Starter motor won’t disengage and keeps turning
 

I’m recommissioning a an ES that’s been in storage for 26 years. Today I fitted a new starter solenoid to the motor as the old one had seized.

I bench tested the starter with new solenoid and it functions just fine out of the car. The problem I have now is that when I turn the car over the starter motor remains engaged and keep on turning until I disconnect the battery.

I’ve tested all the wiring and can’t find any faults. The relay and ignition switch appear fine and even when I disconnect the trigger wire from the solenoid it still stays engaged and spinning.

I even tried to jump the trigger on the solenoid with a positive feed and it engages but still doesn’t disengage when I remove it.

I’m completely stuck now and can figure out what’s going on?! When I disconnect and reconnect the battery the starter disengages and it’s not until I turn the key that this happens again.

Anyone got any suggestions for what the problem might be?

P;

Solenoid problem of some sort...I'd remove Starter and have a closer look at Solenoid...you could disable pivot which engages Gear into Flywheel and check Sol independent from Motor also.

See: https://www.sw-em.com/starter.htm#bo...arter_solenoid

Good Hunting!

Could it be that the bendix is sticking in the ring gear, and only releases when there is no feed to the starter. Everything would appear fine on the bench.

To be clear, when tested off the car the starter motor starts up when you energize the 'trigger contact' and stops when you de energize the trigger contact?

As Ron suggests, I think the problem is related to the solenoid contact operation; but, since it worked OK off the car; but, not on the car I think the 'cause' may be the start drive attached to the solenoid (the Bendix 'thing'). Typically you energize the solenoid which simultaneously closes the main contacts to the starter and engages the starter pinion gear with the ring gear on the flywheel. It seems like when you de energize the solenoid the starter pinion is not unable to retract from the ring gear which is preventing the solenoid from opening the main contacts keeping the starter energized. It is not until you disconnect the battery that the pinion is free to retract and the solenoid armature moves to the open position.

With the starter removed from the car, check to make sure that the armature of the solenoid is free to move back and forth and also check the fork / actuating arm to make sure that it moves freely. Finally, examine the actual starter drive to look for signs of damage - not exactly sure what that would be because I have never had a problem with the starter drive.

Guys;

I'm thinking if it's found not to be a mechanical issue (which it doesn't sound like it is since when power is removed, the Sol does drop), then I'm thinking there is some issue with Holding Coil in the the De-Energization phase, where the mag forces of the Pulling Coil are cancelled so that it drops out... further details at the previous link.
https://www.sw-em.com/starting_system2.jpg

Cheers

Reversal of the polarity on one of the coils could potentially cause the starter to stay engaged after terminal 50 is de energized. However, I would expect that problem to show up in the bench test of the starter. I presumed that when P1800 ES says 'functions just fine out of the car' that when he energized terminal 50 the starter motor started and when he de energized terminal 50 the motor stopped.

Thanks for all the wisdom and help so far. I found some time to go back to the car again today as this has been really bugging me. I did have the cold start valve disconnected as it was faulty but I sourced a replacement and wanted to connect it up to see if that would make a difference.

The cold start valve is controlled by the two white wires on the starter trigger spade connector and I was hoping that connecting to the valve would somehow complete the circuit; but connecting the replacement vale made no difference.

The green trigger wire to the solenoid is earth with the ignition off and it switches to positive when you turn the key. I tested this again and it's fine.

With the keys out of the ignition I jumped a positive signal to the trigger wire on the solenoid and it cranked over and didn't stop. I can only conclude the new solenoid is faulty, but what is really bugging me is that it functions as it should when bench tested - with a ground to the starter chassis, a direct feed to the post and a positive trigger. When i release the positive trigger on the bench the starter stops and retracts.

I'm at my wits end so I'm going to buy a replacement starter and solenoid unit and hope for the best. That's all I can think to do right now!

And for anyone looking for a replacement cold start valve for a b20e/f, the jaguar xjs v12 from the same vintage uses exactly the same valves. I managed to find a pair on ebay in good working order for £35 - a whole lot cheaper than the £200-300 prices I see listed for the Volvo.

Hi, a bit of a shot in the dark, have you checked, cleaned and or renewed all the fuses? Also thinking the ignition switch might be a culprit here, as it’s in play when your problem occurs and not when bench testing. Maybe try disconnecting the wires from the ignition switch with the starter in the car, and energizing the starter to see if that makes any difference.

A couple of thoughts for what they are worth:

There's a thick (braided?) copper cable that goes from the solenoid to the field-coil of the starter motor. If that were in accidental contact with the trigger wire to the solenoid then once you'd triggered the solenoid the trigger wire would stay live and the starter would keep on turning.

The solenoid activates a plunger. The push end of the plunger makes the electrical contact for the starter motor. The pull end pulls a lever that pushes the pinion forward to engage. If there's too much friction in the mechanism the plunger may not slide back to the "off" position. The motor works on the bench when not under load, so maybe the extra friction of being under load is stopping the mechanism sliding back? Maybe some cleaning/lubrication around the bit of the mechanism that slides the pinion forward? Perhaps around the plunger too? The Haynes manual shows the lubrication points.

Lastly, when I fitted a later starter motor to my Amazon I initially couldn't get it to start at all. I found that the later solenoid had two similar-looking spade terminals and I'd connected my trigger wire to the wrong one. It might just be worth checking that your solenoid doesn't have an extra terminal that does strange things if connected in error.

Thanks... I have checked all fuses and they’re fine. It also does this even when the keys are out of the car and I run a separate positive feed to the trigger terminal on the solenoid. It engages, cranks the engine and doesn’t disengage until I pull the terminal off the battery