Blowing 12V Solenoid Fuse

DieselScout · #1 10-02-2020, 01:29 PM

Replaced the Injection Pump on my '82 245.
Got the car timed and running.
A few hours later, it started blowing the 16a fuse, 3rd from the bottom.

If I disconnect the 12v Solenoid cable on the Injection Pump, the fuse works.

Any idea what may cause the 12v solenoid to be shorting the system?

Currently can't drive car, because it blows the fuse the moment I switch the key to ignition.

Goteborg Vapenfabrik · #2 10-02-2020, 04:58 PM

Its probably time for a new engine wiring harness.

ngoma · #3 10-02-2020, 07:16 PM

As a test for that (bad wiring) you can disconnect the original wire from both ends, and run a fresh temporary wire from the fused end to the solenoid. If that works, just make it more permanent. That at least buys you more time to assess whether the rest of the wiring is in need of replacement (probably) as Goteborg Vapenfabrik suggests.

See this post:
1984 rotting cables

DieselScout · #4 10-04-2020, 07:30 AM

My wire harness was cracked with lots of exposed wires, so i replaced it with a new one I had on the shelf; the results were the same.

The resistance of the solenoid reads 0.9, where as the solenoid on my other D24 reads 7.7.

I suspect the solenoid may have become compromised during the installation, so I ordered a new one; which will hopefully this week.

ngoma · #5 10-04-2020, 11:08 AM

Good method. And you have solved many future electrical problems by changing out the bad harness.

You CAN run the car with a bad solenoid by removing the plunger and reinstalling the solenoid without it, leaving the wire disconnected. Shut the engine off by stalling it in gear.

DieselScout · #6 10-06-2020, 06:06 PM

Installed the new Bosch Thermostat and the car started right-up without blowing any fuses. :-)

ngoma · #7 10-06-2020, 07:54 PM

That is surprising and doesn't make any sense but we'll take it as a win!

v8volvo · #8 10-11-2020, 08:51 AM

Quote:

Originally Posted by DieselScout

Installed the new Bosch Thermostat and the car started right-up without blowing any fuses. :-)

You might have meant "solenoid" rather than "thermostat"? Just checking in case any need for correction to avoid confusion for anyone who finds this thread in the future.

Nicely done, good outcome. I think that is the first time I have ever heard of one of those solenoids failing shorted, interesting. Now we know it can happen.

DieselScout · #9 10-12-2020, 05:10 AM

Yes, I did mean "Solenoid" instead of "thermostat," lol.
Must've been right after I replied to the other thermostat thread.

I didn't know those could fail either, but just as a precaution, I am keeping a spare in my glove box with a wrench in case it ever dies while I'm driving.