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Tom
Tom, ASE Certified Technician
Category: Car
Satisfied Customers: 25346
Experience:  ASE Certified Master Technician
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gmc k3500: hi,, i have a 94 GMC K3500 6.5 turbo diesel dually...

Customer Question

hi,, i have a 94 GMC K3500 6.5 turbo diesel dually... it has a problem that i cant find... i just bought it 2 weeks ago and i did alot of work done on my truck it was running just fine till yesterday... while i was driving it yesterday suddenly it just cut the power.. the speedometer shows 50 mph but i feel like i was doing 10 mph... when i lower the gear it feels worse and feels like its goin to shut down.... i really dnt know what could it be.. some people say it could be injector pump some says it could be the turbo but i have no idea about diesel trucks...
Submitted: 1 year ago.
Category: Car
Expert:  Chris (aka-Moose) replied 1 year ago.

Hello, I'm Chris. Thanks for visiting Just Answer.

 




Sorry for the long wait, many have looked at your post and have not felt comfortable helping. This area of concern is not my strongest point but I will try to help as best I can at least with some information. I have access to a lot of repair guides so I should be able to at least do something to aid you if your still needing help and willing to let me try

Customer: replied 1 year ago.
Yes I really need help to get this truck done soon as possible
Expert:  Chris (aka-Moose) replied 1 year ago.

Was the engine running rough misfiring or just running weak?

Was there excessive exhaust smoke?

Can you hear the turbo working or not?

Any warning lights on?

 

Customer: replied 1 year ago.

it was just fine running good.. suddenly it just cut the power... the speedometer shows 50 mph but it feels like im making 10mph... when i hit the gas pedal it stalls ...when i downshift it it stalls more ... it smoke a little bit only when i up shift theres black smoke comes out from the exhaust pipe... its only when i upshift ... after thatt it goes normal with no smoke...

Expert:  Chris (aka-Moose) replied 1 year ago.
Can you hear the turbo working or not?

Any warning lights on?
Customer: replied 1 year ago.

it drives fine first half hr.. after it warm up it starts stalling...even today i replaced the pdm which is injection pump driver module people saying thats a common problem with these truck.. i spent $350 for pdm and it just did the same thing after i drove half hr...


theres no warning lights on but check engine light comes and goes one time before it stalls..

Expert:  Chris (aka-Moose) replied 1 year ago.

I can not figure this one out not being there, I am going to let others try to help.

 

Expert:  Tom replied 1 year ago.
Different expert here did you still need help?
Customer: replied 1 year ago.
Yes I do need help
Expert:  Tom replied 1 year ago.
Ok from your description it sounds like you possibly have an exhaust blockage like a failed catalytic converter was this checked?
Customer: replied 1 year ago.
I didnt check that... But normally first half hr it runs like a champ with no problem. After it warm up it stals.. When I shut it of and wait 15 mins it runs ok then after another half hr later it stall againb
Expert:  Tom replied 1 year ago.
Yes thats when the converter starts to break down.See if you disconnect the exhaust before the converter to see if you still have this issue .If not thats the problem and sounds like whats happening.Also a lot of times you can listen the the converter will rattle.Another common issue is a faulty throttle position sensor.THese need to be checked next for this issue.Remember if you need any further assistance for anything at all it will be for no further charge.Please rate excellent service so I can get credit for my help thanks.Bonuses greatly appreciated.
Tom, ASE Certified Technician
Category: Car
Satisfied Customers: 25346
Experience: ASE Certified Master Technician
Tom and 15 other Car Specialists are ready to help you
Customer: replied 1 year ago.

what if the catalytic convertor is good what would be the next step.? also last nite when in replaced the pdm i test drive it and it was same thing .. i saw the check engine comes and goes only one time then after that i connect my scan tool and it was saying that somthing about the throttle service .the code number is 49 .... also it has another codes that showing all the cylinders balance fault... it just gave these code yesterday ... when i had check engine light is before it was only giving service throttle..

Expert:  Tom replied 1 year ago.
Ok if the converter is Ok then you need to have the throttle position sensor checked next which can give you that code as well as the distributor and ecu. I'm here if you need any further assistance.
Customer: replied 1 year ago.

this is a diesel truck dont have distributor

Expert:  Tom replied 1 year ago.
That's was for a different customer similar problem gasoline vehicle sorry about that. . You would need to check the injectors for clogging or the injector pump.
Customer: replied 1 year ago.

ok i put new injectors and new injector pump from dealer but still car dont run.... i took the water pump and the braket to make sure align marks are correct... so the marks are on the right spots...i thought there might be air in the fuel lines and then i bleed the air out of the fuel lines still dnt run...what else could be it .?????


 


when i crank it it cranks just fine.... i spray starting fluid in side the air filter it starts few second with a wierd noise then when the spray is fnish it cuts...

Expert:  Tom replied 1 year ago.
Have to you checked compression on this engine just to rule it out?
Customer: replied 1 year ago.

how do you check the compression on diesel engines?

Expert:  Tom replied 1 year ago.
This is will show you how.
ClickHere
Customer: replied 1 year ago.

i took my truck to dealer for diagnoise and they said its deffenetly the injection pump i took the new injection pump off it was from dealer and dealer told me that some time new pumps could be defect and they gave me another one i put that on again also i put new filter and new oil presseure switch and new fuel pump relay still dnt work... i dnt know what else could be it... delaer said its injection pump problem but i put 2 times new one it cant be defect eveery time... the aligh marks are good....all the parts are brand neww i checked the fuel coming to injection pump but not to injectors.... please help me to find the problem....

Expert:  Tom replied 1 year ago.
Ok so there is still no fuel coming from the injectors correct?
Customer: replied 1 year ago.

yes

Expert:  Tom replied 1 year ago.
The only other issue I can think of is a faulty Cu or cam sensor not allowing the injectors to operate were these checked?
Customer: replied 1 year ago.

theres no cam sensor on this truck .... also injecters not electronic... its old style..i unplug the injector lines from injectors but no fuel coming when i crank

Expert:  Tom replied 1 year ago.
Ok but you have fuel going to the injectors correct?
Customer: replied 1 year ago.

no theres no fuel goin to injectors thats the problem..

Expert:  Tom replied 1 year ago.
OK are you 100 percent that there is no air in the fuel system ?
Customer: replied 1 year ago.

when i crank it, fuel coming to injection pump i took the hose off the pump and i see its coming...

Expert:  Tom replied 1 year ago.
Ok but if you leave the fuel line off to the injectors and continue to crank the truck until the air is out will it eventually reach the injectors?
Customer: replied 1 year ago.

ok ill try that .. but if still not coming what else could be it>?

Expert:  Tom replied 1 year ago.
It can be a damaged or kinked fuel line or weak pump.
Customer: replied 1 year ago.

the lines are new i replaced them when i changed the injectors.. i put 2 new pumps in it.. it cant be defect everytime

Expert:  Tom replied 1 year ago.
No its not the injector pump what ever the dealer says.Have you replaced the in tank pump also ?
Customer: replied 1 year ago.

yes tank pump is new...its on the frame out side of the tank... i cranked the engine since u told me to but still not starting... i dnt know what else i have to do....

Expert:  Tom replied 1 year ago.
Ok check the pressure from the tank pump and lines also .
Customer: replied 1 year ago.

ok i check the fuel pressure coming from the lift pump to injector pump and the pressure is around 3.75 - almost 4

Customer: replied 1 year ago.

i think the regular presure should be around 4-5......but the lift pump is brand new it works ok ...

Expert:  Tom replied 1 year ago.
Ok thats low it has to be air bound or there is a blockage somewhere causing this or air leak in the fuel system and its not priming.
Customer: replied 1 year ago.
If there's a leak the pressure woul drop. But the pressure is steady.still should enough to deliver the fuel. I'm cranking it since 2 hour sand nothing changed.
Expert:  Tom replied 1 year ago.
Ok its highly doubtful the injector pump is bad .If you can get a reading from the tank pump for me that would help.
Customer: replied 1 year ago.

the probblem looks like somehow the pump dnt get power... what can i do next to give power to the pump...?? i allready replace the crank sensor and the oil pressure sensor... all the parts are new.. so... the thing is it was working before i replace the pump.. the reason i replacing the pump it was stalling and the dealer told me that its the pump so i replace the pump and didnt work... the dealer told me that its a defect pump.. i put the second time and still same... i took it bac to the delaer again and they said the pump dont get power...

Expert:  Tom replied 1 year ago.
Have you check the actual fuse box connections?Also if you hook it up to direct power and ground will the pump work?
Customer: replied 1 year ago.

i ve checked all the fuses before...i ve seen nothing wrong actualy,,, i didnt try to give power to pump but i dnt know if it will work or not because it has pmd on it that actually controls the pump.. and its brand new from dealer too...

Expert:  Tom replied 1 year ago.
I understand .Let me see if I can upload a diagram for you for this entire circuit schematic .
Customer: replied 1 year ago.

oh ok that would be great... i have another think in my mind im not sure if its the problem or not.. do you think it could be a ecm problem ? thats the only thing i didnt replaced..

Expert:  Tom replied 1 year ago.
Absolutely I think I did mention that earlier I would try another one if you have one to swap.
Customer: replied 1 year ago.

it cranks ok all the lights working still you think it could be the computer???

Expert:  Tom replied 1 year ago.
Absolutely it all depends where the computer shorted out internally.
Customer: replied 1 year ago.

ohhh okk... ill try that then.. its around $115. we will see it will work or not .. thanx for your help ... ill get back to you soon...

Expert:  Tom replied 1 year ago.
Anytime thats why Im here.

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