Starsavage11

Hey all, I just wanted to throw this out there to see if anyone has input. I rock a 1991 Cherokee XJ, 4.0L, automatic transmission. Last summer we replaced the engine (currently at approximately 12,000 miles), and over the past few months we've replaced the crank sensor (twice, I finally learned my don't-buy-AutoZone lesson), front brakes, rear differential, heater control valve, headlights, taillights, sparks and plugs, distributor, etc. etc. (you know the dance.) In short, it looks haggard but it's basically a new car.

Most recently we had the fuel pump replaced by a mobile mechanic from yourmechanic.com because I was out of town without the toolbox. After the first fuel pump replacement, we started experiencing a venting issue. In hot weather or over long distances pressure builds up in the fuel tank and stresses out the pump, causing a loud humming noise. It also takes about 20 minutes for all the pressure to be released after loosening the gas cap before the cap can be removed without gas spraying out, and it is difficult to get the tank to take gas (to cool down the pump.) YourMechanic replaced this first pump under the warranty, and the second pump was improperly installed. The mechanic actually bent the inlet by trying to jam in an improperly seated/threaded pump, and completely failed to install the gasket, resulting in a ridiculous gas leak if we put more than a quarter tank in. Finally, we replaced the pump ourselves (properly) and everything seems to be working much better, though without the giant hole the mechanic left in the tank, the venting issue has returned and the tank builds up pressure very quickly in hot weather (I'm currently in Albuquerque, so this is a huge issue.)

So Question 1: I have been trying to verify whether the 1991 XJ has the fuel pressure vent in the top of the tank. We didn't have to drop the tank to replace the pump so I have no idea what the top side of that thing looks like. From what I've read, the vent didn't come into play until 1993 or 1996, but something is still effed up with my gas tank. Haynes Manual and the owner's manual have been no help in answering whether or not this model has a vent in the top of the tank. We have inspected the evap system and everything seems to be in working order. I just replaced the gas cap with a pre-release cap and it helps a little but has not solved the issue. Any other ideas about what is causing the pressure buildup or how to deal with it?

Question 2: Though everything runs great 94% of the time, there is still an intermittent long crank issue when starting since replacing the fuel pump this last time. It happens fairly rarely, and may just be a gremlin. However, today I had an issue where I had to prime the pump multiple times before I could get it to start. It sounded like the long crank was draining the battery and by the third turn of the key I had to pretty much jam on the gas pedal to get it to catch before the battery died. It sputtered and struggled but finally started. It felt and sounded like maybe an injection or fuel line issue. Once the car started it drove just fine, but I'm hesitant to go out in this heat without knowing whether I'll be able to get the jeep back home again. Thoughts?