I have had a '90 Bronco II with the stock 2.9L and 4WD for a dozen years or so. A couple weeks ago, I went out to start it up. The starter started, the engine did not start, but the starter would not stop. I removed the key, but the starter kept running.

I admit I kind of freaked out, so what I did next might not have been the best thing to do, but it's what came to mind. Don't tell me I'm a mechanical idiot - I will readily admit to that.

It was parked up against a curb, so I put it in gear and let out the clutch to stop it from turning the engine over and over and over. Then I grabbed a wrench from my tool box in the back and removed the negative battery cable, but by then the positive cable from the battery to the relay was getting warm.

So, I replaced the starter (the old one had a Motorcraft sticker on it and might have been the original, but oh, did it ever stink like burned wire). I also replaced the relay on the fender wall. I drove it on errands around town with several starts and stops - all seemed good until it did the same thing again. I did the same trick and pulled the negative cable, but was relatively quick about it this time because I had the wrench handy.

I put the negative cable back on the battery, it started up normally, and I got it home OK, but I haven't tried to start it again.

So what should I replace now?

We had replaced the ignition switch connector block a few months ago.

Is it time to replace the cylinder key lock or ???

TimC "mystified in Oregon"

 

If it keeps cranking when your foot is off the clutch, the "ignition switch connector block" (AKA ignition switch) and cylinder key lock are not the problem.

What you need to do is remove the wire with the rubber boot from the starter relay the next time this happens. If it stops cranking the most likely problem is in the clutch safety switch

The cruise control cut off & starter circuit come together in that switch. Could be voltage from the CC circuit is crossed with the start circuit.

 

Very interesting !!

Yes, it would keep cranking after my foot was off the clutch and the key was out.

I will let you know what happens.

Thanks!

 

See attachment. As they say a picture is worth a 1,000 words, that's all there is to the start circuit

Shove the clutch in, turn the key to start and voltage flows thru the clutch switch to the starter relay, the relay closes & connects voltage from the battery to the starter motor.

 

Aha! Yeah, you're right - thanks for the picture.

I've had a dozen good starts in the last two days running around town, but I'm thinking it would be good to replace that part anyway.

I'm looking online. Talk about parts with a bunch of similar names: neutral safety switch, clutch interlock switch, Clutch Pedal Position / Starter Safety Switch.

Am I looking for the boxy looking part or the cylindrical push button part?

And where does it fit? Somewhere on the clutch pedal?
Thanks again!

 

Oh drat! I found it. It looks like a (insert non-family friendly word) bear to change with the clutch push rod going through it.

 

Well go figure, I thought it would be a simple button switch.

As you can see from the drawing 12 volts is somehow getting to the starter relay when it shouldn't. Might be in the switch or somewhere else along the wire.

BTW if you need to you can start the car by simply pulling the rubber boot off of the starter relay & jump from the battery cable side of the relay to that pin. It will crank & if the key is turned to run it will start. Just be sure that it's in neutral when you do it.

 

Several more good starts this week with no false starts.

In looking at the circuit diagram in the old Haynes book, it shows that the circuit to the starter motor starts with the ignition switch (I don't see the key switch in the diagram), then it goes thru the clutch interlock clutch to the starter relay. So, in order to keep the circuit to the starter relay trigger complete, both the ignition switch and the clutch interlock would have to fail - which doesn't make sense.

As near as I can see, in order for the starter to keep running, it would have to be the starter relay that got stuck.

Does that make sense?

 

What happened to me with my 87 Ranger was as I was driving the starter would grind every time I shoved the clutch in. popped the hood and removed the rubber boot/trigger wire from the starter relay so I could drive to Autozone & pick up a new ignition switch. Got it home and tested the ignition switch. My guess was right as the BATT & start pins were shorted together in the switch. Replaced the switch and problem solved.

If a wire with voltage on it rubs against the trigger wire and the insulation rubs off the wires the starter relay will close.

Yes if the contacts in the starter relay weld themselves together the starter will crank non stop. But you still had the problem after replacing the starter relay.

If this happens again be ready to remove the rubber boot/trigger wire from the starter relay. Odds are it will stop cranking and you can get home