I am at a loss for ideas here! The truck starts up and idles perfectly, then about 30 MPH cuts out and falls on its face! It even dies sometimes!....Installed a clear fuel line and cant see any bubbles...dont know where else to look!

 

BTW...1992 5.9 swaped into a 1972 GMC 4x4 automatic

 

Installed new filters all around and new fuel lines....Could this be a fuel issue or electrical? Would a seeping number 6 injector cause this?

 

My first thought would be a bad fuel pump. I'd need to know a little bit more about your setup, but you might want to post this in the 1st gen section, they can help you out.

 

Ok...I will try that section. Sorry, first post on the forum

 

No worries...

 

Check fuel pressure. My 2nd gen did simulair. Changed OFV and ran great...

 

I would check the connection of the power wire to the fuel shut down solenoid.

 

That would be my first guess as well ^^^^^^^^^^^

 

Start with this, get the connection secured first, if it still does it you can remove the plunger and spring to eliminate that from the equation and if it still dies it could be broken plunger return springs in the pump, its been known to happen, I had two different pumps do that.

 

^^ This first.

 

I was going to say to check your fuel filter, but it looks like you already did that. It wouldn't hurt, or cost much to install a new filter anyway. I'd also check your lift pump to make sure it is good. A fuel pressure guage is your friend.

Could this be fuel or electrical?? Yes. About the only electrical issue I could think of is the shut off solonoid. An otherwise healthy 1st gen Cummins will run if it is getting fuel and air.

I don't think a seeping injector will cause more than a miss and or wasted fuel.

A Cummins in a GMC?? Isn't that like a diamond in a goats hinder?? Just kidding, sounds like a cool truck.

 

My guess would be lift pump. When mine started getting weak this started happening.

Stomp

 

AMEN, to checking the power lead to the solenoid, this weekend my 93 would build 5lbs of boost at any speed then fall on its face. The third time it did it, it died and the connector to the solenoid was very loose, mushed it down with some pliers and good to go.

 

Mainly wasted fuel all six of my injecters seep lol doesn't miss...just wastes fuel....