Starter motor issue

[Hugo Sheers]

Hi all,

I've had my 6v starter motor rebuilt by a recognised specialist here in the UK including a new solenoid. I've re-installed the starter motor, but the starter is turning the engine on fewer than 10% turns of the key, though a click is heard.

The starter was tested in a rig at the specialist, and when I connect terminals 30 (big cable to battery) & 50 (activation circuit to ignition switch) on the solenoid using a screw driver, the starter turns the engine.

I am reliably reading 5.58, 5.59 volts at terminal 50 (solonoid activation circuit) when the ignition switch is on. The manual states 'When installed in the starter the solenoid should pull in the armature when 4 volts are applied between terminal 30 & earth.' Does this mean that 4 volts at terminal 50 should be enough to activate the starter motor?

Some solenoid adjustments are mentioned in the manual (solenoid armature travel for contact making and distance from plunger to solonoid flange). Is it possible that one of these adjustments is out and that the lower volt / amp combination of the activation circuit won't engage the starter, but the higher volt / amp combination of the heavy wire direct to battery will?

The Optima battery is reasonably new, has been charged and is reading 5.95 volts.

Hoping I don't have to remove and re-install the starter for a 3rd time and that I'll make the Spring drive Wednesday...

KTF
Hugo

[David Jones]

Off load battery voltage should be at least 6.3 volts on a freshly charged battery. Go get the battery checked out with a load tester. The fact that it turns over easily when you jump across the ignition switch does not necessarily point to a bad ignition switch because that should not affect current draw to the starter motor one the solenoid has engaged. It would be a good idea to put in a starter relay though as that will prolong the life of the ignition switch. When was the starter bushing last changed because that is the more likely cause for a sluggish starter if it is worn?

[Martin Benade]

I would next check the voltage at the activation terminal under load- during starting attempts. Try it a number of times, if it varies there is probably a ignition switch or wiring problem. I am not sure if this is the test you mentioned already performing. By ignition on do you mean key turned to "start" position?

[Hugo Sheers]

Thanks chaps,

The battery is not fully charged so I wasn't expecting to see 6.3v. I also tried a borrowed partially charged Optima which is reading 5.98v with the same result. The ignition switch was replaced a couple of years ago.

I haven't replaced the starter bushing in the bell housing, though cranking speed was not an issue prior to the failure of the solenoid. If I am interpreting the manual correctly 4v should be enough to engage the solenoid via the activation circuit, at which point the direct cable from the battery delivers the volts / amps demanded by the starter.

The starter turns the engine with direct power from the battery, but not the indirect power via the activation circuit / solenoid. Is it possible this is due to a physical setting within the starter / solenoid?

The 5.59v / 5.58v readings at terminal 50 (activation circuit) was a result of 2 readings taken with my daughter then wife turning the ignition switch as you would when trying to start the engine, ie key pushed in, rotated and held fully clockwise, past the red / green light on 'click'.

Cheers
Hugo

[David Jones]

Hugo, you cannot adjust the pull in or hold in position of the starter solenoid relative to the contact closure but you can adjust it relative to the pinion position which only affects mechanical position of the starter dog on the flywheel so I doubt that is the problem. As you have a new solenoid I would discount that as the issue.
If the starter solenoid is working it is not looking as though it is a volts drop problem in the starter/solenoid circuit as once the solenoid is activated the hold in circuit comes in to play and the current draw is decreased significantly and there is no reason to expect a drop in available current that would degrade starter rotation torque. I would still suspect a bad bushing and would change it out and at the least it will remove another variable form the equation.

[Martin Benade]

Since it is acting a little inconsistent cleaning all connections including ground cables and starter mounting flange ground might get it working. Your voltage test shows that the key should work just as well as when you jumper it under the car, but that is not the case. It does also seem that the bushing can act a little strange and inconsistent as well.

[Dick Weiss]

Hugo,

Are all the connections cleaned off--especially the braided chassis-to-transmission nose and the battery's ground strap?
I once had a rebuilt starter w/an unknownsolenoid (no name or number on it) so it was exchanged to a Bosch and problem solved.
Years ago when solenoids weren't readily available, I repaired the solenoid's worn on 1-side armature and solved its action.
I also checked the large internal contacts and cleaned them while apart.

Dick

[Jim Alton]

Hi all,

I've had my 6v starter motor rebuilt by a recognised specialist here in the UK including a new solenoid. I've re-installed the starter motor, but the starter is turning the engine on fewer than 10% turns of the key, though a click is heard.

The starter was tested in a rig at the specialist, and when I connect terminals 30 (big cable to battery) & 50 (activation circuit to ignition switch) on the solenoid using a screw driver, the starter turns the engine.

I am reliably reading 5.58, 5.59 volts at terminal 50 (solonoid activation circuit) when the ignition switch is on. The manual states 'When installed in the starter the solenoid should pull in the armature when 4 volts are applied between terminal 30 & earth.' Does this mean that 4 volts at terminal 50 should be enough to activate the starter motor?

Some solenoid adjustments are mentioned in the manual (solenoid armature travel for contact making and distance from plunger to solonoid flange). Is it possible that one of these adjustments is out and that the lower volt / amp combination of the activation circuit won't engage the starter, but the higher volt / amp combination of the heavy wire direct to battery will?

The Optima battery is reasonably new, has been charged and is reading 5.95 volts.

Hoping I don't have to remove and re-install the starter for a 3rd time and that I'll make the Spring drive Wednesday...

KTF
Hugo

First, I must admit that my electrical engineering degrees compel me to answer this even though it's not necessarily the cause of your problem.

It actually means 4 volts between terminal 50 (positive actuation terminal on the solenoid) and the starter's ground (i.e. the starter's case). Any resistance between the starter and the battery ground will subtract from that. In particular:

• both ends of the transmission ground strap
• both ends of the battery ground cable

In theory, bad cables or bad bonding of the starter case to the transmission could also add to total resistance and voltage drop.

Remember, voltage only exists between two points and resistance anywhere in a circuit causes voltage drops.

[Tim Berardelli]

Hugo,

Did the shop paint the starter to "pretty it up", if so it's not grounding well-remove all paint from the flange that mates the starter to the trans.

Tim Berardelli

[Al Zim]

no one has asked, did you replace the starter bushing? If you did not the armature could easily be rubbing on the pole shoes. To remove the bushing use a 1/2 inch national course tap. As you turn the tap in it will pull the bushing out. While you have the starter our take the end cap off the starter two small and two large screws and check the brushes. Then take your air hose and blow through the starter from the pinion end (opened) to the rear (facing the front of the car) if stuff comes our your re-builder cheated you by just cleaning the armature and possibly not replacing the brushes. Zim's is now rebuilding 6 volt VW generators is this a lost art? al zim

[Doug McDonnell]

I have always used this when sorting out starter problems. http://www.cyberwerkstatt.com/Members_O ... ooting.htm

[Heidi Frances]

Once you get it sorted (sounds like a grounding issue), I second David in his suggestion to install a starter relay. I installed Joe Leoni's and it made a big difference. There is a huge amount of initial current to the latch of the solenoid (over 40A I think). Short-lived, but puts a real stress on the system for an instant.

[Mervyn Hyde]

+1 on the starter relay. You can make one up for less than $15.

[Hugo Sheers]

Spot-on Dick; the starter had been fitted with a new unbranded solenoid. The specialist sent me a used Bosch solenoid, I pulled the starter (which took much less time 3rd time around) fitted the Bosch solenoid and she's now starting consistently. Be sure to look me up next time you are in the UK, I reckon I owe you a beer!

Presumably bench testing with a fat cable doesn't replicate the lower amperage of the thinner wires from the ignition switch. The unbranded solenoid may have worked with a relay as has been suggested.

Prior to fitting the Bosch solenoid I cleaned up the earths (including transmission to body) but this did not make any difference (I had last done this a couple of years ago, but worth a try).

Jim, the voltage I measured was between starter solenoid terminal 50 and the transmission bell housing (to which the starter is earthed). Is my reading not reflective of the voltage available to the solenoid? If not, where should I be placing the +ve & -ve terminals of the multi-meter?

Tim, I wanted to keep the character of the starter so asked the specialist not to repaint it.

Thanks again all for the great advice
KTF
Hugo

[Jim Alton]

Jim, the voltage I measured was between starter solenoid terminal 50 and the transmission bell housing (to which the starter is earthed). Is my reading not reflective of the voltage available to the solenoid? If not, where should I be placing the +ve & -ve terminals of the multi-meter?

Tim, I wanted to keep the character of the starter so asked the specialist not to repaint it.

Thanks again all for the great advice
KTF
Hugo

The solenoid actually "sees" the voltage between terminal 50 (on the end of the solenoid) and the starter's case. If the junction of the starter to the transmission's dirty you might see a voltage drop between the starter and the transmission case. However, the bolts holding the starter to the transmission give an alternate current path so I doubt your measurement between transmission and terminal 50 is a problem.

Measuring voltage between terminal 50 (on the end of the solenoid) and some handy point on the chassis wouldn't be as valid.

You don't see voltage drops without current so behavior with everything switched off mightn't be the same as when you've actually turned the key and sent a lot of electrons on their way to close the solenoid. I had to put a bigger fuse in my hard start relay and it only handles current to the solenoid--not the starter.

Really investigating that would be challenging--you'd probably need an oscilloscope to track voltage as the solenoid tries to close to see how far the voltage drops before the solenoid actually does its job.

Sometimes it's just more practical to try things to fix the problem rather than attempting to get 100% certainty of the cause.

Wolfbürg West makes some handy relay kits with wiring harnesses attached:

1. HARD START RELAY (part # 111998611) $38.00, or
2. HARD START RELAY, 12 volt (part # 111998611A) $24.95

These are resold by some Vintage Porsche Parts Places.

You can also get bare relays and add your own wires:

1. Fog Light Relay, 6 Volt (25A Sicherung) $14.95
2. Fog Light Relay, 12 Volt (20A Sicherung) $14.95