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SalParadise17 05-29-2013 05:38 PM

Sending Unit/Idle Help
Hey guys, this is my first real post. If it is not thorough enough (I’m sure it won’t be) I will do my best to update the information that is needed. Unfortunately, this is my first “real” jeep so I’m still learning.

1979 Jeep CJ7- 258 (Originally a 304-PO swap not sure why)- Automatic Transmission- Quadratrac- (Locking Hubs so I think the conversion has been done, but haven’t done a thorough go through, Sorry).

When I first got the CJ it was running a little rough- I dropped the tank and then replaced it with a new 15 Gallon. Replaced the sending unit also. This did not solve my problem. There is a clear plastic filter, about a foot to the rear of the mechanical fuel pump, which was installed in lieu of the traditional filter near the carb. There is no return line. The lines have been “cleared”, but I am planning on replacing them as soon as I am able. The idle has been adjusted to keep it running to about 1300 RPM. I believe that the vacuum lines are all good but will be doing another go through in the near future.

Issue/Question- As you can see in the pictures below, the fuel filter never fills with gas. At most, there is 1-2 oz. of gasoline in the filter at any given time. About a week ago the filter filled all the way for the first time. Thinking most of the gunk from the lines was clear; I swapped filters for a new one. Since then, I have still been having the idle problem, and the filter does not have, what seems to me, enough gas flowing through it.

Is this a problem with my Sender Unit? Maybe not getting power?

Does anyone know what the fuse for this is labeled in the fuse box?

Any other suggestions? (I know I’m opening myself up here)

Photo Library address: Sorry if the Picture above isn't working:

LumpyGrits 05-29-2013 07:22 PM

You have either a misfire, vac. leak or a clogged carb jet.
Fuel tank had nut'n to do with it.

86cj74.2L 05-29-2013 07:29 PM

What carb do you have.

Don't be too worried about the filter being mostly empty. If you tilt it up the air pocket will go away.

SalParadise17 05-29-2013 08:18 PM

I am running the carter 2bbl right now. I plan to upgrade to a MC2100 in the future but not an option now.

Since I've changed the idle to 1300 it hasn't stalled out. Before it would typically run for 3-6 minutes, begin to stall, and over a period of 5-8 seconds it will eventually shut off.

I'm hoping to rebuild the carburetor this weekend. I'm at least going to try. It's not something I've done before but figure there's no better time to learn.

I've inspected and replaced some of the vacuum hoses but I'll give it a once over again.

robs7 05-29-2013 08:36 PM

I don't believe the tank had anything to do with it either and the sending unit simply controls the gauge showing your fuel level. I'd also check around the base of the carb and the intake for air leaks. An air leak or a vacuum leak would cause it to run lean and stall at idle. How is everything on the ignition side of things? Plugs and wires all good? Sure there isn't a cylinder misfiring? I don't have the same carb but I recently rebuilt mine and is wasn't too bad. Take pictures along the way and don't throw anything away until your done!

86cj74.2L 05-30-2013 07:18 AM

2 Attachment(s)
While your doing the rebuild don't forget to clean out the emulsion tubes. Those when clogged screw up the idle.

Did you try resetting your lean best idle with the idle mixture screws?

Matt1981CJ7 05-30-2013 07:44 AM

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A simple and effective way to monitor fuel delivery is to install an in-line pressure gauge just before the carb.

A stock mechanical pump should supply 6-8 psi of pressure to the carb without a bypass filter. With a bypass filter between the pump and carb, the pressure should be 2-4 psi, which is what most carbs seem to prefer.

Good luck,


SalParadise17 05-30-2013 08:23 AM

Thanks for the help guys.

I actually removed and cleaned the Venturi cluster a few days ago hoping that would solve my problem, but it is still stalling.

I'm replacing the wires, cap, and rotor today. Will be checking the timing with a light I am borrowing tomorrow afternoon.

As far as Vacuum system goes, can I cap all of the lines with the exception of the distributor line and adjust it from there? I have a fuel pump gauge I think I can use to test the vacuum lines, I'm just not sure where to attach the gauge for the different lines.

LumpyGrits 05-30-2013 08:38 AM

Buy a copy of the Factory Service Manual(FSM).
It has some good troubleshooting info in it.
Did you blow compressed air through the v'cluster? They are a know clog point in the Carter carb.

SalParadise17 06-04-2013 10:08 AM

The Venturi cluster was cleaned out pretty well.

Before I rebuild the carb I had one quick question. Is it possible for the vacuum lines running to the transfer case to cause my idle issue? I didn't think of replacing them since I didn't think they would effect the idle.

LumpyGrits 06-04-2013 10:20 AM

ANY leaking vac. line can/will cause idle issues.

texasdave 06-04-2013 10:37 AM

Bad fuel evaporation cannisters will also cause idle problems. I don't know whether 79 had one or not.

SalParadise17 06-09-2013 11:30 AM

Hey guys,

So I spent the last couple days rebuilding the carburetor and put it back on this morning. There was about a 1/4" of crud in the bottom of the float bowl.

After installing the carb I seem to be having the same type of problem. The jeep starts up and runs for about 2-3 minutes and then stalls out. Now instead of running at 1200 rpm it is running at about 200 rpm and I can't seem to get the idle to go up.

I'm about at the end of my rope and I really need an Ah-ha moment so any help would be greatly appreciated.

LumpyGrits 06-09-2013 03:33 PM

Did you make sure the float is set 'rite'?

BagusJeep 06-09-2013 07:58 PM

So what are you currently running? Have you capped off all the other vac lines apart from distributor? How about brake servo?

When it is running and you look down the carb at idle do you see the fuel dripping or slowly pouring?

The time now is 11:24 AM.

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