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Old 08-25-2010, 09:32 AM
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Default 74 FJ40 still running terrible... ignition?

It seems like fuel is flowing.. . new pump, new filter. 3lbs of vacuum prior to pump, 2lbs at the carb after the filter...

This thing is running terrible....

Thought it was running out of gas at the carb, because it runs so rough at steady rpm, misses, sputters. Bad initial hesitation upon acceleration.

If I advance the timing, it accelerates great, but still runs rough upon steady rpm going down the road.

timing never seems to stay where I put it, always different when I go back and look. advance too far and it is backfiring through the carb.

compression test yields 130lbs -+ 2-3 lbs on every cyl...

I need to check coil for spark, but think it is there, starts, runs, acclerates...

Distributor is original, new cap, rotor, wires. Points have been replaced with electronic points... vacuum advance seems to work,

where do I look now?! Dang it, I'm missing the summer!

Doug
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Old 08-25-2010, 10:12 AM
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If you want bring it over so we can check it out, it's really difficult to diagnose stuff like this remotely.

If your timing is changing then either the hold down clamp is loose, the distributor gear has busted the pin and is rotating on the distributor shaft, the distributor and/or cam gear is worn and slipping a tooth, the cam/crank timing gears are worn and have slipped. These are listed in the most likely to least likely order. If you have the old style cam timing gears that has a rubber mounted gear, those do eventually go bad and start slipping.

A steady miss is usually not fuel related and is a more likely spark issue, especially since you checked compression and essentially ruled out a bad valve or low compression. Could be a bad spark plug, plug wire, or you could have something goofy going on inside your distributor.

The easiest thing to do is swap in a known good distributor and see what the impact is. By doing this you can rule out a whole bunch of stuff very quickly.
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Old 08-25-2010, 11:33 AM
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The timing not holding would account for what you are experiencing with the running. in addition to the physical aspects of the distributor that Randy mentioned, I would also expect that an intermittent ground connection for the ignition system might cause the running behavior.
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Old 08-25-2010, 11:44 AM
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would love an experienced eye!!!!!

I live in Golden, am pretty flexible on schedule... thurs is only day that does'nt work for me, around all weekend....

813-453-4236

I'm gonna put on new cap, wires, plugs today... couldn't hurt.

seems to run okay when I advance the timing up the wazoo except I get to the point of the backfiring
starts fine...

don't have much of any emissionstuff on here. was running fine until this rough running at steady speed which was instantaneous....

Doug
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Old 08-25-2010, 11:47 AM
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hmmmm put new ground wires from battery to chassis and from battery to engine. helped solve my electrical problems with the dashboard/turn signals/ horn
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Old 08-25-2010, 12:00 PM
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I had these same symptoms with my 40 last fall. It was a combination of a bad rotor and a bad ground to my electronic ignition box.
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Old 08-25-2010, 12:12 PM
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Cleaning the battery to chassis and battery to engine grounds is very important, and you will not be disappointed that you did this.

Thinking through the ignition ground; the ignitor should be grounded because it is mounted on a metal bracket which is attached to the metal fender, which is attached to the metal body, which is attached to the metal frame, which is attached to the battery ground - each attachment point could be the source of a problem. To make sure the connection is good and reliable I took a "belt and suspenders" approach to holding my britches up and ran a ground connection directly from the ignitor/coil bracket to the battery.
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Old 08-25-2010, 01:10 PM
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ignition coil....
1.4 ohms on the primary coil
15,6 kohm on the secondary

shouldn't this be between .7-.8 on primary
10k-11k on secondary??????????????????????
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Old 08-25-2010, 11:19 PM
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Coils are cheap, replace it if you have doubts. A weak coil would allow easy starting but bad running under load. Be sure and check all of the grounds first though like ricardo said.
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Old 08-26-2010, 10:26 AM
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Default new coil/plugs

I picked up a new Accel coil... My old coil had a higher resistance in the secondary, the new one is withing the spec range.
This seemed to help.

the "missing" is not as pronounced. but it is stilling "missing"...

The mechanical advance is working on the distr. but although I DO have vacuum at the carb TO the distr, It is not advancing the timing upon acceleration.

So, at least THAT is not working on the distr.
It seems to be tight in place and very clean on the inside. has an electronic box in place of points.

What is the function of the "igniter"? Can this be causing a problem? How would I check it?

I think your'e right, may need to try a known good distr....

Doug
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