Urgent help needed please: non starting engine

[911hillclimber]

I have an MoT booked early this Wednesday and the 911 won't start, so looking for some help please.
The car is a 73T with a 3.2 engine in it on Bosch DMS.
It has worked perfectly for 18 years until these last few weeks.
The starter will not energise. recently the starter position on the switch would do nothing, total silence, then on the second try it would fire and run superbly.
I thought it was the ignition switch, but the new one has the same 'effect', non starting.. The old one will not start the engine now.

The starter will not work, have checked the continuity of the yellow lead from the body rubber female connector (that the switch plugs into) to the starter, and that buzzes through, just no volts.
The car is fitted with a competition kill switch which is working correctly.
There is a red leadoff the comp switch that I presume goes to the ign switch plug and socket to give 12V to the ign switch.

With power on, the fuel gauge jumps to life, hazards work, side lights too and wipers, but the starter will not move. No buzzes, clicks, nothing.

So, I have tomorrow all day to try to fix this.
Questions:
Something has started to falter and now will not work. Ideas what?
If the fuel pump does not energise, will this stop the starter working? Pump is off a C2 of the mid 90's.

In recent days, when the engine had started it ran faultlessly.

I have changed the relay on the DME but that did nothing.

Could do with some inspiration please!

[jwhillracer]

Assuming that the starter motor itself is in working order, fit a 30A relay before the starter, energised by the wire from the ignition switch to the starter solenoid, then use it to switch a short lead from the heavy battery terminal on the starter to the solenoid coil. The relay won't need the current demand through the starter switch and elderly wiring to operate, and the starter should bang in like a new car.
I think I've had to do this mod to every aircooled VW and Porsche that I've ever owned .............

JW

[jwhillracer]

Here's one I prepared earlier - I forgot I had the engine and gearbox on the floor!





Wire the solenoid lead across the coil (85/86) and to earth
Main live from starter in to 30
Wire 87 out to solenoid on starter

Hopefully clunk/whizz and away!

JW

[911hillclimber]

Thanks Jonathan, but I'll never get that done tomorrow.
Read on google just I am not alone.
Might simply cancel the MoT and take my time.

On the ign connector bulkhead socket, there is 12v on all the pins!
Lots of hours witha multimeter tomorrow morning...

[jwhillracer]

Thanks Jonathan, but I'll never get that done tomorrow. - It's a couple of hours' work at the most, Graham
Read on google just I am not alone.
Might simply cancel the MoT and take my time.

On the ign connector bulkhead socket, there is 12v on all the pins! There's a big difference between having 12v there on "no load" and under load. You can have 12v, but the switches/wiring/connections are not probably good enough to provide a heavy enough current. The little relay requires a fraction of the load.
Lots of hours witha multimeter tomorrow morning...

[911hillclimber]

It's getting the bits locally, but will try.
Why should this suddenly happen though after all these years?

[Berny]

If it worked before it should work now! check the starter!

[jb]

I seem to remember this - not sure if it helps
https://www.ddk-online.com/phpBB2/viewt ... +connector

[911hillclimber]

All ideas help!
Before changing the switch I removed and cleaned the already clean box to body earth.
I'll go over all I did before removing the switch, but it was doing it before anything, so something had changed.
There are no sounds at all when I try to start it, nothing moves.

[rhd racer]

It sounds like the starter in gnacked to me Graham. Intermittent working (like it was doing before total failure) is a classic symptom of imminent failure. For the relatively low cost, and given the years of service it has already given, I would swap it out with a Euro exchange unit and still make your MOT…

[911hillclimber]

Hope you are right, but getting another in time..?
I'll take it off tomorrow and try to energise it on the bench, just a quick stab of 12v to see if the solenoid jumps, the Bendix moves and the shaft its on rotates.

Every duff starter I've had has clicked at the solenoid and no rotation, this one is just silent when the key is turned.

however, the yellow wire to the solenoid bells through as continuous from the body socket terminal but no volts, so no 12v getting through the body connection.
The switch has a simple 4 lead layout output that mates with the body so I need to put 12v into the switch via the plug and when the switch is turned see if that 12v comes out of pin '50' which runs to the starter solenoid.
It is a simple circuit that has been totally reliable for 26 years when Bob Watson altered the wiring for the 3.2 engine albeit on the stock '73 starter.
I don't think I still have the stock motor sadly as that would be a good substitute for this lightweight one.

The starter slowly deteriorating makes sense, it's the only part in this circuit that could break down.

[911hillclimber]

Just might have found the culprit

Waiting for the Loctite to set...

All the wires bell through.
All the wires have 12v except the starter yellow. (pin 50)
The only break in the circuit is the ignition KEY movement.
The switch is rotated to the start position against a light spring. The old and new switch makes contact to pin 50 when the input hole is turned to it's full rotation against the spring. However, the key barrel has a tang that locates in the switch and that was loose, so the turning of the key barrel to the max was not enough to mover the switch to pin 50.

I have now loctited (red) the tang tight (it is screwed in) so there is no radial play between the key barrel and the tang. Easier to sketch all this that describe it!

Thus, I'm waiting for the Loctite to set and test.

What a faff to say the least, but I feel this is the reason, you simply could not rotate the switch enough using the key as the tang was loose!

[Nine One One]

I thought you replaced the ignition with with a new one last week?

For last few 'starts' of the 911 (above) the starter etc has not kick-in immediately, after moving the ign switch/key against the usual spring resistance nothing would happen, not a click or a buzz, nothing.
This happened as I prepared to leave the Caffeine/Machine event so a heart stopping moment. Second try it fired in it's usual lumbering manner (so called high-speed starter fitted yeares ago, no quicker than stock, but a lot lighter). Drove home a dream.
Also on the way home a sudden loud rattle appeared in the passenger door, and also I felt I was sitting too low in the car (hill climb FIA seat installed).
So, 3 jobs to do today.
Ignition:
Just for once I thought I would start with the simple stuff. Checked all the leads to the starter, battery etc and all solid, but cleaned the clean earth points also. Noted that the silver Bosch batteries are 11 years old.
Got to be the ignition switch, the original 1973 item. Got that out after a bit of a fight and remembered this is the first time I've disturbed this snakes nest of wires since 1989.
Ordered a new one from Design911 and saved £40 over the same thing from another supplier. That never happens to me normally.
The original looks ok, but the starting position spring only covers about 3 degrees of the key rotation with an awkward 'step' before it, so pleased to be fitting new.
Should add the car started on the first key turn this morning

Remembered the steering column lock has gone. Bob Watson insisted I removed it for racing..Long time ago now.

To the seat:
and fixed in 5 mins by raising the seat on it's racing side mounts, amazing what 15mm can feel like.

And then the door:
Found the rattle easy, the door glass drop limit stop had come adrift, so readily fixed and a dab of Loctite applied for good luck, dangerous to have an irritated Mrs H on board.

Final bonus was she enjoyed the run/event at Caffeine and is looking forwards to the pending Silverstone Classic and the PCGB stand.
The tides might be turning.

[911hillclimber]

Correct, and the new one feels far worse in action than the original!
The cast slot for the tang to go into (about 6mm deep) is too shallow for the tang by 0.25mm so when you tighten the switch unit on the lock casting the tang is compressed and the key very very stiff to turn.
I then put some thin M5 washers between the key casting and the switch which cured that but then the switch was poorly located....
NOTHING I try to do is easy, that only happens to everyone else on DDK.

However, all my theory above was correct. I now have a starting 911 on the key so nearly ready for the MoT ...except....

The bloody horn of all things only beeps on one side of the butterfly, so putting my old Momo wheel on for the MoT.

I HATE with a vengeance those silly rubber under panel connectors used all over the 911, what a real pain.
Wish me luck for tomorrow.

The same garage has MoT'd this car for the last 28 years, but I get zero tolerance.

[rhd racer]

Well done Graham, an odd one that but well diagnosed