Whats the crank fuse do? - S-10 Forum
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Whats the crank fuse do?

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Old 02-06-2011, 05:44 PM   #1
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Whats the crank fuse do?

Okay so I was checking for power on all fuses and everything checked out except the crank fuse :/ What does it do and do you know where the wires go and come from?
Old 02-06-2011, 07:10 PM   #2
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Re: Whats the crank fuse do?

It sends a crank signal to the ECM, while the key is in the start position.
Old 02-08-2011, 02:07 PM   #3
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Re: Whats the crank fuse do?

So if there is no power to the fuse it wont start?
Old 02-08-2011, 03:50 PM   #4
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Re: Whats the crank fuse do?

the motor cranks right? And it says a fuse amperage right? So put a fuse according to the amperage in there and see what happens. Thats all that I can really say.

Not only that you might have some electrical issues.
Old 02-08-2011, 06:46 PM   #5
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Re: Whats the crank fuse do?

The CRANK fuse will only have power when the engine is cranking(start portion of ignition switch).
Power flows through the ignition switch in the start position, through the neutral switch(manual)to the starter and crank fuse then to the ECM from the crank fuse.
It is a 5A fuse in the fuse block.
Old 02-08-2011, 07:37 PM   #6
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Re: Whats the crank fuse do?

Powers the solenoid on the starter when key is held to start. Fuse blown, no power to coil on starter solenoid.
Old 02-09-2011, 09:30 AM   #7
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Re: Whats the crank fuse do?

Quote: Originally Posted by lesterl
Powers the solenoid on the starter when key is held to start. Fuse blown, no power to coil on starter solenoid.

Uhh, no.

It is simply a connection, split off from the starter wire from the ignition switch that connects to an ECM input. The truck will still crank without that fuse, just the ECM doesn't use the start tables when that is not enabled and may have difficulty starting.
Old 02-09-2011, 05:40 PM   #8
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Re: Whats the crank fuse do?

Raven, my bad, I've been over my schematics so much I could have sworn I have seen that in the ign circuit feed, went and checked, the only thing I have is a schematic of it in the block but they dont show where it goes, Guess with a 3 amp fuse it wouldnt be a solenoid fuse anyway......

AFAIK, the ICM has built in start tables and when it detects the engine fire it hands over control of the ignition to the ECM..... AFAIK....... But I dont know about fuel control either.
Old 02-09-2011, 06:02 PM   #9
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Re: Whats the crank fuse do?

The ICM doesn't have any "tables" built into it, though there is some measurable latency that varies with RPM an is different between different ICMs.

It is actually the ECM that sends a signal to the ICM for it to take over timing control, this is a 5V signal applied to bypass wire to allow the ESC signal to become active.

Some MS users have played with having the 5V signal active as soon as the key is turned on, to be able to adjust spark timing during cranking, with some success.
Old 02-09-2011, 07:14 PM   #10
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Re: Whats the crank fuse do?

Cool....
Old 02-09-2011, 07:53 PM   #11
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Re: Whats the crank fuse do?

I will post a nice schematic from Mitchell in a bit.
Old 02-09-2011, 08:54 PM   #12
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Re: Whats the crank fuse do?

Cool, mine suck.....
Old 02-09-2011, 09:03 PM   #13
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Re: Whats the crank fuse do?

This is the starting system diagram for an 1988 S10(random choice).
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