good injection pump but...

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08-18-2014, 18:41
tomtaylor

good injection pump but...

Was hoping I can get a couple of ideas about my pump. I have what appears to be a new 4879 Humvee pump so I had it tested at a local diesel shop here in Edmonton and the tech said sure operates like a brand new pump, it runs perfect except for one thing, it doesn't produce any pressure down at low starting RPM 75 on the test bench.
He said something in the starting circuit must be sticky so, I took it home to deal with later as he was saying it could be up to $1000 to rebuild it if it needs parts!

I read through the entire Stanadyne rebuild manual and I didn't read about or see anything called or resembling a "starting circuit" within the pump!

So is it possible that something really is just sticky from sitting for so long or is it more likely that it was a poor rebuild and someone did something incorrect and that is why there is no pressure at 75 pump RPM?

I there something I can check or do i need to get it redone?
08-19-2014, 06:52
Kennedy

It is my understanding that the pump that you have has a head/rotor design similar to the DB2 4911. The 4911 had issues with hot starts due to low fuel viscosity and the fuel bypassing/leaking internally.

Odds are this is the case.

My sources tell me that most anything military (hard parts) gets pretty much wiped out in service requiring lots of parts which is why you got the high price quote.
08-19-2014, 21:03
tomtaylor

Quote:

Originally Posted by Kennedy

It is my understanding that the pump that you have has a head/rotor design similar to the DB2 4911. The 4911 had issues with hot starts due to low fuel viscosity and the fuel bypassing/leaking internally.

Odds are this is the case.

My sources tell me that most anything military (hard parts) gets pretty much wiped out in service requiring lots of parts which is why you got the high price quote.

Ok that's good to know, so I will just have to bite the bullet and do it then.

Would you think this would happen with a cold pump on a test bench and then still produce factory spec injection pressure/volume at higher engine operating RPM?