Hi All. New to this site, but you all seem to be very active in helping, so I hope somebody can. Here is what's happening to my 95 GMC 6.5L Turbo Dually:
Started out with an air leak in fuel system (leaking at fuel lines from tank, had that replaced. Still had problems, found bad injector, had replaced. Two day later, had two more injectors go, replaced them. Next day, another injector went, had the rest of the injectors replaced. 3 days later, fuel solenoid in IP started leaking, had IP Replaced. Now truck starts OK with the exception that it "Pops" about three times when it starts and once when it stops. No smoke. Ran ok for a couple of days, but didn't have near the power it had, even when it was sucking air. Now it is a little harder to start, still pops when started or stopped, but when put in gear had no power in reverse, but drive seemed to work ok ( sluggish, but ok), next day, some power in reverse, but none in drive. Seems to be shifting, just no power ( will hardly move ). Getting codes for 34 and 78. Tried to clear codes to see if that would fix temporarily, no such luck (code won't clear). Runs worse now than before. Items replaced in past 2 weeks: Injectors, PMD, IP, OPS, LP, Fuel sending unit, Replaced intake manifold gaskets, MAF. Can't figure this one out, please help! Also a new PMD came with new IP but old one was working ok. This is getting old AND EXPENSIVE !. Truck has 232K has run like a champ up til now.
Thanks for any help or ideas.

 

Howdy laser it sounds like a timing issue with the popping did you do a relearn on the truck? and that MAF is actually a boost sensor put the old one back on as it is more than likely a AC DELCO these are the only parts you should use on any 6.5 BWD is crap right out of the box including the OPS.

 

I agree, sounds like a timing issue with the IP, you cant set it by ear.

 

What do you need to make the ECM "Relearn and how?

 

[QUOTE=RSLaser51;1081754]What do you need to make the ECM "Relearn and how?[/
try looking at this link it may help you.6.5L Diesel Engine Tdc Offset Relearn Procedures - Diesel Place : Chevrolet and GMC Diesel Truck Forums

 

Did you replace the IP or a shop? What brand? Also, what brand of injectors did you use? I'd agree with the guys above, get the timing set correctly. You can search for a how-to on dieselplace. Leroy Diesel sells this software that you can use to set timing and TDCO: Leroy Diesel

DTC 78: Turbo Wastegate Solenoid Fault. This could explain your lack of power. I would check all the vac lines and the WG solenoid. Are you getting any black smoke? Making any boost?

DTC 34: Injection Timing Stepper Motor Fault
For some info on that go here: Code 34 stepper motor.. - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Edit: You should always start with the lowest numerical code first. I would get the timing set correctly, clear codes, and go from there.

Good luck

 

Your '95 doesn't have a MAF sensor, do you mean the sensor on the intake plenum or the one on the driver side firewall? Those are both MAP sensors, the MAP mounted on the firewall is a 1 bar (atmospheric pressure) and the intake mounted MAP is a 2 bar (can measure twice atmospheric pressure). I learned this the hard way because a previous owner had put a 1 BAR MAP on the intake, took me awhile to figure out his mistake. Good info here: GM MAP sensor identification information 1 bar 2 bar 3 bar

 

These are also known to have issues with the plastic spacers between the rocker arms failing and improper rocker action-a valve held partly open can cause a pop.

Also for a 95 ONLY the dealer can do TDCO relearn or someone with an aftermarket laptop scan program called GMTD ScanTech Pro version.

You can buy the licence from leroy diesel or engh motors and download the pro version here:
Engh Motors - GMTDScan Tech
buy or build the cable as exampled here:
OBD Diagnostics, Inc. - OBD2 All-In-One Scan Tool w/ USB
DIY: How To: Scan your OBD1 6.5 for less than $10! - Diesel Place : Chevrolet and GMC Diesel Truck Forums


Every owner of a 94/95 should also own GMTD ScanTech pro.