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post #1 of (permalink) Old 10-17-2000, 10:54 AM Thread Starter
 
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Fuel filter question

My '84 CJ-7 (4.2, TR upgrade, stock carb)developed a problem over the weekend, and I'm trying to narrow it down. At idle, it began stumbling/stalling as if there was a vacuum leak or the choke was shut. Well, neither of the two were the case. I did a full tuneup, which didn't help. At a little above idle, there is a definite flat spot where the Jeep is almost stalling out at that rpm (1100 ish). I'm thinking its something with the fuel delivery, but on the highway its fine. Here's the one thing i noticed: the clear Fram filter I have just prior to the mechanical pump does not fill up at any rpm's. It stay 1/4 at all times. I took the fuel line off and cranked it, and it was pumping, but shouldn't there be more pressure (i.e. shouldn't the filter be full)? Is it something with the carburator, and what should i look for?

Also, right now it's idling much better, not perfect, but when I started it in the morning the motor could not maitain a high idle, it slowly dropped within a minute or two down to a stumble.

Any suggestions would be appreciated. I don't feel like spending this wekend at Pep Boys.

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post #2 of (permalink) Old 10-17-2000, 12:11 PM
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Re: Fuel filter question

If it still has the electric carb on it, I would look into doing the nutter bypass.I had similar problems with a 83cj.I bypassed the computer, and it ran like a top.

post #3 of (permalink) Old 10-17-2000, 03:25 PM Thread Starter
 
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Re: Fuel filter question

Fortunately it is not computer controlled, which is why I'm sure it's something simple that I'm overlooking.

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post #4 of (permalink) Old 10-17-2000, 10:47 PM
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Re: Fuel filter question

Uhm i had the same problem before with mine.. I just replaced the fuel filter in my 304, Put some fuel system cleaner in a fresh tank, ran new fuel lines and it started working again.. Not sure what the problem was but it helped..



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<font color=red>[img]/wwwthreads_images/icons/cool.gif[/img]'79 CJ7 "Issues"-304-35s</font color=red>[img]/wwwthreads_images/icons/cool.gif[/img]
post #5 of (permalink) Old 10-18-2000, 08:02 AM
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Re: Fuel filter question

[img]/wwwthreads_images/icons/tongue.gif[/img] Er.....guys. I cannot believe that you missed the fact that our Jeep in question here has a fuel filter installed ahead of the fuel pump. Any good moonguy[img]/wwwthreads_images/icons/wink.gif[/img] can tell you that if you DO that, you encourage vapor-locking. The high suction condition that is right at the fuel pump causes the gasoline to give up entrained air and the air pocket can be big enough to actually restrict flow through the filter. Detroit HAS made plenty of vehicles.....especially trucks......with gasoline filters on the frame between the fuel tank and the pump. Those units, however, had HUGE elements in them which had very low friction losses, and were virtually a zero-restriction filter. What this Jeep needs is a nice three-port filter mounted where it is suppposed to be, and a nice flow loop back to the tank. Let's be careful not to try and re-invent the wheel here, this work has already been done and re-done. The third line to the tank is a very good solution and it's no big mystery why Detroit finally figured that out.[img]/wwwthreads_images/icons/smile.gif[/img]

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post #6 of (permalink) Old 10-18-2000, 08:32 AM Thread Starter
 
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Re: Fuel filter question

Thanks CJDave. I purchased the Jeep like that, and I actually do have the stock three port filter and retuen line also. I guess the previous owner wanted "extra" protection. I will remove the filter before the pump, but that has been there for the last year and a half (i did change both filters 9 months ago). Any suggestions on how I go about fixing the flat spot. Like I said, at a little above idle the carb is sucking in air, and sounding like it is starving for fuel. Any thoughts?

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post #7 of (permalink) Old 10-18-2000, 08:43 AM
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Re: Fuel filter question

[img]/wwwthreads_images/icons/smile.gif[/img] I suspect that the fuel tank may have a partially plugged up screen, and it is finally getting the restriction to a point where the fuel pump is sucking air from pinhole leaks in the long line to the tank. This continues to sound like a fuel feeding problem. So check for pinholes, and check the strainer.[img]/wwwthreads_images/icons/tongue.gif[/img]

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