Hi yall im new here and I look forward to the give and take of this site. Im having an issue with my 1995 gmc 3500 6.5. Its got a home made TM that dumps just about at 12lbs. It seems to run good until about 1/3 throttle after that it doesnt give it more go it doesnt bog down it just does nothing. If anyone could help it would be great. Im new to diesels and spent 3 years cutting the rust from this thing. I welded everything up slapped new paint on it and it looks like new underneath now. I lifted it 6inchs made a front bumper. I also made a stack out of a couple old fire extiguishers. I dont have alot of money so i make what i need/want. I have a small shop so if anyone local needs something fabricated or welded let me know. Im in southeast PA.

 

Do you get any trouble codes?
What RPM does it stop performing at?
These things are run out performance wise beyond 2400 even though they contiue to rev the turbo can't keep up.

Boost is also load dependant so unless you are accellerating hard,towing or hill climbinmg you won't get much boost.

 

Its not an rpm its the response from the pedal to make more power after about 1/3 of the way depressed the pedal makes no difference if i floor it or not and seems to work normal the first 1/3 meaning it gets more power the farther i move it until that point.

 

Better make sure that the lift pump is working and that you have a clean fuel filter.

Open the water in fuel drain or Tee-valve mounted to the water crossover with the engine running and safely parked.

If the engine stalls the LP is not working,if it keeps running while fuel drains from the line then the LP is good.

If no operating LP then the oil pressure switch is a common failure point since it powers the LP when the engine is running-AC Delco ONLY for replacement.
Google "OPS relay mod" for long term reliability and install it.

Also check that there is not excess vacuum from the fuel tank when you remove the filler cap-a plugged vent in the cap can help starve the engine of fuel.

Another area of concern would be a plugged soot trap/cat converter but with decent boost I doubt that is the trouble?

Do the "paper clip code check" for trouble codes.

 

Thanks guys will look into your suggestions. My pipe comes from the turbo to my stack of which the first 24inchs is a single chamber muffler of 3inchs in 3inchs out thats the only restriction on that end. Its gotta fuel i would think. I dont even know what the gas pedal does. There isnt butterflys that it opens is it all electronic? Iv been blessed to understand anything mechanical so im sure in a short time with your guys help ill have a good understanding of these engines.

 

Yes the throttle and IP are both electronic"drive by wire" systems.

Interstingly I don't know of any diesel that has butterflies besides a ford dexta tractor since fuel is the control and not air in almost all cases,but there are some european engines that do use a combination of airflow and butterflies to control fuel output somewhat like metering rods on a quadrajet.

 

so i put the hose from the drain in a bottle and opened it while i cranked the motor and about 4 ounces of water came out. Then i closed it and started it. I opened it back up while running and it didnt affect it but nothing is coming out of the hose. Since the truck sat along time and was run out of fuel i assume the filter should be changed thats next but need to get cash first.

 

The drain hose is unfiltered fuel.

Fuel/water should have still come out when the engine ran,perhaps the hose is plugged?

 

as long as its cranking fuel/water comes out the second it starts all fluids stop. i can shut it off start it backup and while cranking fluids flow soon as it starts the drain stops. same thing no matter how many times so i dont think a blockage there is a problem got any ideas. im going out to change the fuel filter now.

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well changed the filter unscrewed the black ring pulled it out put the new one in lined up the slots pushed it down tightened ring. and now the truck wont start. I loosened the black ****/screw on the top of the filter and cranked it until fuel came out tightened it and truck still wont start.

 

You now have 2 problems.

#1 when you tried to start withou bleeding the new filter first you got air in the high pressure side of the injection system-easy fix.

#2 your oil pressure switch is bad-it supplies power to the electric lift pump when the ngine runs to send fuel to the injection pump.

Replace the OPS with AC Delco ONLY!
And do the OPS relay mod for long term reliability.

Once the OPS is replaced and mod is hopefully done you can bleed the air out.

Crack a fuel line loose at an easy to get to injector and crank the engine over for no more than 15 seconds at a time without a 1 minute starter cooldown period between cranking sessions.

By the 3rd session it should be running and once running carefully tighten the injector line.