Intermittent ignition fault.

[Steed]

Hi all.

Couldn't find a relevant thread already posted, so help required please.

I have an intermittent fault with my P5B ignition.
After a healthy immediate start from cold after 40 or so minutes driving, stop to fuel up and on restart ....nothing.
Ignition lights and other instruments, fine. Just no ignition/turnover. This has happened repeatedly over a some months. Having tried the jiggling and trying neutral to start, I find (inconclusively?) but that loosening the ignition key ferrule/barreland after a time it starts no problem?  Is this just random coincidence? Is the reason, heat, expansion vibration or 'sods law'?

It isn't easy for me to do any investigation, as without test equipment or experience and having spoken to many people,(regards the gearbox inhibitor switch), is it a good idea to just replace all the 'usual suspects' relay, gearbox switch, inhibitor et al?? And where do I find the relay switch?

Thanks.
Andy

[frans]

Andy,

I had the same problem with my P5-MKI-1961 and the priblem was the intermittent failure of the starting relay. After replacing it, the intermittent starting refusal had gone.

Frans

[Steed]

Thanks Frans.

Presume the type and location is the same?
Is it steering wheel side, in the engine bay bulkhead?

Andy

[frans]

Andy,

The starting relay is in enginebay underneath the heating unit approx. in the middle. I assume it is the same model, but you better check it. Disconnect the battery before working on it!

Regards
Frans

[Steed]

Thanks again Frans, I'll get on to it in the morning.

Regards

Andy

[johnwp5bcoupe]

Andy If the Inhibiter switch is working ok you should hear the start relay click when you turn the key? if you hear the click it could be the start relay contacts not supplying the 12v to the Starter Solenoid or the Starter Solenoid is the problem, no click it's the Inhibitor switch on the gearbox or the Starter Solenoid coil is intermittent/OC.

[Steed]

Thanks John.

Had the car serviced and checked this morning. I 'assisted' my mechanic!. Car started fine every time. We checked wiring etc as best we could see.
I drove away then 10 minutes later stopped the engine for 5 minutes, to get a coffee and ...would not start again with same issue . Then after 20 minutes tried in Neutral and 'presto'. I had a feeling the ignition switch barrel had too much movement? Are the starter solenoid/relay 'get at'able' and are they in engine bay visible at back bulkhead?, as we could not see any other 'box' of tricks. Looking at engine from the front is it to the right of the heater matrix, or is it in the fuse box frame?
 By the way when I got home and switched it off, immediate tried a restart in Park....nowt...then in Neutral, started straight away.......what fun for a rookie!

The 'click' of the relay seems intermittent too.

Thanks again John

[enigmas]

The gearbox inhibitor switch (park & neutral) is playing up or the linkages are out of adjustment.

[johnwp5bcoupe]

Aug 21, 2018 2:39:23 GMT enigmas said:

The gearbox inhibitor switch (park & neutral) is playing up or the linkages are out of adjustment.

I agree with Vince check or change the inhibitor switch! when it didn't start did you hear the click from the starter relay? which is located on the Right Hand side of the heater box on the bulkhead mounted vertically.

[Steed]

Thanks guy's.

Presume the inhibitor is the least easy to remove/replace? I will try the exercise again at home,  (in the quiet with fan not running!) to listen conclusively for that 'click', but usually only occurs when everything is well warmed up?

Does the inhibitor switch get out adjustment due to vibration over time? The starter relay is in my sights, more easily though!

Thanks

[johnwp5bcoupe]

The inhibitor switch is not too bad to get at on the side of the gearbox and would need to be set as per service manual, (available from the Club if you haven't got one?) if you do hear the click? another common fault is the spade terminals on the starter solenoid they can get loose and make and break and they are usually covered in cr*p!

[Steed]

We looked at the switch when on the mechanics ramp yesterday, but obviously just a 'visual'.

I have some manuals, but I'll check with club otherwise.

The GB was refurbed in 2015, would this affect the original settings adjustment given in the service book?

I'll check ALL terminals as a necessity.

Thanks , yet again , John.

[ray]

Andy,
I had a problem with my inhibitor switch late last year. Have you got 'Take Five' for the last year, I put an article about replacing/refurbishing this inhibitor switch (Can't recall which edition it is in?). There are two types and I found both are in fact adjustable, despite the manual saying only one can be adjusted. Mine was the non-adjustable type "always the way!" But I found, in a P5 V8 manual, how to adjust it. My belief is that they do 'wear' and simple adjustment solved my problem. This unit is also the reversing light switch and that was also coming-on when in drive. All solved by the adjustment. You will need to be under the car and will need to identify all four wires and where they attach to the switch, and keep a careful note, so they can be put back correctly!
Send again if you need more info. ( I may be slow to respond )
cheers

Ray

[Steed]

Thanks Ray.

I have all the copies, I'll take a look.

I'll be an expert after all this advice ( I wish)!

Andy