HELP PLEASE B7500 blows 30 amp fuse during start

Guss

New member

Equipment
B7500
Oct 10, 2014
2
0
0
Trenton
Looking for help. I am blowing 30 amp fuse when I turn key to start, (I temp installed a reset breaker) I read some other posts to gather info, so far no luck.
1. If I remove glow plug wire the engine turns over, no breaker tripping.
2. If I remove the starter control wire the glow plugs glow.
3. I could not find a short (have the harness apart).
4. I bought a new switch and glow plugs.
5. I jumper wired the controller under the dash and safety switches.
6. Had starter tested at rebuild shop, and tried new solenoid

This is a simple start system, I must be missing something. I have a few pages from the shop manual for the start sequence and wiring diagram. The shop manual even shows the energy flow from battery to each component depending on start switch position. I have been to a local shop--they never worked on 7500 and didn't have shop manual. Any help would be great! Thank you.
 

Daren Todd

Well-known member
Lifetime Member

Equipment
Massey Ferguson 1825E, Kubota Z121S, Box blade, Rotary Cutter
May 18, 2014
9,088
4,577
113
Vilonia, Arkansas
Theres a short in the wiring somewhere. Possibly bad glow plug. Short is probably somewhere near the motor, by exhaust or engine block. Had a similar short on mine. Wiring looked good, till i tried to move the wiring where it crossed over by the engine. Realized it had melted down and was glued to the motor.

Could be an issue with a glow plug causing too much draw, starter could be going. Could be moisture in a pin connector.

Could try running a temporay wire from glow plug to switch and see if it fixes the issue. If it fixes it, then there is definitely a short in the system
 

Guss

New member

Equipment
B7500
Oct 10, 2014
2
0
0
Trenton
Thanks Darren,

I have three new glow plugs, no help.

I have the wiring harness out and apart, traced each wire for chaffing/bare spots none found. No moisture or corrosion in plugs.

I suspect a short too, but it is strange the starter spins and the plugs glow, just not together.
 

Daren Todd

Well-known member
Lifetime Member

Equipment
Massey Ferguson 1825E, Kubota Z121S, Box blade, Rotary Cutter
May 18, 2014
9,088
4,577
113
Vilonia, Arkansas
Tough when you start running into those stubborn electrical issues. I find when i finally figure out what is causing it, it ends up being stupid and simple.
Is there a fuel selonoid in the system?