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72 510 Auto No start - Inhibitor switch issue?

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Hey Guys -

 

New to Ratsun but long time Roadster and Z owner.  Just bought a 72 510 4 door.  Hasn't been on the road since 96 after some bodywork on the driver side. 

 

Spent a couple of hours trying to diagnose a no start condition.

 

Net result -

 

If I jumper the two black/yellow wires in the starter relay and bypass the automatic transmission inhibitor switch, the car starts effortlessly and runs like a champ. 

 

I have checked the wiring, testing for continuity and everything to the inhibitor plugs and from the inhibitor plugs appears to be good.  AND I tested the switch function by looking for continuity when the car is in park.  I can watch the continuity come and go moving in and out of park, so I think the switch works. 

 

The problem seems to be that the power doesn't make it back from the inhibitor switch to the starter relay to power up the coil in the relay - I can't get power on the black/blue wire... 

 

Anybody have any ideas what is going on? 

 

The car only has 31000 miles, so I am reluctant to yank the automatic, and I don't want to just leave the starter relay bypassed because that just seems bush league...

 

Thanks for the help.

 

dw

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Is the start relay clicking when you shift in and out of park? should also click in the neutral position???

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Not on a datsun but another automatic same issue.. make sure the shifter isn't loose.. when in park move the shifter back and forth see if you loose connectivity with that switch.. If I was easy putting it in park it would not restart if I slammed it into park it worked fine.

 

Jumping The 2 black/yellow makes no sense to me, they should both be ignition from the same source and get spilt supplying power to the 2 switches...

I looked at the diagram and saw this... black/blue at the fuse box...

Screenshot_20170228-131140_zpsnh154pds.p

I'd start there at the fuse box....

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With ignition in the on position, I hear the linkage moving from park to reverse, but no audible electrical "click". 

Same with moving from drive to neutral.  No audible click to speak of. 

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As I understand it, the black/yellow wires basically loop through the inhibitor switch to create the circuit that powers the starter circuit.  By jumping the black/yellow, you take the inhibitor switch out of the circuit, and power the starter circuit directly.  Right now, the starter relay itself gets power on one side, but doesn't get power on the blue/black that sparks up the relays coil to actually trip the relay... I was working on this with my friend Jim, who is way smarter than me.  We were pretty thorough I think and found the right wiring diagram as there is one floating around that is supposed to be for the automatic, but doesn't show the starter relay.  As it stands, the correct diagram has some of the wrong wire colors for my starter relay, which is absolutely original...

 

So, Mike, I am guessing from your question that there should be an audible click at the inhibitor switch when the shifter moves - is this a serviceable part or am I looking for a new one?  I would prefer that it work properly, only because the car is so original... I am however incredibly conflicted as this would be a totally different car with twin mikunis, a 5 speed, minilites... sigh.  Why did Grandma's always have to drive the automatics.  Nevermind.  I know.

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And thanks Crash!  That is the diagram we are working from.  I will check out the black/blue at the fuse box - and I have slapped the shifter silly into every different possible angle and direction to try and get it to do something.  Nada.

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If colors are different that sucks to try to help without being there to help you.... I noticed that on my 521... original harness didn't quite match the diagrams.....

Have you tried starting it in neutral?.. not sure what that will tell you but I know my Chevy I can start in park or neutral....

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Same condition whether in park or neutral.  I followed the black/blue around on the wiring diagram and it looks like it could be involved somehow because of where it ducks off to the ignition switch... be nice if some of these things were a little more linear.  I can't think about all the other directions some of these circuits can be going at the same time without feeling like I am going to have an aneurism...  I will take a good look at the fusebox underneath.  There was some corrosion on a couple of terminals there that cleaned up and gave me back some function in the car too.

 

I also still don't have a couple things in the car working - that could be related??? - no signal lights, no radio.  But fan, headlights, brakelights, dash lights, horn all work...

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Personally sounds like that switch could be bad... you said its been sitting a while maybe just corroded inside.... probably in park... check that one for power at the fuse panel, and try in neutral if it works in neutral it has to be the switch not making contact in the park position.... goodluck...

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When I tested the switch, we could get continuity both in the park and neutral positions, but not in Drive, Reverse etc... So that seemed to suggest that the switch was doing it's job... but, I don't know what it looks like inside, and I am not sure whether it does anything else - because even though we could get continuity, we couldn't get the power to come back up from the switch to the relay...

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Well switch sounds like it works. I'm good with wiring and my test light but without it in front of me it's hard to say. It gonna be a matter of chasing the supply voltage, but your probably aware of that... I'll look at the diagram again tomorrow to see if I can spot anything else.. I get bored at work sometimes. I think I have a 510 book I can dig out too. maybe a couple pics might help with the difference in wire color....

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This was a slightly different wiring diagram that sounds like it may be closer to what you have...

20170228_192029_zpsp2hlqj0f.jpg

I'll examine more tomorrow but what you said seems to folow this wiring....

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So, Mike, I am guessing from your question that there should be an audible click at the inhibitor switch when the shifter moves - is this a serviceable part or am I looking for a new one?  I would prefer that it work properly, only because the car is so original... I am however incredibly conflicted as this would be a totally different car with twin mikunis, a 5 speed, minilites... sigh.  Why did Grandma's always have to drive the automatics.  Nevermind.  I know.

 

Yeah I meant to say is the start RELAY clicking.  It is electrical and if there is continuity through the inhibit switch in PARK that signal should trip the relay.

 

If the relay is not clicking then the Black wire to it (the ground) may not be grounded... or the relay simply no good.

 

 

The '80s and '90s Nissan cars and trucks have oodles of really great relays in them. They are color coded and a Blue one is perfect. Two wires to the coil (one to ground and one to the inhibit switch) and the other two (one to the ignition Start and the other to the starter solenoid) These relays are Nissan and are square and about the size of your thumb. They look like these but you want a Blue one. Be sure to get the plug and trim the leads off as long as you can....

 

Old Pathfinders and Hardbodys have them maybe even turn of the century vehicles too? Best of all they fit in your pocket.

76%20headlight%20up%20grade%20005.jpg

 

 

 

 

 

 

This was a slightly different wiring diagram that sounds like it may be closer to what you have...

20170228_192029_zpsp2hlqj0f.jpg

I'll examine more tomorrow but what you said seems to folow this wiring....

 

 

I think you'll find this is a pre 70s diagram with the old BW35 automatic. The inhibit switch goes directly to the starter solenoid.... there is no start relay.

.

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We actually opened up the relay.  There is power on the black/yellow, but no power on the black/blue that actually trips the relay.  The ground is good.  We tested that too.  I am going to go fiddle with the black/blue circuit from the ballast resistor back to the fuse box and around to the ignition switch and make sure everything looks ok there... any other ideas?

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What does the ballast resistor have to do with this? IT, the auto choke heater, the idle cut solenoid (and the ballast resistor) are all powered from the ignition switch when in the On  and START positions. If your engine runs.... the ballast is fine.

 

The relay should trip in Park and Neutral and connect the wire between the START position on the ignition switch and the solenoid on the starter WHEN THE IGNITION IS IN THE ON POSITION 

 

When the key is turned to the START position (the relay has already made the connection) the signal can go straight through to the starter solenoid..

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I don't think there is a problem with the ballast resistor... but the black/blue wire seems to run into the starter relay from the ballast resistor and would appear to be responsible for powering the coil inside the relay.  There are two different sources of power to the starter relay performing different functions - black yellow for the starting circuit, and black blue for the relay coil to activate the starting circuit... at least that is how we figured it to work... if this seems like hoakum, please advise... it would not be the first time we failed to interpret something properly...

 

If we take the relay and trip it manually, it completes the circuit and starts the car with the key in the on position, but there is no power at black blue.  if we put power to black blue, the relay trips... so it seems that the relay is functioning properly.  But there is no power getting to the black blue to trip the relay when the key is in the start position.   

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It may seem to be wired that way but the ballast, choke heater, idle cut solenoid and the start relay all get power from the ignition switch in the on and start positions.

 

If you disconnect the ballast resistor, you will still have power on the relay wire that seems to come from the ballast.

 

 

 

In the start position the relay should close the connection between ignition and starter solenoid. The relay clicking just means it's clicking or energized. It's possible the contacts inside are dirty and still not making any connection. Usually this style of relay can be pried open to expose the contacts. Folding a thin strip of emery paper and placing it between the closed contacts and then pulling it out will clean them.

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We actually opened up the relay. There is power on the black/yellow, but no power on the black/blue that actually trips the relay. The ground is good. We tested that too. I am going to go fiddle with the black/blue circuit from the ballast resistor back to the fuse box and around to the ignition switch and make sure everything looks ok there... any other ideas?

So something I don't understand are you seeing constant power on the black/yellow wire or power only with key in the crank position?

 

Again colors your saying are off from diagram but as far as I can see black/blue only supplys power during crank like the black/yellow start wire...

 

This how I think the ignition is set up..

20170301_075218_zpswvvrdudy.jpg

1- 12v power

2- ignition out

3- start

4- acc

5- hot start

 

3/5 should show 12v during crank..

That's seems consistent for most datsuns.

 

Next the inhibitor and start relay..

20170301_075041_zpskedibymm.jpg

 

So the way I see this...

Inhibitor seems like a pass through circuit.

Look at the back up relay first, just to understand the system setup.

you can see it has power coming in on the middle wire rb/w

Rb is the relay output and b/r is ground coming from the inhibitor....

So if you look at the inhibitor

B comes in ( I believe that's ground)

In reverse inhibitor sends the ground signal to the backup relay via b/r..

 

Now if you look at the other 2 wires in the inhibitor b/y is suppling power during crank coming from ignition switch...

When in park/neutral b/y will connect by/r which should supply the power to trigger the start relay.

That same b/y powers the middle wire and completes the circuit to the starter...

Don't know if that will help or not...

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Work firewall doesn't allow me to see pictures. I'll look when I get home.

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If the car is indeed a 72 510, there is NO starter relay!  You mentioned that it would start when you jumped the black/yellow wires.  What is the issue, just always start it in PARK and you're good go

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The car only has 31000 miles, so I am reluctant to yank the automatic, and I don't want to just leave the starter relay bypassed because that just seems bush league...

 

dw

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I could only find a 620 starter relay for reference. I know the earlier 510 didn't have a start relay so I assumed you had one on the '72 510. The April '71 510 was the first 3N71B automatic replacing the Borg/Warner 35 so maybe this was added then? Or not?

 

 

You do NOT need to remove the automatic to service or get at the transmission interlock. It's right there on the pass side.

 

 

 

 

That wiring diagram that was posted showing the start relay may have been for the later '78-'81 A10 (also called a 510) 

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