A new hesitation/bucking thread

[Joebronco]

1984 CJ7
AMC 258 i6 / 4.2l with 4.0 head and EFI
Hesco harness
1995 Cherokee CPU

My CJ has been bucking in all gears. It reacts as if I don't know how to drive a stick. There are two things that make this situation different. One, it only bucks when the truck is warm. Two, if I turn the truck off and on again three times it drives fine for about 3 minutes, then starts acting up again.

Normally this is a fairly simple fuel delivery issue.

These are the new part that I have
(less then 2000 miles)

*plugs-wires
*tps
*fuel filter
*O2 sensor
* fresh tank of gas
*seafoam
*oil change
* plugs
*dizzy cap and rotor

I'm stuck... I really thought it was going to be the TPS. Any insite?


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[Joebronco]

Re: A "new" hesitation/bucking thread

Little more information on the Buck...

Only acts up when I'm accelerating. When I pull my foot off the gas everything is fine. Add gas, its loses power and kicks.

Accelerating harder into it only makes it worse.

It idles just fine, when it's not in gear I can bring the RPM up to 3000 with no issues.


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[hole]

Re: A "new" hesitation/bucking thread

Have you checked the CPS? I'm assuming you have the one on the front of the engine. Have you given the guys at Hesco a shout? Make sure you only use OEM or NDK sensors, for some reason other brands dont always react well. Junk yard build/CPU? My wifes Cherokee (200k on the clock) started randomly stumbling/dying. Took a few hours of checking everything else, but I eventually wiggled the connector at the CPU and got it to stumble with every wiggle. Opened it up and found a solder had broken free from the board. Expensive fix, $380 for CPU and $200 for dealer to flash it

 

[Joebronco]

Re: A "new" hesitation/bucking thread

I do have the the Hesco CPS. Its brand new and installed to spec. Normally if its out or bad jeeps will have a hard start or not start at all.

I'll give the boys at Hesco a ring when I get off work.

FYI - 100 psi fuel pump, only 6 months old.




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[Joebronco]

Wow... after tons of cash and time. Getting stranded twice and lagging home.

I threw the multi meter on the pump and it read a solid 13v. The pump surged and died, no change in volts. I went to o'Riley and picked up a E2000 pump and plugged it in.

First thing I noticed was how much quieter it was. The old one sounded like a sump pump. This was smooth and quiet.

Warmed the bugger up and took it for a spin.

Winner, winner chicken dinner.

It was the ty fuel pump from amazon. Don't buy ty parts!

Back up and rolling again.



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[hole]

Glad she's off the DL

 

[Lumpy Grits]

Take that old pump apart and see if it's gunk'd up or what.
I'd suggest that you carry a spare FP with you....
LG

 

[Joebronco]

Sounded like it threw a bearing... loud and obnoxious. I'll pick up another good one before I fix up this pos.


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[Torxhead]

Joe, just how do you have the pump set up? I believe Hesco has you mount them as close to the gas tank as possible. You should have full battery charge volts while the engine is running. The fuel tank vent system should be operating properly as well. Have you confirmed the correct fuel pump operating pressure as well?

 

[Joebronco]

Passenger side frame Welded mount.

100psi to the rail/pressure regulator.

Vent lines and overflow lines back to the pump work fine.

I run fuel in this order

Tank -
Low pressure fuel filter -
- Pump ----
High pressure filter -
Pressure gauge -
Pressure regulator -
Fuel rail -

Overflow line is directly connected to the fuel rail and back to tank.



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[hole]

100 at the rail is about 60 psi too much, if Im reading your post right.

 

[Joebronco]

100 at the rail is about 60 psi too much, if Im reading your post right.

Pressure regulator drops it down to 40 psi. 100 psi is standard until you hit the reg


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[hole]

Gotcha, figured it was me reading it wrong

 

[Lumpy Grits]

OP-What are you running for a fuel filter, before the pump?
What dia. fuel line?
Do you have a fuel pressure gauge to confirm the 40psi at the rail?
Sounds to me like the injectors are not seeing the minimum psi they need to work.

LG

 

[Joebronco]

OP-What are you running for a fuel filter, before the pump?

What dia. fuel line?

Do you have a fuel pressure gauge to confirm the 40psi at the rail?

Sounds to me like the injectors are not seeing the minimum psi they need to work.



LG

Pressure gauge/regulator about 8" before the rail. 40psi to the injectors.


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[Lumpy Grits]

Is this regulator adjustable?
Is the fuel pump on a dedicated circuit?
LG

 

[Joebronco]

Is this regulator adjustable?

Is the fuel pump on a dedicated circuit?

LG

Yes And Yes.

The issue has been fixed. I've been driving it the last two days with no issues. The pump was shot.




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[Lumpy Grits]

Great news!

LG

 

[Joebronco]

I'll put the F150 back in the garage and the jeep in the sun.




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