My brother-in-law has a 1997 Dodge Cummins that backfires or pops after it sits for a few days and just starting. Any ideas where to start looking? It starts normal whether warmed up or not.
Thanks

 

Sounds like the timing has slipped.

 

How about a leaky fuel return hose?

 

I think it is the overflow valve. Those are the symptoms I had when mine failed.

 

Thanks - Where is the overflow valve and what does it do?

 

The overflow valve is on the front left side of the injection pump (if you are looking from the front of the vehicle). It is designed to put resistance on the fuel system allowing it to build pressure. Try ebay for an adjustable one.

 

 

Thanks again for the information. I'll pass this on to him and he will have a place to start looking.
Jack