1993 F350 blowing 20A maxi fuse for IP/fast idle/glowplugs HELP!

[sweet66monza]

Well about a month ago my 93 would blow the 20A maxi fuse occasionally (about every 15th startup) right when the wait to start light would go out and glow plugs begin to cycle. I got tired of fighting it and didn't have time to dig any deeper, so I unhooked the glow plug controller and insulated the wires. No problems for a month. yesterday I went to start it, it fired and ran for 2 seconds and died. Blown 20A fuse. Put in a new fuse and it blew while cranking. Unhooked fast idle solenoid, put in a new fuse, fired up and died...blown fuse. Wires from glow plug controller STILL insulated, verified my short wasn't there.

Where do I start from here? I cant afford to throw $$$$ at it that I don't have to. Is there a good way to test the IP shutoff solenoid, and is there anything else on that circuit I can check that isn't listed in the owners manual?

thanks in advance!

 

[79jasper]

Check the harness plug where the two meet together. Follow the big harness off the engine.
I was thinking the fuel heater could be shorting, but looks like it's on a different fuse.
Down behind the thermostat neck is where you'll find the temp switch that controls the high idle and timing advance. You could try unplugging it.

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[Dieselcrawler]

Unplug your fuel heater too.

 

[sweet66monza]

After sleeping on it, I realized I forgot to mention one thing. In the last month and a half, the truck has been randomly kicking off and on fast idle. Outdoor temp or engine temp didnt matter. I would start it cold and it wouldnt idle up. Let it warm up a few minutes, get on the road and about the second stop (with engine temp up) fast idle would kick on. Few more lights it would be off. Pull into wherever im going etc and it would be bak on fast idle. Didnt affect how it ran, was just annoying.

Hopefully this helps isolate my issue. Ill try unplugging fuel heater and the temp switch after work today and report back.

Thanks again!

 

[direwulf23]

The fuel heater will blow the 20 amp maxi Fuse for your transmission control.

 

[fsmyth]

Don't rule out a bad ignition switch. Mine was blowing that same fuse.
It was completely worn out, and grounding that circuit sometimes.

 

[Agnem]

Since you mention the cold idle cycling, the temperature switch or connector is suspect. Disconnect it, and make sure the prongs are not grounding somewhere.

 

[sweet66monza]

The temp sensor behind the thermostat was it! You guys are awesome, thanks a million! Old reliable is alive and running again. Got the new $50 sensor from Ford yesterday, hoipefuly ill get it in tomorroe

 

[79jasper]

Yeah them things are pricey. Lol
Glad you got it though.

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