Starter motor / Earthing issues
Discussion
Hi Guys,
I'm having an odd problem.
For a while now, when I try the ignition, quite often, the solenoid clicks, but nothing happens. However, if I use a second battery/jump start the car, the starter engages and she fires up - so it seemed it was a slightly flat battery.
To be on the safe side, I had the started rebuilt, bought a new battery, and cleaned all the earths I could see. It worked for a while, but I now have the same problem - the solenoid clicks, but the starter won't engage, even with a fully charged battery.
I'm tempted to have the starter motor re-checked, but my initial thoughts are poor contacts.
I'm wondering if I have missed an earth, or if I should improve the earthing with an additional earth cable from the battery to the block?
Would it be an idea to re-wire the battery feed to the starter with a heavier gauge cable?
Any suggestions? Has anyone else suffered a similar problem?
Bruce
'91 S3
I'm having an odd problem.
For a while now, when I try the ignition, quite often, the solenoid clicks, but nothing happens. However, if I use a second battery/jump start the car, the starter engages and she fires up - so it seemed it was a slightly flat battery.
To be on the safe side, I had the started rebuilt, bought a new battery, and cleaned all the earths I could see. It worked for a while, but I now have the same problem - the solenoid clicks, but the starter won't engage, even with a fully charged battery.
I'm tempted to have the starter motor re-checked, but my initial thoughts are poor contacts.
I'm wondering if I have missed an earth, or if I should improve the earthing with an additional earth cable from the battery to the block?
Would it be an idea to re-wire the battery feed to the starter with a heavier gauge cable?
Any suggestions? Has anyone else suffered a similar problem?
Bruce
'91 S3
I don't think you need to be concerned about the battery main power cables and earths.
Your problem is either with the starter/solenoid mechanism, or the circuit that operates the solenoid. Since you have already overhauled the starter and solenoid that suggests it is probably not the cause of the problem. This leaves the solenoid operating circuit. You can verify that it is an electrical problem by putting a volt meter between the solenoid operating terminal and the battery negative terminal and measuring the voltage when you try to engage the starter. This should be very close to the battery voltage - if not, you have confirmed there is a problem in this circuit. The battery voltage itself should be at least 12V and typically nearer 13V - if it's below 12V it suggests you have a flat battery, possibly caused by a charging problem.
The problem could affect the positive or negative side of the circuit. The negative side is provided by the same circuit as the main starter motor so if this is sufficient to operate the starter at all, it is very likely to be sufficient to carry the small current from the solenoid.
On the positive side the circuit is interrupted by the ignition switch, the dreaded yellow connector to/from the ignition switch, and probably an alarm/immobiliser, as well as the connection to the solenoid itself. Any/all of these could be contributing to the problem. You should be able to find where the voltage drop is occurring using a volt meter, but simply looking at the state of the various connections may give you a good clue.
Your problem is either with the starter/solenoid mechanism, or the circuit that operates the solenoid. Since you have already overhauled the starter and solenoid that suggests it is probably not the cause of the problem. This leaves the solenoid operating circuit. You can verify that it is an electrical problem by putting a volt meter between the solenoid operating terminal and the battery negative terminal and measuring the voltage when you try to engage the starter. This should be very close to the battery voltage - if not, you have confirmed there is a problem in this circuit. The battery voltage itself should be at least 12V and typically nearer 13V - if it's below 12V it suggests you have a flat battery, possibly caused by a charging problem.
The problem could affect the positive or negative side of the circuit. The negative side is provided by the same circuit as the main starter motor so if this is sufficient to operate the starter at all, it is very likely to be sufficient to carry the small current from the solenoid.
On the positive side the circuit is interrupted by the ignition switch, the dreaded yellow connector to/from the ignition switch, and probably an alarm/immobiliser, as well as the connection to the solenoid itself. Any/all of these could be contributing to the problem. You should be able to find where the voltage drop is occurring using a volt meter, but simply looking at the state of the various connections may give you a good clue.
Just to build on what Pete suggested.
1. Measure the battery voltage across the battery posts (not the cable clamps) when cranking the starter. - Record voltage
2. As Pete said, put the red meter lead on the solenoid connection and the black lead on the starter motor casing. - Crank the starter and record the voltage
The voltage on step 2 should be almost, but not exactly the same as that recorded in step 1. If it is exactly the same (to the hundredth of a volt, you have a problem with the solenoid)
If the voltage is low, move the black lead to the negative battery post; crank the starter and record the voltage. If it is almost the same now, you have a starter earth fault. If it is still low you have an issue in the +12v line, so of course the cable; connectors, ign switch etc.
The above test checks the primary side of the starter. You can check the high current side by putting your meter across the starter earth and the red cable connection of the solenoid (tests the solenoid contacts). Crank the starter and record the voltage which should be very close but not the same as the battery when tested under load.
Obviously if you are uncomfortable about doing any of this then do not do it. Also you should of course use crocodile clips for the meter rather than lying underneath a car that someone is trying to start.
1. Measure the battery voltage across the battery posts (not the cable clamps) when cranking the starter. - Record voltage
2. As Pete said, put the red meter lead on the solenoid connection and the black lead on the starter motor casing. - Crank the starter and record the voltage
The voltage on step 2 should be almost, but not exactly the same as that recorded in step 1. If it is exactly the same (to the hundredth of a volt, you have a problem with the solenoid)
If the voltage is low, move the black lead to the negative battery post; crank the starter and record the voltage. If it is almost the same now, you have a starter earth fault. If it is still low you have an issue in the +12v line, so of course the cable; connectors, ign switch etc.
The above test checks the primary side of the starter. You can check the high current side by putting your meter across the starter earth and the red cable connection of the solenoid (tests the solenoid contacts). Crank the starter and record the voltage which should be very close but not the same as the battery when tested under load.
Obviously if you are uncomfortable about doing any of this then do not do it. Also you should of course use crocodile clips for the meter rather than lying underneath a car that someone is trying to start.
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