Lunging

[CUCVmike]

I have a rebuilt fuel pump and it's supposed to be turned up 10% over factory spacification for my banks turbo. Now I've got my NV4500 installed and when you let off the accelerator without pressing the clutch in to slow down you get whip lash. I'm assuming it's the mechanical fuel pump causing this issue. What should I do? I can't send the fuel pump back its been installed about a year now. I heard the motor rev or fluctuate from what I assumed was the fuel pump before but with the TH400 I didn't feel it now I get jared from it with the manual.

 

[gimpyrobb]

I don't see how the fuel pump could cause that. Does the motor die?

 

[Jeepsinker]

Check your motor and transmission mounts. Use a pry bar and try to lift up on them.

 

[cpf240]

Fuel pump? Do you mean lift pump or injection pump?

 

[Jeepsinker]

A fuel supply issue would buck and snort on acceleration, not deceleration. It sounds like you have a bad mount or mounts somewhere or maybe a bad U-joint, could be some major axle wrap or other axle movement causing it too.

 

[Drock]

Just throwing this out there, (I'm NO diesel expert) , But sense going from auto to stick. Shouldn't there be some vacuum lines that needed to be plugged? Does the vacuum pump have ah line going to the injection pump? For that matter what does the vacuum pump feed anyway? Besides the auto trans.

 

[cpf240]

... For that matter what does the vacuum pump feed anyway? Besides the auto trans.

Nothing...

 

[CUCVmike]

The injection pump idols fast 80% of the time and idols low the rest of the time. When you push the clutch in the motor is still reved up. When you let off the accelerator it lunges.
When I unplug the cold advance on the side of the pump it barley starts and has a bad miss and lots of black smoke. When it warms up it idols to low, even adjusting the idol screw in all the way it idols low and smoke more than normal. It does shift and act normal with no acceleration while shifting.
On the cold advance I have the line that used to go to the transmission plugged but it's still hooked to the oil pump.
I can't get a happy balance. By sure if I should hook up the cold advance and high idol to switches but not sure how to get the rough idol and excessve smoke to stop. It drive and shifts properly but am afraid I'm going to tear it up starting it that way.
hopefully I've shared enough of the right information for a diagnosis now. Thanks for the input to my rough idol.

 

[cpf240]

 

[eme411]

is it just me or does this belong in the CUCV mod section , you messed with it now you need to figure out what you did , we can only guess,

 

[Stonepicker1]

I have a rebuilt fuel pump and it's supposed to be turned up 10% over factory spacification for my banks turbo.

Turn down the fuel and see if it solves the problem. You might be getting to much fuel. Its a starting place.

 

[Barrman]

I don't have a turbo, but I do have a 6.2 hooked to a NV4500. No such problems as you report. I agree with the several post above suggesting motor mounts, trans mount, tcase mount, rear axle locator pins, etc be checked.

 

[nyoffroad]

After checking all the mounts (mentioned above) I'd check the IP timing, You mentioned smoke and rough idle and the lunging, your timing may be to far advanced.