Hi. I am brand new to this forum and this is my first diesel, so please forgive newbie questions. I have searched online and found mixed results. 3 weeks ago I bought a 1994 C3500 Crew Cab Dually with the 6.5TD with 121,000 miles on it. Driving it home, I noticed the SES light coming on with acceleration over 1,400 - 1,500 RPM, and the light would go out with deceleration. It would stay on steady on the Interstate and would stumble under hard acceleration. Also, maybe 3 or 4 times, with the truck sitting idling either warming up or cooling down, I would hear a bang/pop, and one small puff of grey/back smoke roll out the exhaust. One and ONLY one pop and puff. It has happened 3-4 times in the three weeks I have had it. Ironically at the bank drive in all 3 times, which is about 1/2 mile from work, so I let the truck warm up for a minute or two, drive to the bank and sit in line and that's when it has done it. Not every trip, but each time has been after that scenario. I took it to a local garage and had the oil, filter, tranny fluid, and rear diff fluids changed and the chassis lubed. I told him of the issues and he said he would just plug it in and clear the codes, which he did. I specifically asked him to check the fuel system out. He told me when he was done that it was running lean because of the K&N style intake and wide open 4" exhaust, but he cleared the codes and it ran perfectly. Which was BS. The SES light came on as soon as I drove it out of the parking lot. After some poking around on this forum, I determined the lift pump to be the culprit. I ordered one from SSDiesel, along with a #9 PMD resistor (the PMD by the way is mounted with a "L" bracket to the side of the plastic 6.5 Turbo Power engine cover, which I know is not the preferred location. It had no resistor and is not mounted with a heatsink.) While I was replacing the lift pump and fuel filter yesterday, I left both batteries unplugged for over an our so the system would immediately recognize the new #9 PMD resistor. Truck drives great. No more stumbling, but the SES light still flips on and off under the same conditions as before. Sometimes I can slowly take it to 1,900-2,000RPM before the SES light comes on. Using paper clip and pedal method, I checked codes this morning and got DTC 36 flash around 20 times before I interrupted it and cleared codes. Since the truck would not perform over 70MPH until yesterday, I do not know if this next thing would have happened, but today I took it on the interstate and once I got to 74-75MPH, the SES light went OFF. Came back on under 71MPH. I have not checked the codes tonight since this morning's reset, so I don't know for sure, but I suspect I will see the same thing.

My question is this. The reasons I have found for DTC #36 is IP or PMD potential failure. Is one more likely than the other? Any other possibilities? Is there a way to test either one without buying one and "hoping" I got lucky and chose the right one? Any help would be great!

Thanks,
Ryan

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I just checked the codes this morning and I got 3 about 30 times an 36 about 30 times then interrupted the sequence with the pedal clear...

 

welcome to DB


think code 36 on OBI is injector pump our maybe have bad OPS going which run the LP you need to test

 

Thank you for the reply. What is the best way to test the ops to see if it is GOING bad?