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Fuel Pump Prob?


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Took the jeep wheelin' Sunday and had a recurrence of a previous prob. Jeep is cutting out like gettin no fuel.When ocurred before,found broke vac line at intake manifold,fixed that and replaced fuel filter also. Well it did it again and this time I could hear fuel pump growling non-stop till it finally stalled again and wouldn't restart. Turned key on on off a few times and heard pump kick on and off but not every time. After sitting while rigging tow strap,it started and had no issues all the way home. Other than hearing the pump "growling" non-stop. Ran into a XJ on trail and he said he had same prob and it was his pump going out. Does that sound right? Or does a pump slowly die or not? Thought maybe someone else might have had same type prob. Any input would be greatly appreciated as always, thanx ko

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I had my pump give pressures all over the chart when it was going out to where at one point it stalled. Luckily it never stranded me (on that pump at least). For me though it would be really low on power in the low end the all of the sudden jump and take off (not literally). my new (2nd) pump was defective though and it just died instantly after about 1mo use. But my properly working pump now still whines when I'm at low speeds after it warms up, but i wouldnt call it a "growl".

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Thanx for the reply. This new "growl or loud "hum" I never noticed before. Would just hear pump kick on and off at start up.And the new noise is much louder than the 1-2 sec. start up whine.

 

yeah, its relly loud in mine too. I have it [whinning] in ALL 4 of the XJs i have and have had it in all 6 of the xjs i have had (including in the MJ w/ a brand new pump). As long as its not a growling or grinding its probably ok. I would get a pressure test done though just to be sure. [/i]

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Check the resistance of the ballast resistor, if you still have it not bypassed. The ballast resistor is relayed in the FP voltage supply circuit after the engine starts, and it drops the FP voltage down to 9-10 VDC to lower the noise and supposedly prolong the life of the FP. But if the connections are corroded on the resistor, or anywhere else on back to the pump, the actual operating voltage will be significantly lowered. This can cause low fuel pressures and weird noises from the pump. Get back in there and measure the actual operating voltage AT the pump after startup. This will give you a good starting point for troubleshooting.

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my pump howled for about 3 years, then one day I started it up, it ran for about 3 seconds and then died. Had to put it in 1st gear and crawl it with the starter for about 100 ft to get it to a safe place to work on it.

 

Moral of the story......replace pump.

 

Jeff

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My pump was relatively quiet (or at least I thought it was) when I first started the truck, but after 5 minutes or so it got so loud you could hear it from 20 feet away. Drove like that few a number of months until one day I was 90 minutes from home and I was losing power. The truck started bucking and missing whenever I got on the gas, but idle and low throttle was fine. It got worse and worse until I could only get it up to 45 mph on flat ground (and take 5 miles to get up to that speed). Since it wasn't safe to get on the freeway like that I ended up taking back roads, and one last steep hill 2 miles from home I limped over the top at less than 1 mile an hour.

 

Next morning it ran fine again, but after 15 minutes started losing power just like the day before. Replaced the pump and had all the power back even at WOT. And I couldn't even hear the pump unless I had the window open and listened very carefully.

 

I took the old pump apart, but there was nothing visibly wrong with it. It must have been worn out pretty bad, though.

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Sending unit for Comanches are not being made anymore. Do not be fooled by parts stores saying they have them. Their computers say the Cherokee is the same as the Comanche, but in fact the Comanche is supposed to be mirror image.

 

There should be no need to get a sending unit unless it is leaking (and usually if it is you are better off fixing it.) If you do get one it will be a used one that is guaranteed to be at least 16 years old.

 

The pumps themselves are interchangeable between Cherokees and Comanches and are held to the sending unit assembly by a single screw (and a rubber busing in a bracket). Don't forget to get a new sock to put on the pickup tube. If the pump comes without you will have to buy it separately, and installing a new pump without a new sock will void the warranty.

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The sendER unit is the whole assembly, The sendING unit is the fuel gauge.

 

More than likely, you'll need to order one, although Advance seams to stock alot of parts for our MJ's ;)

 

Most of the OEM fuel pump I've come across are the Bosch pumps, both Rockauto and Advance (parts America) offer the Carter Fuel Pump And Strainer Set, Part # P74155 which is a good replacement.

 

Picture Here

 

One thing, when changing the fuel pump, plan on taking the drive shaft off, provides the necessary additional room needed to remove the sender unit out of the tank. Also a good time to change the O-ring behind the lock ring.

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The sendER unit is the whole assembly, The sendING unit is the fuel gauge.

 

Thanks for the info. Didn't know that

 

More than likely, you'll need to order one, although Advance seams to stock alot of parts for our MJ's ;)

 

Most of the OEM fuel pump I've come across are the Bosch pumps, both Rockauto and Advance (parts America) offer the Carter Fuel Pump And Strainer Set, Part # P74155 which is a good replacement.

 

Picture Here

 

One thing, when changing the fuel pump, plan on taking the drive shaft off, provides the necessary additional room needed to remove the sender unit out of the tank. Also a good time to change the O-ring behind the lock ring.

 

That's the pump I got, but Advance had to order it. Took two days to get it in.

Anyway, I have been very pleased with it, I had just one little snafu when installing it on the senDER unit, which was easily solved with tin snips. The kit comes with a new O-ring for the tank, btw, and I did not have to remove the drive shaft. 2wd or swb may be different. I have a lwb 4wd.

 

Since the unit goes into the tank from the side, you do not have to drop the tank, which is good, but you want to make sure the tank is no more than half full if you don't want to shower in gasoline. The side mount does cause another problem and that is that the O-ring on the tank does not want to stay in place, as it wants to slide down. Gravity sucks! I used a little dab of RTV silicone to help it stay in place.

If for some reason you are reusing a used O-ring, let it dry for 24 hours first. They soak up some gasoline causing them to swell up. It will not fit in place unless it has completely dried and shrunk back to original size.

 

I myself will be doing this again later this weekend (sender unit has rotted through causing gasoline to leak at the base of both lines as well as the wire grommet and possibly some other pin holes). have fun!

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Yeah, you don't HAVE to drop the driveshaft, but doing so gives you alot more room to fiddle, especially when trying to reinstall the unit.

 

And because the metal lines tend to crack where they enter the unit, I prefer to disconnect the soft lines up toward the front of the bed where they reattach to the hard lines versus trying to pull them directly off the sender (if you plan on working on the unit on the bench).

 

Some models of replacement pumps now contain a flat ring instead of the rounded-type OEM one. They are a bit more of a pain to keep centered than the old style, but do work. When reinstalling the lock ring, make sure all three metal tabs are engaged under the "ears" on the tank before you start tapping the ring to tighten. Those lock rings are pretty thin, and can bend easily.

 

Jeff

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I think that this question is relevant to this thread...

 

My fuel gauge (huge one in place of tach) will vary by up to 1/2 of tank depending on if I am going down or up a hill and how hard I am on the gas, would that be a bad sending unit?

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I think that this question is relevant to this thread...

 

My fuel gauge (huge one in place of tach) will vary by up to 1/2 of tank depending on if I am going down or up a hill and how hard I am on the gas, would that be a bad sending unit?

 

 

bad float in the tank, wouldn't worry about it unless you want to redo everything with everthying apart.

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I think that this question is relevant to this thread...

 

My fuel gauge (huge one in place of tach) will vary by up to 1/2 of tank depending on if I am going down or up a hill and how hard I am on the gas, would that be a bad sending unit?

 

Not really a bad float, or sending unit, just that these gas tanks have no baffles in them, so the gas slushes around alot.

 

On the good side of this........doing down hill, you got a full tank of gas......but going up hill, you running on empty :eek:

 

Always park facing down hill, and your tank will alway be full :D

 

Kind of solve the high price of gas for you :teehee:

 

The real check would be when your sitting on level ground, and what your gauge is reading. Like 1/2 tank, and you fill up a half a tank, then you know the true reading of the gauge.

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