Stall after start
 

I have a 2000 jeep cherokee classic 4wd 4.0 with a big problem. About 6 months ago I had to get the fuel pump swapped out for a new one. I got this job done at Firestone Complete auto care and I’m not sure if they changed the fuel filter too. So tonight I was fishing with some buddy’s and we got in, I started it and it cuts out right after start. For instance if it’s started you can rev it all the way to redline but the rpms just drop and you can sit there and jam the gas and it does nothing and still dies. This is the same thing that happened the first time 6 months ago.

Lets go with the problem was the fuel pump the first time.
Everything was OK and now it is happening again after 6 months.
Let's assume it is the fuel pump this time too.
First thing is to find out what fuel pump they used.
Guys have expressed problems with certain aftermarket ones.
The general consensus is OEM or Bosch if you can find one.
If it were me the first thing I would do is check fuel pressure.

Do you have a SKIM? Security Key Identification Module. Is the light on? If it is, the PCM isn't reading the key as being valid. This will allow it to start, then run on residual fuel pressure because it shuts off the fuel pump.

I have already had problems with that too in the past and the light is not on so that is not it. Could this be a bad alternator? I was reviving it up to 5k rpms and it still dies. I also get low oil pressure at idle and occasional random misfires too.

Get a fuel pressure gauge onto the Schraeder valve on the fuel rail. You should see 49PSI +/- 5psi at idle. If not, it's a fuel system issue and we can go from there.
I bought a gauge for £cheap because we don't have the Free Rental type deals you guys have in the states. Either way, it's an easy test and lots less drama than dropping the tank to get to the fuel pump.

We towed it to firestone this morning and the fuel pump was still under a warranty, this was again the problem. Thanks for the help.

Immobilizer SKIM not communicating correctly
 

So two days later and still it doesn’t stay running. Turns out it was not the fuel pump. Firestone Complete Auto Care has no clue what was causing this. All they came up with was a code P1686. I’m planning on towing it to the dealership so hopefully they can fix this. Any suggestions or things to do before I’m completely out of money would be nice. Thanks. I do hear the fuel pump turn on when the ignitions turned. I am not getting the key with a line through it on the dash. Also I sprayed WD40 in the hole pictured below in all four doors. Not sure this would cause anything but I saw on another forum that someone did something similar and has the same issue.

https://cimg6.ibsrv.net/gimg/www.che...85087acea0.jpg

WTF does that have to do with it not starting?

It starts it just doesn’t stay running. Some one on another Jeep forum had the same code and also mentioned he sprayed something there too.

You have not made it clear whether your Jeep stalls when allowed to return to idle, if so 2 known causes for that are faulty IAC, or low voltage from battery/alternator

P1686 indicates an electrical fault with the SKIM module or its connections

SKIM Delete?
 

Can a dealership remove the skim module from the dash and the ecu?

my opinion (based on only limited knowledge and experience of dealers )

As your car is now "old" they will quite likely either not have access to new parts, not have access to a mechanics with good experience of working on XJ model, or not want your old heap of **** to darken their doorway, or some combination of all three

They almost certainly could remove some dollars from your wallet though

In order to avoid a frustrating outcome, the only alternative is to ring the dealership and directly put the above 3 questions to them

Bypass Skim
 

What would be the easiest and cheapest was to bypass the SKIM module?? Is there any way to hot wire the fuel pump? If I was to hot wire the fuel pump and have a manual switch hidden in the cab somewhere to turn the pump on and off, would the stupid SKIM module shut something else off on the Jeep?? Someone suggested to me that I run an in-line fuel pump?? Which would be my best option.

my vehicles are '96 and they work in a somewhat different manner, the information needed to diagnose your issue would be contained within the 2000 Factory Service Manual, which can be downloaded free from Cruiser54 website

As far as I know, no method of "jury rigging" the fuel pump is possible on your ( or my model )

The cause of the fault must be identified and rectified, as the fuel pump is controlled ultimately by the vehicle computer pocess

I would use the forum "Search" function and/or Google to search "Jeep Cherokee XJ SKIM module fault" etc etc