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78 620, L20B foreign matter in combustion chamber.


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#401 datzenmike

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Posted 15 December 2017 - 12:17 PM

Cold starts should be overly rich, this is what the choke is for. The choke should force a fast idle if adjusted correctly. Once warmed the choke/fast idle should should be off.

 

 

Often a lean mixture adjustment is hidden by the choke being on. (extra rich) Once the choke is off the lean condition asserts itself and it runs badly. Mixture adjustment and jets changes must be done with the choke off, engine warmed up..


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#402 Atikin9000

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Posted 17 December 2017 - 07:47 PM

any ideas for a half working clicking speedometer?

Is it the cable?

#403 datzenmike

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Posted 17 December 2017 - 08:16 PM

Most likely.

 

The inner drive cable, the part the turns, is a small diameter but very long coiled spring. If it should catch on the outer sheath the drive end in the transmission will keep turning and the spring will just store the energy. When the spring frees itself the energy is released and the needle will jump to catch up. A speedometer the jitters or jumps regularly is like this. Naturally if the cable cannot free itself the spring will simply twist and break.

 

Use vice-grips to loosen the transmission end of the cable and pull straight out. Have lots of cloths ready or a container to catch the cable in and keep it clean. Once free pull the inner cable out and collect it. Have a care as it's slithery and oily and hard to handle. If the cable is dry, lube with a graphite powder or molybdenum grease. Inspect the outer cable for kinks or damage from catching on something. In this case it may be better to just replace it.

 

When installing the inner cable, twist it (both ways) with fingers and confirm the speedometer is engaged and jumps then engage the transmission end and tighten the nut. The end has a ferule and only goes in one way.

 

HUYFAqE.jpg


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#404 Atikin9000

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Posted 17 December 2017 - 09:47 PM

Most likely.

The inner drive cable, the part the turns, is a small diameter but very long coiled spring. If it should catch on the outer sheath the drive end in the transmission will keep turning and the spring will just store the energy. When the spring frees itself the energy is released and the needle will jump to catch up. A speedometer the jitters or jumps regularly is like this. Naturally if the cable cannot free itself the spring will simply twist and break.

Use vice-grips to loosen the transmission end of the cable and pull straight out. Have lots of cloths ready or a container to catch the cable in and keep it clean. Once free pull the inner cable out and collect it. Have a care as it's slithery and oily and hard to handle. If the cable is dry, lube with a graphite powder or molybdenum grease. Inspect the outer cable for kinks or damage from catching on something. In this case it may be better to just replace it.

When installing the inner cable, twist it (both ways) with fingers and confirm the speedometer is engaged and jumps then engage the transmission end and tighten the nut. The end has a ferule and only goes in one way.

HUYFAqE.jpg



Thanks mike, I’ll have a look behind the gauge as well.

#405 Atikin9000

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Posted 26 December 2017 - 07:22 PM

I’ve been replacing dead bulbs all over the truck, and there’s a few spots that still don’t work.

I’m not getting power to the license plate light, and pass side side marker in the rear. And the cabin light comes on only once and a while.

Any ideas? wiring seems whole and all connected, fuses all look good and everything else works.

#406 datzenmike

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Posted 26 December 2017 - 08:19 PM

If the other marker is working then power is getting there. License, L&R side markers and running tail lights are all from the same wire.So bad bulb, bad socket or poor ground.

 

The door switches get rusty. Push then in and out a few dozen times to polish the contacts. You might even use a butter knife and un-clip them from the body and clean the rust off.to get a good ground.


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