Dropping a Tank (What you don't see on YouTube)

[NC Tom]

Good morning all,

 

Just a tale, not asking for advice. My MJ has been on jack stands for several weeks now undergoing many tests and parts changes. My latest adventure was dropping the gas tank to check/replace the fuel pump. Like many of you, I have watched several videos on the processes of removing/installing the parts I need. What I have decided is that the people who make these these videos rarely, if ever, show you what really happens when you start wrenching on these trucks for the first time. For example, the guys who have the vids on dropping a gas tank must drop their tanks several times a year just for fun. If you watch these vids, keep that in-mind so when your journey is not so smooth, you don't loose your $#!&e like I do!

Now, to be fair, what they show is mostly helpful. However, they never seem to encounter the obstacles that I do.

Pics attached for your viewing pleasure.

 

Strap nuts that broke off.

Vacuum hoses crushed and pinched under the straps.

J-bolts seized and while trying to UN-seize it, it popped out and the tank fell right on my stomach! OOF!! Glad I had emptied it.

Odd vent hose clamps so rusted I had to cut the lines to get the tank out. None of the vids I watched had clamps on the vent hoses?

Worm Clamps so rusted and seized, I had to cut the hose. This was my point-of-no-return moment.

 

 

Having done all this I have found small holes in my tank. So, along with all the parts and pieces I needed to put the tank back, I am now replacing the whole tank!

 

Sincerely,

NC Tom

 

[Gojira94]

The rollover valves serve 2 functions: 1) they prevent fuel flow out of the tank into the evaporative emission lines and toward the engine in the event of a vehicle rollover; 2) their 'normal' job to allow fuel vapors to get to the canister when the fuel temperature rises and the fuel vapor content of the tank needs a place to go.

 

The valves aren't expensive and Dorman makes a replacement. Mine were ok after 35 years. I cleaned them off and blew them out gently. Flipped them upside down and blew through them and no flow. The grommets are not hard to find either. 7/32" emissions hose (1 bar rating) is what you want to replace the lines. Available at most parts stores by the foot. You won't need clamps on the lines to the valves, they're not going to go anywhere.

 

You'll notice on the tank there is a recess around both valves. You can run new lines, the idea is to route them away from the tank in a way they don't get pinched with the tank secured. The front one can go toward the outboard side of the vehicle and come around the front of the tank. The rear one can drop inboard toward the driveshaft and then forward from there. Use a T junction to join both lines into one. Then the single line from the two joins the fuel feed and return lines' routing. There is a small plastic loop attached to the bottom of the bed from the factory that holds that line secure just above the front strap hole. That may be gone, just zip tie the line somewhere secure and up away from harm.

 

Filler hoses are hard to find but it seems XJ hoses can be modified to serve the purpose. Dorman also makes the straps - Dorman 578-054, about $40-$45 on Amazon, etc. The j-bolts probably will clean up. I went to town with a wire brush on my filler neck, taped over the ends and hit it with engine enamel and then baked it with a heat gun to preserve it. 18 gallon tanks are easy to find, I think you already know about the MTS pump/sending units if you need one of those. Lock ring/ o-ring kit is same as GM stuff.

 

If you replace the soft fuel lines from tank to hard lines, get fuel injection hose and use fuel injection clamps, not worm clamps, obviously. Sorry I'm not closer, I'd be happy to come help if I was!

[NC Tom]

On 4/2/2023 at 1:43 PM, Gojira94 said:

I cleaned them off and blew them out gently. Flipped them upside down and blew through them and no flow. The grommets are not hard to find either. 7/32" emissions hose (1 bar rating) is what you want to replace the lines. Available at most parts stores by the foot. You won't need clamps on the lines to the valves, they're not going to go anywhere.

 

You'll notice on the tank there is a recess around both valves. You can run new lines, the idea is to route them away from the tank in a way they don't get pinched with the tank secured. The front one can go toward the outboard side of the vehicle and come around the front of the tank. The rear one can drop inboard toward the driveshaft and then forward from there. Use a T junction to join both lines into one. Then the single line from the two joins the fuel feed and return lines' routing. There is a small plastic loop attached to the bottom of the bed from the factory that holds that line secure just above the front strap hole. That may be gone, just zip tie the line somewhere secure and up away from harm.

 

Filler hoses are hard to find but it seems XJ hoses can be modified to serve the purpose. Dorman also makes the straps - Dorman 578-054, about $40-$45 on Amazon, etc. The j-bolts probably will clean up. I went to town with a wire brush on my filler neck, taped over the ends and hit it with engine enamel and then baked it with a heat gun to preserve it. 18 gallon tanks are easy to find, I think you already know about the MTS pump/sending units if you need one of those. Lock ring/ o-ring kit is same as GM stuff.

 

If you replace the soft fuel lines from tank to hard lines, get fuel injection hose and use fuel injection clamps, not worm clamps, obviously. Sorry I'm not closer, I'd be happy to come help if I was!

 

Thanks for the epic reply! While I wasn't asking for help, you did provide some good info.

 

I too, am reusing the rollover valves. I did get the Cherokee filler hoses, a new tank, and an MTS pump.

 

Why fuel injection hose?

[Gojira94]

3 hours ago, NC Tom said:

Why fuel injection hose?

 

 

because regular ‘fuel line’ is only good for low pressure fuel delivery < 20psi and our trucks make 39psi. FI hose is rated for a lot higher than our pressure but better safe than leaky. 

[NC Tom]

4 hours ago, Gojira94 said:

 

 

because regular ‘fuel line’ is only good for low pressure fuel delivery < 20psi and our trucks make 39psi. FI hose is rated for a lot higher than our pressure but better safe than leaky. 

Yeah, I realized that after I sent the question. Senior moment, I guess.

 

Would you happen to know where I can find detailed instructions on placing this dang fuel sending unit into the tank? I can't figure out the proper orientation of the filter and the float. I've watched a few videos, but that info is not covered.

[Gojira94]

Facing the hole in the tank, the float goes to the left in the ‘basin’ in the bottom of the tank and the rubber foot on the return pipe goes in the hole at the right corner of that basin. Shine a light in one vent hole and eyeball it through the other to get it seated. A very light smear of Vaseline on the o-ring and back side of the lock ring helps get that seated once the sending unit is in place.

[NC Tom]

12 hours ago, Gojira94 said:

Facing the hole in the tank, the float goes to the left in the ‘basin’ in the bottom of the tank and the rubber foot on the return pipe goes in the hole at the right corner of that basin. Shine a light in one vent hole and eyeball it through the other to get it seated. A very light smear of Vaseline on the o-ring and back side of the lock ring helps get that seated once the sending unit is in place.

I'm going to try and work this pump in the tank. However, there is no hole in any corner of the basin.

[Gojira94]

Upside down pic, but here's mine. It's not in the corner, now that I'm looking at it, my bad. That raised hole should be there, though some aftermarket tanks may not have it, I suppose. 

 

[NC Tom]

3 hours ago, Gojira94 said:

Upside down pic, but here's mine. It's not in the corner, now that I'm looking at it, my bad. That raised hole should be there, though some aftermarket tanks may not have it, I suppose. 

 

Nope. Definitely no not have that.

 

So, I have installed the new tank, pump, sending unit, lines, etc. and still no start. I am certainly lost on this one. I guess I should order a new fuel pressure regulator.

[Gojira94]

You might want to step back for a minute and make a troubleshooting chart through fuel and spark. I don't have a stock pre-1991 rail to look at but if yours has a Schrader valve go ahead and see if you get fuel to the raIl and what the pressure is. Double check fuel pump ground, fuel pump ballast resistor, relay, etc. if not. See if you get spark from the coil wire during cranking. If you have good fuel pressure and spark but still no start- get going through the sensors testing guides on this site and Cruiser 54's site.

 

At the very least so far, you've discovered and corrected an unsafe fuel condition you didn't know about beforehand.   You'll get it!

[NC Tom]

3 hours ago, Gojira94 said:

You might want to step back for a minute and make a troubleshooting chart through fuel and spark. I don't have a stock pre-1991 rail to look at but if yours has a Schrader valve go ahead and see if you get fuel to the raIl and what the pressure is. Double check fuel pump ground, fuel pump ballast resistor, relay, etc. if not. See if you get spark from the coil wire during cranking. If you have good fuel pressure and spark but still no start- get going through the sensors testing guides on this site and Cruiser 54's site.

 

At the very least so far, you've discovered and corrected an unsafe fuel condition you didn't know about beforehand.   You'll get it!

Yes, I have the valve. I've never had a big spray of fuel, but now, it just leaks out when pressed. I thought the fuel pump built pressure and that's why I changed it. I've tried starting fluid in the TB without success.

[Gojira94]

Do you have a decent multimeter that can measure ohms of resistance? The ballast resistor has a spec on it on the ceramic body if I recall correctly. If it’s way higher than spec it’ll only let the pump have a little voltage, not enough. But that’s problem 1. Problem 2 is apparent lack of spark. If you pull the coil wire off the dizzy and have an assistant crank it while you hold the wire against the head, do you see spark? If not go upstream and check the coil’s primary and secondary windings resistance. I can pull those specs and how to test from another post in the “things you’d share” thread. If the coil is good, the module is not easy to bench test, still looking for a way to get that. You can see if there’s 5V between its reference voltage signal from the ECU and its ground. If you do have good spark at the coil wire, distributor sync may be part of the issue. Re-indexing the dizzy couldn’t hurt, and I’m sure someone can chime in with info on testing the dizzy sync module itself. And proper testing/ adjustment of the CPS is always good to eliminate. And triple check the fuel pump ground lol…

[NC Tom]

12 hours ago, Gojira94 said:

 

Jeeess! All I wanted to do was to change my fuel injectors and it's turned into a project of biblical proportions. The truck ran well before I started this thing. It would occasionally stall at a stoplight, but would start back up. I noticed an injector leaking, decided to change it and Blamo! Dead.

I can't wrap my brain around why all these electronic things are popping up. I touched nothing but stuff around the rail. I'll start checking the things that you suggested. If I can figure out how to use my old analog multimeter. 

[Gojira94]

I guess the first thing is whether the fuel pump is turning on and getting enough voltage. if you unplug the pump connector, set your meter for DC volts and probe the harness side with key on, see what you get. If it's a lot lower than what your battery reads between +/- posts, disconnect the ballast resistor and jump across it with wire instead and see if the voltage at the harness side of the pump changes to what your battery voltage is, or close to it.

(That's task 1)

[NC Tom]

I ordered a simple digital meter today from Napa. I guess I'll get out Sat and start taking readings.