Vacuum Advance??

Hi All,

I think the vacuum advance on my distributor is not working. I pulled the cap/rotor and the cover under these off. I sucked on the vacuum line and checked the linkage on the advance. It does move. I'm wondering if my suction line off the carb is not suppling enough suction? or could the advance still be bad even though the linkage moves?

'75 CJ5 258 1BBl carter

Thanks again,

Paul

Reply to
Paul Brogren
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You really need a timing light to tell what is going on for sure, but a visual on the advance linkage outside the bottom of the distributor cap will give you an idea.

Depending on your plumbing, the vacuum advance will do one of two things. First it will do nothing at idle and advance as you give it gas Or, it will go full advance at idle and back off when you give it gas to a point, then slowly climb back up.

Looking at/ watching the linkage with it running will tell you.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Paul Brogren wrote:

Reply to
Mike Romain
12 deg is up there, but within the limits. I run mine at 9.

You have two kinds of advance, one is a set of weights that slowly climbs up, the other is vacuum that gives an instant jump.

I have mine set to ported vacuum, so the advance moves instantly with the gas pedal.

I can 'hear' it snap to full advance inside the distributor when I give it a quick shot of gas.

My distributor has the linkage going to the vacuum pot out in the open on the front side of the distributor, I guess yours has a cover on it?

If you disconnect the vacuum line at the distributor with the engine running does anything happen? If no, then it is a ported vacuum like mine that does nothing at idle. Mine comes off the nipple on the valve cover side of the carb up near the top.

You also should be able to have it idling and be able to suck on the vacuum line and see the timing mark move with the light on it.

The mark also should move under the light way differently with the vacuum line off. It will climb slow with the line of and just snap to attention with a shot from the gas pedal with the line on.

Mike

Paul Brogren wrote:

Reply to
Mike Romain

I've put a timing light on it. The timing is set at 12 deg. btdc. As I give it gas, the climbs 14, 15 on up until I can't even see the mark anymore. As far as looking at the linkage when it's running, I don't know if I can? The distributor doesn't have any visible linkage or clear parts. The advance is white plastic. The linkage I've looked at is under the rotor and within this white plastic housing. I'll bring a mirror out and see if there is anything I can see from undernearth the distributor itself maybe just above where it mounts down to the block.

Reply to
Paul Brogren

Hi Mike, This is what I've got. At idle I can suck into the tube connected to the advance. The timing light shows that it only is able to jump up 2 to 4 degrees, but no more. Should there be more? There is virtually no difference in the advance with or without the vacuum line hooked up when I open the throttle up full. Should I disassemble the distributor / advance and see if somethings binding up? The advance I think was replaced less than a year ago.

Reply to
Paul Brogren

It sounds to me like something is jamming it up.

If you take off the rotor, there should be a foam piece down the center of the distributor shaft that is supposed to be oiled. I would oil it and maybe pull the pad out to get oil down the shaft. I would then hand work the advance or put the rotor back on and twist it back and forth to get the oil down the tube and loosen it. The rotor will turn the advance plate.

The distributor shaft is two pieces, a solid core goes down to the timing gear and an outside tube holds the timing advance and electronic pickup/points and rotor.

If this tube get sticky on the center shaft, it can/will stop the vacuum advance. The centripetal weights will still have enough power to advance it for a while longer, but they too will stop working if the outside tube seizes solid on the distributor shaft.

Bet that is why the advance was replaced, the old one likely didn't work also.

It is dark out right now, but I can set up my timing light on mine tomorrow and suck on the vacuum to see if I can suck hard enough to have an effect, but I bet I can.

If you want to go oil up yours and try again before I do this, post back.

Mike

Paul Brogren wrote:

Reply to
Mike Romain

Sounds good Mike. What I've done prior to reading the lastest post was:

- I removed and cleaned up the distributor.

- Removed and cleaned up the exterior of the sensor and advance module.

- Oiled up that inner shaft and manually operated the summing bar and linkage.

I re-timed the motor and will drive it in to work in the morning. I'll post you from work. I'll bet your right with that inner distributor shaft. I've overlooked it many times not realizing it's importance.

Thanks again Mike!!! Paul

Reply to
Paul Brogren

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