1990 4.2 weber fuel pressure issues - JeepForum.com
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Unread 05-23-2009, 12:39 PM   #1
tippmann243
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1990 YJ Wrangler 
 
Join Date: Dec 2005
Location: st louis
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1990 4.2 weber fuel pressure issues

so i have had my weber installed for about a year, havent had any issues with it the whole time.

yesterday i noticed i had an oil leak when i was leaving work. it wasnt bad so i proceded to drive home. i got home and started rooting around under the hood to see if i could locate the leak. turns out its a valve cover gasket.

while i was under the hood i noticed my fuel pressure gauge was acting funny.

here is a video of what it was doing.



when i installed the carb and pressure reg it fluttered a little bit. maybe about 1/8-1/4 of a psi. im not to savvy with carbs but i assumed this was some what normal and it wasnt a drastic change so i went about my business.

also i tried to adjust the pressure on my reg and it would not change if i went 100% open. it still jumped from 0-2psi.

it runs great. starts the first time every time. never had any vapor lock issues.

is this a sign that my fuel pump is going bad?

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89 blazer, L31/t56 28mpg.
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Unread 05-23-2009, 01:30 PM   #2
Jeepsr4me19
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1976 CJ5 
 
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clogged filter will do it too. Or a bad gauge.
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Unread 05-23-2009, 01:36 PM   #3
tippmann243
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filter is only about a month old. i replaced that last time i changed the oil.

if you put your hand on the fuel pump you can "feel" it working. everytime that lobe comes over and works the pump you can feel it. every time this happens the gauge jumps to 2psi.

this is why i was wondering if it was a bad pump. maybe the diaphram is going bad or something?
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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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Unread 05-23-2009, 02:30 PM   #4
Jeepsr4me19
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pump is cheap and easy to replace. Might as well change it. But a pump that is working hard to pull fuel will also do it. Filter can get clogged in a short period of time. I had a test chart on how much fuel a manual pump can move. You take the hose off and put in a bottle and crank the engine for only 10 seconds. It would fill about 1/2 way on a coke bottle.
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Unread 05-23-2009, 02:32 PM   #5
tippmann243
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so about 8 ounces of gas in 10 seconds for a mechanical pump.

thats en easy enough test. i will do that tomorrow when i install my valve cover gasket
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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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Unread 05-23-2009, 05:14 PM   #6
dbikers
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hey tippman...
mine is exactly the same...i thought it was the fuel pump..now i have a brand new pump, no fpr, and it does exactly the same thing.
i don't know what to make of it but really don't have any problems with it
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Unread 05-23-2009, 05:24 PM   #7
Jeepsr4me19
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I just had this same problem on my VW dune buggy. the needle bounced around like crazy. But my pump is electric, and I could hear it running. I replaced the filter and bam solid 7psi. It would even pump a bunch out using the test, but not under pressure.
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Unread 05-23-2009, 06:07 PM   #8
tippmann243
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maybe i just got some junk in the filter.

filter is cheeper to replace so i will try that first when i do my valve cover gasket tomorrow.
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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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