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2000 XJ power train in my MJ


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anybody find out anything as far as the size of a 15 gallon tank or whether you can use the dodge pump assembly? I have monday off so I'm gonna hit a few salvage yards looking for one to try out.

 

the other day I said I changed the pump and regulator in mine and it didnt seem to help the first few times ive started it, i'm not totally sure on that yet. the past 4 times its been started the truck has started without a problem :hmm:

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The only thing I was able to do is measure the resistance in the fuel level sender on my '98 or '99 fuel pump assembly in my 15 or 22 gallon tank (still haven't figured out which it is.

 

Anyway - the range is 20 Ohms (full) to 220 Ohms (empty).

 

When I am able to drop the tanks on my XJ and ZJ donors, I intend to measure the resistance on those, too. This will at least tell us that the fuel level gauge will work properly with a Dakota fuel pump assembly. I'm not worried about the pressure - I know that will work since the 4.0L and all of the Magnum-series engines all use the same rail pressure. Even if they didn't, the fuel pressure regulators look to be swappable. Remember, the fuel pump is not the sole determining factor of how much fuel pressure you get. Fuel pumps are designed to pump out more than you need - it's the regulator that keeps it at the right pressure.

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Well, you got me curious. I crawled underneath my '99XJ donor and decided to measure the resistance of that fuel pump assembly. Below is the last video of the truck before I sold the engine/trans. Basically, what is shown in the video is the last known fuel level:

 

9yEOfPy4J-s

 

Looks to be a little under a half tank. The measurement I got was 180 Ohms. So, kind of hard to really say if the two fuel pump assemblies read the same. Based on my measurements on the Dakota fuel pump, a half tank should be 120 ohms and as it goes below a half tank, the resistance should increase...so we seem to be going in the right direction. I won't have a good answer until I can drop the tank and remove the XJ fuel pump assembly and move the level arm up and down.

 

Wait a second, didn't you say you had 2 XJ pump assemblies? Measure the resistance across pins 3 and 4 for me.

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Curiosity got the better of me...again.

 

Hooked the fuel pump up to a spare battery and drained the fuel in the tank into a couple of gas containers (will come in handy for my generator in case the hurricane takes my power out). Kept draining the tank until it started to just trickle out and disconnected the pump so I didn't overheat and burn it out. With the tank damn near empty, the resistance reading on the XJ fuel pump assembly is about 440 Ohms.

 

So, knowing that, it looks like the Dakota fuel level sensor won't quite work with the XJ PCM and cluster. If my theory is correct, the Dakota fuel level sender will never drop the XJ cluster below a half tank. I'm not sure what will happen when the Dakota tank is full, but it would likely just peg the fuel needle to the right on the XJ cluster.

 

I wonder if that sort of variable can be edited in the programming with the SCT tuning software or possibly even a DRB III scanner...

 

Time to do more research...

 

BTW, this was all pretty much a moot point for me since I will be using a ZJ PCM in my 5.9L Magnum build, so there is still hope. Just need to see what the ZJ fuel pump assembly measures...hopefully it's the same as the Dakota!

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your tank is a 22 gallon just like mine, i probably looked at ten of them today and not a single one was the 15 gallon......

 

I'm getting really frustrated trying to find a 15 gallon tank. i even looked at a 88-90 15 gallon tank (cause its the only one I could find) and it doesnt use the same style of pump assembly. I even had one yard tell me they didnt put a 15g tank in, only 17 and 20 :fs1:

 

I have an xj pump assembly taken apart in the garage cause i robbed the pump and reg. out of it so if I can get my ohm meter to work I will see what I get out of it.

 

I am starting to run out of local places to find a 15 gallon tank so if anybody knows where one is at let me know, maybe I could call the yard its at and just have them ship it to me

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I was doin a little more research before I went out to the garage and I found out that dodge used the 15 or 22 gallon from 91-99. 2000 and up had a 22 or 24 gallon tank. i believe the older 88-90 had the 15 and 22 as well but don't use the same style pump assembly

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Got mine running and driving it when home and not working outta town. Have 75 miles on it and only issue is alignment. Plan on charging the a/c this week and keep on driving it....Very pleased with iy so far and have been enjoying the guys who can't stop checking it out in parking lots :cheers:

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I can't wait till I get a paint job on mine, that looks good.

 

just curious, was the tail lights a personal choice or did you use them because of the newer harness? either way it looks good and its a way to get away from using stock lenses that nobody makes anymore.

 

on your lift, did you do a spring over in the rear or a massive aal? it looks like it sits on a 4" lift in the front and spring over in the rear which I think gives it about 5.5" lift in the rear which gives it kinda the "raked" look, not bad I'm just surprised you have that much clearance in the front with 35's. I had a 88 xj with 35's on it but it had 7.5" lift and tj flares

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Well the taillights were made by me and my neighbor who works for Michael waltrip racing and I installed leds. The wiring is just more custom with them and easier.

 

The lift is a 4.5" short arm kit and a soa in the rear and I actually took a leaf out ti drop the rear down a little. The clearance is due to some sheet metal work done before paint.

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  • 4 weeks later...

still driving your mj around without any problems? I'm still confused on what's wrong with mine except that the fuel tank is too big, still have the no fuel at startup issue and its getting greatly upsetting, I do not want to stick my modified steel tank back in but I can't find a 15 gallon tank locally... I found some on ebay with a buy it now of 50 plus 50 shipping but really do not want to spend that much on just a plastic tank when I need 2 of them right now. :fs1:

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still driving your mj around without any problems? I'm still confused on what's wrong with mine except that the fuel tank is too big, still have the no fuel at startup issue and its getting greatly upsetting, I do not want to stick my modified steel tank back in but I can't find a 15 gallon tank locally... I found some on ebay with a buy it now of 50 plus 50 shipping but really do not want to spend that much on just a plastic tank when I need 2 of them right now. :fs1:

 

 

Yeah man, still driving it on a regular basis...(when at home). No issues known except for my exhaust manifold is cracked and i think i want to install a dakota fuel pump since the tank is deeper than the cherokee pump. ( only getting about 10 gallons of 15). Running 35" goodyear mtr w/kevlar and 3.55 gears. Good luck with your search.

 

Whats your suggestion header or new manifold???

 

Oh forgot to mention i am building a tiregate as we speak :wrench:

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