Car won't start when turning key

[94GTStang]

I have had this issue for quite some time now, but just now had the time to get around to fixing it.

The problem is that motor will not respond when you turn the key to the start position. Everything else works just fine, just when you go the extra turn to start the car, all is quiet.

Ended up running a push button to the starter to get it to start and this has worked just fine for years. However, I'm getting tired of doing this and I think having a button constantly hot is putting a drain on the battery.

I changed the tumbler and the ignition panel that is under the dash and still no go. What else could it be? A popped fuse somewhere?

 

[HISSIN50]

Check in/out voltage at the clutch safety switch. Also check the values at the starter relay in the underhood fusebox.

FWIW, a push button switch should not cause a drain.

 

[99FiveOh]

Also, that push button switch shouldn' be carrying all the current either. I hope you have it wired to a relay.

There was someone else who had this very same issue not too long ago, but I can't remember what he ended up doing to fix it.

 

[94GTStang]

Thanks. I'll check the voltage at the starter relay. It is an automatic, so there isn't a clutch safety switch unless the autos have something similar.

I'm not sure if it's hooked up to a relay since it's been so long ago when this happened.

 

[HISSIN50]

On an auto, the juice goes through the MLPS on the side of the trans.

When you test at the underhood fusebox relay, first try swapping the relay with the fog light relay and see if you simply had a bad relay.
If that doesn't help, check starter-relay pins 85 and 86 for voltage while someone turns the key to start. If you have voltage at one of them (only one will show 12V), check pins 30 and 87 for voltage while trying to start. Both should have voltage.
Post what you find and you'll know what direction to go.

Good luck.

 

[HISSIN50]

Here's your underhood fusebox

 

[94GTStang]

Thanks for that information! I'm off tomorrow so I'll look into checking it out then. Thanks!

 

[94GTStang]

Silly question, but where are the starter relay pins? That going to be in the fusebox or the MLPS?

 

[94GTStang]

Swapped the starter relay and still no go

 

[HISSIN50]

The starter-relay pins are the pins that plug into the starter relay (in the underhood fusebox). IF you look at the bottom of the relay (after you remove it), you'll see numbers. Those correspond to the numbers I posted above.

You kinda need to do that or some other sort of testing (like at the clutch safety switch) to know how far the signal is making it.

 

[94GTStang]

The starter-relay pins are the pins that plug into the starter relay (in the underhood fusebox). IF you look at the bottom of the relay (after you remove it), you'll see numbers. Those correspond to the numbers I posted above.

You kinda need to do that or some other sort of testing (like at the clutch safety switch) to know how far the signal is making it.

Ah ok I follow you now. When the wife gets home, I'll have her try to start the car while I test the circuit! Thanks!

 

[94GTStang]

OK, just got done with the relay. Only the back pin was getting power. All the other ones were completely dead.

 

[HISSIN50]

I don't know which one is the 'back pin' but we will assume that you have constant power at your common terminal.

I'd check the in/out voltage at the MLPS (driver side of the trans). The two wire colors are white/pink and red/lt blue IIRC. Both should show voltage while (and only while) cranking. If you have no cranking voltage to either, you need to test the starter circuit output right at the ignition switch (it's the white/pink wire).

 

[94GTStang]

Sorry, it is the pin that is closest to the strut tower. Those numbers are near impossible to read!

Tomorrow, I'll jack the car up and check the MLPS wires. Perhaps I'll do the easiest first and look at the starter circuit at the ignition switch.

I did replace the MLPS sensor a while back ago if that helps.

 

[94GTStang]

I did not have a chance to check the MLPS sensor for power today, however I did look underneath the dash at the ignition switch.

Apparently the car had a Prolock alarm installed before the car was purchased in 97'. The white/pink wire was cut and the alarm was spliced in. The alarm I'm almost certain had a kill switch because there was a black override button by the fuse box. I checked where I reconnected the white/pink wire and it is getting power when I turn the key to start.

I ripped the whole entire alarm out since it obviously could be the source of my slow power drain and maybe the reason the car doesn't start. Unfortunately that wasn't the case. The car still does not start.

Where else can I go looking other than the MLPS?

 

[HISSIN50]

Look at the MLPS and then the starter relay again. Those are the big items in the circuit. Also make sure the AODE jumper is in place (driver kick panel). If you have to, you can rewire the open part of the circuit.

 

[Labora]

Had a similar problem recently, ended up being a grounding issue that should have been pretty obvious to me.

Anyhow here is the starter diagram, hope it is of some help.

View attachment 242780

 

[94GTStang]

Look at the MLPS and then the starter relay again. Those are the big items in the circuit. Also make sure the AODE jumper is in place (driver kick panel). If you have to, you can rewire the open part of the circuit.

Alright. I'll try and get under there sometime this week to look at the MLPS.

I found this thread http://www.stangnet.com/mustang-forums/769594-neutral-safety-switch-photos.html with a picture of the jumper. That is what that entire alarm was connected into. You're telling me I can connect the ends of that together with one wire?

Had a similar problem recently, ended up being a grounding issue that should have been pretty obvious to me.

Anyhow here is the starter diagram, hope it is of some help.

View attachment 242775

Thanks for the chart!

I actually thought it was a bad ground too and replaced the entire ground wire length

 

[94GTStang]

Alright, on my way out to work today I looked at the old alarm. It looks like they cut the wire loop that is seen in the picture in that thread I posted. Is that fuseable link wire or just regular wire?

 

[Chythar]

Hah, my old thread! Yes, if you rejoin that wire you should be able to start the car. As I mentioned in that thread, that wire is a bypass for AODE cars. Manual tranny cars have that removed and rely on a switch on the clutch to engage the ignition. It is standard wire, not a fusible link.