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New 720 Owner in Need of Help with High Idle


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#21 Paulz

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Posted 29 December 2017 - 04:25 PM

Hi, new member here with a newly acquired 1980 720 4x4.  I am having the opposite issue as above, my fast idle on choke is not operational.  In the photo below, the linkage arm with the pin removed does not go into the top area of the slot, which is supposed to pull the fast idle cam into position when the choke is closed. I can manually slide it in place by manipulating the linkage but it just falls back into the slot when the throttle is operated.  Anybody dealt with this?  Thanks in advance, Paul

 

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#22 datzenmike

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Posted 29 December 2017 - 05:28 PM

Looks like a thin washer and a cotter pin is missing...

 

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#23 Paulz

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Posted 31 December 2017 - 07:28 AM

Thanks Mike. I've been wondering if that is just a washer or a bushing. Do you happen to know if and when the rod is supposed to slide down the slot?

#24 datzenmike

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Posted 31 December 2017 - 07:37 AM

Cold engine... step on the gas the choke is released and rotates to on. As it turns it pushes that linkage down and that rotates the fast idle cam into position to block the throttle from returning to it's hot idle setting and the engine revs up.  As the choke warms up it rotates back and the linkage is free to slide along that slot. The choke can move to a lower setting but the fast idle remains. The next time you step on the gas there is nothing to hold the fast idle cam in place now, and it drops out of the way and the throttle closes to it's normal position.


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#25 Paulz

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Posted 31 December 2017 - 08:11 AM

Got it, thanks. Now I see I have no power at the choke wire with engine running as noted. I have power at what I think is the correct fuse, second from rear on the horizontal panel above drivers kick panel. Two relays above but not sure either is choke relay. Do you know where it is? 1980.

#26 datzenmike

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Posted 31 December 2017 - 09:03 AM

The 80 model is wired differently. I think power for the choke heater comes from the farthest left hand side of the fuse box. The rear most one. 

 

The choke heater relay needs a charging alternator to send that power to the choke heater. If low alternator output, the relay usually buzzes. The choke heater is located up under the dash on the passenger side just above the kick panel.

 

 

If you can't find or fix the problem just connect the Blue choke heater wire to the Red idle cut wire at the carburetor. The idle cut is switched on and off by the ignition so it will work the same.


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#27 Paulz

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Posted 31 December 2017 - 12:09 PM

Thanks Mike, you sure know these things. Boy what a complicated choke!  Tempted to hook up a cable..The idle cut wire is also referred to as anti dieseling wire I believe, it's the only other wire at the carb and I did jumper to it yesterday when testing.  I'm away from the truck now but I don't recall any fuse in the rearmost slot, and I also looked between the glove box and kick panel and didn't see any relays.  I'll have another look on Tuesday.  Thanks and Happy New Year!



#28 datzenmike

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Posted 31 December 2017 - 12:54 PM

The '80 was a one off 720. There is a lot of differences to the '81 and up including the fuse box.
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#29 Paulz

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Posted 02 January 2018 - 05:01 PM

Hi Mike. Got to work on the 720 today. Running pretty well with the choke wire jumpered to the idle wire. I have power to that rearmost fuse but still can't locate the relay. Nothing above pass kick panel. I read something about one being behind the glove box or console? Like to find it.

#30 Paulz

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Posted 12 January 2018 - 08:09 AM

Progress!  I bought a factory, 1980 only 720 service manual.  The choke relay is one of the two attached to the fuse panel, and the fuse is indeed the rearmost.  What I found was, the previous owner added an electric fuel pump (the mechanical one is still on the engine, disconnected), and ran it off of the input wire to the choke relay, thereby disconnecting power to the relay.  I jumpered it back and got power to the choke.  The remaining question is: should I power the fuel pump like it was (straight off the 10 amp relay fuse), or splice into the blue choke wire (thereby sharing the relay with the choke), or from another location?  



#31 Toxicrain

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Posted 08 February 2018 - 10:50 AM

Yea I see a lot of unplugged holes and missing lines. I would suggest finding a donor or parts car and put it back together because you still have stock carb. or weber and remove. If you look at my 85' fuel issue post. we kinda went over most of the lines and i have many pics posted.



#32 Charlie69

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Posted 08 February 2018 - 08:04 PM

Use you 1980 Factory Service Manual (FSM) as the 85 post will be completely different.  Different engines and carbs not to mention wiring vaccum diagrams.  It is like Mike said 1980 720 is a 1 off.