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please help 6.5 surging problem

T

tyler95 k2500

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dryden new york
I have a 95 k2500 6.5 turbo vin f. And since I have owned the truck I have had a skipping/surging problem on heavy acceleration and up hill. And list of mods to the truck are as followed: full four inch exhaust and three inch downpipe. Remote pmd. Cold air intake. Turbo master with illimination belt. And full gauges. What I have replaced is: boost solenoid. Map sensor. Fuel tank sending unit and lines. New lift pump. New ops sensor. New fuel filter. And after replacing fuel system had no serging. For a couple of days and now its back. The truck has 130k and at 110k injection pump was replaced by previous owner and when serging truck does not smoke or lose boost pressure.
 
Mebby air in the fuel system,wont show up on the gauge.
Do the clear IP return tube test
How much vac in the tank?...(leave the fill cap loose)
 
Surging could be from fuel supply, but the PMD is a likely suspect. Have you tried another PMD, is yours remote mounted on a heatsink or still on the IP?

And by surging, how much is the RPMs going up or down?

Other issues could be air like Bison said. Or clogged sock in the tank or clogged last ditch screen under the fuel filter. Need to check fuel pressure at the IP, and for air like Bison mentioned.

Torque converter lockup could also be the issue if its only on acceleration or load. What gearing and tire size do you have?
 
surging problem

Yeah I a brand new sock and sending unit in tank, pmd is brand new and is on heatsink behind grills. Tire size is lt 285/75/16 and not sure bout gears.
 
Sounds like fuel delivery. Blow out the lines. Remove lines to LP and tank cap, blow from line toward tank to clear the sock off. On mine I could only get to 30mph turns out the line from LP to FFM was cloged, so disconnect rubber hose at back of FFM and blow down to LP into a bucket. I was shocked at the amount of crap mine had.

This was a clean bucket to start with!
Junk in fuel line. 1996 black truck 001.jpg
 
still surging

I have a new sending unit with new sock on it and all new lines to lift pump and have new lp and ops as well. Today I took fuel filter housing apart and cleaned very well and put new filter in and started truck and let idle for about 20 min then drove and was better but still there. I opened t handle valve and got solid fuel and top of filter had good pressure
 
That is the fuel filter manager assembly
The hose there is sublect to detoriation and loose hose clamps at the filter and at the steel line from the LP
 
Any codes in the computer?
How does the trans oil look?
How many miles on the injectors?

Borrow or buy a pressure gauge - flow does not mean pressure and your lift pump could be weak or intermittently cutting out. Test pressure at the water drain. Test while the problem is happening would be a great help.
You have drained some fuel to look for water?

X2 on Bison's suggestion of air. I'll expand the how too for you: You need to swap in a clear 1/4" tube from the Injection Pump to the fuel return pipe, top front of engine. look for air bubbles with the engine running and a bright flash light. Shut off engine and look for bubbles in the line floating to the top.

Surging can be engine or transmission.
 
if your truck is an early 95 it may still have fuseable links. If it does remove and replace them with maxi fuses. The fuseable links can go bad over time and wind up working intermitently or they can not pass enough electricity causing things not to work right. I had this issue on my 94.

Also, you have no garuntee the PO put in a good pump, I have had an IP last less than 5000 miles. I put 3 of them in my truck last year. Mine is a 94 vin code F.

If memory serves the newer style trucks also have fusable links in the fuse box, they are a fuse that appears to be made out of stainless or aluminum. They can go bad as well causing issues, try replacing them with fuses.

It would also be a good idea to check your fuses for corrosion and if any of them are the cheap chinese fuses throw them out and get good quality ones. I have seen the metalurgy in chinese fuses so bad they would hardly conduct electricity.
 
still having problems

Where about would these fuseable links be located on the truck exactly and what do they do and look like? The injectors have 130k on them they are stock still
 
Are you using DTech aka Flight System PMD?

Another possibility is the Optical Sensor Filter harness? This usually cause a code.
 
I bought a grey pmd with heat sink. Is says standyne on it. Is optical filter harness a myth or can that cause a problem. Awhile ago I did have codes 34 and 35 and 78 I believe I read them correct but havnt had no check engine since then. I just checked codes again and got 12
 
tyler95 k2500 said:
Where about would these fuseable links be located on the truck exactly and what do they do and look like? The injectors have 130k on them they are stock still
Click to expand...

They will either be white plastic deals moulded around the wire on the fire wall by the ac dryer, or they will be in a black plastic fuse box on the drivers wheel well.
 
Also now that I think about it, how old is the turbo and does the seal leak?

If so it can push oil into your boost sensor shorting it out, I had this issue with mine, took me 6 months to find it. What will happen is when it shorts out the computer shuts down and goes into protection mode. If it only happens for a split second it wont throw a code.
 
Or maybe youre burning oil, like if your CDR is stuck open and turbo is sucking oil out of the valve cover. Try venting the CDR with a hose down below the engine and plug the intake. See if it helps. Or maybe turbo seals causing excess oil. Or take top intake plenum off and have a look see. Or pull off turbo coupler to see if there is a good coating of oil.
 
code 78 waste gate solenoid,you got a TM so the turbo is not the cause.
Might it be a fluttering solenoid causes the engine to go in limpmode for a sec when the ECM detects it?
Only other thing i can think of beside fuel supply surges is a drifting advance piston under heavy acceleration
 
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