Starter fuse keeps blowing

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Apr 16, 2017 | 12:48 PM

Cooter126

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Starter fuse keeps blowing

Just bought a used 15 F-250 with 57,000 miles, yesterday tried to start it and nothing happened. Checked the starter fuse and it was blown, replaced it and it immediately blew when i tried to start the truck. Pulled the starter and had it tested and it was good, replaced the relay and still blowing fuses. I have got it to start a couple of times but as soon as you kill the engine and try to restart it blows the fuse. Has anybody had this issue and what was the fix? Truck had no problems trying to start before this problem started

Apr 16, 2017 | 02:37 PM

seville009

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Has anything changed on the truck since you started having the problem - ie: was something installed, replaced, etc?

just a wild guess, but maybe you're getting a short somewhere; maybe a chafed wire.

Apr 16, 2017 | 03:09 PM

R&T Babich

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From: Thousand Oaks, CA

Quote:

Originally Posted by Cooter126

Just bought a used 15 F-250 with 57,000 miles, yesterday tried to start it and nothing happened. Checked the starter fuse and it was blown, .... as soon as you kill the engine and try to restart it blows the fuse. ....

Assuming you're talking about the 30A Starter motor fuse.
If the same color wire is being used in 2015 find the YE/LB wire from the Central Junction box to the starter motor solenoid.
That wire goes straight from the starter motor relay contacts to the starter motor solenoid.
You could pull the wire from the starter solenoid and check it with a multimeter to see it is grounded.
The wire should be open on the relay end.
While the starter relay to starter solenoid wire is off check the resistance thru the starter solenoid to ground.
My spare starter solenoid measures .5 ohm (= 24A draw).
If yours measures closer to .4 ohm the fuse may not blow all the time, but the circuit is drawing 30A.
The starter solenoid could pass a test, but is drawing too much current.

Last edited by R&T Babich; Apr 16, 2017 at 09:08 PM. Reason: Added more info and wrong year

Apr 16, 2017 | 07:31 PM

projectSHO89

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From: St Louis

The drawings for a 2005 are useless for a 2015. Color codes, fuse numbers, etc are all different. The CJB no longer exists. It really is mandatory that the reference documents at least be from the same production generation for the data to be useful.

Quote:

just a wild guess, but maybe you're getting a short somewhere;

On, absolutely, it's a short circuit. That's why fuses blow.

Someone is going to need to inspect the BN-GN wire from the the starter back to battery junction box and look for the fault.

Apr 16, 2017 | 08:33 PM

Cooter126

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No nothing has been added or removed since i bought it, i have been trying to chase down the wire to the fuse box but get lost following it. Does anyone have a wiring diagram cause if its a single wire from the fuse block to the starter then i may just run a new wire but i want to make sure. Thanks for the input i was hoping someone had the same issue and it was something easy to fix

Apr 16, 2017 | 10:00 PM

R&T Babich

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Joined: Feb 2011

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From: Thousand Oaks, CA

Quote:

Originally Posted by projectSHO89

The drawings for a 2003 are useless for a 2015. Color codes, fuse numbers, etc are all different. The CJB no longer exists. It really is mandatory that the reference documents at least be from the same production generation for the data to be useful.

On, absolutely, it's a short circuit. That's why fuses blow.

Someone is going to need to inspect the BN-GN wire from the the starter back to battery junction box and look for the fault.

Which is why I said "If the same color wire" and didn't state a fuse no.
According to a 2015 F250 Super Duty Owner's Manual I think the OP is talking about blowing fuse #89 40A which is in the Power Distribution Box (new name for the Central Junction Box).
Since it's 40A it is probably a diesel.
I don't think the general design of a starter motor, solenoid and relay has changed so a simple test at the starter solenoid will help determine if there is a short in the BN/GN wire back to the Power Distribution Box or if the solenoid is degraded drawing too much current.
For a 40A fuse the load should not be more than .3 ohm.