Testarossa starting pause

Many reports by TR owners of this same problem -- try a search on "TR solenoid ace" both here and at the old site for prior discussion.

The root cause seems to be the stock Bosch TR starter solenoid getting flaky when hot coupled with a bit of a voltage drop on the +12V start command line going to the solenoid. The two solutions are:

1. Add another relay to put a true +12V onto the start command terminal 50 of the Bosch solenoid, or

2. get the better Ace Electric 7-851 (now WAI) brand solenoid.

 

I had the same thing happen to me two weeks ago. The first thing I checked happen to be the problem. The nut that holds the wire on the starter was very lose for some reason. I tightened it back up and problem has been solved. It only caused starting problems on humid hot days after the engine was warmed up.

 

The TR's have a disconnect for the cable to the starter located under the car below the oil tank. These also can cause your problem. Disconnect it and clean it.

 

Been there done that with my 512TR.
Serious embarassment at the filling station
Worked hard on it.
Symptoms are that on a warm day you go for a blast, park up for refreshment and then you can't get the engine to turn over.
I've even had a meal to while away the time ~45min to 1hour.

In my experience a replacement won't help - see the following

In order to turn the engine over the starter solenoid has to energise AND the piston travel its FULL distance to operate the main contacts.

I measured a normal temperature at the solenoid of 80 + deg C, reasonable enough when the engine is water cooled at 90-95 deg C

What happens is that once the fans turn off there is a heat build up in the upper engine bay from the silencer and cats. In my case it seems a bit worse because of the custom stainless steel silencer. All the heat rises to the top and heats up the solenoid before it gets out of the grills. The temp of the solenoid goes up much more.
You can help a lot by opening the engine cover as soon as you stop.

The issue is the clearance in the solenoid of the Bosch assembly
I measured the piston diameter at 1.0665 inches or 26.91 mm at say 20 deg C (70 F)
I also measured the inside diameter of the brass liner, this varied a bit around the diameter but the worst case showed the same value ie no clearance at all.

It is pretty clear that as the unit heats up the piston grows a bit and unfortunately slightly more than the brass liner.
This causes it to stick and not start moving or start moving and not travel far enough to actuate the main contact.

I believe that a close tolerance is probably deliberate since it creates a bit of an air cushion which avoids shock at complete travel.
I also think this is a manufacture tolerance problem although the working dimensions are not known to the public.
The fact that most starters are under/side located means this is an unusual circumstance.

People often grease the piston to "improve things".
This is WRONG, it stops air escaping and makes the contact closure a slow business leading to arcing of the contacts and another common failure mode.

Fortunately its only a 5min job to remove the starter on a TR and a bit longer to dismantle it.

I have first polished the piston with fine grade abrasive (400) by holding the piston in an electric drill. It is hard to remove much metal this way but it all helps.

Secondly you polish the inside surface of the brass liner again with a drill and abrasive. You can take a thou or two off fairly easily over most of the surface but the last part deepest into the solenoid is problematic.

Wash out the parts with petrol or alcohol and reassemble
I have found a VERY substantial improvement indeed.

No more than a 5 min wait to cool from an hour

My final solution
I have obtained a second piston and intend to reduce its diameter in a lathe by about 0.003 inch. If I hadn't polished the brass tube interior I would go for 0.005 inch
Haven't done this yet due to other work but am confident it will do the trick.
Will post again when its been done and successful but wouldn't hesitate to recommend that course of action to others with the same problem.

 

This is an old thread but I promised a report.

I took out the solenoid plunger and removed 0.01 inches(10 thou) off the diameter and left a highly polished finish. Made sure that the corners were smoothed round.
Rubbed it all over with a very soft pencil to provide graphite for lubrication.

Have had no more problems whatsoever in 12 months or so even on the hottest days.

 

I'm going to try this tomorrow with the piston from the old solenoid. I'll spin it in the lathe and take a smoo hair off it and see what happens.

 

Steve, do you know if the WAI 7-851 is the solenoid used on an '86 TR (not sure if there were any differences b/t early and late model TR's)? Could you recommend the best place to order one from? Got stranded this weekend for over an hour until the car cooled down... of course this was right after a few folks checked out the car and said how jealous they were, then turned the key and nothing... how emabrassing.

 

I'm not aware of any TR starter or solenoid changes vs year so the 7-851 = 66-9131 or 66-9131-1 should be OK:

http://search.waiglobal.com/partsearch/partsearch.aspx?part=7-851&Submit=Go

No, not really. The WAI website used to list distributors who you could call for a retail seller in your area, but that seems to be gone. I'd suggest you look in the yellow pages under "auto electric" and call some repair shops and ask if they can get Ace Electric or WAI parts, or maybe call the 800 number that comes up on the web page above.

BTDTGTTS

 

Thanks so much for the info. I'll hit the yellow pages in the AM.

 

Called WAI this morning and got the name of the closest distributor. It was Metropolitan (800-562-6975) out of New Jersey. The part number was 7-851 as Steve mentioned above. The part was $18.00 + tax + shipping. I think this might be the cheapest part I ever bought for the TR.

Joe

 

Great to hear! And it's one of the easiest part to swap too!

 

At that price, I think there is no downside to replacing the solenoid (with a better part ), but, if you still have trouble, you should check/reseat the w connector, the y conector, and the C11 connector under the coolant tank (thru which the white "start command" line passes on its journey from the ignition switch terminal 50 to the solenoid terminal 50):
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Old thread, butttttttttttttttt......

Does anyone know what the voltage should be around at both white wire terminals shown in the pic above? I'm getting like 9V - 9.4V ?? To me is a little low, thus won't engage the solenoid? I would presume it should be in the 11V to 12V ?????

My starter was just rebuild. The car is sitting in my garage cold, so no piston issue there.

I wonder if there's an issue at ignition switch or maybe the connector in the steering wheel column?