I'm dumb I'll just get that out of the way first. Car is a stock 1988 T2.

The condensed version is I (uh I mean "A friend") hooked up the battery backwards when I was jump starting it.

After much searching around on the forums and parts store trips, I've now a new battery, and new 80A fuse, and two fuses that had blown under the kick panel ("Room" and "Meter")

I opened up the ECU to see if anything looked obviously fried up, it looks clean and not toasty, it also doesn't smell like any toasting has gone on in there, but I guess there's no way to be sure until I can actually attempt to start the car.

Now:

When I go to start the car everything is normal except the starter itself wont engage or spin. The lights and everything, blinkers, cluster, all work as they should. I turn the key and I get a big 'Click!' as well as I can hear the fuel pump turning on for as long as I hold it to "Start." But no actual starter action.

I went under and touched a +12v source to the starter's post to see if it was working at all, when I do this, the starter does spin up freely, but still does not engage or actually turn the engine. I'm not sure if this is normal or not, but regardless of that it does not spin at all when I try to do it by turning the key.

So, I'm going to guess I've messed/cooked some component(s) up! I'm not sure if it's the stater, or a relay, or what it could be. Though it be helpful if someone could tell me where to start.

 

You have a relay next to the Main Relay called the Starter Cut Relay and it has just one plug w/four wires. There are two Black/Green wires in this four wire plug, one is rather thin while the other is a thicker gauge. It is this thicker gauge wire that must have voltage w/key to start when the clutch pedal is depressed. If it does then the Black/White wire in the same plug should also have voltage as well w/key to start. This B/W wire runs to the starter although it goes through an intermediate connector before reaching the starter solenoid.

And to clarify something you said, the solenoid on the starter would have to have voltage placed to it in order to get the starter to spin and not the positive terminal on the starter that originates from the battery.

 

Pardon my not knowing anything, but where exactly are the two relays located? I'm trying to open the FSM online, but unfortunately the system I'm on cannot open .pdf files correctly.

And yes you are correct, I was on the solenoid and not the starter body itself. The one closest to the driver side. Is it normal for the starter to spin freely when you do this, or should it engage the flywheel?

 

Both relays are located side by side and bolted to the fender and near the Trailing coil. I would think the starter would engage and rotate the engine. Perhaps the starter was damaged as it receives both a constant source of voltage plus a ground or maybe it was just one of those things.

 

Okay, thank you for that. I will check them with the Multimeter tomorrow when there is light again. I'm not sure if it's worth mentioning that I also had the stater all the way off the car at one point to examine it, and by putting a -12v to the body, and a +12v to the solenoid stud, the stater would turn, but would also not do the forward engagement action while it was spinning.

Either way this seems like a separate problem of its own, as I can't even get the starter to spin what-so-ever with the key.

 

re clamp your battery cables to the battery post....... not making a full ground contact happens all the time.

To test starter by bypassing the key...........take a 12g or 14g wire clamp to +ve on battery, and touch the +ve on the starter (u will need to jack up the car to get under) it should turn over and varify the starter is good
hybrid g

 

had this happen with a jeep of mine years ago, jump starting a neighbor and he reversed them on his side, chased issues for a few weeks burnt out a lot of items but hopefully that 80amp blowing saved some other stuff from getting damaged- good luck!

 

Push your clutch in when trying to start it? Don't ask how I know...

 

the clutch interlock switch is after the starter cut relay, so voltage should be tested also after that point either at the connector itself or at the starter.

even if there is voltage present when trying to crank it still doesn't mean there is sufficient amperage though to kick over the starter solenoid. basically meaning the cut relay, interlock switch or the ignition switch are faulty with corroded connections.

when trying to jump the starter manually you also need to make sure you are applying voltage to the small spade connector at the top of the posts versus jumping from one post to the other on the starter, this applies power to only the starter motor and not the solenoid which pushes the gear onto the flywheel.

to find out which circuit is causing issues you have to do a draw test, with everything hooked up use a DMM to measure voltage across one connection to another. ie hook up the DMM from one post on the clutch interlock switch wire to the other, while cranking there should be no more than a 1-2 volt measurement present on the DMM, if the measurement is closer to 9-12v then that connection is faulty and absorbing all of your power.

i would suspect the starter cut relay got cooked though, since the interlock switch shouldn't be contacting anything when idle unless you attempted to start the car with the polarity reversed, in which case everything listed above can be suspect.

 

^ In this particular case his car is an S4 thus the Interlock comes before the relay as opposed to the S5 which is completely the opposite as pointed out in your post.

 

Unfortunately I did try to start the car a few times while the polarity was still reversed, so I guess I'll be troubleshooting in order.

Today now that I had someone to help me with the car, I got underneath while they were attempting to crank it over. And the starter does obviously make a click when the key is turned to 'Start' but doesn't actually engage nor spin. However this time when I ran a jumper from the +12v of the battery, to the driver side terminal on the solenoid, the starter did both engage and spin, and the engine actually did start and run. Which was a relief because the ECU is functioning as it should be. Obviously this was all done with the key to the 'on' position.

I have a feeling the clutch interlock is functioning as it should, as when I am holding the key to start, I can pump the clutch in and out and there's a big obvious click that happens when I put it to the floor. That's not to rule out that the switch itself might be drawing way too much current as Karrak/RotaryEvolution was saying.

Asides from that, I'm going to go out with the DMM and check the starter cut relay, I'm hoping that it will be what got burned out, after that/and if that fails, I'll pull up the diagrams and start some real troubleshooting :6

 

At the Starter Cut Relay you can jumper a wire from the thick B/G wire to the B/W wire and in doing so it will bypass this relay.

 

I forgot to give an update for this curious. Or more like I was a bit too embarrassed to report back.

Turns out when I had put the new battery in, one of the cables on the positive battery terminal connection has slightly slipped out, the problem was a loose connection at the battery. Everything else electrical in the car (aside from the fuses) is thankfully okay.

 

So,does it start?.run?.

 

Starts, Runs, is generally very happy!

But then this happened: https://www.rx7club.com/2nd-generati...ithin-1012645/

 

That will not buff out...lol!
Every day is an adventure with these cars!