[Hillbillydeluxe]

I am a newb member looking for some additional information about my "hard start issue". I, first of all have a 2000 Classic and a 2000 Sport both Autos with 4.0Ls, the Classic runs like a top and is my DD the Sport I just picked up on the cheap because it has a hard start/stall issue.

The issue is as follows (yes i have used the search function):
The Sport will turn over, sputter, backfire out the air intake. When it does finally start it revs high then drops down to a normal idle speed but still stutters sometimes. If i give it gas it will rev up no problem, and as soon as i let off the gas it instantly stalls, even if i get back on the gas once it starts to stall it still goes.

I have read through numerous posts describing hard starts etc and have replaced the CPS on the Sport. I also switched TPS, and IAC from my fully functional Classic to the Disfunctional Sport and found no differences in the performance of either. I also did a tune up on the Sport with new plugs, i even swapped coil rails from the Sport to the Classic and vis-a-versa with no effect on the performance of either Jeep. I have fuel at the fuel rail, and spark. I am beging to think this may be a fuel related problem as i have spark but i keep getting ODBII code P0351, P0352 and P0353. I have done a fuel pressure test at running conditions with both, and both the Sport and Classic have around 47 psi when idleing. If i shut them down, and let them sit for a half hour my Classic drops to about 35, and the Sport drops to around 15, is this an indicator that the fuel pump is gone? Or that i need a really big hammer?

If anyone has any ideas i would great appriciate hearing them!

Thanks a ton in advance!

TJHillbilly

[CJ7-Tim]

The low fuel pressure points to a failed check valve on the fuel pump. The fuel pressure drops, allowing vapor lock, and causing hard starts and poor idle for up to 30 seconds. Turn the key to on and wait for the fuel pump to prime, turn the key off. Turn the key to on, wait for the fuel pump to prime, and start the motor.

Locate, remove, clean, and reinstall tightly all the braided ground wires on the engine. Do the same for the battery, alternator, and starter wires. Have the battery load tested for a bad cell. A bad battery may start the motor but will drop the voltage low enough to freak out the ECM/engine computer.

Determine the cause for the P0351,2,3 fault codes. Check and clean the connectors for the ECM, especially any ground connections. Use some dielectric grease on all connections.

What spark plugs are you running ?




P0351 (M)
Ignition Coil A Primary/Secondary Circuit
Peak primary circuit current not achieved with maximum dwell time.

P0352 (M)
Ignition Coil B Primary/Secondary Circuit
Peak primary circuit current not achieved with maximum dwell time.

P0353 (M)
Ignition Coil C Primary/Secondary Circuit
Peak primary circuit current not achieved with maximum dwell time.

[Hillbillydeluxe]

Tim,

I am going to jump on your suggestions first thing tomorrow. I already replaced the battery as the old one would not hold a charge, but no difference was noticed in the Sports behavior.

The Sport had NGKs in it to start but the gapping was all messed up on the plugs (some had 0 gap, totally bent and touching) and my buddy had some new auto-lites laying around as he had decided not to use them, so i threw those in for the tune up... I run Champion Trucks in my Classic, and will probably do the same for the Sport if i get it running.

So braided ground wires, dielectric grease on connectors, and i may swap Cam position sensors from Classic to Sport to see what happens.

I still have not be able to figure out what "Ignition Coil A Primary/Secondary Circuit Peak primary circuit current not achieved with maximum dwell time" means in english :0/ i figured it had something to do w/ the coil pack but swapping them had no affect.

Thanks for the suggestions and I will let you know how they go tomorrow.

Thanks so much for you help and time.

TJHillbilly

[CJ7-Tim]

My 2000 runs its best with plain old Champion plugs. Lots of other threads report about the same, the 4.0L doesn't run well on Splitfire and Platinum type plugs. Some 4.0L don't even like the Autolite plugs.

One or more wire connection may be loose after the battery install or corroded inside the insulation.

GOOGLE the MIL fault codes, I think the codes may relate to poor connections at the spark rails or the ECM/computer ground connections.

I would try to get some electrical contact cleaner for the wire connector plugs.
.

[Hillbillydeluxe]

So far today did the following:

I swapped my Cam position sensor from Classic to Sport, no change in behavior of either, then i swapped MAP sensors, no change in behavior.

Cleaned all the grounds i could find, put some electrical contact gel stuff in every sensor connector i could find and undo.

I believe cleaning the grounds has helped to stop the no start problem. The little key trick you described works a charm, on till pump stops, then off then on till pump stops then start, and she fires right up settles to idel perfectly. If she has sat between starts or if she stalls i have to do the trick over again, if i shut her down, then fire he back up she starts right up.

Now i only get the P0531-0532 codes when i rev engine, it will idle without codes no problem, as soon as i step on the gas or rev it even a little bit the codes pop up and she stalls. I am going to check all the boots and springs inside of the coil rail later today or tomorrow morning which ever time allows.

Interesting thing about the fuel pressure, when i drain my fuel pressure in my working Classic and turn the key to the on position the pressure jumps right to about 48, when i do the same thing in the Sport the first time it goes to 15-20, then the second time i turn it on it jumps to 45. Could this be my fuel pump starting to crap the bed?

Thanks agian for you help Tim!

TJHillbilly

[CJ7-Tim]

Originally Posted by Hillbillydeluxe

I The little key trick you described works a charm, on till pump stops, then off then on till pump stops then start, and she fires right up settles to idel perfectly. If she has sat between starts or if she stalls i have to do the trick over again, if i shut her down, then fire he back up she starts right up.

Interesting thing about the fuel pressure, when i drain my fuel pressure in my working Classic and turn the key to the on position the pressure jumps right to about 48, when i do the same thing in the Sport the first time it goes to 15-20, then the second time i turn it on it jumps to 45. Could this be my fuel pump starting to crap the bed?

You can do the key trick forever. It is easier than dropping the hitch, gas tank skid, gas tank and then changing the pump assembly. I have been avoiding a new fuel pump for 2+ years. I think, but can't be positive, that the fuel pump priming one time is simply not enough volumn to fill the fuel lines and fuel rail.

If you decide to replace the pump assembly be sure and get one from JEEP. The cheap parts store pumps have been known to fail again inas little as 12-18 months.

[Hillbillydeluxe]

Tim,

Some great news, the P0353-P0351 was caused by the cam position sensor on top of oil pump drive not being aligned properly with the engine, so i rotated the oil pump drive till the sensor lined up (0 Degrees to the engine) and wallah all my problems went away, the codes are staying clear and the jeep runs great!

Thanks a lot for you time and advice, I'm off to buy new champion plugs!! Thanks again!!

TJHillbilly!

[tangofox007]

Originally Posted by Hillbillydeluxe

and wallah all my problems went away...

The rumbling sound that you hear is from thousands of dead French teachers rolling over in their graves.

[Hillbillydeluxe]

[hockey369]

How did you make sure the sensor was lined up properly. I think i have the same issue as you as i have changed everything out and the codes and problem wont go away. Is this something i can do easily enough?

[Hillbillydeluxe]

"cam position sensor on top of oil pump drive not being aligned properly with the engine". I measured the distance between my engine block and the cam position sensor on my Working Classic, then set the Sport (the one w/ the problem) at the same distance and the codes disappeared and it ran fine. I dont remember what the distance was, or where i measured too.

[hockey369]

Hmmm thanks for the help. Is there anyway you could get some sort of measurement before i bring it to the shop monday? Thanks!!!