Engine Tuning Problem

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jrcotner
United States of America
Posts: 153
Joined: Fri Aug 21, 2009 2:17 pm
Location: New Ulm, MN

Engine Tuning Problem

Post by jrcotner »

I just finished my annual engine inspection and tune-up, but the Pinz isn't running as well as it has. I inspected and gapped the plugs, replaced the fuel filter, checked the cap and rotor, adjusted the valves, adjusted the timing 10 degrees at 900 rpm (Petronix), inspected the brass idle screws, and balanced the carbs. It seemed to be running fine, but once I replaced the air cleaner cover and restarted to double check the timing, the RPMs dropped to 700 and it started running rough. It is also hard starting, which was a problem just before the tune up. I did the carb balance again and double checked that both carbs were opening at the same time when the throttle was pressed, and upped the RPM a little.

Once I replaced the air cleaner cover I could get a rough idle between 800 and 900 rpm. One other mystery is when I close the brass idle screws completely there is little drop in the RPMs. The truck ran great up until my recent move. I was at sea level and now am at 1700'. I didn't think this was enough of a climb to affect the truck, but I leave it to the experts.

Any help or advice is appreciated.
Thanks,
John Cotner
1946 Willys CJ-2a
Elizabethton, TN
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audiocontr
United States of America
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Joined: Fri May 01, 2009 1:30 pm
Location: Buffalo NY

Re: Engine Tuning Problem

Post by audiocontr »

Did you forget to tighten the distributor after your adjustment?
1973 712m
1968 Haflinger
1965 Pathfinder
1978 GMC Palm Beach (Hey, its got 6 wheels!!)
jrcotner
United States of America
Posts: 153
Joined: Fri Aug 21, 2009 2:17 pm
Location: New Ulm, MN

Re: Engine Tuning Problem

Post by jrcotner »

No, and double checked.
Thanks,
John Cotner
1946 Willys CJ-2a
Elizabethton, TN
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audiocontr
United States of America
Posts: 1868
Joined: Fri May 01, 2009 1:30 pm
Location: Buffalo NY

Re: Engine Tuning Problem

Post by audiocontr »

I brought that up as its something I did once. Caused mayhem.. Beyond that, there are so many variables that it's difficult to suggest a solution.
1973 712m
1968 Haflinger
1965 Pathfinder
1978 GMC Palm Beach (Hey, its got 6 wheels!!)
Pinzcat
France
Posts: 21
Joined: Sat Jan 24, 2015 4:53 am
Location: France, Evian

Re: Engine Tuning Problem

Post by Pinzcat »

Air filter correctly mounted?
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Jimm391730
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Re: Engine Tuning Problem

Post by Jimm391730 »

Carbs tight? Tight to manifold, base tight to center section, top tight to center section? Putting the air horn on should not affect the idle or performance, UNLESS there is some restriction in the horn and/or filter assembly.

1700' elevation difference should not be noticeable IMHO; I have driven over 11,000' difference and this does make a difference, but your small variation should be invisible.
Jim M.
712W and 710M
jrcotner
United States of America
Posts: 153
Joined: Fri Aug 21, 2009 2:17 pm
Location: New Ulm, MN

Re: Engine Tuning Problem

Post by jrcotner »

Thanks for all of the advice. I checked the carb bases and they were fine. I replaced the rotor and cap, which looked fine on first glance thought the rotor needed a little cleaning up. New parts did the trick.
Thanks,
John Cotner
1946 Willys CJ-2a
Elizabethton, TN
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