412 starter gremlin

[Chris Hobbs]

I have recently developed a starter problem and I'm about to break out my wiring diagrams and troubleshooting manuals to see if I can track it down. In the meantime, perhaps someone has a suggestion or tip on where to concentrate my efforts that will save me some work. I have a 1974 412 Variant that has starter cranking problems with peculiar symptoms. After a short bit of cranking the starter stops working, as though the starter solenoid isn't getting enough power. Sometimes the solenoid will continue to click, sometimes it goes completely silent.

Now here's the peculiar part: by accident, I discovered that after I disconnect and then reconnect the battery negative, I regain starter cranking ability and can continue to start the engine. Sometimes, after a bit of additional cranking, the problem repeats itself, but again disconnecting the battery negative restores cranking ability. This continues until the engine eventually fires up.

I already made sure that the battery is fully charged. I tried solving the problem by putting in a new starter/solenoid. I also have a hot start relay kit installed (definitely required, based on past experience), which I also replaced just to be safe. None of these steps have made a difference so far.

Any suggestions or tips on what may be causing the problem, that I haven't checked yet?

[david58]

Chris I would start on the ground side. I know nothing about Variant's, but all cars are similar when it comes to the starting system. Check and clean the ground cable, and the ground strap. Don't just look at them and assume they are OK clean the connections. This hard start relay you refer to is it a ford solenoid? Or a relay? Our old cars seem to have this same starter issue, usually it is between the positive side of the battery and the solenoid. The ignition switch can be the culprit of the long run of wire from the battery to the switch, or the long run from the switch to the solenoid.

[Marc]

`74s are equipped with a seatbelt interlock system that inhibits starter action if a front seat is occupied and its belt not fastened. Due to public outcry, NHTSA backed off and allowed owners to disable the interlock - easily done by simply unplugging the seat sensors.
However, the relay contacts are still in the current path between the ignition switch and the starter solenoid...over time, they can develop enough resistance to prevent the solenoid from working. I suspect that when you disconnect/connect the battery cable, it's causing the relay to cycle so the contacts work better - temporarily.
The final solution here is to cut the 4.0 mm² wires going to & from the relay and butt-splice them together.
Look at this diagram, the relay is J34; you need to splice the white/red-stripe wire going to C to the red/black-stripe wire coming from 50.
http://www.vintagebus.com/wiring/Type_4 ... 1973-2.jpg

[wildthings]

If you have bad connections between the battery post and the cable terminal (or elsewhere) things are going to get hot as you crank the engine. As they get hot the connection(s) may get worse causing the starter not to work at all. Cleaning all your connections and then coating them with Vasoline or dielectric grease can save a whole lot of head aches. Replace any cables that have the junky replacement style ends or that otherwise look worn or corroded.

[Chris Hobbs]

I'm going to try the Moderator's suggestion to bypass the safety belt warning system relay J34. But where do I find it? Somewhere under the dash? Under one of the seats? In the side panel with the fuse block? None of my Type 4 maintenance manuals are any help here.

[MGVWfan]

Chris, you're UK or SA, right? I'm not sure anywhere outside the USA got the seatbelt interlock nuisance system...but in case it's there on your car, here's a little info...

I believe the relay is in the seatbelt warning lamp module itself, but I could be wrong on that. I'd follow the White/Red wire from the ignition switch, Terminal 50, and see where it goes...

J34 is the seatbelt interlock nuisance module on the following diagram: http://www.vintagebus.com/wiring/Type_4 ... 1973-2.jpg

Here's the "magic decoder ring", in German (Babelfish is a wonderful thing): http://www.vintagebus.com/wiring/Type_4 ... 1973-5.jpg

The Red/Black wire on Terminal 50 goes to the starter solenoid through the neutral safety switch on the gearchange (if you have AT), or direct to the solenoid if MT.

The relay inside J34 connects 50 and C (Red/Black and White/Red) when the interlock's conditions to allow starting have been satisfied. Those are the two terminals to bridge to bypass J34, as others have noted. You could also connect the two wires wherever they're easiest to access, like near the ignition switch maybe.

The White/Red wire from terminal C goes to Terminal 50 on D, the ignition switch (Zuendanlasschalter). When in "START" position, terminals 50 and 30 are connected. Terminal 30 has a Red wire, and goes to the fuse box, where it's connected to the Red/White wire that goes to the battery. No fuse is in the starter solenoid feed, the fuse box is just used as a junction box.

If it's not J34, it's gotta be a bad contact on a switch, or loose connection somewhere, or a flaky starter solenoid. I put a 40A ice cube relay under the right (passenger) seat in my 412, connected to the battery directly with a 30A inline fuse, with the coil voltage coming from the Red/Black wire from the neutral safety switch. That way, I take the 20-ish A that the starter solenoid draws before it's sealed-in off the ignition switch and (unobtanium) neutral safety switch, and give the starter solenoid as close to battery voltage as possible.

Hope this helps a bit.

[raygreenwood]

These vehicles are not commonly notorious for having hard start issues and I have never seen one require what we would call a hard start relay. The seat belt interlock is a good call...and if that is it...simply look under both front seats on the bulkhead near where the "Y" fork is bolted to. On the drivers side it is that forward 3" high ledge that the front side of the battery comes up against. If memory serves the plug is down low near the floor on this bulkhead and is two prong and connected by a phone cord looking wire coming down from the seat. Just pull it out on both sides.

Typically this problem is caused by excessive wear in the starter armature causing ecessive heat and load....or a crack on the starter switch housing...common.....or carbonized contacts in the solenoid.....and commonly high resistance in the grounding system...especially the transmission tail cone strap. Ray

[Chris Hobbs]

Happy New Year, everyone!

It appears that I have found the elusive safety belt warning system relay, plugged in to the underside of the main fuse block along with the turn signal flasher relay, et al. Found it by tracing the red/white wire from the ignition switch as suggested. The relay has 14 wires connected to it, 12 of which are small gauge (I'm guessing 0.5mm per the wiring diagram) and 2 of which--the red/white from the ignition switch and one red/black--are larger gauge (I'm guessing 4.0mm per the wiring diagram). I'll try splicing the latter two tomorrow and see what happens to my starter solenoid gremlin.

As for my hard/hot start problem--yes, I do need the relay. As the saying goes, "ask me how I know." The third night of a cross-country trip 10 years ago, I thought I was stranded at my motel when the 412 refused to restart. Next morning, no problem. That last day of the trip we kept the car running all day just to be safe. Things got pretty dicey for a couple hours when we got stuck in one of the most monstrous holiday traffic accident backups on I-81 ever seen. Soon as I shut off the car at home, bingo, did it again. A Bosch relay kit fixed the problem (or at least the symptoms) and the car has been fine ever since.

Also, note per my first post that my starter and solenoid are new! I eliminated those items from consideration right away.