If you do a search here for variations on "leaking fuel injectors," you're going to see a lot of the advice you've gotten here.
You'll also note that this is a known problem with 1987-1990 Jeep w/4.0, and also note that the ONLY fix is replacing the injectors - all six (if one is leaking, the rest aren't far behind...)
FiveOMotorsports (I think that's who they are,) sells replacement sets for the Jeep 4.0 - they're Ford 302 "pulls" (pulled for upgrade) that won't have the leaking problem that you're having now.
The RENIX injector leaks are caused simply by the plastic/metal junction on the body - and the fact that it's crimped. Since there isn't any real sealant there, engine vibrations are going to loosen that join slightly, and there's no easy way to fix it. Later units on the 4.0, as well as SBFord and SBChevvy units, are all assembled and ultrasonically welded together, so the leak isn't a problem.
If you have a choice, go with the "four-hole" SBFord injectors, since they give more efficient fuel atomisation and therefore will increase economy and power (both slightlly.)
And, the Bosch-style fuel injector (which is what we've got in RENIX, what ChryCo used until 1995 or 1996, and what Chevvy and Ford used for the longest) use a standard connector. However, if you have to replace the connector, you should be able to find them locally in a parts house that carries the Motormite/HELP! brand.
When looking for replacement injectors, 19#/hour are stock replacements, but the RENIX system will adjust for injectors rated slightly higher - 20# or 21#. DO NOT go smaller, or you're going to get an uncorrected "lean burn" condition, which can eventually cause parts damage...
Sorry if I sound a bit cranky here, but it's a combination of taking a break from changing my throwout bearing (again! Damn internal slave cylinder...) and the fact that this topic has not only been done to death by me personally, but by a number of others here as well - and all of us with about the same level of detail (explaining the hows & whys, &c.) I just happen to have no particular shortage of donor parts to tear to bits for failure analysis and comparison... Why do you think I'm always collecting them?
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