My '99 GMC K3500 Crew is suffering from a loss of power @2000rpm. Recent (within last 8-10 months) changes and maintenance includes, PMD relocator kit w/heat sink and #9 resistor(SSDIESEL), new lift pump, wastegate solenoid, OPS, larger downpipe, marine injectors,glow plugs, in-tank strainer and fuel filter strainer. TRUCK ONLY HAS 105K on it, purchased it with 84K on it a year ago.

Original reason for changing glow plugs was hard cold starts, rough idlling, and surging.
Now I'm lacking fuel in the filter with a second NEW LIFT PUMP. Truck only stalled once after a hard acceleration and stop. Could a bad vaccum pump cause this? My ABS light comes on and off sometimes and its hard to press the brake pedal when that occurs.

 

Let me know how you make out on this. it sounds like i am having the same problem. but mine is around 2500 RPMS. I have done everything you have done beside injectors. But i did a few more like clean grounds and mine has a new IP

 

I sure will let you know. Let me ask you this; Where are all the grounds located on the engine? Is there a diagram of this available?

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What causes a lift pump to lose power @2000 rpms? Is there a relay for it? I'm not familiar with the electrical details of all diesels yet, more specifically my own, but I will be by the time I figure my rig's issue out.

 

JASDONDUKES- Check your other posting "6.5T misses"; I posted a lengthy reply about my situation now. It may help you out. End result is a faulty 2 wks OPS I guess. Makes no sense to me.

 

OPS crapping out is a common problem. i changed mine several times when i first got my truck. i got the OPS SAVER along with a PDC/PMD remote kit manufactured by a1customs Custom Vehicles & innovative products! & GM 6.5 diesel products. I had both the next day! super service easy installation just plugged it in and mount on firewall away from engine heat and the problem was fixed instantly. a1customs specializes in the gm 6.5 diesel and the products cover the weak links of the 6.5 and been around a long time. after researching all possible PMD options the pmdcable one mentioned by 2 guys here and i appreciate the info but i didn't like the looks of that and i learned of bad things about failures of that aftermarket dtech pmd so i definitely wanted the improved oem PMD the gray one and $75 for just a pmdcable wire sure seems high.
The OPS SAVER installed with only 1 splice and the a1customs.com products are of much better quality than expected, looks like factory stuff probably better. It may cost more than the cheaper stuff but the quality is there and i want only the best stuff on my trucks the PMDs are expensive and i don't think it's a place to cut corners on cheaper stuff because having to replace it again costs more than getting the good one designed to last in the first place.

 

Well after that last troubleshooting post, I still have the same results; HICCUPS, AND POWER LOSSES @ cruising speed. My fuel bowl is only 1/4 full as opposed to when it use to overfull before I had any issues. Any advice or suggestion would be greatly appreciated.

DONE:
REPLACED "SOCK" in tank
REPLACED FUEL FILTER STRAINER(UNDER FUEL FILTER)
REPLACED OEM injectors with MARINE INJECTORS
REPLACED LIFT PUMP 2Xs.
REPLACED OPS 2Xs
JUMPERED LP and condition still exist.

TO DO:
drop tank again and see if there's any interence with the sock; New sock mounted diffferently on sending unit from OEM piece. Possible problem with placement inside tank.

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What exactly does the OPS saver do? Why do the OPS' fail so frequently?

 

sounds like it could be sucking air from a small leak somewhere.
did you test fuel pressure?