Left Turn Surge
 

First post so bear with me....
I have a 1992 Gmc K2500 6.2 j code, Auto 4l80e. My uncle Factory ordered this truck in 1992 and has never been modified in any way. I now own this vehicle and Love it. Thought I would never be a truck guy but Wow I'm Hooked.
Anyway. I seem to be having some issues mostly when turning left from a Stop or even when turning off a main road without stopping. Coming off the highway and coming to a full stop and waiting for the light to change ,accelerate normal and half way thru the turn the truck goes into supercharger mode. The engine gets very loud and just GOES... If your not ready for it , Its almost dangerous.. After a few seconds or maybe a minutes of driving like this, it calms down again with normal throttle and gets quiet ,well quiet for a diesel anyway. The truck runs well with really no other issues , no lights on ,starts great ,shifts smooth,(except for the occasional hard shift once every 2 or 3 months rectified by a simple engine restart)
Changed the Fuel filter at the back of the motor as that was the obvious, then changed it again 2 month later thinking maybe I got a bad filter. Then I changed the lift pump on the frame rail as I did not know how old it was, but still the occasional surge was present especially going left...? I have also changed the oil pressure sensor a few years back.

This one has me stumped.... Some mechanic friends have suggested a possible Transmission TCC issue. There is no transmission shudder or hard shift or slippage or anything while this is happening.
The gauges all read normal, oil pressure, engine temp, fuel, volts.
It feels like air entering the system or huge fuel being dumped in or timing being advanced or something. I don't know..Help:argh:

Does it go into "supercharger mode" with you foot steady on the throttle? or is it more like turning left activates "supercharger mode" and it runs like a scalded dog for the next few minutes, regard less of throttle position? Not a runaway situation, correct?

With just what you described above, my first thought is a hole in the fuel tank pickup tube, which then starts sucking fuel, no more air. But that may be a misdiagnosis. Do you ever fill the tank up completely? If so, does it run better than when it only has 1/4 tank?

Thanks cviola2005's

The supercharger thing happens after initial acceleration and then it takes off. I have complete throttle control over it and not a runaway situation.

I usually fill the tank full ,usually it's never below 1/2 a tank. I'm currently looking at the tank level thing and seeing if it is fuel level related. Ill let it go down to maybe 1/4 or less.
I'll post if there are any revelations.
Let me know if you think of anything else.
Also I have been reading up on fuel lubricants(additives). I pretty new to diesels and wonder if this is something i should be adding to my fuel?

Yes. With the ULSD, a lubricity additive is a must. If you haven't been adding anything to the fuel, it's a possibility that it is causing a delayed reaction with something like the advance piston inside the injection pump. But left turn only sounds like fuel slosh problem.

Ok thanks.
I'll add some .

Welcome. Hope that solves your problem. If not, we will discuss further.

:tu:
Alright. So as my Co-worker always says, Everyone is always lying to you...trust no one...
On that note we have come to the end of my Left turn surge issue. I did a bunch more reading on the forums about these trucks and came across some interesting facts. "just because your OIL PRESSURE Gauge is working in the truck doesn't mean it's working the lift Pump". Also a side note, just because you ask you mechanic friend to replace the Lift pump, because my hoist was busy, doesn't mean he tested it to see if it's running....grrr
Anyway turns out the Fuel filter at the back of the motor never got enough fuel to fill all the way up and when I turn Left ....LEFT TURN SURGE....(dramatic Music playing in background)..... Apparently these oil pressure switches go bad about as often as fuel filters..LOL..
So it was a little old pressure switch.
Many thanks to the members who read my post to see if they could help.:c:

Interesting..... Glad you figured it out. Thanks for posting the found problem.:tu:

Google OPS relay mod or search the fourms here because I have posted a drawing I made that takes the strain off the OPS and makes it last a lifetime.

Also ONLY AC Delco OPS is acceptable-parts store OPS are underbuilt,they know it and won't change.

Here is the diagram;
Note there should be a fuse matched to the wire size you choose comming from the glow relay,this added circuit gives a prime when the glow plugs operate.

If you want you can also add an underhood bump button or momentary switch between terminals 30 and 87 so when you change fuel filters you can press that switch to run the LP and bleed the filter.