thedave360 Posted August 23, 2009 Share Posted August 23, 2009 So I was driving my Comanche today. I tried to accelerate, and all I got was sputtering. I tried to get up to highway speeds but it could only manage about 20mph and it was running rough the whole time. I pulled on to the shoulder and put it in neutral. When I revved the engine, everything sounded ok. As soon as I tried to take off in drive it would sound like its about to die. Does anyone think this isn't the fuel pump? Because it sounds like it to me. Also, has anyone ever changed one before...and if so, how did you go about doing that?? Link to comment Share on other sites More sharing options...
mvusse Posted August 24, 2009 Share Posted August 24, 2009 Does definitively sound like the fuel pump, or at the very least a plugged sock or filter. Check those first. I have replaced my pump several times. You do not need to drop the tank to do so, but removing the drive shaft (easy) will give you more room to move to get the pump assembly out of the tank. Make sure the tank is NO MORE THAN HALF FULL!!! Do not buy the entire assembly, as it will be for a Cherokee, even though the store personell will swear up and down it is for a Comanche as well. It will not work as it will be mirror image of what you need. Just buy a new pump and install it on your original assembly. ALWAYS INSTALL A NEW SOCK! I can not stress this enough. If the pump comes with one, install it. If it doesn't, buy one! Every time the pump is out of the tank for whatever reason, install a new sock. If your tank is nearly empty, it may also be worth your time to remove it, drain it, and wipe out any crud inside it. Link to comment Share on other sites More sharing options...
thedave360 Posted August 24, 2009 Author Share Posted August 24, 2009 Make sure the tank is NO MORE THAN HALF FULL!!! Any other ways of draining the tank besides siphoning?? BTW, thanks for all the tips! I definitely wouldn't have thought to disconnect the drive shaft! Link to comment Share on other sites More sharing options...
Wildman Posted August 25, 2009 Share Posted August 25, 2009 Disconnect the supply line at the fuel filter, put the line in a gas can, and cycle the key on and off, many times, that will turn the pump on for a few seconds, and it will stop on it's own, and turn the ignition off, and back on, it will "pump" the tank down for you :D Link to comment Share on other sites More sharing options...
Oizarod115 Posted August 26, 2009 Share Posted August 26, 2009 Disconnect the supply line at the fuel filter, put the line in a gas can, and cycle the key on and off, many times, that will turn the pump on for a few seconds, and it will stop on it's own, and turn the ignition off, and back on, it will "pump" the tank down for you :D or get a 12v (ish) battery and connect some jumper wires to the pump Link to comment Share on other sites More sharing options...
veritas4156 Posted August 26, 2009 Share Posted August 26, 2009 If the pump is totally toast though, that's not gonna work. Link to comment Share on other sites More sharing options...
mvusse Posted August 26, 2009 Share Posted August 26, 2009 My pump which was toast enough for me to limp into my parents driveway in Canada after spending an hour to cover the last 20 miles still drained 3/4 tank in under an hour when I hot wired it to a battery charger. Disconnected the pressure line, and lined up 5 gallon buckets to pump it into. Link to comment Share on other sites More sharing options...
thedave360 Posted September 1, 2009 Author Share Posted September 1, 2009 Thanks for the info guys. I'm currently tackling the thing right now. The turning the key thing is not really working, it seems like every 3rd key turn the pump doesn't run and won't for the next couple key strokes. I would really like to hot wire the pump to run constantly, but I have a few safety concerns. There is a REALLY strong concentration of fumes under the truck. I'm concerned that if I start stripping wires and rigging a battery charger to power the pump it may start a fire with all the fumes. I'd really like to not blow me, my jeep, and my patio all to hell while trying to change my fuel pump. Siphoning didn't work. It seems there is some sort of thing blocking the hose from going into the tank :doh: . I'm almost at the point where I could just jam a screwdriver through the bottom of the tank let it drain and figure out how to patch that later :wall: ...almost Link to comment Share on other sites More sharing options...
dasbulliwagen Posted September 1, 2009 Share Posted September 1, 2009 Pull the fuel pump relay and stick a wire in to where terminal numbers 30 and 87 go, this will make the pump run as long as you need it to. Link to comment Share on other sites More sharing options...
thedave360 Posted September 1, 2009 Author Share Posted September 1, 2009 Well in between my last post and now, I decided I would just deal with the mess and take the fuel pump out anyway. After breaking the rusted out retainer ring, it came out with no gas. Apparently you can do something like this with more than half a tank--if you park on an incline :brows: The hoses connected to it did, however, leak gas everywhere...but there isn't much I could do about that. So the retainer ring is on order from my favorite auto parts store and should be here tomorrow morning. I should have it all back together tomorrow morning-ish. The key word there being SHOULD. Now I have to get the gas smell off my arms and out my hair :ack: The little woman says its not very attractive lol. Link to comment Share on other sites More sharing options...
cluricaunne Posted September 2, 2009 Share Posted September 2, 2009 I just replaced my pump too... took me twenty minutes, didn't disconnect the drive line, but I am small enough I was able to sit up between the wheel well and the drive line so that I was staring right at the pump assy... this is my second pump in the last year, when this one goes I am going to drop the tank, and scrub the inside of it. Link to comment Share on other sites More sharing options...
mvusse Posted September 2, 2009 Share Posted September 2, 2009 when this one goes I am going to drop the tank, and scrub the inside of it. That is what finally solved my fuel pump issues permanently, after having replaced 3 pumps in a half year. Last "bad" pump has been working fine after a new sock (again) and wiping the inside of the tank clean. That was 9 months ago. Link to comment Share on other sites More sharing options...
ratrapp Posted September 2, 2009 Share Posted September 2, 2009 i wonder what the problem is with the mj going through pumps?my original pump lasted 12 years.it went and i replaced it with a mopar pump and also bought a brand new gas tank because the inside was eating out with crud.it lasted 8 years and it died and i replaced it with a bosch pump.it seems like it doesn't get full pressure when i first start it and take off until i've drove it a mile or two.maybe these trucks like water pumps and fuel pumps.at least the 4.0 trucks do,lol Link to comment Share on other sites More sharing options...
thedave360 Posted September 4, 2009 Author Share Posted September 4, 2009 well, I got the fuel pump in, hooked it up and everything is working great. I really wouldn't enjoy changing this pump again anytime soon. Next time (which will hopefully be a long time from now) ill take the tank down and clean it out. Turns out, if you have a 4" lift, you don't need to drop the drive shaft. Also, my comanche has no exhaust system after the catalytic converter, so I was actually able to sit under truck to situate the pump...pretty handy! Link to comment Share on other sites More sharing options...
ratrapp Posted September 4, 2009 Share Posted September 4, 2009 i have no lift on mine and i never dropped the d/s on mine to take the fuel pump out. Link to comment Share on other sites More sharing options...
mvusse Posted September 4, 2009 Share Posted September 4, 2009 Dropping the drive shaft is not needed, but does make it easier. With a lift it may not make a difference. Link to comment Share on other sites More sharing options...
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