Loss of Power

[Shawnethan]

All Just had an issue with my 6.5 1996 GMC 1500. I lose power after 1/4 throddle it starts to hesitate and cough. I replaced the fuel filter and noticed no excesive smoke, just at anything above 1600 RPM it begins to load up and loses power. When heading up hills it has no power - any help?

[grancito]

Check the fuel pressure, may be bad lift pump, or restriction in the fuel tank sock or fuel line.

[Shawnethan]

OK dropped the tank and cleaned the inside (what I could reach), cleaned the sock, replaced the lift pump and blew out the lines from the tank through the fuel filter, bled the air out and started it up. All systems seemed very clean for the age and mileage. Drove about 100 miles and the problem came back but now intermittantly. I will lose power and hesitate and cought at about 1500RPM - I let off the accellerator and it seems to correct after not pushing it above 1500RPM for a couple of minutes - any other help or suggestions would be greatly appreciated.

[Garth J]

check the fuel filter ..you could have sturred up some debris...G

[Shawnethan]

Changed the fuel filter and was giving it a test drive, it stalled at a stop sign and when I started the truck it dumped two codes
P0251 Injection pump metering control A
P0370 Timing refernce High res signal A malfunction

BTW - I use 1 qt. of two stroke oil in the fuel every fill up.

Any ideas where to look next - thanks for the help!

[Buddy]

Have you made sure the LP is actually running while the engine is?

It gets power from the PCM through the lift pump relay, and if that fails it gets power from the OPS. You have a pressure guage you could attach to the end of the drain line T valve next to the thermostat housing?

[Buddy]

Oh there youre having Optical Sensor issues. What size fuel tank do you have? If its 34 gallon you really only need a half quart and I'd ude TC-W3 2-stroke oil.

Where is your PMD located? Can you fill out your signature, tell us all the mods you have done.

Sounds like maybe your turbo isnt working, do you hear it spool up? Do you have a boost guage?

[Shawnethan]

I have a 24 gallon tank, I will reduce the amount of 2 stroke oil. The PMD is stock and mounted to the pump (stock location). The problem is very intermittent it runs fine about 95% of the time. I do not have a boost gauge I will chedk the turbo to see if it is cutting out - is that possible that it would just stop 5% of the time or are you thinking PMD and what exactly is the function of the PMD?
Thanks for all the help!!!!!!

[Buddy]

The PMD recieves a fuel inject signal from the PCM, then it amplifies it and makes it an alternating current, sending it to the fuel solenoid so that it switches fuel to the cylinders between 1 and 2 milliseconds at a time depending on the resistor value inside the connector. So can it be the PMD, yes, its very important for fuel delivery. It gets itself hot and being on the pump is the hottest place as the IP itself is a heat maker. the IP will commonly run 150*F itself and add two 500watt transistors in the PMD and you are going to hit the operating limits of 180*F of the Stanadyne PMD. You need a remote mount system, and the new PMD type rated to 257*F. So thats a must do investment either way.

I would still put a pressure guage on the fuel drain line and monitor the lift pump pressure while driving a few times.

[Buddy]

I relooked at the 2-stroke and it should be half a quart or a little more for 26 gallons. On a 34 gallon tank 3/4 or a little less is good.

[Shawnethan]

Ordered the pressure gauge from Walt, in the meantime the truck died on the expressway. Pump is running and fuel will come out of the top of the fuel filter showing pressure. I have learned a ton about PMD's so I have one on order to be mounted on the bumper. I have had the stalling issue as many have outlined with bad PMD's also it did not drop any codes when it died. Any additional thoughts, am I on the right track?

[Shawnethan]

New PMD and away we go, just took a 570 mile trip with no problems. Used the hacksaw blade to remove the wiring harness and the bent wire to fish it out. Installed the PMD behind the bumper - thanks to all for the tips. This site has saved me so much frustration, time and money!

[Buddy]

Good deal, nice having a running truck. What kind of PMD did you get?

[Shawnethan]

There was a Stanadyne on the pump (which went bad) so I went with a Dtech.