I have a 1995 K1500, 124K miles. Orig, FSD and locatio5-6n. Stock with Banks pyro, boost and trans gauges. K and N Filter. Heads replaced at 115K Currently getting 16Mpg mixed driving.

Throughing DTC 34, consistently. Mostly under no load. under acceleration CEL will go out and return under coast.

Using GMTD Scan Basic.

Confirmed Boost, Turbo RPM, Fuel Deliver Idel 9.5 warmed up.

Desired Injection Timing floats 12.8 13.2 no matter what.

All else seems normal except boost will spike to 13 and drop hard to 5 or 6psi. Rarely can maintain above 6. Also hesitation and 2 occurances of
stall at 60mph and once at 15mph in last 2 weeks.

Looking for advise, seems like IP is unable to determine actual injection timing feedback.

Ok, Desired floats as expected. Measured bottoms out at 11.9 and observed close follow with desired under load/rpm when I took a buddy with me to read the laptop.

Thanks
Tim

Is there good pressure from the lift pump

Let me check to see if my signature is getting up there now

Tim I was looking over other post and ref material You might check out the ref for lift pump/ops switch. http://dieselplace.com/forum/showthread.php?t=53309

I had DTC 34 on my '95 and it was the stepper motor. Stepper motor was jammed. Removed it from the pump (not an easy task) and soaked it with WD40 till it was free. Replaced it and code went away. Should be a thread on here somewhere about it...

Correct - acts like the timing stepper is binding - could be something done during the head replacment procedures - check for the fuel return line or the electrical harness in the way

Fuel flows seem good, idel 9.7 mm cubed up to 60 or so mm cubed at higher rpm's. Could it be pump alignment on reassemble? I thinking if I rotate the pump 3-4mm clockwise it would bring the measured timing down about 7-9 degs close to the 3.5 I've read. Then consider a timing learn?

I would think if I have a binding issue the measured would stay put.
Tim

It may be staying put on occasion - thinking about it won't cut it - some hands-on checking it out will give the answer, then you can move on to the next step in diagnosis and troubleshooting

I'll be hands on this weekend, picking up another 1995 6.5l TD in the morning. 1995 GMC 2500. I'll be playing with the trucks this weekend. Pump rotation will be tested, I'll post results. Also the GMC has no gauges and no power, blowing black on accel. I'll get some readings with GMTD Scan Basic on the reaid home, 80 miles and post my planned troubleshooting outline and results on sunday. Thanks for the replies

Tim

Adjusted timing today by following the pump rotation procedures. Reading measured timing with GMTD Scan Basic. Went from min of 13 deg to 7 rotating the pump to passenger side. Large movement required, theory is the guy who put the engine back togeather was of my one tooth. Guesing about 30 teeth on this beast (360/30=12 deg). Got it close enough to not through codes anymore. Going to wait to check to tooth off theory for when I have to get that far into the engine....

Thanks
Tim