View Full Version : 94 6.5 No turbo boost
I picked up a 94 with a broken crank, replaced the crank and got it running, i have two problems. 1 i have abosolutely no boost from the turbo and with my mt 2500 scanner i cant get the timing below 10 degrees. my books show 3.5 degrees, is this correct? i have checked the vacuum system, i have appropriate vacuum at the wastegate, i checked the flapper for the waste gate and it is working, i have held the waste gate closed and reved it up still no boost. the turbo is spinning. no turbo codes are pulling up. any ideas would be appreciated thanks alot rob
Are you trying to get boost in the shop?
Truck has to be driving with engine under load to get boost
its hard to get boost in the shop unless you have a dyno
ron
To get the timing right you will need to do a TDC learn procedure and this requires a scan tool that is setup to work on the OBD1 6.5 engines.
The engine will not boost unless its under load.
With vacuum to the wategate actuator and such things should work fine.
The onkly time it would set a code would be under load anyway.
It takes a fair load to get boost. Drive the rig down the road and when you have the power on it should boost fine. Max with a stock system should be about 7 PSI
NO turbo engine will boost by reving it sitting still. The turbo requires a large volume of hot gas to spin it at the speed needed to compress the volume of air needed to make any pressure.
Best
Robyn
I have tried driving with a load and a shop test either way no turbo. will a snap on mt 2500 with diesel insight to a tdc learn? thanks again rob
The wastegate solenoid (LH VC to the rear) could be toast.
Robyn
Mark Rinker
07-03-2008, 14:11
Call Heath Diesel and buy a Turbo-Master. Lose the solenoid, vaccuum pump, vaccuum tubing, etc from underhood. Lots of information here on TDP about this effective mod.
The solenoid is working otherwise i wouldnt have vacuum at the wastegate? this is the second 6.5 i have and i am working on the third (evil grin). anyway, i have a mechanical on my other 6.5 and as soon as i get this one running correctly i will elimenate the vacuum system. i think i need to keep it for the egr. but i would rather elimenate that also if possible. i still dont know if my snap on 2500 will do tdc learn, my cartridges are bad, so i have to borrow them from a bud. it should work it is snapon and they are awesome (yeah right most of there tools are made in taiwan) anyway any suggestions are looked and thankfull for your time. also what are the possibilities of the wastegate flapper not making a good seal, thinking about re-surfacing the faces on the valve and turbo, any sugestions? thanks again rob
ronniejoe
07-04-2008, 08:23
also what are the possibilities of the wastegate flapper not making a good seal, thinking about re-surfacing the faces on the valve and turbo, any sugestions? thanks again rob
The wastegate pivot shaft wore on mine causing the flapper valve to bind up and not close properly. If you can wiggle the shaft around excessively with the engine off, this could be the problem.
I don't subscribe to the "lose the vacuum system" plan for the stock turbo. I know that the vacuum system gives you more control and higher boost during transitions. The turbomaster is nothing more than an exhaust backpressure regulator and does not control boost directly.
Mark Rinker
07-05-2008, 06:13
...I know that the vacuum system gives you more control and higher boost during transitions. The turbomaster is nothing more than an exhaust backpressure regulator and does not control boost directly...
Tell that to your wife and kids stuck in the back seat, while you are broken down during your next vacation, or better yet, to your best paying customer - when the freight is late because one of the ~5 points of failure on the ill-conceived, over-engineered 6.5L boost control system takes a crap when you need it most...:mad:
ToddMeister
07-05-2008, 12:03
As far as boost control, I prefer the turbomaster setup. Simple. But if you like the factory ECM system, that's your choice, and I don't have a problem with that. I do feel the factory system can provide better cruising fuel economy, but I would rather have the reliability.
Does the truck have a cat converter? If so, it might be plugged up, that will stop boost for sure.
If you tie up the wastegate and force it closed, it should make some boost driving down the road...maybe the turbo is shot? Does the shaft spin free?
Just some ideas to throw out there...
As far as boost control, I prefer the turbomaster setup. Simple. But if you like the factory ECM system, that's your choice, and I don't have a problem with that. I do feel the factory system can provide better cruising fuel economy, but I would rather have the reliability.
Does the truck have a cat converter? If so, it might be plugged up, that will stop boost for sure.
If you tie up the wastegate and force it closed, it should make some boost driving down the road...maybe the turbo is shot? Does the shaft spin free?
Just some ideas to throw out there...
The shaft does spin free, i just scanned it again, i have a code 34 set, injection stepper motor. i still have no boost. does anyone know if a snap on mt 2500 will do a tdc relearn? and if so how.if not what kind of scanner do i need. also the tdc timing is at -0.03 i am not sure what it is supposed to be at. thanks again rob
Do you have any exhaust leaks around manifolds or crossover pipe, I had a leak at the back two cyls on turbo side, fixed it and got 3 more lbs of boost
I had a mt2500 scanner but I never had to do a tdc relearn, recently purchased a Snapon Solious Pro and it does the tdc relearn, apparently Snapon is not going to support the MT2500 much longer or at least thats what my stealer told me:eek:
Good luck
Ron
Well things go worse today my other 6.5 just blew a head gasket, so now both trucks are down. no exhaust leaks, does anyone know of a inexpensive scanner that will a tdc relearn? as i said before i cant get my timing below 10 degrees, is that because i need to do a tdc relearn? (that with it turned to the stops to the passenger side) or is it possible i missed a tooth on the timing gears, i am almost positive i got it lined up right., but mistakes happen. would the timing being way off mess up my boost. thanks for any and all help in anyway. rob
You need to troubleshoot the waste gate system first. It's the most common cause of low boost.
A DP advertiser, GMTD Scan, I think, sells a very reasonable PC program that can do everything you need as far as a scanner goes. Click on "Advertiser's Section" above.
My wastegare system is working properly that was the first thing i checked, thanks for the suggestion
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