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Unread 01-11-2016, 05:24 PM   #1
SteveHolly
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1982 CJ7 
 
Join Date: Dec 2015
Location: Modesto, CA
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1982 CJ7 fuel pump hums / vibrates

Hello all, There was a post on this from 2011, but didn't see a solution, so I am starting again. Here's the scoop. A couple times after starting the engine, i take off and when shifting into 2nd gear (and 3rd) and accelerating, it would start to lose power, like it couldn't handle the extra gas or air and it would sputter. I didn't give it much thought because after turning the ignition off and back on, the problem went away. Today, it did it again. As I was sitting at a stop light heading back home, I heard a weird hum/vibration sound... kinda like a high-pitched air compressor. Anyways, I got home and left the engine running... I got out and walked to the back... I could feel the fuel pump vibrating. Now, this jeep has an aftermarket 20 gallon fuel cell and the Mopar MPI conversion. I can go down there and replace the fuel pump and filter, but wondered if anyone else has had this issue and how it was solved?

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Unread 01-11-2016, 06:49 PM   #2
PERK
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1983 CJ7 
 
Join Date: May 2007
Location: LIVERMORE, CA.
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whens the last time you changed the fuel filter ?
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Unread 01-13-2016, 01:36 PM   #3
SteveHolly
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1982 CJ7 
 
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Location: Modesto, CA
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PERK - it was done before I bought the jeep, but it was about 10k miles ago... Im thinking the fuel filter should last longer than that. But, I think replacing it is the cheapest and quickest 1st step to take.
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Unread 01-13-2016, 02:47 PM   #4
texasdave
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Simple stuff first is always a good rule. Will save you a lot of money in the long run.
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Unread 01-13-2016, 04:19 PM   #5
jeepwhore
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1984 CJ7 
 
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I'd hook up a temporary fuel pressure gauge in the cab so you can see what it's doing when it bogs. External pumps (which I assume you have?) hum and vibrate quite a bit even in good working order so it could be a filter as suggested or even a bad injector. Knowing what the pressure in the rail is when it happens will point you in the right direction.
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Unread 01-13-2016, 08:11 PM   #6
jeepdaddy2000
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Quote:
Originally Posted by jeepwhore View Post
I'd hook up a temporary fuel pressure gauge in the cab so you can see what it's doing when it bogs. External pumps (which I assume you have?) hum and vibrate quite a bit even in good working order so it could be a filter as suggested or even a bad injector. Knowing what the pressure in the rail is when it happens will point you in the right direction.
This^^^
I fought a power loss issue on a fuel injected KFX450 for about six months. Start and run fine when cold, but then fall on it's face. Threw some parts at it (stupid) until I checked the fuel pressure. 42 LBS at idle (perfect), but anything after 1/3 throttle, the pump would drop pressure and the Quad would fart and sputter.
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Unread 01-14-2016, 12:04 PM   #7
PERK
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a loud pump is working to hard and going to fail. you should check that the pump is mounted in the correct location, that all the fuel lines are F I rated and hose clamps are tight. (You could have a leak in a fuel hose that sucks air but wont leak fuel). the fuel filter should be mounted between the tank and fuel pump. find the HESCO site on google and read their boards for common F I problems. read the installation instructions to see how the kit should have been installed.
And they are correct, you need to get a fuel pressure gauge and connect it to the fuel rail to check pressure, their about $40 Napa and such...
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Unread 01-18-2016, 11:02 PM   #8
SteveHolly
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1982 CJ7 
 
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Location: Modesto, CA
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UPDATE: I replaced the fuel filter today. Now, I can't get the engine to stay running. It acts like it will start, but then dies. Or, it will run for a second or so, and then dies. I have it installed correctly...meaning the direction of flow is correct. Any ideas now?
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Unread 01-19-2016, 11:44 PM   #9
SteveHolly
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1982 CJ7 
 
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A last ditch attempt fixed the problem... The fuel rail has a Schroeder valve that needed to be bled. After doing so, it fired up like a champ.
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