Best injectors for Renix

The original Renix injectors made by Siemens-Deka were only “one holers”. That means the fuel was discharged through only one hole.

Not the most efficient design by today’s standards. Modern injectors have at least 4 spray holes for better fuel atomization.

Another issue is the original injectors were prone to leaking fuel at a seam and spraying gas all over hot manifolds. Not good!!

A nice upgrade is to use Volvo injectors. The use of these injectors was pioneered by Programbo from Cherokee Forum when he suggested them to DFlintstone there. Flintstone was the guinea pig and reported excellent results. I have experienced the same results as have many others. The 746s, as they’re called, have the 4 hole design  and the complete Bosch part number is 0 280 155 746. Volvo injectors

These injectors can be purchased refurbished for not much money and are a direct bolt-in.

You will experience smoother idle and better throttle response. Perhaps some MPG improvement also.

37 thoughts on “Best injectors for Renix”

  1. Not to mention a slight boost in mpg. Injectors plus the ’89 or 90 ECU in an ’87 Renix Cherokee equals one smooth running vehicle.

  2. Flintstone Here. I thought I picked more MPG “mucking around”. Yarden logs and getten wood on the trailer might have gone from 10 something to closer to 16. That might be a stretch. Hwy MPG went up, but less than two Mpg. Tough to isolate the two and other things changed as well. I’m pretty sure the swap pays back In $, (at some point), and the smoothness and snappy throttle response is welcome as well ! Testominails here> http://www.cherokeeforum.com/f2/1990-renix-volvo-bosch-19-280-155-746-injector-swap-163105/

  3. With a little tail wind on the Hwy, I logged 24 MPG once, in my 90 with over 280K, and packen over 500 Lbs. of tools and stuff.

  4. Thanks for the mention. Actually I stumbled upon the 746’s based on someone suggesting the Volvo 702’s as an alternative to the Neon 703’s for mid-90’s XJs. This was based on a mis-print on the Bosch data sheet which shows the 702s and 703s being identical. In reality the 702 is just another version of the 746. That being said I first learned about injectors from Rainman who posts regularly on an Aussie XJ forum.

        1. Negative on the 703. I tried them in my 89 with the snap on scanner hooked up and it went into closed loop for a minute. Then slowly the fuel trim went down to 0 from 128 and default to open loop.

          Thing is, it ran great and couldnt tell it was in openloop save for the scan tool. I was due for a smog check that week so I’m glad I bought the snap on when I did.

          Changed back to stockers and new 02 sensor passed smog. Now I have the yellow 746 and have passed smog withthem

  5. I have an ’87 with 89 computers. tried the 703’s and they were too much so went to the 746’s. It runs great; starts, idles, pulls better but the MPG seems to have gone down the tube. I am not sure where to start checking. I did not remember the procedure for resetting the computer. Any help is welcome because my hopes were up and are now are rather deflated.

    1. “Seems to have gone down” isn’t a scientific conclusion.

      You need to do the calculations based on miles traveled divided by gallons used based on a full tank.

      Drive it for a while. You’re not getting heavy on the skinny pedal now that it’s more responsive, are you?

      1. Thanks for the quick response.
        You are right. I should have been more explicit. I will do those things. It is typically driven to town, 50 miles each way, about every three weeks or so. The last trip the gauge went from just over 3/4 to just under 1/4, but sill not very scientific.

  6. Hey cruiser,

    First off, thanks for all the tips. My coworker and I both own MJ’s and we refer to your word as gospel.

    I just installed the 746’s in my 92′ Comanche Elim. Reason being, the Renix and HO both come with the same stock fuel injectors, so I figured why not try it out. The install went fine, and when it’s running it feels smoother and there is less noise coming from the engine. Power feels the same. Haven’t tested for mpg.

    Only one issue: When I crank the motor is needs help turning over with a little tap on the gas pedal. I haven’t heard of anyone else having to do this. if I don’t tap the pedal, half the time it will start. I’m gonna recheck all my vacuums and such, but what’s your opinion on why this is happening? Maybe the 4-port injectors aren’t properly cleaned? Or the HO needs more juice? I’m not sure.

    1. I would double check things around the installation process. Vacuum lines and such.
      I’ve never used 746s in the later application, but I certainly see your logic.

  7. Great work in developing these helpful, correct, and welcome Renix Jeep upgrades, Cruiser54. The tips on sensor tests and ground improvements worked quite well for me. Installing the dual-diaphragm brake booster upgrade has paid back in performance and safety. But my vote for “best tip” has to be: 4-port fuel injectors!

    For 86-90 Renix Jeeps you nixed the 703 fuel injectors and confirmed 746 injectors: I heartily agree. My ’89 Wagoneer had developed one leaky injector, so I hunted a full replacement set. Another website had rec’d 703’s (nowhere stating the properly applicable year Jeeps), but with them my engine ran black-smoke rich and its ECU refused to learn to adjust for them. I resold the 703s on eBay, and then luckily found your website.

    I followed your recommendation to install 746 injectors. Mamma mia! Now the Wagoneer idles and runs more smoothly than I’ve ever experienced. In a week or so I’ll have two 150-mile highway trips for MPG data to post here, too. Thanks!

      1. January 30, 2018: in 400 miles of mixed speed-and-terrain highway travel, mostly 65 MPH, it averaged a familiar 20 MPG. So no MPG increase, but heck, the nice idle, smoother power curve, and quieter engine with the 746 injectors makes it a winner.

  8. Hi. Firstoffall sorry for bad english. I did the injector upgrade to my -88 4.0 renix, i buyed the 746 injectors, and installed them. But there is some issues, iddle is 1000rmp on D when car is stop, and car shakes litlebitt. On driving it feels like some power is missing. I just cleaned the throttlebody and adjusted tps. With the original injectors it worked fine, and there was huge different after adjusting tps and cleaned throttlebody. Could it be like too low fuelpressure, or what could it be? Thaks beforehand!

    1. Hi Sami.

      Did your injectors come with new o-rings? I would suspect you have a leaky one or two. easy to check. With the engine running, spray some carb cleaner around each injector. If there’s a vacuum leak there, you will notice an immediate change in engine rPM.

      1. Yes they came with new o-rings. I l try that carb cleaner tomorrow, and report back, if there was some leaks. Thanks for the tip!

  9. Okay good.
    Please inspect the hose/tube from your throttle body to the MAP sensor on the firewall. It may have been damaged during the injector installation.

    1. Hi again. So, i did test with startpilot spray to injectors, no leaks. And that mapsensor tube, is ok also. I measured fuelpressure, and it was 2bar when idlle, if reved it dropped to 1-1,5bar and raised to 2bar when idle. I tryed to raise pressure to 3bar, but no change. Feels still heavy to drive, like power is missing. And i just changed fuelfilter, so thats new.

    1. Woulda been a long time ago if Mopar hadn’t discontinued the windblocker parts.

      In the meantime, make sure the weatherstrips on the A pillar are sealed from top to bottom. The gaps between those plastic rivets creates wind noise.

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