85 Chevy k10 6.2L Diesel Fuel Pump Problems

Hi there, I’m new here, but here goes. As the title suggests, I’m having problems with a 85 Chevy k10 6.2L Diesel, specifically the fuel pump. I’m interested in buying this truck from someone, but not unless I can fix the fuel pump issue and drive it home. He’s put a little work into it and said this about testing the pump and replacing it:

“I did the bucket trick with the old pump and a new one. Both pumps moved fuel on the bench but not when bolted onto the motor. With the motor cranking you can feel the push rod moving. I also primed the pump with an external hand pump with it on the motor, that didn’t help. I have primed the motor by using the return line and compressed air, no luck there either. The new pump is currently on the motor.”

What do you guys think? My thoughts are that if the pump works, but isn’t pumping, then it’s either a blockage or a leak in the fuel line. So I was going to disconnect the fuel line leaving the pump and crank the engine, see if I get air being pushed out (if so, it would seems like a fuel line or connection is leaking air). If it’s not pushing anything, then I would guess blockage in the fuel line. Test this by disconnecting the intake into the fuel pump and try to get fuel to come out either by gravity or an auxiliary fuel pump. If neither of those work out, I was thinking of just bypassing the mechanical pump and putting in an electrical one a la https://www.youtube.com/watch?v=OLDFZit_KzY

What do you guys think?

Tell him to fix it then call you with a price to see if you still want it,

How old is the diesel fuel in the tank?


Volvo- I don’t think he can fix it…

Tester- Fuel is a couple months old (definitely bad and will replace if I can get her started (might try putting the electrical pump into a jerry can at first…) You think the old fuel could be causing blockages?

How much diesel fuel is in the tank?


1/2-3/4 full. I guess I could test the fuel blockage theory by hooking up the fuel pump intake to a jerry can.


I’d check to make sure the fuel pump can pull fuel from the tank.

Because if it can’t, it can’t push fuel to the injectors.


That’s our problem. The fuel pump isn’t pulling fuel from the tank. I’m trying to figure out why

With the electric fuel pump shown in the video wired to the battery with the suction in a can of fuel and discharge to the filter, you would at least know if you had a “runner.”

that’s what I’m thinking. Any advice on how to clear fuel lines if they are the problem?

You’d have to disconnect the fuel line at both ends. Then used compressed air to blow it out, and use the electric pump to flush with mineral spirits, or spray some carb cleaner through it.

Well, I went a checked it out, hooked up an electric pump to the mechanical pump intake and the electrical pump pulled fine… I guess something weird with the mechanical pump but just gonna bypass it I think.

Did you ever figure
this out?

If you want to know if he figured it out, you should click on the name of @Yams‌

Once you do that, you will have the opportunity of sending him a message directly

Personally, I don’t think he’s reading this thread anymore

However, if you send him a message directly, his email will notify him that he received a messge

Ok Im new on site .Thanks

How many miles on the truck/engine? If the compression pressure is not high enough, NOTHING will make it start…