SuperRA

87 4.0L 4WD

Hello everybody. I am in the midst of diagnosing a part throttle hesitation my XJ has and right now I've just removed the fuel tank and drained it completely to rule out water in the gas. This brought on some questions about the tank and fuel pump.

1. Are there differently pumps for the 20 gal vs. 13 gal tank? I recently replaced the fuel pump. I thought I had a 13gal tank but I found out it's actually the 20 Gal. I saw listing for a "20 gal tank" fuel pump. The old fuel pump was a different size but I figured Bosch's newer style pump (part #69302) was smaller. Everything fit ok with the adapters provided and it runs fine as far as I can tell.

2. For those with 20 gal tanks, when does your low fuel warning light come on? Mines always comes on when I've used about 14-15gal. I drive around and the light comes intermittently mostly because the fuel is sloshing around and the sender goes up and down. But when the light stays on when I'm at a stand still I go and fill up. It never fills more than 15gallons. (i figured it was a 13gal tank that was filled beyond it's "full" capacity) So by this observation, and now knowing I have a 20gal tank, so assuming the gas station pump fills it completely, that means the light is coming on when I have 6 gals left in the tank? Or is 20 gal the complete volume of the tank by which it will never be completely full?

3. Are the level sending units different for 20 vs 13 gal? Or is mines mis-adjusted somehow? The jeep has been in my family since new and I don't see any records of it being changed (my bro owned it for 20 yrs), but it could have been changed and not recorded. My bro always took it to a shop. I may keep it the way it is, I mean it gives me some security now knowing I have that much reserve fuel.

Also, the instrument cluster was swapped out for one with a tach. I bought it off ebay so I don't know for sure what it came from (that was 7 years ago), but if it came from something different like a 4 cyl or a 13gal XJ, would that cause any of these issues?

Sorry for the long writing, but I just wanted to give all the details. If the new gas doesn't fix the hesitation, I'll be back bothering you guys about that. I just want to hammer out all possibilities first and do all of Cruiser's renix tips.

Oh and also while I have the tank off, is there an upgrade for the tank skid or should I not even bother since this jeep will rarely see off road?

SuperRA

Can anyone answer one of these questions?

Fred/N0AZZ

I have no idea but all you need to do is go online (Rockauto) and check the fuel pumps for each and check the part numbers for each.

sycoglitch

Iirc, all 4.0 xjs had a 20 gal tank but the "13 gal" ones had the smaller sending unit. They dropped the unit further to make use of the other gas. This is what I've heard so maybe someone can clarify. Getting the longer sending unit is a way to get more gas.

cruiser54

2. 2.0 gallons per the owner's manual.

As to tank size, they were all 20 gallon, just used different sender/pickups.

sycoglitch

Yes. I was right. Lol

SuperRA

I just looked at the original window sticker. One line item is "extra capacity fuel tank" So I guess I have the 20gal option. So I guess I just have to figure out why the low fuel light comes on so early.

I did look at rockauto before, that's what brought up the question. It seems only three brands (airtex, carter, & spectra premium) had 20 & 13 gal fuel pumps, but Bosch did not. It seems to work and fit fine, so I guess it's ok.

Thanks

Comanche1987

Carter is a airtex sendng unit assembly. As far as for sending unit assemblies I would use a airtex because they are cheap and simple, for the pump your going to want the oem pump.

https://www.cherokeeforum.com/f2/fue...arning-195504/

SuperRA

Ok so I did some searching on some other forums and it seems that the consensus is that the pumps are the same. In fact the tanks are the same except for the filler vent which extends down further thus preventing more fuel from entering. That's how the 13 and 20 gal tanks differ. As for the sending unit, others have reported the same 15-17 gal fill up. So there is in fact 3-5 gals "reserve" after the light comes on.

cruiser54

So, you're saying a guy could shorten the filler vent and have a 20 gallon tank?

XJwonders

I thought that applied to the TJs not XJ Cherokees

cruiser54

I thought it applied only to XJs.

XJwonders

Lol oh well maybe we are either both wrong or both right

sycoglitch

I thought we answered this thread already. Why were other forum needed t be brought in. And I've filled up 18.5-19.2 gallons before on below empty (during the gas shortage after hurricane sandy). There's 2 gals reserve.

cruiser54

2.0 gallons til empty after light comes on.

Now we're on to the difference between 13 and 20 gallon filler tube vents and gauges.