Intermitent Starter issue Options

[914itis]

My starter was fine, until the weekend.

The weather was nice and I decided to take a drive; started fine. when I got to my destination, I turned the key and it attempted to start the car and the battery cuts off.
I have a 60 amp fuse on the red wires going to the battery, check the fuse it wast toast. I replaced the fuse and it blew it instantly as soon as I turn the key on.
Since there is a wire coming from the the main fuse that I installed from the battery to my amp and air horn, I isolated the wire and replace the fuse again the car starts fine.

When I got home, I installed a dedicated fuse for that amp wire.

Since then, the starter becomes a hit and miss. sometimes starts on the first try, sometimes i have to turn the key on and off before the starter spins. Sometimes it would start spinning for a short time and stops before the engine can start.

The starter positive wire is straight from the battery.
I know that there is an issue with the 74's where a relay is installed, but why would it burn the fuse to begin with?

All my grounds are intact.

Any ideas??

[914itis]

Thanks. Will follow your advice and do more troubleshoot Friday . I will report the results.

[AE354803]

My question is, can a starter going bad blow that main fuse?

The starter going bad could blow that fuse, depending on if it shorts or open circuits. After you removed the amp from the circuit you said you can get it started sometimes, might have done damage to the starter relay. Either way it seems you are developing a ground in the starter circuit if it used to work and now, suddenly, you are blowing fuses with everything else the same. Fuses don't blow for now reason.

If you are blowing a 60 amp fuse with ~12.5 volts then your system resistance when cranking is <0.2 ohms. The only issue with measuring the entire resistance of your starter circuit is that normally the resistance of the motor is low with no current flowing through it and increases once current is driving the motor.

I'd just start by removing the starter relay and measuring resistance from the starter relay incoming + to a ground (it should be pegged high)

If that checks out remove the + wire from the starter and measure resistance from the starter relay output pin to ground (again should be pegged high).

If neither of those have grounds I'd suspect you may have a developing issue with your starter. It could have short circuited. You can try to read the resistance of the windings by measuring resistance using your lowest setting. Measure from the + to the - (or case of the starter if no - ) a resistance of 0 means you may have short a circuit, you should get a low resistance but not zero.

Or if you have a spare starter relay just try throwing that in but you could fry it.

Good luck!

[914itis]

My question is, can a starter going bad blow that main fuse?

The starter going bad could blow that fuse, depending on if it shorts or open circuits. After you removed the amp from the circuit you said you can get it started sometimes, might have done damage to the starter relay. Either way it seems you are developing a ground in the starter circuit if it used to work and now, suddenly, you are blowing fuses with everything else the same. Fuses don't blow for now reason.

If you are blowing a 60 amp fuse with ~12.5 volts then your system resistance when cranking is <0.2 ohms. The only issue with measuring the entire resistance of your starter circuit is that normally the resistance of the motor is low with no current flowing through it and increases once current is driving the motor.

I'd just start by removing the starter relay and measuring resistance from the starter relay incoming + to a ground (it should be pegged high)

If that checks out remove the + wire from the starter and measure resistance from the starter relay output pin to ground (again should be pegged high).

If neither of those have grounds I'd suspect you may have a developing issue with your starter. It could have short circuited. You can try to read the resistance of the windings by measuring resistance using your lowest setting. Measure from the + to the - (or case of the starter if no - ) a resistance of 0 means you may have short a circuit, you should get a low resistance but not zero.

Or if you have a spare starter relay just try throwing that in but you could fry it.

Good luck!

Great info and thanks .

Where is the starter relays located ?

[AE354803]

Where is the starter relays located ?

I don't have a 914, only an engine from one so I'm not sure what's on your relay panel but what I described is in general how the starter circuit functions. If it works like the 912 then the ignition switch serves the function of the relay. You can "fix" this by wiring in your own starter relay so that your ignition switch contacts will take less current/wear.

I'm sure someone will chime in, but if you check out this diagram, number (2) is the starter, looks like you may have a relay board (number (90) in the bottom left).


With Starter:
http://members.rennlist.com/warren/914wiring2.jpg

Directory of diagrams:
http://members.rennlist.com/warren/