If you never had a vehicle catch fire on you, you have not yet known that unique feeling that comes with the first few seconds of realizing your Jeep is burning, to the next minute or two of doing everything you can to put it out, which then moves to that hopeless realization that you have no choice but to watch it burn, and trying to get as much as possible out of it before it burns to the ground.
Let's just say that none of those feelings are any fun, even less so when you just spent a half a year bringing the Jeep back from one tire in the junkyard only to lose it all again. Hopefully this story will help you from ever going through the agonizing pain that is a vehicle fire.
We were shocked at how much smaller the new injectors (foreground) were compared to the old. Lubricate the O-rings before installing to avoid O-ring damage.
In the month before the our MJ caught fire, we smelled fuel while driving it. When parked, regardless of how high we revved the engine we couldn't recreate the problem. We looked real hard at the entire fuel system and found moisture tracks in the dirt near a couple of injectors. So, rather than spend the $300 to replace the injectors, which we had no proof were shot, we spent seven bucks and replaced all the O-ring seals.
It then ran fine for a month until we smelled fuel again the Jeep lost all power and nearly burned to the ground. We then researched fuel injectors and discovered that the '87-'90 4.0L used a three-piece injector. Two pieces of metal and a chunk of plastic all pressed together. If you ask us, pressing plastic into metal that is in a hot area and carries pressurized gas is a bad idea.
Supposedly the four-holes in the new injector will provide a finer mist than the stock one-hole injector. We didn't notice a mileage change on our otherwise stock MJ, but we did notice the idle smooth out. Of course, that could have been from the fact that all of the stock injectors were visibly clogged and gummed up somehow.
Fast forward to our new-to us '89 MJ. After driving it less than 1,000 miles, we smelled the fuel smell again, and got flashbacks. The difference was that this time, after towing it home we could see where the fuel was leaking between the separate sections of three out of the six injectors.
We spent $300 for a set of Bosch fuel injectors of a similar flow rate (PN 02801580444) to put in our truck that didn't cost us much more than that. We needed the length to be the same so the fuel rail still bolted in correctly, the flow is important so the vehicle runs correctly, and the diameter of the seals and holes they go in is important to prevent leaks. What we ended up with were injectors for an '03 Ford truck or SUV with a 5.4L V-8 (Ford PN 4L3Z9F593CA). You can likely find different injectors that will fit, or just use our research and make your life easier.
If you are still running stock injectors on your '87-'90 XJ or MJ, we advise you to look real hard at whether or not your Jeep is worth this $300 insurance policy. Bosch injectors are available at any decent auto parts store.