stumbling and CEL 02 TJ 4.0

[AZG23]

welp...couple weeks ago...jeep started sputtering and stumbling on itself, (kinda like when I engage the kill switch) and almost dies...CEL fluttered but never threw a code.

Fast forward to a few mornings ago, and it started doing it again, and finally threw 2 codes P1282 and P0304.

I looked these up...and it looks like Fuel pump relay system has a problem and misfire in cyl #4. I remembered back to a time or two when I have had the kill switch ON and the jeep started when it shouldnt have...so thought maybe a faulty kill switch.

So tonight I pulled the battery cable and rewired the fuel pump relay back together. Hooked it all back up and will see what that does over the next day or so....

My question is though....is this what happens when the fuel pump is about to go..?? I should have replaced it when I dropped the tank to install the Kilby...but didnt think about it then...Ive got 85k + on it...and its dies on me on the trail quite a few times as the idle drop slow and kills it. (dunno if thats pertinant to this)

Im thinking its either the kill switch wiring has shorted, the relay, fuel filter or fuel pump...and thats what caused the misfire in #4 code.

What say the experts..?:fashizzle:

[1toughxj]

Brad, the way to check the fuel pump would be to check the fuel pressure at the fuel rail. There should be a schrader valve that a fuel pressure test gauge can be connected to. The fuel pressure should never drop under load. The factory computer senses a slight change in engine speed and attributes that to a misfire in a specific cylinder. This can be due to a fuel delivery issue, or perhaps an ignition issue such as a bad spark plug, coil wire or even coil. Fuel pressure would be my first check though.

[1toughxj]

BTW, if you happen to be on the east side of town you can swing by the shop and we can hook up the gauge and check it pretty easily.

[AZG23]

Im gonna be...but not til Monday...on my way out to a run...so wanna check before that..my neighbor should have a gauge..maybe I can get him to hook to it and see..if not I may have to take ya up on it...

thanks for the info bro!

[yellow_X]

Brad, if you still need to check fuel pressure I can do it for you Friday, pm me with your contact info, I will be at work 51st and Indain School

[AZG23]

Welp...no CEL today so far...and it seems to be running better after removing the Kill switch and wiring...

So will see how it goes from here...may have to rewire the kill switch later...

[ademster]

P1282 Fuel Pump Relay Control Circuit Malfunction

Possible Causes Setting Conditions


* Fuel pump relay control circuit is open or shorted to ground
* Fuel pump relay power circuit is open (test power from Ignition)
* Fuel pump relay is damaged or has failed
* PCM has failed

Key on or engine started, system voltage over 10.5v, and the PCM detected an unexpected voltage condition on the Fuel Pump Relay control circuit during the CCM test.
This code sets in 1 Trip(s).

[AZG23]

so a grounded or shorting kill switch that interrupts the Fuel Pump relay could cause this issue.

[ademster]

it is possible, or during install of the kill switch you might have accidentally frayed a wire near the fuse block.

or a shorting relay

[AZG23]

cool...so far so good...all the way to work this am, and out at lunch running well...no CEL.....we shall see if taking it out fixed it...

[AZG23]

welp...this am ran fine to work...just left for lunch, idleing just a little rough...blipped the throttle and it popped...then threw P0304 code again...???????????

[ROKCRLR]

That sucks dude, I hope you get it figured out before Monday.

[AZG23]

Me too....

Im gonna pull the coil packs tonight and take a look at the plugs....Ill keep ya posted


Anyone had anything similar.....?

[AZG23]

ok....soooo got home tonight and pulled the throttle body off and cleaned it all out...IAC and all..then pulled the spark rail off and pulled each plug..regapped and reinstalled...all looked good to me. None were white, and none were black...just a light milk chocolatey look and the gaps were still spot on .35

I cleared the code again..and I guess will see what it does Monday on my run as it seems to be a bit smoother. I also added some Sea Foam cleaner to the fuel tank (bout 3/4 can) to about 1/2 tank of gas to clean out any crud from the fuel system...and have been running it thru since lunch today. Unless of course its a bad injector..then tht aint gonna help.

Would a bad injector cause a lean mixture..?? and if so...wouldnt a plug or few be white..? Im about done with my trouble shooting...but dont wanna be raped with sandpaper at the dealer, guess I could see if Absolute can take a peak....heya Joe..you awake.?

[AZG23]

bump for the Monday crowd

[Antman]

The kill switch on mine is a double throw, single pole as in the switch has 3 positions,
left center and right with one connection at each spot. I split the
hot wire from the fuse block and soldered one side to the left and one to the center
connection, with nothing on the right connector. With the switch in the
up position my ignition works normal. With the switch in the center it's killed.
On my first switch, if you put it in the down positon, the jeep would eventually
start, but run so crappy that I doubt you could get it out of the driveway. I
suspect there was a low resistance across the down position to allow enough
voltage to start the jeep, but it was so low it ran crappy.:confused:

After changing the switch to a more expensive made one, it now works like it
should. Therefore if your switch has a low enough of a resistance to allow
current to flow to give a minimum starting and running voltage, it could be
the switch.

[FrenchChili]

ok....soooo got home tonight and pulled the throttle body off and cleaned it all out...IAC and all..then pulled the spark rail off and pulled each plug..regapped and reinstalled...all looked good to me. None were white, and none were black...just a light milk chocolatey look and the gaps were still spot on .35

I cleared the code again..and I guess will see what it does Monday on my run as it seems to be a bit smoother. I also added some Sea Foam cleaner to the fuel tank (bout 3/4 can) to about 1/2 tank of gas to clean out any crud from the fuel system...and have been running it thru since lunch today. Unless of course its a bad injector..then tht aint gonna help.

Would a bad injector cause a lean mixture..?? and if so...wouldnt a plug or few be white..? Im about done with my trouble shooting...but dont wanna be raped with sandpaper at the dealer, guess I could see if Absolute can take a peak....heya Joe..you awake.?


You may want to check your injectors just in case. Sometimes the wiring to them can crack, become brittle overtime. Easy way to check is move the wires of the injectors while the engine is running, if it shorts out you'll know:eek::D