Maybe the neutral safety switch is TOO safe?

July 30, 2010 7:07 AM

I have a few questions regarding a 1995 Ford Escort with an automatic transmission that periodically refuses to start. It has already been to a mechanic, so there is "more inside"...

Okay, I have a 1995 Ford Escort wagon with the automatic transmission. It has 85,000 miles on it as it used to be my grandfather's car. It has been a fuel efficient and reliable car that is a bit sluggish on hills, but otherwise nice.

From the time I got it (at about 58,000 miles) it would periodically have a bit of trouble starting. Previously, it was as if the starter itself was failing, since it would turn over but not catch spark. You just had to crank it a few times, briefly, and then it would start.

I had the timing belt changed at about 75,000 miles and, at that time, I had the mechanic put in a new starter. That didn't really help. I put in new spark plugs and my father and I tested the plug wires. That made it a little better, but it would still periodically take two turns of the key to start.

A few months ago, my wife tried to start it and she turned the key and nothing happened. Electricals came on, such as the dash lights, but there was no sound when the key was turned. The battery was fine. Eventually, the fan in front of the engine got "stuck" on and then we smelled a burning smell with a faint whisp of smoke coming from under the passenger's side of the engine. We quickly disconnected the battery and had a tow truck come get the car. It was towed to our trusty local mechanic who pronounced it too complicated for him to handle and suggested we send it to a nearby dealer. We did that and after one hefty bill, we had a new starter, new ignition switch and new neutral safety switch. The car was at the dealership so long that we finally broke down and bought a second used car.

I got the Escort back and rarely drove it as we had the other used car which is much nicer and more fun (a manual trans 2003 Mazda Protege5). Plus, we just adopted a baby and moved to Charlotte, NC, where I will begin teaching in a few weeks.

When we started the Escort to begin the drive from Eastern KY to Charlotte, NC, it wouldn't start. It has the same conditions as before - dash lights but no ignition of any kind. I was able to disconnect the battery and reconnect it and the car started with a turn of the key. I have tested it a few times since and it mostly starts, but occasionally won't start. I can disconnect and reconnect the battery and then it will start. My assumption is that the neutral safety switch's signal is cleared by the battery disconnect and then it will start.

I would simply take it back to the dealer and try to negotiate a better fix (with no bill), but now I am 500 miles away from where I took it. So, I am going to try to do this myself and this is where the questions come in. I have read that the neutral safety switch can be adjusted, so that is where I might start… I have a Chilton's manual and some light-to-moderate experience working on cars and also on other mechanical or technological things. I can figure out spatial things pretty well, generally, but I am not very experienced with electrical systems... My father and I have done a fair amount of work on my cars together, but he doesn't like electrical issues, as his main area is the engine and other general systems of the car.

Does anyone have experience with a similar starting issue?

If adjusting the neutral safety switch doesn't help, can I try the starter solenoid next?

If it is not a widget like the above listed things, do I assume that I have bad wiring somewhere? If so, how do I begin to diagnose this? I know I would need to consult a wiring diagram, but I don't know how to test wires for good "flow"… Can anyone outline the steps or point to a resource that would help? If you could list tools I would need and general techniques, that would be great.

Thanks in advance for help! I will start going to the office next week and would like to have this sorted at that point.

posted by Slothrop to Travel & Transportation (6 answers total)

When the car refuses to start, try wiggling the shift lever or put it in Neutral instead of Park. That will often jar a bad P/N safety switch into working.
The easy test is to grab a test light, hook the clip up to the negative battery terminal, put the point on the terminal of the starter where the big fat cable bolts on and then have someone turn the key. If the test light lights up nice and bright (or if you get 12V on your meter) then you can be reasonably sure that the ignition switch, PN switch, and starter relay are in good shape. There's no light, then you'll have to trace the circuit back until you find the defective component. If it lights up dimly or there's a signficiant voltage drop, then you're looking at a bad connection or some corrosion.

Another good test, if you have a voltmeter, is to perform a voltage drop test. Connect one lead to the battery positive and the other lead to the positive terminal of the starter solenoid. When cranking the engine, the voltage drop across the positive side of that circuit should be about 0.1 volts. That indicates the positive side is a good conductor. Then, connect the meter's leads to the negative battery terminal and the engine block. Crank the car. That circuit should also be about 0.1 volts. This test shows the quality of the circuit. The simple way to explain it is that none of the volts should want to go through the meter as a parallell path. If you're getting voltage readings during the voltage drop test, then the meter is effectively behaving as a viable alternative to the circuit. Voltage chooses the path of least resistance and that path should NOT be the voltmeter, as far as this test goes.
For example, if you have 12V circuit and a switch that's turned OFF, putting the volt meter in parallell to that switch should give you reading of 12V. Since the switch is open, then all of the volts want to go through the meter. When you close the switch, the voltage reading should go to about 0.1V since the switch is a better conductor than your meter. If you're still getting a voltage reading, like 2.0V, that means there's some resistance in the switch and some volts are choosing an alternative path, simply speaking.
That's how to test "flow" in a live 12V circuit, in a nutshell.
Other tests may involve a current clamp or additional equipment, but this one is cheap and easy.
posted by Jon-o at 7:19 AM on July 30, 2010

For starters, this is wrong: "it was as if the starter itself was failing, since it would turn over but not catch spark." The starter's job is just to turn the engine over. Whether the engine then starts running is dependent on many parts, none of which is the starter.

I'm wondering whether you've got a bad battery cable. Have you tried having someone hold the key in the start position while you wiggle the cables (rather than disconnecting and reconnecting them)?
posted by jon1270 at 7:23 AM on July 30, 2010 [1 favorite]

Once upon a time, I too owned a 1995 Ford Escort.

I would lay dimes to dollars that, despite the erratic function, it's your alternator. I think I replaced the alternator in that damnable car at LEAST five times. And a couple of those times, it displayed exactly the symptoms you describe.

Look out, however. Even refurbished alternators are shockingly expensive for that particular car.
posted by kaseijin at 7:49 AM on July 30, 2010

(and I know it's counter-intuitive to say "alternator" when the car still occasionally starts... but I swear that's what ended up being wrong with my '95 Escort when it did that)
posted by kaseijin at 7:51 AM on July 30, 2010

I agree with the jons. Something is up with the connection to the battery. And yes, all the starter does is turn the flywheel on the engine. For an engine to run it needs three things: air, fuel, and spark. Getting it to turn over is seperate. So no turn over = starter/electrical problem.


a manual trans 2003 Mazda Protege5
we have one of these too! ZOOM ZOOM!
posted by Big_B at 9:28 AM on July 30, 2010

I just realized that I gave bad advice. The big positive lead to the starter will always be hot because it's wired directly from the battery positive. Following my instructions above will result in the test light always illuminating, regardless of the condition or position of the ignition switch. To check the ignition switch, relay, and park neutral switch, you have to unplug the small terminal on the solenoid and check for voltage when cranking. The small lead is the control signal to the solenoid and the large wire is battery power. I got myself mixed up, thinking about voltage drop testing. Carry on!
posted by Jon-o at 1:33 PM on August 1, 2010