tetrad Posted January 1, 2015 Share Posted January 1, 2015 88 4.0L short bed. My gas tank apparently has a decent leak when it's filled over a certain point (had it out on the road for the first time today since I got it, so it's the first fillup). It looks like it's coming out of the pump assembly mating surface, but the pump face and a big swath underneath it are pretty well rusted. I'm guessing it's not something that pulling the pump and throwing in a new gasket would fix. Does anyone have recommendations for a replacement tank (new, salvage, etc)? What else is it a good idea to replace while I'm doing it? Will the tank out of a 2.5L fit and work, or do they have any differences in the pump, sender, etc? Link to comment Share on other sites More sharing options...
johnj92131 Posted January 1, 2015 Share Posted January 1, 2015 Just buy a new replacement tank. Ebay has any number of new replacement tanks with prices all over the place. But do save your old tank and everything in or on it till you get the new tank working. Finding a gas tank in a salvage yard will take you a while. Finding a good one will take even longer. BUT, you can give the new gasket a try while you look for that new replacement. Alternatively, you may want to look at the 22 gal. Dakota plastic gas tank as a replacement. Think it can be made to work on the short bed. Here is the link to the Dakota plastic gas tank: http://comancheclub.com/topic/30755-dakota-22-gallon-tank-and-fuel-pump/page-2?hl=dakota&do=findComment&comment=369352 Link to comment Share on other sites More sharing options...
tetrad Posted January 1, 2015 Author Share Posted January 1, 2015 Just buy a new replacement tank. Ebay has any number of new replacement tanks with prices all over the place. But do save your old tank and everything in or on it till you get the new tank working. Finding a gas tank in a salvage yard will take you a while. Finding a good one will take even longer. BUT, you can give the new gasket a try while you look for that new replacement. Alternatively, you may want to look at the 22 gal. Dakota plastic gas tank as a replacement. Think it can be made to work on the short bed. Here is the link to the Dakota plastic gas tank: http://comancheclub.com/topic/30755-dakota-22-gallon-tank-and-fuel-pump/page-2?hl=dakota&do=findComment&comment=369352 Awesome, thanks for the info and advice :) Link to comment Share on other sites More sharing options...
Keyav8r Posted January 1, 2015 Share Posted January 1, 2015 If you replace the tank with a JY tank remember to replace the vents and tubing on top of the tank that go to the evaporative emissions canister. I had leakage there the first time I completely filled the tank on my 91. Dropped the tank, replaced them and no more gas odors or spillage. Dropping the tank also allowed me to test the sending unit and eliminate it as the cause of my inop gas gauge. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted January 1, 2015 Share Posted January 1, 2015 Dropping the tank will also allow you to easily check out the roll-over valves on the top of the tank and the vacuum lines attached. The valves can also be a leak point since the tops are plastic and disintegrate after 25+ years and a disconnected vacuum line on the valves can cause a fuel smell that's hard to locate. If the valves are disconnected, broken or not working properly you WILL NOT pass smog in CA. New valves are available at the dealer for about $25 each...worth replacing while the tank is out. Link to comment Share on other sites More sharing options...
Keyav8r Posted January 1, 2015 Share Posted January 1, 2015 I think I got my new valves on eBay or Amazon for less than $25 each. If I could find the receipt I'd post it. Link to comment Share on other sites More sharing options...
gogmorgo Posted January 1, 2015 Share Posted January 1, 2015 Rockauto sells the new tanks as well. Going the JY route may not work out so well. Not only is it a crap shoot to find an MJ with a decent tank, lots of yards drain the gas by drilling a hole in the tank. Link to comment Share on other sites More sharing options...
91Pioneer Posted January 1, 2015 Share Posted January 1, 2015 For the cost of a new tank and the safety factor, I would not trust a used tank unless it was plastic. But I live in the land of rust. Link to comment Share on other sites More sharing options...
Eagle Posted January 1, 2015 Share Posted January 1, 2015 Before you buy a new tank -- be SURE the leak isn't where the metal tubes come through the fuel pump mounting flange. I made that mistake. I had a leak. I put in a shiny new tank, drove to the gas station to fill up, and just over the half tank mark it started peeing gas all over the place. A leak at that mounting flange is a very common problem -- perhaps even more common than needing a new tank. Link to comment Share on other sites More sharing options...
tetrad Posted January 3, 2015 Author Share Posted January 3, 2015 Before you buy a new tank -- be SURE the leak isn't where the metal tubes come through the fuel pump mounting flange. I made that mistake. I had a leak. I put in a shiny new tank, drove to the gas station to fill up, and just over the half tank mark it started peeing gas all over the place. A leak at that mounting flange is a very common problem -- perhaps even more common than needing a new tank. Does that help at all? I initially thought that it was leaking out of the circle about 1.5" out from the center of the pump, but maybe it was just pooling there to drip. Are you suggesting it could be those metal lines coming out of the pump face that are leaking? If so, a new pump and the same tank ought to fix the problem, right? Link to comment Share on other sites More sharing options...
BlackBeast Posted January 3, 2015 Share Posted January 3, 2015 Have someone hit ignition switch to turn pump on as your under truck but don't start it!!!! Looks like possibly the lines or lid peice. If tank is bad get new 1 not used. Also when tank is installed I took bicycle inner tube and layed around my tank straps to keep my tank cushioned so the straps wouldn't wear on tank. There is a big Oring between lid and tank and that leaks when it gets bad or is in wrong! I also put new fuel pump in but it's not a must it's easy enough to get to as you can see! Link to comment Share on other sites More sharing options...
BlackBeast Posted January 3, 2015 Share Posted January 3, 2015 Plus the salvage yards over here won't take a car without the tank having a hole threw it for saftey. So if you lived here u wouldn't find a good tank in yard. Link to comment Share on other sites More sharing options...
Eagle Posted January 3, 2015 Share Posted January 3, 2015 Are you suggesting it could be those metal lines coming out of the pump face that are leaking? If so, a new pump and the same tank ought to fix the problem, right? That's exactly what I'm suggesting. You may not even need a new fuel pump. Siphon off enough gas to get the level below that hole in the tank. Then clean off all the gasoline residue. I would use carb cleaner first, followed by brake cleaner -- and then maybe wipe it down with alcohol. Mix up a bit of epoxy and press it tightly around the tubes to seal them to the flange. I used to use an epoxy that came in ribbon form. It had the consistency of clay. You tore off a strip, mixed the two colors together, then applied. That stuff would stick even to a surface wet with gasoline -- as I proved conclusively by doing it. The problem is, I haven't seen that product for sale for several years, and I don't know what epoxy to recommend in its place. Link to comment Share on other sites More sharing options...
88whitemanche Posted January 3, 2015 Share Posted January 3, 2015 Double check this thread...at the link at the bottom...this may be your problem.... http://comancheclub.com/topic/38404-gas-leak-at-sender-unit/?fromsearch=1 Link to comment Share on other sites More sharing options...
tetrad Posted January 3, 2015 Author Share Posted January 3, 2015 Awesome, thanks guys. Sounds like a new push-nut + o-ring on the plug and/or epoxy on those hard lines will fix the problem. I now feel confident enough to tear into it and see what the damage is :) 88whitemanche, the link you put at the bottom of the other thread (http://comancheclub.com/topic/38976-gas-tank-leak/?do=findComment&comment=393159) was very helpful as well. I just had CA smog fail due to the gas tank not holding pressure (they pinch the two lines at the charcoal canister and then pressurize it through the filler tube). I think this leak is the source of the problem, but I want to cover my bases to minimize retests. I'm considering also dropping the tank to make sure the ventilation line(s) on top are in good shape, but I'm worried about being able to reuse the straps and nuts. Link to comment Share on other sites More sharing options...
tetrad Posted January 3, 2015 Author Share Posted January 3, 2015 I pulled the sender and pump assembly. I'm gonna clean it up and go pick up my new o-rings, lock ring, and push nuts. When I put the new o-rings in, do I lube them up with petroleum jelly or just set them in dry? Link to comment Share on other sites More sharing options...
88whitemanche Posted January 3, 2015 Share Posted January 3, 2015 I did them dry...idk if jelly would help seal them? Link to comment Share on other sites More sharing options...
johnj92131 Posted January 3, 2015 Share Posted January 3, 2015 Petroleum Jelly should not do any harm and will help hold the O ring in place (I think). Link to comment Share on other sites More sharing options...
Knucklehead97 Posted January 4, 2015 Share Posted January 4, 2015 Quik steel is a good epoxy for fixing a leak on those metal lines. Have had mine fixed with it for over a year and it doesn't leak at all. It is gas resistant. Also only about 4$ from Walmart for a tube that will last a long time. Just make sure to knead it well and press it ALL around the tube. Link to comment Share on other sites More sharing options...
Steve Gregory Posted January 5, 2015 Share Posted January 5, 2015 I replaced my leaky gasket, then found one of the metal lines had a crack in it right where it meets the face of the sending unit, J.B. weld works wonders. Link to comment Share on other sites More sharing options...
Knucklehead97 Posted January 5, 2015 Share Posted January 5, 2015 I had thought to use JB weld at first but researched and found that JB weld was not rated for gas exposure. Best to be safe than sorry lol Link to comment Share on other sites More sharing options...
tetrad Posted January 5, 2015 Author Share Posted January 5, 2015 Well I used JB weld, so here's hoping :) I wasn't able to verify exactly what was leaking, so I did all three fixes (new main o-ring, new wire o-ring and pushnut, slather with JB weld). I got everything put back together and reinstalled. The assembly is missing one of the tangs on the mating surface (rusted off) so it's not sitting entirely straight. I think the lock ring is pressing it into the o-ring tight enough that it won't leak, but it's probably only a matter of time before road vibes wiggle it loose again. Link to comment Share on other sites More sharing options...
Eagle Posted January 5, 2015 Share Posted January 5, 2015 Let us know what happens the next time you fill up. Link to comment Share on other sites More sharing options...
tetrad Posted January 7, 2015 Author Share Posted January 7, 2015 I filled it up with about 2 gallons of gas I had sitting in a tank, and no leaks. Idled it for a few minutes, and no leak. Took it into the smog station and it failed the pressure test and then started leaking again :( I went to a salvage yard where they just got in an 88 MJ, and pulled the sending unit. It looks in much better shape. Not sure which pump I'm going to use. I'll probably be back in the next couple days to pick over it more (it was nearly closing time). It had a 3-piece slider that I'd love to get my hands on :) Link to comment Share on other sites More sharing options...
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