tank, clean pick-up, all rusted fuel line replaced, new lift pump, new fuel filter (spin-on), new rubber hose throughout, fresh air filter and the injector pump was rebuild within the last two years. I also cleaned the fuel return check vavle and the glass plunger is clean and moves freely. I'm new to diesel troubleshooting, but from what I've heard doesn't the lighter color smoke result from the motor not being able to burn through the amount of fuel? It also seems that it happens faster if I drive on the highway after initial start-up. Also, what is the best way to bleed the lines thoroughly?

 

[southdave]

I had an 7.3 that did similar thing it turn out it was the injection pump worn out the Hyd. head started to leak . that is my opinion see what turns up here

 

[masonbytrade]

Okay. Well I noticed yesterday that after I got her warmed up I cracked the lines at the injector and when cranked it spit out foam. When cold it's just fluid. So I guess I get to track an air leak.

 

[stampy]

Air was my guess! I would re check all of the connections you recently replaced chances are one fitting is not seated drawing in air (start near the filter at the rubber lines)

 

[masonbytrade]

I checked all the rubber hoses and fittings and everything seemed to be in good shape. I have some spots on the metal lines that are pretty rusted but I don't see any pinholes or fuel residue. Where are the common spots that they leak from? I replaced the fuel filter with a spin on and I know that before I did I was bleeding air from the top of the filter. That means the air is before the filter right?

 

[addinquir]

I had a similar problem. The hard starting got worse over the years. Installed a check valve, blocked diagnostic sensor on fuel filter, installed electric fuel pump, then one day it started surging and a month later it would stall after 5 minutes. That was the last straw.
After extensive investigation, I found out that the air was comiing from inside the fuel tank. Attached is a photo of the hole in the pickup of the "sending unit." The fuel tank was completely encrusted with chunky rust scales. I replaced both sending unit and tank along with the straps.
Also installed extended clear lines so I can see whats up and drop the tank with no worries or struggle of disconnecting before dropping. Problem solved sort of. It starts quicker but I can still feel a struggke of all the cylinders trying to catch on during starting. I know I can do better. I want to turn the key, and have it fire up immediately without hesitation. Thats the goal. I am keeping the electric pump in to work with the mechanical pump. Eventually, I will replace the mechanical pump with an upgraded one and start rebuilding an extra injector pump that a friend gave me. So basically, problem solved, sort of. The other things can wait.
Thats it for now.

 

[addinquir]

Sorry, I forgot to upload the photo before. I hope it is showing up now because I found it difficult to figure out how to associate it with this text.

 

[cucvrus]

Very Interesting. As I always say. If you never had the fuel tank out of your CUCV and want a dependable vehicle. It is important to disassemble the fuel tank, sending unit and replace/remove/clean the fuel sock. That rust came from condensation inside the tank. I can imagine the inside of the tank being full of rust barnacles and other moisture related crap. I have taken everyone of my CUCV's apart and reassemble them over the years and have had little to no issues during the 20 years of ownership. Both my Son's used them will they were in the military hundreds of miles from home. They never had any issues and drove them back and forth for the full term of their enlistment. But good find on that rotted pick up tube. I hope it all worked out for you and didn't let you sitting to far from home. That would be next to impossible to keep primed with 2 fuel pumps. Have a Great Day and thanks for sharing. It may help someone else find and avoid the same issue.

 

[Russm]

my fuel filter with water separator was spitting rust colored goo after 2 years... i can only imagine what the fuel tank looks like.
as soon as im living in a place thats my own I will take your advice ;P

 

[cucvrus]

The BOX with PN The new fuel sock The new on left
the old on right. Now you see. I picked mine up on Amazon about $11.00 delivered. Good Luck. Report back with your results.

 

[cucvrus]

View attachment 747968View attachment 747966View attachment 747967
The BOX with PN The new fuel sock The new on left
the old on right. Now you see.

I picked mine up on Amazon about $11.00 delivered. Good Luck. Report back with your results.