89 YJ 4.2l engine trouble - JeepForum.com
 
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post #1 of 12 Old 08-03-2015, 09:44 AM Thread Starter
WarEagleMcGraw
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89 YJ 4.2l engine trouble

89 YJ 4.2l Weber carb. nutter bypass, ignition upgrade. i believe a 4.0 head. I am losings highway power. I was able to run 70 mpg no problem in 4th gear with 35" tires. i have 3.07 gears. recently i made a 40 mile trip and couldn't get over 70 down hill. I have done compression check, and had cat cut out. still same problem. i tried changing fuel filter with one from advanced and it started running like crap. choking out. reinstalled old fuel filter and runs the same as before. So i have two questions.

What is correct fuel filter?

What could be wrong with loss of power?

Also it has a sending unit and i haven't tested fuel pressure yet.

Thanks for any and all help.

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post #2 of 12 Old 08-03-2015, 10:18 AM
rustisexpected
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fuel filter by Crown, Part No: 33000076.

Is there a rough idle as well as a loss of power? If yes look at ignition as well, if no your looking in the right direction.

Why is there a sending unit on a carb'd engine? Do you mean the mechanical pump?
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post #3 of 12 Old 08-04-2015, 08:12 AM
mike134
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The fuel filter is directional, but I have seen some filters that were not labeled with the arrow. Check to make sure your fuel filter has an arrow.

Also, is your maintenance up to date? copper spark plugs, wires, distributor cap, rotor, air filter, battery, clean battery terminals? small problems here can cause performance problems under heavy load.
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post #4 of 12 Old 08-04-2015, 08:57 AM
Mike Romain
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The fuel filter is only one type, it has a return line sitting at the back top of it. Having the wrong one and a Weber usually means the charcoal canister has been messed with. That is the gas tank vent. A vacuum on the gas tank can act like yours. To see if the venting is the issue, just crack open the gas cap and see how it runs.

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post #5 of 12 Old 08-05-2015, 07:29 PM Thread Starter
WarEagleMcGraw
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Sorry I do have a mechanical fuel pump with a sending unit in the tank. Routine maintenance is up to date. Have iridium spark plugs. Charcoal canister has been taken out of system. Haven't noticed vacuum on tank. But haven't drove it since this post. Had rear ended go out on me. The problem is only at highway speeds. 0-50 no problem. 50-75 I loose lots of power. Also there is only one way fuel filter can go on. Can't put it on backwards. Has three lines and I hooked up properly. Thanks for input. Any other ideas?
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post #6 of 12 Old 08-06-2015, 01:24 PM
rogerv
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Where is your base timing set ?

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post #7 of 12 Old 08-06-2015, 03:28 PM
dancytron
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Get some regular copper spark plugs.

Fancy spark plugs foul and don't work as well.
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post #8 of 12 Old 08-06-2015, 04:32 PM
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I had basically the same problem on my 86 GMC pickup.
My speed was 55 mph. If I tried to go 56, it would lose power and slowly creep back up to 55.


It turned out to be the fuel pump had a crack in the edge of the diaphragm just big enough to only pump a little gas.


If the fuel pump is old or unknown, it would be cheap insurance to just change it out and see if that makes it better.

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post #9 of 12 Old 08-11-2015, 10:14 AM Thread Starter
WarEagleMcGraw
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Ok plan on changing fuel pump... timing is set 8-10 from last i remember... i check but cant remember exactly. i will also prob pick up some new plugs. In the process of swapping axles out as well. would it be good idea to drop fuel tank and check lines as well? i had tank off about year ago and everything looked good.
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post #10 of 12 Old 08-11-2015, 10:17 AM Thread Starter
WarEagleMcGraw
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Does anyone have an idea on fuel filter? thanks for help so far...
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post #11 of 12 Old 08-11-2015, 10:18 AM
Jeff88
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Just another idea. I had a buddies CJ doing similar things. It had a replacement piece of rubber hose on part of the metal fuel line. It looked fine from the outside, but under pressure from the fuel pump at a certain RPM under load, it was collapsing on itself and cutting off fuel. Then you would let up and it would open up just enough and run fine again.

So... just make sure your fuel lines are good. This one was hard to find because it pumped plenty of fuel right up until it sucked in on itself and shut off the fuel flow entirely.
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post #12 of 12 Old 08-12-2015, 11:18 AM
Drednot
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Quote:
Originally Posted by WarEagleMcGraw View Post
Does anyone have an idea on fuel filter? thanks for help so far...
This is the wix filter. You can search that part number and try and find it cheaper. But this is how it needs to look with the fuel return line offset like that.
http://www.summitracing.com/parts/WIX-33040/

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4.2 liter , carb , fuel filler , loss of power

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