onlyinajeep726 Posted June 8, 2013 Share Posted June 8, 2013 A while back, I posted a thread asking y'all for help diagnosing my '86 MJ 2.5L TBI. It runs funky sometimes, works fine at other times. I could be driving along, doing fine, and then all of a sudden, it would act like it wasn't wanting to take the gas and would just bog down and die. Anyway, I still haven't diagnosed it. Thought maybe fuel pump was dying, but I dropped the tank and pulled the pump, and it has been replaced. There wasn't a ton of sediment in the bottom of the tank, but the old sock and some kind of rubber grommet was sloshing around in the bottom, leading me to believe the pump is not the one the the Jeep left the factory with. Anyway, the problem is the vacuum lines on the top of the tank. They weren't securely seated, and I'm not sure how important those line are to making the engine run right. Anyone here know? Are these grommets still available at some parts store so I can replace them? Also, a side note, I found out that I have a 27.5 gallon tank. Edit: That "27.5" is not in reference to capacity... Once I cleaned the outside of the tank with Purple Power, I was able to read the stamped plate that states it's a 16 gal tank. I should have known that 27.5 was a little much lol. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted June 9, 2013 Share Posted June 9, 2013 Those are tank vents...aka rollover valves. The individual vac lines come together in a T and go to the charcoal cannister, then vented into the intake manifold. someone likely tried to replace them and dropped it in to the tank. They really don't affect the driveability, but they are required for emissions testing...at least they are in California...AND they also keep fuel from pouring out if the Jeep rolls over...just sayin' Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 9, 2013 Author Share Posted June 9, 2013 Ok, gotcha. Well, I was really hoping that was going to solve the issue I'm having as stated above. No such luck, I see. On another note, is this the correct way to hook up the lines coming from the fuel pump? This is a picture from before I dropped the tank. I'm just wondering if they are hooked up correctly. I assume it's correct since the truck was running and I can't imagine the engine would work if the fuel was trying to go into the throttle body through the return line... Link to comment Share on other sites More sharing options...
CRF136N Posted June 9, 2013 Share Posted June 9, 2013 If you got an oxygen sensor on it try unplugging it and see if that solves the problem; I had a similar problem with my '87 4.0, acted like it was starving of fuel at times but otherwise ran fine...in fact I think it was cause I would stand next to it with a can of ether and when it bogged I'd squirt the intake and it would immediately recover the idle. Could not drive it 20 miles without it acting up on a good day. Replaced every damn thing from the fuel pump to every sensor and ignition part (including a new o2 sensor) and even got creative with a few things, nothing worked...decided to try unplugging every sensor one at a time trying to find consistancy in the idle/running, starting with the o2 sensor...with just the o2 sensor unplugged I have put almost 7,000 miles on it and it runs like new...tried replacing that new o2 with another new one and it did the same tweaky thing...wires are crossed somewhere, not worth chasing down...leaving the o2 sensor unplugged, getting 19 miles per gallon and driving it daily; I'm ok with that :) A bad o2 caused my '96 xj to run like crap too but in a different way. Hope you find the problem...never fun with mysteries like that. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 9, 2013 Author Share Posted June 9, 2013 I *think* I tried the O2 unplug trick, but I'm not positive. I will try it again and see if that does anything. I still want to know if the fuel supply and return lines appear to be hooked up correctly lol. If anyone would be willing to crawl under their MJ's and snap a picture, I'd be forever grateful. :bowdown: Link to comment Share on other sites More sharing options...
Biotex Posted June 9, 2013 Share Posted June 9, 2013 Aren't the two lines different diameters? If so, then small to small etc... Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 9, 2013 Author Share Posted June 9, 2013 That's what I would think too. But they look to be the same size which is why I wanted to know for certain. Link to comment Share on other sites More sharing options...
Bornindesert Posted June 9, 2013 Share Posted June 9, 2013 If you trace the lines back one of them connects to the fuel filter along the drivers side frame. That's the supply line. I'm pretty sure that line connects to the more centered port on the fuel tank feed through. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 9, 2013 Author Share Posted June 9, 2013 Good thinking lol. I should've thought of that. :doh: Thank you for pointing that out. :cheers: Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 10, 2013 Author Share Posted June 10, 2013 Ok, so tonight, after doing some thorough research, I have found out that other guys across the interwebz have had a similar problem with there 2.5L TBI MJ's (this one for instance: http://www.justanswer.com/car/0o7nh-1986-jeep-comanche-pickup-2-5-4-cyl.html), and I ordered a new Bosch turbine fuel pump and new Bosch strainer/sock. Got it all from RockAuto.com and got a 5% discount code from RetailMeNot.com. In total, I paid just shy of $78. Woot! I really hope this solves my issue. Wish me luck guys and gals! Link to comment Share on other sites More sharing options...
Bornindesert Posted June 11, 2013 Share Posted June 11, 2013 So, glad to see you're replacing the pump and strainer. Replaced my strainer (from Rock Auto) and the large O-ring that seals the pump assy flange/lock ring. You'll want to look at the rubber gas line that connects the new pump to the rest of the assembly. It's not standard fuel line, it's special submersible fuel line designed to be...submerged lol. I got some from NAPA...it's not cheap either. The little vent thingy's on the top are so easy to pop out, as someone probably did at some point with your tank. They are impossible to put back in, as indicated in the pics you posted in this thread. Here's the trick - carefully use a small screwdriver and separate the rubber grommet from the plastic vent. Not easy, but they will separate. Then, use some vasoline and install just the rubber grommet in the tank. So much easier. I used the handle of the screw driver to force the grommet outward to seat it. Once you do that, the plastic vent piece pops right in and your done with those thingy's. Also, be careful when you install the pump assy, it has to be seated in the slosh tray which has a grommet type of press fit. Leave the vent thingy's out until you get that situated, you can peer into the tank if they are left out. good luck with the install Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 11, 2013 Author Share Posted June 11, 2013 Thanks for the tips. I will definitely pay close attention to all of what you just mentioned. As I wait for the pump and strainer to arrive, I'm taking this time to paint the outside of the tank to keep it from rusting further. The inside has been cleaned by sloshing Purple Power around in it, then vacuumed out with a shop vac. I'm going to replace the vacuum lines going to each of those check valves while I have the tank down. Figure I might as well take care of as much as I can so I don't have to touch it for a long time (hopefully). Link to comment Share on other sites More sharing options...
Biotex Posted June 11, 2013 Share Posted June 11, 2013 Tip! After you get the bulk of the inside of the tank clean with purple power, do a final rinse with acetone. Acetone dissolves varnish like nothing else. Also, it is more compatible with gasoline in case you have any residue left over from the purple stuff. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 12, 2013 Author Share Posted June 12, 2013 Good to know! Thanks! Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 12, 2013 Author Share Posted June 12, 2013 Good news guys (I think). So, I tested the old fuel pump with a 12 VDC power supply in a bucket of water and some hose. I turned on the pump, kinked the hose about four times (to build pressure) and the fuel pump went crazy with the shakes for a while, then finally cut off when it got up to "primed" pressure. Well, after I unkinked the hose to lower the pressure (which it should come back on to keep supplying fuel), it didn't turn back on. Only when I cut power and reapplied it did the pump come back on! This explains why when I would restarted the MJ, it would "work" for a while until it started going crazy again. So... hopefully this new Bosch unit is the pot of gold I've been looking for! :crossfingers: :wavey: :banana: :clapping: :rock on: :wrench: :group beer: :jump: :driving: Link to comment Share on other sites More sharing options...
Bornindesert Posted June 12, 2013 Share Posted June 12, 2013 Pretty smart way to test the pump. Nasty failure mode, works when it's reset but not after it builds pressure. Like you said, makes sense why it would start up and then stall. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted June 13, 2013 Share Posted June 13, 2013 The rollover valves installed fairly easily for me...I did use some lube on the grommet...BUT, once I had it in, I wasn't sure I had it in, so I pulled it back out and the little metal part at the end popped off...and in to the tank. It's still in there and after four years it hasn't caused any issues. I reused the metal part off of the old valve. Lesson learned, once it's in...don't pull it out... There's a sig line for you. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 13, 2013 Author Share Posted June 13, 2013 I verified that I had it in correctly by peeping through the check valve holes on top of the tank. However, the problem I had initially was getting the lock ring to grab since the whole assembly didn't want to sit flush with the side of the tank. I had to remove the whole thing and adjust the height of the pump since the sock was bottoming out too quickly. Had to stick my hand in the tank to pull out the return line grommet that was stuck in the flange. But, I got it back in so as soon as my check valve grommets get here tomorrow, I will get my tank reinstalled and some gas pumped in to see if my issue is corrected. :crossfingers: And I quoted you in my sig, lol. Link to comment Share on other sites More sharing options...
Bornindesert Posted June 13, 2013 Share Posted June 13, 2013 Hey glad to hear it's coming together....where did you ever find the grommets? RockAuto? Would have thought only the vents with grommet would be available, but anyways it's cool you were able to replace those mangled rubber ones Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 14, 2013 Author Share Posted June 14, 2013 I found it at 4wheelparts.com. It's called a Fuel Check Valve Seal, Part # CRO52018823. They were $3.99 each, plus tax and S&H. Cost all of $11. Got a 5% off coupon code from RetailMeNot.com Link to comment Share on other sites More sharing options...
Bornindesert Posted June 14, 2013 Share Posted June 14, 2013 Nice find, added to my list of things to have around. Thanks Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 14, 2013 Author Share Posted June 14, 2013 The rollover valves installed fairly easily for me...I did use some lube on the grommet...BUT, once I had it in, I wasn't sure I had it in, so I pulled it back out and the little metal part at the end popped off...and in to the tank. It's still in there and after four years it hasn't caused any issues. I reused the metal part off of the old valve. Lesson learned, once it's in...don't pull it out... There's a sig line for you. It just occurred to me, after re-reading this post, that I misread it the first time. I started talking about the fuel assembly reinstallation as if that was what you initially said. I really need to learn to read... Anyway, now that I know what you're talking about haha... One of my check valves has the metal thing on the end, and the other does not. I did not, however, find anything in the tank other than some rubber bits and sediment. Not sure where the other metal piece got to, but I don't seem much of a need for it, so I'm not going to sweat it. Link to comment Share on other sites More sharing options...
LowerEnder Posted September 3, 2023 Share Posted September 3, 2023 Did that fix it? Link to comment Share on other sites More sharing options...
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