The jumper wire test will definitely help narrow it down.

 

If it does come down to it, the switch is pretty easy to change. You don't have to pull any of the mechanical parts (the lock cylinder or housing), just the electrical part on the back. This is also good, because it means you don't have to get anything re-keyed.

Sorry to resurrect this ancient thread but I seem to have this exact problem. I replaced the copper contacts and plumber in the solenoid but still no start about 50% of the time. I am interested in adding this relay but I've never done it and therefore wonder if someone has a walk-through video or guide. Thanks!

Here is what I did.  I bought a relay at Advanced Auto and installed it off one of the screws on the fire wall.  Then I took the wire that energized the starter solenoid [this has a female spade], and used it to energize the solenoid.  Then I ran a new heavy wire [12 gage?] from the battery through the contacts on the solenoid and to the starter solenoid.  I also added a fuse on this wire for safety but probably not necessary.  

 

Now when i start the car, I first hear a nice "clunk" as the relay picks up.  It completely eliminated the starting problem.

Here is what I did.  I bought a relay at Advanced Auto and installed it off one of the screws on the fire wall.  Then I took the wire that energized the starter solenoid [this has a female spade], and used it to energize the solenoid.  Then I ran a new heavy wire [12 gage?] from the battery through the contacts on the solenoid and to the starter solenoid.  I also added a fuse on this wire for safety but probably not necessary.  

 

Now when i start the car, I first hear a nice "clunk" as the relay picks up.  It completely eliminated the starting problem.

This is very useful information. Any photos available? Can you sketch it out for me? This would be my first time doing this sort of thing.

The fuse is nesisary. If somehow that wire ever shorted to ground, you have an instant flash fire. I almost burned down my first Subaru years ago due to fuse not in the proper location, ie. Close to the power feed source.

Here is what I did.  I bought a relay at Advanced Auto and installed it off one of the screws on the fire wall.  Then I took the wire that energized the starter solenoid [this has a female spade], and used it to energize the solenoid.  Then I ran a new heavy wire [12 gage?] from the battery through the contacts on the solenoid and to the starter solenoid.  I also added a fuse on this wire for safety but probably not necessary.  

 

Now when i start the car, I first hear a nice "clunk" as the relay picks up.  It completely eliminated the starting problem.

This is very useful information. Any photos available? Can you sketch it out for me? This would be my first time doing this sort of thing and it needs to be done ASAP.

Well man, you've had at least 2 people on 2 different threads tell you how to fix this. If you really don't know how to wire a relay, or don't want to do enough research to figure it out, I'm thinking you should really be hiring someone that does to do it for you. 

But here goes anyway:  Attach a #10 wire with a ring terminal to the battery cable connection AT THE STARTER, no need to run a wire from the battery when you already have the biggest wire in the car running from the battery now. Make this as short as possible, like an inch or less with a female spade on the other end. This will plug into one of the switched terminals on the relay. Another #10 wire from the other relay switch terminal to the starter solenoid spade connector. Again, as short as possible. Then, take the wire from the ignition switch, which was on the solenoid, and plug it onto one of the relays coil terminals. Run another wire from the other relay coil terminal to a ring terminal on the battery ground cable where it bolts to the bracket by the starter. This can be a small wire, #14 or so. You could probably even get away with tying that together with the solenoid wire instead of a separate ground, but let's keep it simple. 

All you're doing is providing an electromagnetic switch to connect the big terminal of the starter to the solenoid terminal. they are like an inch and a half apart. Make the wires as short as possible, and there's no need for a fuse. If you're really worried about something shorting to your inch long wire, you can coat the whole works with liquid electrical tape. Oh, and just ziptie the relay to the battery cable.

 

Edit: BTW, I've never done this. This is just how I would do it. I ended up just running a direct wire from my ignition switch to the starter solenoid to bypass all the crap that was dragging the voltage down. Probably a bit more complicated for a novice to do than just install the relay. Many here have expressed the opinion that the relay is the best fix because they don't feel the ignition switch can reliably handle starter solenoid load. And they have a very good point. Many cars throughout history have used relays instead of running full load through the ignition switch. I just happen to feel like it's one more moving part/one more thing to go wrong. But it's really 6 one/half dozen. 

Edited May 26, 20178 yr by Subaru Scott