Electrical problem on start (with engine temp?)

Sergey

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Hello,
Well I nave got a annoying electrical problem. Finally, after 35 years of no electrical issues in my truck now there is one.
Here is how it manifests.
1. truck was sitting outside, not driven, for several months. Batteries were charged periodically to keep in shape, but kept disconnected from truck cables.
2. After that long period of hibernation a start is attempted
3. Connect both batteries. It is about 55F outside
4. Turn key to ON
5. Observe glow plugs cycle happily on and off, red glow plugs light confirms
7. Gear shift in neutral, depress clutch pedal
8. After about five cycles turn key to START
9. Immediately a red warning light "Engine Temp" comes on, and audible relay click is heard
10. no crank, silence
11. release key back to ON
12. immediately a red warning light "Engine Temp" turns off, and audible relay click is heard

Repeated this procedure several times, same result.

I understand that eventually my decades old wiring will give way, but this is an obscured case.
To ensure that there is no fault from temperature sensor (the big one, for the light) I disconnected the rubberized angular connector from that sensor and checked it. Its resistance is infinity as expected.

Schematics I have is from Chiltons book and does not seem to be accurate. So, does anyone have a good portion of schematics for 85-86 for at least under hood part of truck wiring?

Thanks,
Sergey
 

79jasper

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You don't necessarily need schematic. Just inspect the wiring.
Also check the starter solenoid on the fender. And the clutch Safety switch.

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Sergey

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Thank you, but I don't quite get how a faulty clutch safety switch is related to "Engine Temp" red light be on ?
 

ifrythings

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When the key is turned to the start position you should have the engine temp light and e-brake light come on till the key is released to the run position. This is a prove out for those bulbs.
 

Sergey

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When the key is turned to the start position you should have the engine temp light and e-brake light come on till the key is released to the run position. This is a prove out for those bulbs.
Hmmm... Looks like this feature doesn't work this way on my truck. In fact I do not recall if "Engine Temp" red light ever comes on, except now with this problem. The break red light only comes on when I engage parking break. Not in any other case.
Do I have a weird wiring issues ? I do ask for schematics for 85-86 F250 IDI. All wiring is factory original, no changes made.
 

IDIBRONCO

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I would guess that the starter solenoid on the fender is making the clicking, but the starter itself isn't turning over. I agree with ifrythings that the engine temp light is coming on in the start position. Check your starter to see if it's working and then worry about the light.
 

Sergey

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Didn't you say it's not starting?
Yes no crank thus no start. If it were just a faulty starter relay then there should not be "Engine Temp" red light.

I will inspect wiring again, but finding a short or cross-wire connection in that multi wire bundle may be next to impossible with my hands and equipment.
I'm asking for schematics because the theory is that if engine overheat is detected then circuit won't let starter to crank. OK, safety feature. The same way as clutch not pressed would.
But .... say the insulation on specific wire died and it shorts to something. Then should then "engine temp" red light to stay on (as if engine is overheated), but it doesn't, it only comes on when key is in Start position and turns off when key is returned to On position. Odd...
 

david85

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Since you mentioned there is an audible click with the key in the start position, the neutral safety switch (or clutch switch if manual), is probably ok. The ignition switch and other in-cab wiring is also probably good. The click you hear is probably the starter relay on the inside passenger fender...which is also probably good.

I would look at the 10 gauge wire that goes down to the starter itself (the lighter wire, or "trigger wire"). They can get corroded or fall off after so many years. This is the wire that activates the starter, not the relay on the fender. If the solenoid on the starter doesn't energize, the engine won't turn over.

EDIT: The red overheat and water in fuel lights are supposed to come on in the crank position. It's only a lamp check.

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ISPKI

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My trucks have a bunch of lights that come on while starting, including engine temp, water in fuel might also. As far as I am aware, there is no safety circuit to prevent starting the truck if the engine temp light triggers. I have had a truck in the past boil it's coolant while waiting at a lumber yard (thermostat failed closed). Shut it off before it boiled too much out. Fired it back up immediately and rolled it down a hill to get air moving thru it. Engine temp was on but shut off shortly after starting it again. Not like these have a computer to interpret signals or anything.

The wiring from ignition to starter solenoid is extremely simple. If you turn the key to start and your starter doesnt turn, check the starter first and work backwards from there. Wouldnt be surprised if you find one of the posts on the fender mounted solenoid is rotted or burned up inside.

Also - Just because a solenoid clicks, doesnt mean it works. Mechanical solenoids usually fail by overheating a contactor such that it still sounds like it functions, but there is no contact on one side, or it contacts, starts flowing current and the contactor immediately heats up and warps until it loses contact.
 

ifrythings

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Here is some wiring diagrams, the only starter interlock on your truck is the clutch switch or neutral safety switch if auto.

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