99 70hp Temp sensor misfire

[h2oboy83]

Model J70PLBEE
99 Johnson 70hp engine
The motor had a misfire and I learned it was in the temp sensor circuit. When I unplug the sensor it runs perfect. I replaced the sensor and it does the same thing. Idles on what seems like 1 cylinder. Unplug the new sensor and it runs fine. Im wondering if its the power pack now, god I hope not. How can I check the power pack? Any ideas?

 

[oldcatamount]

Re: 99 70hp Temp sensor misfire

If it was a bad power pack, it wouldn't run regardless if the temp sensor was unplugged or not. I suspect a chaffed wire or loose wire connection somewhere.

 

[boobie]

Re: 99 70hp Temp sensor misfire

This may sound stupid but what color wire are you dealing with here that you are disconnecting ?

 

[h2oboy83]

Re: 99 70hp Temp sensor misfire

temp sensor has two wires, one is tan the other is white. I put 12v to the tan wire and the horn didn't sound, which I believe it should have.

 

[boobie]

Re: 99 70hp Temp sensor misfire

NO ! You turn on the ignition sw and ground out the tan wire on the the block and see if the horn blows. When the mtr overheats the temp sw grounds out and blows the horn. The black/white wire is for QS.

 

[Faztbullet]

Re: 99 70hp Temp sensor misfire

If it runs with tan wire disconnected and misses reconnected it being "tricked" into SLOW. Check the tan wire out of pack for nicks and chaffs an if its ok check the blocking diode in harness....

 

[h2oboy83]

Re: 99 70hp Temp sensor misfire

Yea, Thats exactly what its doing. I guess I'll undo the wiring harness and check the wires the best I can. And also the horn doesn"t blow when I ground the Tan wire. Im guessing it has a break or something somewhere. What is the blocking diode, and where is it in the harness. Is that the ressistor I see in the wiring diagram?

 

[h2oboy83]

Re: 99 70hp Temp sensor misfire

Ok I found the diode. I have resistance from the power pack to the diode and from the diode to the connector. But there's not any resistance across the diode. Im about to go check for resistance from the harness connector to the dash, but I have a feeling its the diode. You guys agree??

 

[ezeke]

Re: 99 70hp Temp sensor misfire

Ok I found the diode. I have resistance from the power pack to the diode and from the diode to the connector. But there's not any resistance across the diode. Im about to go check for resistance from the harness connector to the dash, but I have a feeling its the diode. You guys agree??

If you applied voltage to the tan wire, you probably blew the diode.

 

[h2oboy83]

Re: 99 70hp Temp sensor misfire

Yea, thats what I was thinking too. But what was the original problem? Bad temp sensor? Or maybe the diode was bad before?

 

[h2oboy83]

Re: 99 70hp Temp sensor misfire

Well the new diode is in. The horn doesn't blow when the tan is grounded but the hot light comes on when it's grounded...so I guess thats good. Im rebuilding the carbs right now so I will test on tues!

 

[h2oboy83]

Re: 99 70hp Temp sensor misfire

Well after alot of research and some testing I have found...
The horn doesn't blow when the motor overheats, the led on the tach just comes on. When tested it does. My temp switch has 2 circuits: One for overheat and one for warmup that changes the timing at 96 degrees.
After testing I have found the problem is in the white/black stripe wire warmup circuit. I can only guess there is a problem with a circuit in the powerpack. But I have think it is cheaper to just cut the white/black wire and just let the motor warm up than unhook the temp switch and risk overheating. Or I could buy a new power pack for $250. Unless anyone has a better idea thats all I have...

 

[h2oboy83]

Re: 99 70hp Temp sensor misfire

bump