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Wayne
Wayne, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 8422
Experience:  worked on, Gmc, Macks, Freight liner,Mercedes Benz,,Ford, sterling
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I HAVE A 04 7.8L DURAMAX 6500 CHEVY ROLL BACK, LOW POWER

Customer Question

I HAVE A 04 7.8L DURAMAX 6500 CHEVY ROLL BACK, LOW POWER SLIGHT MISS WHEN COLD GOOD POWER AS IT WARMS UP LOOSES POWER. THE TEMP AT THE EXHAUST MANIFOLD 160*-178* ON CYLINDERS 1,2,3,4 THE TEMP IS 128*- 141*ON CYLINDERS 5,6. REPLACE INJECTORS ON CYL 5 & 6. CAN YOU POINT ME IN A DIRECTION.
Submitted: 2 months ago.
Category: Medium and Heavy Trucks
Expert:  Wayne replied 2 months ago.

HI i'm Wayne

I will help you with this

do you have any codes ??

if no , you need to do a compression test on them 2 cylinders

Customer: replied 2 months ago.
no codes .i don't have a compression gauge for a duramax
Expert:  Wayne replied 2 months ago.

HI

That is the only way we are going to tell if you

have issue on the cylinders

the only other thing that would cause this injector harness

I hope this helped you

Hi. If this helped you,

Please remember to rate my answer 3 or more stars.

I do not get paid for question, unless you rate my answer

If more info is needed, use the reply button -

NOT THE POOR/BAD SERVICE

Customer: replied 2 months ago.
I already checked the circuit for injectors i have pulswith at each injector
Customer: replied 2 months ago.
Unfortunately you were unable to give me any info that I already know or have tried ,i was expecting to talk A person who is familiar with a 7.8 L Duramax and has worked on them and their problems
Expert:  Wayne replied 2 months ago.

HI

With all do respect, I have worked on them

I asked you to do a compression test on them 2 cylinders

you checked al l others

you need to do a compression Test, Bot***** *****ne

I can not help you if you do not help me

Customer: replied 1 month ago.
I APOLOGIZE FOR QUESTIONING YOUR EXPERIENCE. I CAN'T FIND ANYONE WHO IS KNOWLEDGEABLE ON THIS 7.8 AND WILLING TO HELP. IN OTHER WORDS NO ONE WANTS TO GET INVOLVED.I PERFORMED A COMPRESSION TEST ON MY 7.8 DURAMAX THE CYLINDERS THAT HAVE A LOWER RUNNING TEMP ON EXHAUST MANIFOLD ARE 5 &6 .THE COMPRESSION ON CYLINDER # 5 IS 460 PSI, CYLINDER #6 IS 460 THE COMPRESSION ON CYLINDER #4 - #1 IS 460 PSI. AS I SAID I REPLACED THE INJECTOR IN #5 THE TEMP WAS 30* LOWER THEN #6 NOW THEY ARE THE SAME TEMP 3. SORRY I HAVEN'T GOT BACK I HAD TO WAIT FOR COMP TESTER TO COME IN. I CAN'T GET ANY LITERATURE ON THIS MOTOR FOR DIAG
Expert:  Wayne replied 1 month ago.

Thank you for that

Ok, good compression

but them 2 cylinders are lacking power

2 things I can think of is the injector harness

or issue with the ECM, may want to have that checked

Wayne

Customer: replied 1 month ago.
I have already checked at each injector with a node light and have a pulse at each injector,a couple thousand miles ago I had it into a dealer for the harness repair I searched the harness for the repair to see if a connection had failed but never found it. Is there a common area of the harness that the failure occur,
Customer: replied 1 month ago.
Is there a Place I can get a schematic of for the truck wire harness . This is my biggest hurdle is info I have rhe Ability to repair I just need access to proper info
Expert:  Wayne replied 1 month ago.

Morning

common issue with the harness is at the connector itself

wire diagram can be ordered from

I am going for eye surgery this morning at 8 Am cst

Customer: replied 1 month ago.
GOD BLESS with your surgery, I will look at harness. the place where to get diagram didn't come through.
Expert:  Wayne replied 1 month ago.

HI

Working with 1 eye , (not easy)

check this place starts on page D 92

I hope this helped

Customer: replied 1 month ago.
let know when your feeling better
Customer: replied 1 month ago.
Hi Wayne I hope your feeling better you didn't finish telling where to find a wire diagram for injector harness if you review your text it was incomplete of the info
Expert:  Wayne replied 1 month ago.

Morning

Yes feel great and I can SEE

did that click here not help you ??

Customer: replied 1 month ago.
What click?
Customer: replied 1 month ago.
I found a old repair where the copper had turned black is the system so sensitive that the wire being black could be cause a partial miss
Customer: replied 1 month ago.
other than the wire being broken is there any other tell tail signs of wire failure or is it best to just ohm the harness from computer to out the cab plug
Expert:  Wayne replied 1 month ago.

Morning

click here

yes ohm out the harness