MJanky

Don't forget that the 2.5L came out in 1984 in the XJ. The '84 and '85 models had carburetors and HEI distributors, no CPS or injection.Don't remind me! I sold off an 84 XJ with the carbed 2.5 for less than I'll end up spending for all the parts I need to convert my MJ (It wasn't running)...ugh! Of course I never thought I was going to come across a deal on an MJ, like ever. Or I would have kept it! Now I have a jones for a 2 door XJ! Curse the Jeep gods! Edit: The only part I have so far is the dizzy from a carbed XJ. I guess it is HEI but I meant I can't just change that out and leave it fuel injected like can be done with the inline 6's. Or can I? I haven't seen anything about it but it should work the same as the 6 conversion, no? Idk I don't know enough about fuel injection to be sure.

I've tried that on several vehicles and it did not work, not even close. I'm not sure what is different about the vehicles in the vids (I've probably seen the same ones as you) but at least one was a European vehicle and likely had a low compression engine which makes a huge difference. If someone was to attempt this on an MJ/XJ what you'd find is how hard it is to get the wheel to turn in low gear (practically impossible) and how slowly the engine would turn in high gear (too slow to start.) Stick to roll starting it. I agree with everything that has been said in this thread...2nd or 3rd gear is best, don't use low range (too much drag) reverse can be used if necessary (rolling backwards) and the Renix is evil when it comes to this. BTW, jump starting is when you apply an external power source to the vehicle's battery to give it a boost. What you're asking about is usually called a push start, bump start, roll start, clutch start or pop start.

Thanks for that info, that's the sort of thing I like to know about. I have the 2.5 so no HEI swap for me, but I prefer carbs over fuel injection for other reasons anyway so doing away with the Renix *for my purposes* is a win-win.

Please let us know if it worked. I've always had an interest in bump starting vehicles. A Renix ignition Jeep poses additional challenges in this regard because of the way it works. It is unlikely to start unless moving at a higher and sustained rate of speed compared to more traditional ignitions. I've been collecting the parts needed to change my MJ to a carb if for no other reason than to confirm this for my own information.

What about finding another 2.5 to swap in? Depending on where you are it could be easier and less expensive to source a good one than to put work into the one you have. As a bonus if you don't need to exchange it for the core you'd have a spare you can rebuild at your leisure.

I agree with yxmj. The 2.5 is all iron, not like a lot of other engines with alloy heads and whatnot where once they overheat they warp and crack. Fix the overheating issue and you will probably find rebuilding isn't necessary. Even a high mileage 2.5 that has withstood abuse can give decent service. I hate to sound cliche but compared to other engines I've dealt with the AMC 2.5 is built like a tank.

Is it running rich by any chance?

Thanks for the helpful info. When I get a chance I'll take mine somewhere where I can really get it rolling and try it. That's one thing I haven't done yet. Even if it works I still want to dump the Renix system though.

If it doesn't there will be a carbureted Comanche for sale cheap!

I'm a backwards kind of guy so that will suit me like a glove!

On flat ground? Do you remember what gear you used? And approximately how much distance did you need to get it up to speed?

Yes the problem does seem to be the number of times the engine has to cycle before it fires with the Renix. I'm sure at higher speeds it would bump start fine but that's not going to work for me. And near as I can tell from reading about it there's nothing I can do to alter the way it works. I guess that's fine by me since I'm a carb guy anyway, I just have a really good excuse to dump the Renix now. I get the impression it causes a lot of problems when it acts up too so I'd just as soon not deal with it later. Shouldn't be hard to find a suitable crank for that Lada if you don't need the original one. Hand cranks are pretty much all the same but there are 2 main types. Either the pin on the crank and the one way ramps on the engine or vice versa. They just come in different lengths and thicknesses but for a Lada most of the antique car or tractor ones should do the trick. I had a 73 VW Thing I set up to be hand started and I had 3 different hand cranks that all worked.

Oh and about that Lada...I know some of those actually had hand cranks, so likely they are low compression engines that would be very easy to push start...much like a Willys Jeep with the Go Devil engine. If trucks still came with hand cranks my worries would be over!

Haha if anyone overthinks bump starting it's me. My Jeep starts by itself just fine but I really prefer to have an emergency method to get it going just in case. In any event you sound like the right person to ask about it. However I've tried numerous times in all 4 gears and even reverse (pushing it backwards of course) and no joy. This was within a distance of about 40 feet or so and I'm sure I had it rolling at least 5 mph. I've started similar vehicles under the same conditions so I knew something was different about this one. Knowing how many times it turned over before starting with the starter led me to research that and learn about the renix deal. I might convert it to carb just to get rid of that. Then I think it would roll start easy. It certainly isn't hard to push by myself.

I don't want to run it that low I want to be able to roll start it by myself without trying to push it almost 30 miles an hour. I just don't see how it can be bump started since there is no spark at low speed. I've heard of people bump starting their renix XJs and YJs but they must have been rolling down a hill or getting pushed or towed by another vehicle.

87 Comanche sport, 2.5, Renix ignition. I've read that it doesn't send spark under 300 rpms. Anyone know some way to manually override it so that it does?