• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Mechanical Pump 95 Run Issues

R

Rodd

Recruit
Messages
1,723
Reaction score
1,018
Location
Antelope, CA
Posting this for a friend. He is working a 95 non-military, non-turbo Hummer with a mechanical IP. The issue is the truck will start and drive for about 10 minutes then it dies. Once it cools off it starts right back up and can drive for about 10 minutes again. It has new fuel filter, IP, fuel tank and lines. The only thing not replaced are the injectors. I'm thinking maybe grounds but not sure how much they come into play with a mechanical pump.
 
I'm no pump expert but hard hot starts can be the signs of a worn head and rotor on an IP. Have him run the truck, and when it dies pour cool water on the IP and see if cooling it down gets it to fire up again. Is the IP original to '95? If so it could just be worn out and time for a rebuild
 
95 civilian hummer is a natural aspiration 6.5 same as the 1992 6.2 diesel pickup, just the 6.5 bore.

It sounds to me like he doesn’t have proper fuel flow/pressure.

The grounds are all in the harness- hummers/hmmwv do not ground through the frame or body.

Any smoke when if is dying? Color & smell if so.

Is it weak on power when it does run?

Air in the return line? Any contamination in the return line?
 
DieselAmateur said:
I'm no pump expert but hard hot starts can be the signs of a worn head and rotor on an IP. Have him run the truck, and when it dies pour cool water on the IP and see if cooling it down gets it to fire up again. Is the IP original to '95? If so it could just be worn out and time for a rebuild
Click to expand...
It has a new IP. Issue happened with the old one as well.
 
Will L. said:
95 civilian hummer is a natural aspiration 6.5 same as the 1992 6.2 diesel pickup, just the 6.5 bore.

It sounds to me like he doesn’t have proper fuel flow/pressure.

The grounds are all in the harness- hummers/hmmwv do not ground through the frame or body.

Any smoke when if is dying? Color & smell if so.

Is it weak on power when it does run?

Air in the return line? Any contamination in the return line?
Click to expand...
What should the fuel pressure be? I has full power or lack thereof since it's turboless for 10 minutes before stalls.
 
3-5 psi MEASURING FROM STEEL T AT THE IP INLET!
Hope I emphasized that enough. Haha
It can be up to 8psi but above 5 it will advance timing.

This is so dang critical. So many times people add a gauge somewhere other than at the ip inlet or use a rubber hose- then chase parts and “issues” around and around.

I believe you have my phone number- give it to him if easier.

He has something else going on imo. Something in tank, hummers have one way check valves that can restrict and fail, bad lift pump for so long he has ruined the ip.

He needs that clear return line on there. Air intrusion will make good fuel pressure into no fuel pressure.

There is a hummer run next week in cali that @Hummer H1 is leading again.- he needs it fixed and join in. You have two “K” trucks - join in also. I’m almost sure I can make it in the wife’s FJ Cruiser.
 
Will L. said:
3-5 psi MEASURING FROM STEEL T AT THE IP INLET!
Hope I emphasized that enough. Haha
It can be up to 8psi but above 5 it will advance timing.

This is so dang critical. So many times people add a gauge somewhere other than at the ip inlet or use a rubber hose- then chase parts and “issues” around and around.

I believe you have my phone number- give it to him if easier.

He has something else going on imo. Something in tank, hummers have one way check valves that can restrict and fail, bad lift pump for so long he has ruined the ip.

He needs that clear return line on there. Air intrusion will make good fuel pressure into no fuel pressure.

There is a hummer run next week in cali that @Hummer H1 is leading again.- he needs it fixed and join in. You have two “K” trucks - join in also. I’m almost sure I can make it in the wife’s FJ Cruiser.
Click to expand...
Thanks Will. I'll let him know. Where is the hummer run?
 
Ya might also watch @Hummer H1 and his usage.
He put a ds4 hummer turbo engine in a hmmwv he bought as a basket case.
The ds4 came off and db2 went on. I walked him through turning up the fuel screw a little, and he did a mechanical boost controller.
He lives in Cali but travels all over in it.
Eric- how many miles on your hmmwv since this?
 
Will L. said:
Ya might also watch @Hummer H1 and his usage.
He put a ds4 hummer turbo engine in a hmmwv he bought as a basket case.
The ds4 came off and db2 went on. I walked him through turning up the fuel screw a little, and he did a mechanical boost controller.
He lives in Cali but travels all over in it.
Eric- how many miles on your hmmwv since this?
Click to expand...
Still watching brother of another mother. I can assess the pros and cons.
 
I think the biggest con would be getting the cruise to work, the biggest pro would be having the ability to pour just about anything diesel wise in the tank from red dyed, bio, to the legendary black gold (used motor oil and gas mix) in the tank and running it without any issues!
 
dbrannon79 said:
What about a failing fuel shutoff solenoid?
Click to expand...

Exactly this!!! There is only one "timer" on a DB2 and that's the cold start advance and high idle switch that's engine temperature controlled. It goes open on a hot engine. 10 min is about right.

I bet they have the cold advance and run solenoid wires reversed. Off the top of my head it's pink wire for run and green for cold start. Easy enough as cold start is also wired into the fast idle.

Put a voltmeter on the IP and make sure it has 12V (or 24V) to stay running... And then ohm check that it hasn't gone "open" when engine quits.

This after that parts cannon.... :facepalm:
 
And if not electrical they should have been feeding it out of a 5 gal diesel can a few parts ago...
 
You must log in or register to reply here.
Back
Top