1971 Karmann Ghia 1600CC won't start

[jhanley]

My collectible non-daily driver, a 1971 Karmann Ghia 1600CC, suddenly won't start.

I try to routinely go out into the garage and start it every couple of weeks. I either take it for a quick drive or let it idle for 10–15 minutes.

Because of the infrequency, it usually takes a little grinding, but it always starts up after 3 or 4 tries.

However, last week it refused to start. The engine will turn over a couple of times and then gradually stop--like the battery is low. In the process of elimination, I replaced the battery with a brand new one. I also cleaned the negative cable and insured it was tightly bolted to the engine chassis. Likewise, the battery terminals are tight and corrosion free. And yeah, the car has plenty of gas.

Based on a preliminary search, I found the following possible causes:

-- Worn starter motor
-- Bad solenoid
-- Starter voltage drop
-- Ignition switch
-- Something else...

I'd appreciate getting troubleshooting tips from The Samba community.

Admittedly, I'm a novice mechanic. I can do basic stuff, but that's about it. Worst case, I will flat it over to a local vintage Volkswagen mechanic, but I'd like to eliminate the easy stuff that I can do myself.

[Rob Combs]

Ok here goes,

Apologies in advance for the long post.

All of your listed possible causes can be suspect, but let's step back for a second.

The starter motor circuit is fairly simple, bit in my opinion very overworked. Especially considering you have a 50+ year old harness and switch, and who-knows-what kind of "repairs" that have taken place along those 50+ years.

You can have a voltage drop occurring between the battery and the ignition switch, through the ignition switch in the circuit 50 contacts, between the ignition switch and the starter solenoid circuit 50 terminal - that's a long run of wire for the starter solenoid engagement side, hence my comment about the circuit being overworked. Then you can have voltage drops along the main battery cable from the B+ battery post to the B+ terminal on the solenoid.

So far we've only covered the positive voltage side of the circuit.

Then you have the battery negative cable from the battery post to the generator/alternator stand, required conductivity between the starter case and the transmission case, and the transmission case to body ground strap. In my own opinion you should also have a ground cable or strap between the negative battery post to a lug or strong bolt somewhere on the body itself (I am going to add one to my own '71 shortly - I can explain why but it will get us off track for getting your starter working).

A quick question - do you have a digital volt/ohm meter (DVOM from here), and do you know how to run a voltage drop test with said meter? I can explain that one as well but the explanation is way harder than the test itself and if you already know how to do it I'm going to save myself some typing We'll get back to this.

For the following, "housing" and "case" are used interchangeably, sometimes I am not consistent in my terminology when typing. Please also note that for the following test, an LED-type test light will not give you an indication of whether or not you're on to something - it's got to be a filament-type bulb and it has to draw some real current when it's powered up!

A quick and dirty test would be to take a test light, get an idea how bright the light CAN be by connecting across the battery terminals (baseline brightness), then access the solenoid under the right rear quarter behind the wheel and ground the alligator clip on a good ground, preferably on the negative battery terminal if the test probe cable will reach. You can also make a jumper extension to get directly to the battery post - this will eliminate any bad grounds from skewing your results before we're ready to test the ground side.

Have an assistant SAFELY (meaning assure it's in neutral, get the right rear wheel off, and get it SECURELY on jack stands before you start to troubleshoot!!!!!!) try to start the car with the key while you check the brightness of the test light on both the circuit 50 terminal and on the B+ terminal at the solenoid. If one or the other is dim, you have at least located the circuit to start with. If both are bright, move the alligator clip to the B+ terminal on the solenoid and hold the test probe to the starter case and try to start again. If the light is now dim, you have a voltage drop in your ground side, whether it be the battery negative cable, the ground strap, or the physical connection between the starter and the transmission housing.

If all three are bright, you've either got a voltage drop that you cannot visually see with an archaic method like the test light test above, in which case we'll move on to the more-sophisticated and accurate voltage drop test, or you've got a starter that finally gave up the ghost. I like to test everything I reasonably can before ordering parts, especially if you have to have them shipped to you (I didn't take note of your location).

If it turns out to be a voltage drop in the wiring, a so-called "hard-start relay" might be in order to lighten the load on the overworked starter circuit. They're easy to install and almost required if you're running a replacement ignition switch. Way better than trying to replace wires that might be starting to get excessive resistance.

Hope this helps, let us know how the tests go.

Rob

[jeffrey8164]

Get one of these:
https://www.amazon.com/Lisle-20750-Remote-Starter-...mp;sr=8-31
It’ll effectively isolate the front of the car from the back.
Then you at least know what direction to take.
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[Rob Combs]

No disrespect intended, but you can do the same with a piece of 10-gauge wire and connect between the B+ terminal on the battery to the circuit 50 on the solenoid, or between the B+ terminal on the solenoid and the circuit 50 on the solenoid. If you do it this way, just make sure you're not working around open fuel sources or fumes because it will arc a bit...

However it reacts, whether it cranks over or doesn't, we still have to figure out WHY.

For example, if you short directly between the solenoid B+ and circuit 50, and it cranks over, you know the motor, solenoid, B+ cable, and ground are ok, but you have to check the ignition switch and all of its related wiring. If it doesn't crank, you still need to know whether the B+ cable is shot, the ground connection is compromised, or the starter is shot. After that, there is still no guarantee that the ignition switch wiring is good.

That puts us more or less right back to the testing protocol I laid out above.

Just trying to save you $19 and a day of shipping network latency...

[Foot note: if it's the starter , it doesn't really matter if it's specifically the motor or the solenoid as long as the starter is sold inclusive of the solenoid, unless you intend to try to buy parts individually or crack it open and fix it yourself - and I do not recommend either for the average Joe - just save yourself the headache and buy a complete unit if it turns out to be either part of the starter assy that's gone bad.]

[jhanley]

Please excuse my delayed reply.

Thanks for your responses. The advice is very much appreciated.

I do have a digital volt/ohm meter. I bought it several years ago "just in case," but I've never used it. So now is a good time to put it to use. I will proceed to try and narrow down the source of the problem and report back.

Thanks again.

[Rob Combs]

All right, since you have a DVOM,

You can approach this in a couple of different ways:

1) run a jumper harness as I described or jumper switch as Jeffrey described to isolate which part of the circuit you should be chasing, or

2) Jump right in with your DVOM. To do this you'll need to perform voltage drop tests on all the circuits involved. It is of the utmost importance to remember that the circuit must be loaded for the voltage drop test to give meaningful results.

Apologies if you already know this (if so, maybe we'll help someone else understand a voltage drop test which is one of the most accurate ways to test a wire's capacity to handle a given circuit).

Assuming you have a good battery (you said you replaced it so I am assuming it's ok), here's how it goes - set your scale on DC volts. Not millivolts or wherever the meter defaults. Bypassing the auto-range feature and going manual avoids letting the meter set up your test incorrectly. Then connect the positive lead to the MOST positive part of the wire you're testing, and the negative lead to the MOST negative part of the wire you're testing. We'll test each wire one at a time. Assume the positive post on the battery is MOST positive unless the engine is running, in which case the B+ lead on the generator/alternator would be MOST positive.

Where I recommend you start: This is a little counterintuitive but connect the positive lead on your meter to the positive post on the battery (the MOST positive part of the wire/cable) and the negative lead on the positive terminal on your starter solenoid (the MOST negative part of the wire/cable).

Then attempt to crank it over with the key. Note the highest voltage your meter displays (if it has a min/max or recording feature you can do this on your own, otherwise you'll need a helper or REALLY LONG test leads so you can see the meter and crank with the key at the same time). That highest voltage displayed is the voltage drop across the positive battery cable. Attempting to crank it over is what loads the circuit to put in a failure condition if it's faulty. On that cable if you're dropping 12 volts, your battery cable is completely shot. It rarely works out to be that obvious. If you're more than a volt or so you have a problem beginning to show itself, and the closer to 12v (or whatever your static battery voltage is), the worse your problem is on that wire and the more it's contributing to your problem. It is possible to have several voltage drops on the full circuit if you're working with a complex circuit, so sometimes you have several repairs to make, but let's keep it simple for now. Keep notes on each voltage drop on a cable by cable basis for the remainder of the test so we can determine where to focus our repair work.

Repeat the test with every wire in the starter circuit. I personally like to work backwards once the integrity of the battery cable is established, meaning next you'd run the same test on circuit 50 between the starter solenoid and the ignition switch. Then run the same test across the ignition switch, then from the battery to the ignition switch, and so on until you reveal a wire or switch that is dropping a lot of voltage relative to system/battery voltage.

This will get you through the positive side of the circuit. Testing the ground side is similar but a little simpler due to having fewer cables to test. The drops on the negative side can come from body to ground strap connections, alternator stand to engine case conductivity, the battery cable itself or its connection to the alternator stand, the starter assy to transmission case conductivity, or even the engine case to transmission case conductivity if one or the other has been well-painted or well-coated with some kind of passivating chemical.

Clear as mud?

Happy testing!

Let us know how it goes or if you need further explanation or assistance.

[todmeg]

That starter relay setup is worth its weight in gold. I have found this problem is very common in these 50 year old cars.
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1770 DP Bad ass heads dual weber 40mm 010 headers and glass pack. Rivieras. 1971!!!