Hello Diesel Bombers.

My first post comes to you abouta problem (regretably).

Just bought a rust free 1999 Chevy K3500 6.5TD with 122K on it.

Relocated Standadyne Heat Synk PMD
New Fuel Filter
New Lift Pump

The previous owner mentioned at times (usually when just cruising between 35-65MPH) and not when under load or "hammering" it, and not when idling, that the truck seems to have a wavey throttle, almost like a AC compressor engaging in a smaller car, or a transmission guessing weither to go into OD or not.

The tach seems to stay consistant, and then you'll feel a very minor loss of acceleration and then a very minor acceleration......it seems to do this and you barely loose 2-3 MPH however it is just somewhat aggrivating.

Anyone have any ideas?

 

welcome to DB

are you getting codes check all the grounds ad clean they play big part with these trucks

are at the back of motor right side on intake 2 or 3 wires there for the computer and also there are 3 ground strap right back there under the A/C Dryer one goes to the fire wall to back of the head and the other goes from fire wall to the frame make sure they good and then make sure your PMD thats on the heat sink is grounded to the top of the injector pump and then there one more at right battery on the fender

 

Thankfully no codes.....the PMD was relocated to the top of the intake, attached to the drivers side most 2 bolts where the pressure-air comes into engine, I have been told to buy the extension harness and get it the hell off the engine. I'll check all the grounds and clean the heck out of it.

THANKS

 

Yes you want to get that out from under ASP if it ant to late already that can also be your problem remember after you more to the front bumper you still want it grounded to top of the IP you can make your own harness if good at soldering

Oh check the wiring and plugs at trans make sure they are clean from dirty and the plug at fuel pedal all so

 

Hopefully with a quick cleaning of the electrical and a re-re-location of the PMD my only issues will be the damn steering......I have 2" of play in the wheel and the truck has a mind of its own going down the road. I checked front end.......a hair of play in Idler Arm and only slop is in the box......I'm debating getting her aligned first before I throw some coin into an Autozone box, idler arm, and bracket.

---AutoMerged DoublePost---

Well I checked all the connections and grounds, they all look to be just fine.

It is tough to quite pinpoint when and how the diesel feels weird,but like I said, it's only when you're cruising and just going along your merry way between 35-55 or so MPH.

It almost feels like the transmission is going from OD to 3rd, but at an extremely fast rate, yet the engine RPM remains unchanged.......

If you didnt know better its as if there is a little gremlin just applying the E-Brake ever so slightly and about 5 times a second

 

Well the PMD is know to do that. when it does that are the other gauges reading right is there any smoke coming from tail pipe

---AutoMerged DoublePost---

I know you said put new LP in are sure it working

 

Yeah the surging sounds fuel related. You're describing the symptoms of running out of fuel. How's the truck idle?

Sent from my Droid
Incredible 2 by HTC via Tapatalk.

 

ok I've been able to narrow down these symptoms for you all.

Scenario 1: Normal Driving.

Acceleration steady up to about 40-50MPH. No kicking, no nothing, runs beautiful. Get into OD, engine RPM about 1450-1600. Truck will drive steady at this speed for about 3-7 seconds, then you start to feel the loss of power and the subtle bucking of the truck. If the accelerator is depressed, you notice a 1-2 second pause, then the truck jumps to life and will accelerate flawlessly for as long as you want it to.

Scenario 2: 3rd vs.OD test.

Driving 40MPH, 1500RPM.

Shift truck manually into 3rd. Engine RPM 2000. Truck will hum like it is suppossed to and have zero issue for again, 3-7 seconds. Then you feel a drastic loss of power, and if the accelerator is left untouched, truck will drop 300-500RPM and not run quite right. If the accelerator is depressed once again, there is a slight delay, and then the truck jumps to life and truck will accelerate up to 2500+ RPM no problem.

I know it seems weird.....it only seems to happen UNDER 2000RPM and only when the truck either just shifted gears, and is in the lower RPM range for that gear....and there is a few second delay between the shift/coasting and the problem.



---AutoMerged DoublePost---

and i checked the lift pump.....you can hear it click on and run when truck is glowed, and when its idling you can feel it running.

Truck idles great (no matter how long you let it) and starts without smoke.....also when the truck hiccups, there is no smoke out tailpipe.....hell you stuff it and it barely smokes!

 

Just cause you hear the LP running does not mean it working i have seen many Lp go out and sound like it running

need to put fuel pressure gauge on it take for ride see what it runs at

 

wrong thread