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.

132 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>

  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

        1. I got a set of 746 today.

          Was noticing the 4 tiny pin point size spray holes on the bosch, looking at the factory 1 hole 90 renix injectors it seams like the 1 hole would put out at least 25% more volume than the 746.

          Also what is with the small plastic hat or cap on the end of the bosch 746.

          any input appreciated.

  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. A bit late but i just found your wonderful website (’87 XJ with 305K – I’ve done only the last 3-4K). 1 Bar = 14.7PSI , so he is saying that he essentially has 30PSI at idle and 15-22 when revved.

    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.

    2. Remove interior trim panels from rear passenger seating area to the tail gate exposing the interior metal of rear quarter panels.

      Completely clean all interior surfaces of both quarter panels. Check drain plugs. Correct/ address any rust. Line interior side of both quarter panels with squares of ultra dense home carpet padding. Use 3M 777 spray adhesive to secure it. DO NOT COVER DRAIN PLUGS. Next cover all (nonvisible) sides of the interior trim panels with the padding, the same way. It will make them heavier. Re-install all trim panels. Enjoy! Noise level drops dramatically.

    3. A few guys I know used “stall mats” from Tractor Supply (comes in 1/2 inch to 1 1/2 inches thick). Made a template with cardboard and then cut mats with Sawzall, Install from as high up (as possible) the cabin side of the firewall all the way to the back seating area (or whole interior if you like). Be sure to check under carpet for rust and address it. Ultra dense rubber stall matt reduces noise/ vibration without adding a lot of weight (40-45lbs max.)

  10. As I’m moving my project along on the MJ the next thing on my list is a complete tune-up to include plugs, wires, distributor cap/button and injector replacement. Sounds like everyone is pleased and had good results with the Boschs. I’ve looked on EBay and there are quite a few people selling them, any recommendations on seller(s) would be appreciated if you have one.

    1. Completed the 746 swap today, much better idle and appears to have a little more pep but the verdict is still out. Other than some missing parts on the fuel rail that the PO failed to mention to me I’m satisfied and consider it money well spent.

      1. So get a load of this, the PO evidently swapped out one of the injectors, one of them was basically new, during the installation I found one of the bracket bolts missing that holds the rail in place and the retaining clip that holds the gas line in place on the fuel railing missing. The gas line tubing was just shoved up into it, I’m surprised the pressure in the fuel rail didn’t blow it out. Dodged a bullet on that one, had to order one and won’t be driving it until that is definitely fixed.

  11. Just installed these and it’s like I have a new Comanche. Working my way thought all of these and loving the difference it makes. Cruiser you are awesome from a current Mopar service manager. Thank you for this sure it is amazing.

  12. Was looking through the comments and didn’t see it asked, but am I guessing correctly that this wouldn’t work for us 2.5 TBI folks? If not, are there any options for injector upgrade/refresh? Thanks.

      1. Yes, I’ve completed tips 1-3, installed a new 02 sensor, upgraded to an aluminum value cover, and replaced the battery cables with a MeanLemons kit.

  13. I just ordered bosch equivalent #0280155703 injectors after doing some research that was the part# I came up with. Did I understand the previous comments that thats not right or just that theres better ones such as the 746s, because on ebay part #0280155703 is the most common for a 1990 4.0 cherokee. Frustrated and now confused, and I swear, you can engage the fuel pump and just watch a stream of fuel come out so just about anything is better than that. I didn’t come across mention of volvo 746s, neon and ford but not volvo and cherokeeforum is one of the spots I checked before I ordered. Good job on the site,good real world information

    1. To clarify my post from 9,7,18: I just ordered part# 0280155703 injectors on 9,7,18 because that was the part# I came up with, so is that right and will they work? The ones currently installed (probaly original) are the ones that are leaking. Side question, how do I disconnect the fuel pressure regulator from the hard fuel line? Push the two sides of the plastic connector and pull? I just want to make sure I’m doing it right so I don’t break anything.

        1. Any advice on how to locate injector connectors that are compatible with the bosch 749 injectors and the 1990 renix?

          1. I need to replace my connectors because the wire coating are cracked and hard. So I need one that fit the 746 injectors. And thanks for the replies.

          2. My research shows aftermarket injector connectors with pig tails come with 2 white wires.

            The factory 90 xj connector wires are black and green.

            Does it matter which way the connector is wired in?

            thanks in advance

    1. Sure hope those two quick connects can be reused ’cause I can’t find them anywhere, even tried the dealership and what size are they 3-8 or 5-16? The injectors are #710s (ford I beleive) not #703s, that was confusion on my part. Sorry about that. Thanks for the input, it’s appreciated.

  14. hello guys!,
    I was just wondering which injectors are the stock ones for the xj 88,cause mine’s have two classes of them, have four 53030262 and 2 4554130,and let me tell you this thing consumes big fuel and puke to much black smoke, so tired about it!

    i’m aware of the 703’s ,746’s,but i can’t get those inyectors where ‘im living

    recently i tried the Ford injectors F1ZE-A2B that i have as a spare but they won’t work

    so any tip would be appreciated

    1. I recently changed mine out to the 746s and kept one of them. It’s in my shop someiwhere and I’ll see if I can find it and get a part# for you. I have an 88 MJ but I would think they are the same.

      Just wondering, you mentioned that you couldn’t get the 746s, I ordered my online and had them shipped to me???

  15. Well I replaced the injectors with the Volvo one’s. It does have quicker throttle response and seems to be smoother running down the road. But now at idle it sounds like it has a miss, only at idle though. It almost sounds like its cammed, kind of a lope. Any thoughts?

  16. I did the injector swap and everything is running great with the exception of the fuel rail O-rings. Many years ago I lost (stepped on) the spacer that fits on the fuel rail just before the O-Ring. I double stacked the O-ring and everything was fine. when I did this install the double stacking wouldn’t work so I added another to make it seal. Does anyone know the OEM part number or where I can find this spacer. I do not trust the triple stacked O-rings and I would like to fix it the right way.

    Thanks in advance.

  17. Can anyone chim in on what is the small plastic hat or cap on the end of the injectors?

    Does it get install with the injector?

    1. Yep. Lube up the o-rings with oil and install them in the rail first.
      Make sure you don’t bust the throttle body to MAP line in the process.

  18. I replaced my injectors with 746.

    I then tested the original 90 renix injectors using a 9v battery… but no clicking sound coming from them.

    Do the factory injectors need tested using a 12v battery?

  19. Hey I just want to know is the 746 injectors the only I should on my 87 jeep comanche or is it another compatible type

  20. Do you have any suggestions for the throttle body fuel injector? Would like to upgrade it if I could.

  21. The volvo or bosch 746 injectors flow 20.2 and the factory 1990 4.0 injectors flow rate is 18.6.

    The 746 injectors will cauae a rich condition and throw off your fuel trims..

    1. Hmmm. I wonder why they work so well in actual real world experiences then.

      My advice to you is to not use them then. Ignore the hundreds of success stories across the different Jeep forums and stick to your profound research results.

        1. Just don’t use them if you’re not convinced by empirical evidence.
          I don’t have a horse in this race and I provide this website at my own expense. My time is better spent helping others who are friendly and not contrarians. Please don’t come back here anymore. I’ve had enough of your crap..

    2. You might want to double check the fuel pressure on a 1990 4.0l cherokee before you start spouting the figures. In reality, the flow rate is just a bit over 19.3 lb per hour in my experience. Enough to help, not enough to harm.

  22. My teen sons and I just bought a 89 Cherokee to have fun, learn some basic auto mechanics and have more fun. Is changing the original injectors (225k miles) with 746’s a good basic job to try for us?

      1. We have not completed those tips yet, but sounds like some good weekend projects. Probably got to find the OxGard and other supplies first. We’ll take on these tasks before the injectors. Also, vehicle seems to run rough when gas is less than 1/4 tank and turning corners.

  23. Good plan. Hang loose on the injectors for now. Complete the Tips we discussed first.
    It wouldn’t hurt to have the kids peruse some of the other Tips also.
    Good hands on stuff. I admire your efforts to educate and spend time with them.

  24. 1987 Cherokee 4.0 with the Renix FI system. I’m swapping out the fuel injectors with 746s I got the injectors seated properly but when I tighten the fuel rail bolts to the manifold cover the injectors pull out slightly.

    I’ve tried tightening the bolts in various sequences and progressively without any love. Does anyone have any advice?

  25. I’ve been looking at these on eBay. Some sets of 6 as low as $35. That scares me because I’m thinking Chinese knockoff. Any legit dealers with good pricing?

    1. If you come across an ad for injectors that says something like Bosch “type” injectors then they are junk Chinese knockoffs

  26. You want injectors refurbished in the USA. The Chicom injectors should be avoided like the plague. Pun intended.

    1. USA all the way!

      Wanted to let you know that after completing several other tips, I finally got to check this one off the list. I wasn’t expecting a big difference, but I hopped in – after making sure we were leak free – normal throttle, and flung half the rocks outta my driveway. Hoping this helps with my horrendous gas mileage (broken manifold bolts not helping). Awesome work here!

  27. The 746 conversion for my 1988 Xj is almost complete. I am concerned about the “penetration depth” if the injector in both the rail and the intake port. I have never seen pictures of an installation to notice these details.

    For the rail – There are two scored lines below the upper o-ring. Which of these should we place the injector clip in?

    For the intake – How much of a gap between the yellow injector body and the intake?

    1. I attach the injectors to the rail with the clips. Then, with the o-rings lubricated with engine oil, carefully line the injectors to the intake manifold and then push/hit the rail with my hands until all the injectors are seated and the rail can be fastened with the bolts.

  28. I waited to see how the injectors settled as a result of the pressure from both o-rings before attaching the clips. This resulted in using the lower of the two grooves on the injector for the clip. Strictly, speaking, this is a partial groove because it is not continuous around the perimeter.

    The other comment I should add is that the fuel supply line places a sufficient, yet small, pressure on the rail such that it biases injector #1 to be withdrawn from the intake slightly more than the remaining injectors (i.e., sight down the injector/intake line to check for this potential misalignment). I loosened the fuel rail bolts the following morning and applied pressure with my hand near the front of the rail and then tightened all rail mounting bolts. This improved how my injectors were seated at the intake. I never experienced leaks at any location throughout this process.

    I purchased my 746’s from Motor Man in MI. Great source for refurbished injectors!

  29. Installed 746’s today, they seem to seat right in and no leaks at the injectors. But, I have major fuel leak where fuel line meets the fuel rail with a quick connect piece. Ideas why there is a leak there and how to fix? Also, I am getting a lot more black smoke at the tailpipe after the F.I. Swap.

  30. First off, fix the fuel leak. Here’s what you need:
    Fuel disconnects

    Quick disconnect part numbers

    The Napa part numbers for just o-rings *is:

    Napa 730-5018 3/8 Viton individual o-rings
    Napa 730-5017 5/16 Viton individual o-rings
    *Remember to re-use your old spacer between the 2 new o-rings!!

    Napa CRB 212305 fuel line repair kit 5/16
    Dorman 800-750 trans line repair kit 3/8

    Mopar repair kits:

    83502745 fuel line repair kit 5/16
    83504447 fuel line/Trans line repair kit 3/8

    As for the black smoke, verify that the MAP sensor hose to the throttle body has NO LEAKS. This is easily disturbed when doing the injector install.

    1. I agree with with everything cruiser54 stated. It is common for the o-ring or polymer washers to fall away from the fuel rail fitting when the supply line is separated from the rail when these sealing components are retained by the fitting at the rail.

      I have the parts he suggests for the MAP/throttle body vacuum line upgrade and will be performing this task today. I noticed more black buildup on my tailpipe yesterday while preparing regions of my undercarriage for POR15. This told me I have a leak associated with this vacuum line.

    2. Correct as usual. The vacuum hose from the MAP disconnected from throttle body. I had to make an adapter to reinstall. I will look into O-rings next. The leak is at the end of the fuel rail under the MAP sensor, I think that is the “return” side. Would that be 3/8 or 5/16?

    1. We replaced the o-rings (5/16”) where the fuel rail meets the fuel line return (up near the firewall) and no more leaks. I also re-connected the MAP vacuum tube. The engine is now purring along with no leaks and far less black smoke. Thanks for the help.

  31. Hey cruiser I’m giving up on making my Jeep Cherokee run correct and thinking about going with a carburetor do you have any suggestions

  32. Maybe you could help me it’s a 89 Cherokee and it starts to hesitate after warming up like it’s changing the fuel mixture I’ve checked all the sensors that I know about TPS IAC map sensor coolant temperature sensor manifold air temperature maybe I’m missing one

  33. I had the injectors installed. My 89 definitely runs better, went from 14.5mpg to 18mpg last trip (mostly highway) but idles noticeably higher. Also, a lot of black soot coming out of the tailpipe.

    Any suggestions? Should I reset the computer?

    I truly appreciate what you have done on this site for everyone.

    Have a Happy Thanksgiving!

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