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6.2 humvee engine loss of power.

Ttchutch

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Eagle Colorado
I'm new to the forum. I hope I put this in the correct thread.
I've got a 91 Suburban 2500 with a Humvee 6.2 diesel in it. I've put over 70,000 miles on the motor and it has always ran great. It has just recently lost power. I've changed the fuel filter, air filter and used some BG fuel injector cleaner and that didn't help. It seems fine leaving from a dead stop but once the RPMs are over roughly 2000 there's no power. Going up a hill is extremely painful. There's a mountain pass near me that I could do 45-50mph and now it only does 25. I usually get right around 20-21mpg. I just went on a 275 mile trip and went through about 35 gallons of fuel. I had to keep it floored on the interstate almost the entire time. Oil pressure was normal, right about 45psi. Temp was normal. And there was not any smoke coming out of either exhaust pipe. And no fuel leaks. I checked my oil and it was fine also.
I replaced both mufflers 15,000 miles ago, but it sounds like I have holes all throughout my exhaust system when I'm on the interstate but I don't.
I could understand going through a ton of fuel if I was towing a heavy load and clouds of black smoke was pouring out of the exhaust but I wasn't and there was not any smoke.
Any ideas of what it could be?
 

Jozseph

Member
216
0
16
Location
New York
I'm new to the forum. I hope I put this in the correct thread.
I've got a 91 Suburban 2500 with a Humvee 6.2 diesel in it. I've put over 70,000 miles on the motor and it has always ran great. It has just recently lost power. I've changed the fuel filter, air filter and used some BG fuel injector cleaner and that didn't help. It seems fine leaving from a dead stop but once the RPMs are over roughly 2000 there's no power. Going up a hill is extremely painful. There's a mountain pass near me that I could do 45-50mph and now it only does 25. I usually get right around 20-21mpg. I just went on a 275 mile trip and went through about 35 gallons of fuel. I had to keep it floored on the interstate almost the entire time. Oil pressure was normal, right about 45psi. Temp was normal. And there was not any smoke coming out of either exhaust pipe. And no fuel leaks. I checked my oil and it was fine also.
I replaced both mufflers 15,000 miles ago, but it sounds like I have holes all throughout my exhaust system when I'm on the interstate but I don't.
I could understand going through a ton of fuel if I was towing a heavy load and clouds of black smoke was pouring out of the exhaust but I wasn't and there was not any smoke.
Any ideas of what it could be?
FWIW

Possibly Injector Pump issue.
 

MtnSnow

New member
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Location
NSL, UT
I too would say the fuel pump/Injection pump is probably the culprit of the loss of power with the statements of what and how it is acting.
 

rchalmers3

Half a mile from the Broad River
Steel Soldiers Supporter
1,925
30
48
Location
Irmo, South Carolina
Interesting symptoms. Would it be too hard to loosen the exhaust flanges and take it for a short drive?

Im thinking the exhaust may be restricted. That would give you most those symptoms.

Rick
 

Ttchutch

New member
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Eagle Colorado
I have thought of that too. In a couple days I'll pull the exhaust off the manifolds and see if it runs better. I changed the mufflers about 15,000 miles ago but who knows.
 

Skinny

Well-known member
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Location
Portsmouth, NH
What are the odds that both sides fail at the same time?
If the exhaust is restricted causing low airflow, wouldn't it blow black smoke in the upper throttle range?
 

Ttchutch

New member
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Location
Eagle Colorado
Both sides getting clogged at the same time would be near to impossible. I think I'll still pull the pipes off just to check because it's easy....and who knows. Should I upload a video of what it's doing?
 

Skinny

Well-known member
2,130
488
83
Location
Portsmouth, NH
Maybe the fuel return glass ball check valve is plugged?

This all wreaks of fuel delivery issues. Maybe a plugged sock on the tank pickup?
 

Chaski

Active member
684
56
28
Location
Burney/CA
Maybe the fuel return glass ball check valve is plugged?

This all wreaks of fuel delivery issues. Maybe a plugged sock on the tank pickup?
That could be it, also could be something evil like the governor weight retainer ring coming apart if it is still original (no metal "E" tag under one of the three lid screws).
 

Ttchutch

New member
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Location
Eagle Colorado
Changed the fuel filter about a 1000 miles ago and then again over this weekend when the problems became worse. Changing the fuel filter had no effect.
 

Chaski

Active member
684
56
28
Location
Burney/CA
Here is a PDF copy of the DB2 Manual;

View attachment 628525

The governor weight retainer ring is inside the pump.

Regards

That is a good manual, but it is new enough that it does not show the old style urethane governor weight retainer. Here is a picture of the old style retainer with the urethane ring. The ring degrades after a few decades and comes apart.

17932.jpg
 
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