720 issues

[Darkslide]

Okay, been having issues with my '82 720KC. It ran fine for a few months after I bought it, then it stopped wanting to start (no power from battery) after it got cold out. Managed to get it started a few times by jumping it and then it would start fine by itself up until today when it stopped wanting to start because of power again.

 

The other problem I'm having is the idle is all jacked up. Part of the time it will idle around 1k but the other parts of the time it will idle around 2k even after it is warmed up and it will sometimes go down to 1k only to go back up to 2k at another time. Today it was idling fine for a bit, then started to idle at 2k all the time, then at a few moments it jumped the idle up to 3k until I tapped the pedal a bit and it would drop down to 2k.

 

Any ideas?

[datzenmike]

The battery may be tired, how old is it or is this unknown? Assuming the battery is good, clean the battery terminals and cable connections. Now clean and tighten the other ends, the negative on the intake manifold and the starter lug.

 

Erratic idle and fast idle could simply be dirty linkage for the choke and fast idle. Get a can of carb cleaner and liberally spray the throttle, choke and fast idle cam linkage. Hold the throttle partly open and work the choke open and closed by hand. You should see the linkage drop and position the fast idle cam on a higher step.

 

Choke open. Must be FULLY open when warmed up or you have choke problems and likely a fast idle because of it.

 

Choke closed or partly closed on cold motor.

 

Fast idle cam

 

 

 

.

[Darkslide]

I don't think I've ever seen the choke fully open now that I think about it.

[datzenmike]

A badly charging alternator will cause the choke relay to buzz or chatter from low voltage. Without the choke relay working properly the choke only warms up from engine heat and the fast idle may not shut off at all.

 

Try cleaning the cables first and see if the battery charges properly. Get a meter and see what voltage you read across the battery with it running. Should be just above 14 volts running.

[johny F]

my truck always idles funny but never any problems with starting.wierd.sounds like datzen mike answered ur problem to me^^^^:)

[Darkslide]

Well finally got around to messing with it since classes are done for the semester. Alternator checked out fine (took it off and went to a parts store). Connections look fine from what I've seen.

[Rob W.]

Time to check that choke. Clean it like they said. See if it ever opens. Can you gently force it open at all or is it stuck? Check it out