Clutch and Starter System Intermittent Issue

[weitrhino]

Ever since converting my 85 auto notch to a 5-speed I've had some very intermittent starting issues. Might go for months with no problem and then turn the key and nothing happens. Nothing, except hearing the fuel pump prime.

This problem has vexed me at various times and one particularly bad time.

I was at DFW airport in heavy rain - lots of water on the roads. But down in the departure area it's covered by the arrivals area above. I was dropping off my beautiful wife at the doors when the damn thing decided to.....nothing. Traffic at DFW is always a nightmare and there I sat, motionless, with two tons of immovable iron. Push starting is always an option with a 5-speed but there was a bus parked in front of me far too close to get a good run going. An old baggage handler at the gate check kept hollering at me to come over to him - as if he had the answer to starting the car. Traffic was thick and constant so there was no way to angle around the bus without putting my life in peril. After about 30 minutes there was an opening and I went for it, hufflepuffing my heart out I jumped in, popped second gear and fired her up. At last I was out of there and without getting hassled by a cop.

The best I could think was water had splashed up somewhere it shouldn't have shorting out some part of the starting system. I found a small crack in the clutch interlock relay housing and replaced it with a new one.



Months would go by without issue and then, invariably, the gremlin would return. I discovered I was not the first to try and sort out the issue. The wire from the clutch interlock switch to the relay had been abandoned and replaced. When I removed the clutch switch there was white putty surrounding it with someone (else's) thumbprint in it. All my volt meter testing failed to find an issue.



Eventually I figured there must be a ground issue between the switch and the relay. I had my daughter press the clutch over and over while I measured the response with my meter at the relay location. Every time she press the clutch ground continuity would appear. Every. Time. We must have done this 50+ times and it always worked. So I threw it all together, added a redundant ground, and ran some errands. Six or seven times the car started normally and then left me dead in the grocery store parking lot.

After 15 minutes of futzing around it eventually started. It seems my redundant ground wire didn't solve this. So now I really want to understand why this failure happens and what conditions are causing it. There's no rhyme or reason to it. Facebook advice was to abandon the switch circuit and apparently the US is the only place that requires it for safety, but that doesn't help my understanding at all. Still, it's frustrating. Here's the diagram on top of the OEM relay. The aftermarket has no markings.



Pole #2 has constant 12vdc regardless of the ignition key position.
Pole #5 has ground continuity when the clutch switch is pressed.

What I couldn't understand is how adding ground on #5 activated the relay. It simply makes no dam sense. Then....



Well, it might be hard to see but the poles are marked on the underside in a different orientation than they are on the top. Again, the aftermarket relay has no markings. So now it makes sense and I have sketched out a diagram of the circuit.



I still don't know why this is happening but I can now easily bypass the clutch switch and simply connect poles 3 and 5 as shown in the diagram. Time will tell if this truly bypasses the issue yet it nags me (and apparently someone else in the past) why this damn circuit keeps failing intermittently.

[rednucleus]

So, my stock 85 hatch does not have a clutch interlock relay. How come you have one?

[weitrhino]

Transmission and clutch system were pulled out of an 87 parts car I once had. The 87 had at some point replaced the transmission because it was a 71b.

As I understand it the whole clutch interlock system is a required safety mechanism in US models simply to keep someone from turning the key to start while in gear and causing the car to lurch forward. I simply cannot recall if it was in my 86. If it was I never had an issue with it.

[kelso840]

Every s12 I've owned did not have a clutch interlock safety system. Those have all been 1984 and 1985 cars. Could have started in 1986.

[BOSSMAN]

Had the same problem with my 85 1/2 turbo.  Short answer to my problem is resistant build-up on my starter wires causing grounding problem, once I cleaned the two ring terminal connecting to the starter with sand paper the car started.  I figured it was a grounding issued because the first time it happened  I was in a "small town" after a fill-up at a gas station, I called the auto club and the mechanic just walked over from the gas station next to mine.  First thing he checked was the clutch switch but the car still didn't start, he then reached into the engine bay for the starter and told me he'll go get his tow truck and give me a push start.  Just as the guy went off to get his truck I hoped into my car and tried again but the car started, I asked the guy what he did but he said he had no idea.  The next day when I was about to go out the car didn't start again, I took a quick look at my starter and I could see the rubber covers for the terminals were off.  At that time my thoughts were to do what the guy did so I reached in and touch the starter and the terminals with my hand and it worked.  I didn't have issued with the starter until 8 years later and that time I figured it must be a grounding issue.

[rednucleus]

If the no start recurs, have someone hold key in start position and give the starter a rap with a hammer.  Bossman's comment above reminded me as the symptoms you describe could be a starter going south.

[weitrhino]

Good info on the part of you all however there's a bit more background here.

- I replaced the starter in November, 2018 due to complete failure and at that time assured all connections were polished and covered with a new rubber boots.

- My transmission and clutch system were pulled from an 87 despite the transmission being a 71b.

Because I've collected the full range of S-12 factory manuals I decided to look through them all for this clutch interlock circuit. It does NOT appear until the 87 model year. Even the mid-year 86 Mk1.5 silvertop does not have the clutch interlock system. When I swapped my auto to a 5-speed I just assumed it was part of the system so evidently the pre-existing failure factors were transplanted from the 87 parts car I once had. The putty on the clutch switch pre-dates the swap as does the rewired ground to the relay - someone struggled with this before.

I will need to edit the diagram above to show a 1987 200sx, not 1985.

[BOSSMAN]

I'm pretty sure there is some sort of safety switch on the clutch for my 86 that will prevent the car from starting unless your clutch paddle is engaged unless is only for Canadian market and not US?  I remember the other thing I check and replaced was the fusible link but i don't remembered if it was because my starting problem.

[weitrhino]

Examine the diagram above and it will explain exactly the starting prevention you describe.

Neither version of the 86 factory manual shows the clutch switch or clutch relay in their wiring diagrams, at least for the north American manuals I have. It doesn't appear until the 87 manual so it seems odd you'd have it on your 86, but it's easy to check. You'd see the switch under the clutch pedal, it's very similar to the brake switch under the brake pedal.

BOSSMAN, would you mind confirming?

[BOSSMAN]

i'll take a look and see what there later tonight.  I'm about the same age as you so I can't slide myself under the dash as easily as I use to.  I'll dig out my FSM and see if can find anything else. 
Post Merge

There something there.
Post Merge
Not smart enough to use my smart phone to post pictures on Flickr account...now fixed with Windows

Checked the FSM and the switch is not shown in the starting system wire diagram nor the clutch section.

[weitrhino]

Just a moment ago I was looking through my 85 and 86 Rev. 1 manuals and see the clutch switch illustrated in the Electrical chapter under 'Location of Electrical Parts. The illustration matches the pic you posted above. Below is what my clutch set-up looks like as pulled from an 87.



Notice where your switch is mounted I have only an adjustable bolt which is simply a backstop for the clutch pedal. My switch is engaged by the metal lobe welded to the clutch pedal shaft. It doesn't appear your clutch has this lobe.Wire colors into your switch are different than mine as well.

I wonder why Nissan did that?

[rednucleus]

Remember there's also a clutch switch as well as brake switch for cruise control

[BOSSMAN]

I remembered the car won't start unless my clutch peddle is pressed when I plug the switch back so does that make my switch a NC vs NO as there is no by passing with the plug.

[weitrhino]

Remember there's also a clutch switch as well as brake switch for cruise control

Yes, this is true. BOSSMAN, does your car have cruise control? Mine does not.

Judging by the illustration in "Location of Electrical Units" it looks like your switch is for sending the A.S.C.D. (cruise control) into "coast" mode, otherwise the engine would race if the clutch were pressed while using cruise control. The diagram below doesn't suggest it would defeat starting if not depressed unless I'm just not understanding the circuit. Yours just doesn't appear to be a start-up 'inhibitor.'

[BOSSMAN]

Yes, my car do have cruise control so that would be the "clutch switch".  Maybe my memory is playing tricks with me as Mr. Panda is in storage for many years now.