Al24 Posted July 2, 2022 Share Posted July 2, 2022 A little background. I bought this about 15 years ago. I might even have had an account on this site at the time. Anyways.. 1990 MJ 4.0 5 speed. About 190k on it. I did some of the mods recommended here such as cooling system, it also has an nv3550 TJ trans and clutch set up and some other odds and ends. Due to a job that involved a lot of traveling, I parked it. I would be home about every 8 weeks and would at least start it and drive it a bit. Stopped doing that around 5 years ago and it sat. Last year tried starting it, cranked it over after charging the battery, but wouldn't fire. It was popping back through the throttle body. So I'm gifting it to a friend she towed it to a shop to have it checked out. They haven't got to it yet. Bad gas maybe? Any ideas would be appreciated. Link to comment Share on other sites More sharing options...
Pete M Posted July 2, 2022 Share Posted July 2, 2022 definitely could be bad gas. Link to comment Share on other sites More sharing options...
OldSch88L Posted July 3, 2022 Share Posted July 3, 2022 Well, like Pete said, bad gas for sure for starters. Modern gas is such garbage, it blows my mind, no pun intended. I now work at a tool and machinery rental store, where I wrench on anything from excavators and Skyjacks to chainsaws and snowblowers. All our gasoline equipment (both 2 and 4 stroke) are fueled with super unleaded, as it's the only grade that doesn't have ethanol (yet), and for extra peace of mind, we add some fuel stabilizer during the winter when business slows down. We aslo fix customers' equipment, and of course they use regular gas, no stabilizer nor do they run it once in a while in their downtime. Sometimes, one season is enough to cause problems. As regular gas dries up, it leaves a yellowish, powdery gunk that clogs everything, and junks carburators in my case. Even after dismantling and an ultrasonic bath, they never run right again. So, flush your tank and add fresh fuel, super unleaded if you plan on letting it sit again. Change the fuel filter. Replace or clean the injector. As for the backfiring through the throttle body, I'm leaning towards stuck valves. I'd take off the valve cover and make sure no rockers are loose as you spin the crank with a ratchet through a complete cycle. Link to comment Share on other sites More sharing options...
Al24 Posted July 3, 2022 Author Share Posted July 3, 2022 Gas was the first thing that came to mind. I'll try and talk the new owner to sign up here. Appreciate the suggestions. Link to comment Share on other sites More sharing options...
Al24 Posted July 6, 2023 Author Share Posted July 6, 2023 Only a year later...fuel tank drained and filter and pump changed. It runs really well. My friend doesn't want to build it as she thinks it's pretty cool as a rare old truck. Unfortunately I have a bunch of builder parts for it. I guess it's going to be garage sale time as I'm moving it 4 weeks. Link to comment Share on other sites More sharing options...
Pete M Posted July 6, 2023 Share Posted July 6, 2023 2 hours ago, Al24 said: Only a year later...fuel tank drained and filter and pump changed. It runs really well. My friend doesn't want to build it as she thinks it's pretty cool as a rare old truck. Unfortunately I have a bunch of builder parts for it. I guess it's going to be garage sale time as I'm moving it 4 weeks. that's why you need a second, more beat up MJ too. Link to comment Share on other sites More sharing options...
Al24 Posted August 29, 2023 Author Share Posted August 29, 2023 Unfortunately, my building days are over. I know there is a minimum post limit on selling parts, etc. I am moving soon and have quite a few things I would like to give away...freee just pick up in the state of Colorado. Is this allowed? I'd rather give them away than have the scrap guys pick them up. Link to comment Share on other sites More sharing options...
Al24 Posted August 29, 2023 Author Share Posted August 29, 2023 One fun update. I helped her replace the o rings on the injectors as one was leaking. I did this 16 years ago when I first picked up the rig.. I was pleasantly surprised that I was able to remember what to remove to get to them and how to hook them back up again without digging out any diagrams. Link to comment Share on other sites More sharing options...
Al24 Posted August 29, 2023 Author Share Posted August 29, 2023 Everything went well, Jp fired right up and after a few stutters idled nicely. At first, not a leak in sight...then one of the injectors started leaking out of the body of the injector. So we fixed one leaker and created another. She's going to order a set of rebuilt 4 hole injectors as a little upgrade. Link to comment Share on other sites More sharing options...
fiatslug87 Posted August 29, 2023 Share Posted August 29, 2023 Has she decided to join the site? Any pics of the truck? Has it been added to the registry? Link to comment Share on other sites More sharing options...
jdog Posted August 29, 2023 Share Posted August 29, 2023 You only need two more posts and you can post in the classified section Link to comment Share on other sites More sharing options...
Al24 Posted August 30, 2023 Author Share Posted August 30, 2023 It's in the registry. She has a lot going on so I doubt she'll be around. Link to comment Share on other sites More sharing options...
Al24 Posted August 30, 2023 Author Share Posted August 30, 2023 Link to comment Share on other sites More sharing options...
Pete M Posted August 30, 2023 Share Posted August 30, 2023 1 hour ago, jdog said: You only need two more posts and you can post in the classified section I think it's 1 post for sending private messages and 10 for the classifieds. Link to comment Share on other sites More sharing options...
jdog Posted August 30, 2023 Share Posted August 30, 2023 1 hour ago, Pete M said: I think it's 1 post for sending private messages and 10 for the classifieds. Correct, he was at 8 posts Link to comment Share on other sites More sharing options...
Pete M Posted August 30, 2023 Share Posted August 30, 2023 sometimes I gotta remind myself. Link to comment Share on other sites More sharing options...
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