Two Types of Fuel Pumps?

Okay, wifey's '91 XJ 4.0 started acting up a week or so ago with loooong starts.... 3 or 4 attempts the past few days. Also noticed when accelerating that it wanted to fall flat on its' face, buck around and even try to stall. Did some searching on here and narrowed it down to a fuel delivery problem. So I picked up the fuel pressure gauge, hooked it up and running I'm only seeing 18 psi with and without the pressure regulator vacumn hooked up. Changed out the fuel filter. Still 18 psi. Noticed I was loosing all pressure immediately after shutting it off. Replaced the Regulator. Still getting a mere 18 psi. I assume the regulator and check valve on the pump is bad and allowing all the fuel to return to the tank. Excess cranking has been putting stress on the pump, causing it to slowly become weaker. Is my assumption of the fuel pump correct?

If so, I called all the parts places around me and only NAPA has a pump in stock today. The guy asked if it was a Bosch or a Walbro unit, as he only has the Bosch in stock. I wasn't aware there were 2 differant pump types. And if there are, is there anyway of knowing which one is in the tank before removing it. I also have my '89 Renix XJ which could donate it's pump to the '91 if they are the same, but I need to know before I start tearing them out if they are infact the same. :helpme:

exact same thing happened to me, but it quickly made the xj unstartable(is that a word). anyways yeah, i replaced the fuel pump. there are two different pumps, one for the 13.6 gallon and one for the 20 gallon tank. the most common one is the 20 gallon. also, be careful when you try to put it in the tank. the earlier xj's could have the fule pump replaced without removing the tank because it mounts on the side of the tank. but its real easy to drop the tank and makes it much easier to install the new pump since if you bend the float for the fuel gauge it will read a bit off. i put mine in and bent it ever so slightly and now my guage reads half full when it is really full.

Okay, pulled the pump from the '91. Not too bad... that lock ring can be a real PITA on a stock XJ with only a floor jack. It's a Bosch pump. It pumps when I supply 12V to it, I suppose it's just not pumping enough? My understanding is that fuel pressure at the rail needs to be between 39 and 50 psi. The Bosch pump the local NAPA has specs that the pump has a 28 psi. pressure rating. Other pumps listed at NAPA have a 65 psi or higher pressure rating (the Walbro, for instance). Would a pump with a 28 psi rating give me the 39-50 psi I'm looking for?

that i cannot tell you

well, rather than spend $100 at NAPA, first I decided to pull the pump from the '89 Renix and compare. They were identical! So, I just shoved the whole assembly from the 89 into the 91, and she's running like new again! Granted, now the fuel guage is incorrect :dunno: , but she's running great! :yelclap: