MJ Comanche Tech. Stock & Modified. MJ (86-92)
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I need some help

Old 08-26-2016, 06:36 PM
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Red face I need some help

So I just recently bought a 89 Comanche Pioneer.
The previous owner mentioned he replaced the fuel pump in the few months he owned it. It has an after market switch to turn it on as well.
Today I'm guessing it may have stopped working but I don't know all the signs of that. I can hear it power on, but when I try to turn it over, no gas is going to the engine. I pumped the gas pedal and it didn't do anything promising.
I was thinking maybe I was out of gas, since the gas gauges are famous for not working. Added at least 2.5 gallons, no difference.
So I guess my question about that is, can you still hear the fuel pump TRYING to work when they fail? Or is my problem elsewhere? Maybe in the gas lines?
I'm still very amateur in my vehicle knowledge so I don't know what else to look for. I've only spent a lot of time around mechanics And have learned the very basics...like, VERY basics.

Another issue I'm having is a pretty major oil leak. The whole undercarriage is coated in sludge. It isn't pouring out of anywhere but there's drips under the oil pan, around the rear main seal, and it looks as though it is slowly seeping out of the engine block itself. Looks like somebody used some leak repair because there's red residue around the engine of some sort of sealant. Not sure what those liquids end up turning to when they're old and start to seep out with the oil.....
I was told it's the RMS, but since there's oil seeping so far up, I wonder if there's more than one leak...sure seems like it.
Anyways, some insight would be greatly appreciated. I'm pretty sure I paid too much for this truck already but HEY, ITS A COMANCHE! (;
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Old 08-26-2016, 08:11 PM
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What engine/transmission?
First check fuel pressure something like this: (note: if the tank is bone dry 2 1/2 gallons may not be enough fuel)
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Old 08-26-2016, 08:20 PM
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What he said ^^^ and I would check gas filter too. If it p.o. didn't change it out with the new pump it could be clogged or restricting pressure
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Old 08-26-2016, 09:32 PM
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It's the 4.0
4 speed automatic transmission
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Old 08-26-2016, 09:37 PM
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Thank you for the suggestions! Going to check it out.
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Old 08-26-2016, 10:03 PM
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any replacement pump besides a Bosch is a crap shoot.
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Old 08-27-2016, 07:53 PM
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Originally Posted by ThatMJgirl View Post
Another issue I'm having is a pretty major oil leak. The whole undercarriage is coated in sludge. It isn't pouring out of anywhere but there's drips under the oil pan, around the rear main seal, and it looks as though it is slowly seeping out of the engine block itself. Looks like somebody used some leak repair because there's red residue around the engine of some sort of sealant. Not sure what those liquids end up turning to when they're old and start to seep out with the oil.....
I was told it's the RMS, but since there's oil seeping so far up, I wonder if there's more than one leak...sure seems like it....
Hello and welcome to the world of Jeeps. My experience has shown me that RMS leaks are rarely from the RMS. In most cases it comes from higher up and farther forward and works it's way back. Since the RMS is at the lowest point this is where the oil finally drips off of and people think that is the problem. The most common place it seems to come from is the oil filter adapter. Repeated changing of oil filters over the years wears the o-rings being it down. The oil leaks out and runs along a little ledge on the side of the engine and then down cracks until it leaks out far away from where it started. If it's not the adapter leaking then look at the oil pressure sending unit or valve cover etc.
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Old 08-27-2016, 10:59 PM
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I’d be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn’t own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking. Many mechanics, friends, and good old Uncle Bob seem to enjoy telling you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it?

A simple leak at the back of the valve cover or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don’t jump on the RMS/oil pan gasket bandwagon right off the bat.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons:

First off, the engine sits nose-up and any oil will run back to the RMS area.

Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber’s adage apply here: “Crap flows downhill”.

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first.
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Old 08-28-2016, 11:55 AM
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Yeah I was pretty doubtful about the RMS diagnosis. I can see oil too high up on the motor for it to be that. Not saying it's not both, but I'm for sure going to work my way down first.
I noticed the 4.0 is tilted upwards and that causes the oil to drip down in those areas. They definitely wanted to ruin my day by bringing up the RMS. (;
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Old 08-28-2016, 12:13 PM
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I welcome a minor oil leak.... it's a nice rust preventative lol
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Old 08-28-2016, 02:14 PM
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I think this on has either been going in for a while. Or it is no longer minor.
I like your rust prevention view on the situation though! I just live in a VERY dusty area and so now I have a nice layer of dirt on that oil coat. Not good. Makes my job harder and dirtier for sure.
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Old 08-28-2016, 05:32 PM
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Originally Posted by ThatMJgirl View Post
Yeah I was pretty doubtful about the RMS diagnosis. I can see oil too high up on the motor for it to be that. Not saying it's not both, but I'm for sure going to work my way down first.
I noticed the 4.0 is tilted upwards and that causes the oil to drip down in those areas. They definitely wanted to ruin my day by bringing up the RMS. (;
Diagnose it yourself.
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Old 09-01-2016, 03:16 PM
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Changed the ignition coil
Truck started And drove for about a mile then cut off on me. Cleaned all the electrical connections, turned back on, drove a quarter mile and cut off again. It keeps starting back up with a little struggle....
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Old 09-01-2016, 03:17 PM
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Going to work more on the oil leaks when it starts and runs...
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Old 09-01-2016, 04:23 PM
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Originally Posted by ThatMJgirl View Post
Going to work more on the oil leaks when it starts and runs...
Of my Tips, how many have you completed?
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