Engine no start after 40/50 KM run
 

Hi All,
My 1964 Daimler 250 V8 with BW 35 auto trans will not crank over after a 40/50 KM drive but the fuel pump runs.
I can start it by using the push button on the fire wall mounted solenoid. Is this solenoid or the inhibitor switch subject to heat soak failure?
Comments suggestions appreciated.
David Bruce.

Just to clarify. You have ignition key on. When cold the starter button is pushed and engine starts. After along run and after switch off the car will not start on the button but will start on the solenoid under the bonnet.
OK basics first. None of the electrics suffer from heat soak. They are too basic. You would need sensors as you would find on modern cars for something like that to trip in or out.
The ignition circuit is pretty basic as said. Ignition key on primes the fuel pumps as you can hear. The starter button sends a small charge down to the solenoid which sends a big charge to the starter motor. By pushing the solenoid you have proven you have the big charge so the problem lies between the Key and Solenoid and the only thing inbetween is the push button on the dash. You can check that the solenoid is working correctly by putting a wire from the battery direct to the spade connector on the solenoid that the starter button connects to. If the car starts the problem is not the solenoid. If it does not start you might have an intermittent problem in the solenoid. A new solenoid is only £24 from SNG https://www.sngbarratt.com/English/#...rnedDown=false
Check the continuity between the starter button and the solenoid. Heat can cause expansion in the electrical connector on the solenoid from the starter button.
The starter button though will not work if the gearbox inhibitor switch is activated and I have not checked but I would assume because you are by passing the start button on the dash by using the solenoid button that the gearbox inhibitor switch is also by passed. I had never thought of this before and if this is correct then it could be potentially dangerous if the car was in gear and you started it from under the bonnet. If the inhibitor switch does activate when using the solenoid then the problem lies in the electrical connection between the starter button and the solenoid.
If we will assume that the inhibitor switch is not active when the solenoid is used for now, this only leaves the inhibitor switch as your problem.
The inhibitor switch will stop the car from starting in any gear but you can start the car in P or N. Does yours fail to start in either?
I have a dodgy adjustment on my column change where I really have to lift the gear stick and press it up into P sometimes to get the car to start. Only needs a slight adjustment I just have not around to it yet but it starts in N everytime. Could be yours is the same so check both and try and start the engine. Failing this the inhibitor switch on the BW35 is on the side of the gearbox and is accesses on my S Type via a panel in the left side of the gearbox tunnel. It is exposed to the elements so check the wiring is all in good order. A new inhibitor switch is only £16 from SNG https://www.sngbarratt.com/English/#...20inhibitor%60 so it is not the end of the world to buy a new one and swap them over.
This is a photo of where the inhibitor switch is on the BW35 and the access panel on the S Type.
https://cimg6.ibsrv.net/gimg/www.jag...8966c56eef.jpg

engine no start.
 

Hi Cass 3958,
Thanks for your detailed reply and photo.
The car will start cold in N and some times in P, this is an adjustment issue from when I fitted an EZ electric power steering unit.I will check the connections to the solenoid. I am aware of the danger of by passing the inhibitor switch so i always make I have selected N or P and apply the hand brake.
I don't think the Daimler has an inspection panel in the transmission tunnel so will have to be a hoist job.
As a matter of interest I was Quoted $250.00 for an inhibitor switch by a local auto trans repair shop.
I appreciate your.interest.
David Bruce.

I don't think the Mk2 Jaguar which has the same body has the inspection panel either but even on a hoist is is pretty difficult to get to as it is up the side of the gearbox and tight to the gearbox tunnel. The BW35 was fitted late in production and they obviously did not change the body by putting in an inspection plate. Easy to cut your own panel and it is hidden by the tunnel carpet. The plate on mine is just an over sized piece of metal held in place by six self tapping screws as standard. Photo attached to show where it is on the side of the tunnel.

With regards the inhibitor switch it would be cheaper to buy one from SNG UK and pay for the postage to Aus. Bloody rip off.
https://cimg1.ibsrv.net/gimg/www.jag...fcf4bd7318.jpg