Hot Start Relay Installation

kidrock · 11-02-2012, 06:20 AM

Has anyone here installed our host's Low Voltage Relay (i.e., "hot start) in conjunction with a high torque starter? I attempted to install one recently, but the instructions are for a Bosch application.

The installation still seems self explanatory, but for some reason, it is not working properly.

Suggestions, please.

tobluforu · tobluforu's Garage

If the high torque starter is new, why bother. I had one on my 72 with the org. bosch starter, changed to hi torque and removed relay. Works great.

kidrock · 11-02-2012, 10:43 AM

nope. I've cleaned and replaced EVERYTHING, and the relay is my last stab at an intermittent no-start issue. Has nothing to do with "hot start", but seems to happen more frequently when weather is warm. Definitely a low voltage problem.

Chuck.H · Chuck.H's Garage

Hi Stone -

When you say no-start, do you mean it cranks over but does not start, or it doesn't even turn over?

Chuck.H
'89 TurboLookTarga, 341k miles

spuggy · 11-03-2012, 09:22 AM

Quote:

Originally Posted by kidrock

nope. I've cleaned and replaced EVERYTHING, and the relay is my last stab at an intermittent no-start issue. Has nothing to do with "hot start", but seems to happen more frequently when weather is warm. Definitely a low voltage problem.

You have my sympathy. These can be an absolute swine to track down - and the biggest problem is it being intermittent. Because whilst it's intermittent, you can never say it's fixed - only that it hasn't happened again. Yet.

Last round of my saga 6 years ago, saw new ground straps everywhere, all connectors in the path bothered/cleaned with pins spread - new starter was already fitted (unrelated). I at first replaced - but then eventually put back - the original ignition switch (preferred the older style "no start lockout" behavior) and it's been fine for the last 20,000+ miles, not one single failure.

Last week, went to pick up the car from the wrench and the solenoid clicked and it just wouldn't turn over. Like it was taunting them.

This time, ignition switch and battery positive cable replaced; both probably original. Apparently the cables eventually get corrosion up inside the strands and just won't pass enough juice. Electrical items like the switch can literally fail at any time. Or even worse, they "mostly" work....

kidrock · 10:11 AM

Spuggy nailed it....everything. I've done everything he's done, and I still get a loud "click" at the solenoid from time to time. It just seems as if the system isn't passing quite enough juice. 1-10 re-attempts with the key usually solves the issue. Main cables from battery to starter have no corrosion. Battery, starter, ground cables are relatively new. I've cleaned/brushed every single connection, ground and fuse connector. I originally thought that my 25+ year old Bosch starter was the problem. I've been chasing my tail ever since. The relay is pretty much my last hope, other than replacing the cables.

I've read here that the "14 pin connector" in the engine compartment could pose such an issue. Is this the connector that goes into the electrical compartment where the analysis plug is located? And if so, what systems are tied in with this connector?

Signed,
Frustrated.

spuggy · 11-03-2012, 05:37 PM

Quote:

Originally Posted by kidrock

Spuggy nailed it....everything. I've done everything he's done, and I still get a loud "click" at the solenoid from time to time. It just seems as if the system isn't passing quite enough juice. 1-10 re-attempts with the key usually solves the issue. Main cables from battery to starter have no corrosion. Battery, starter, ground cables are relatively new. I've cleaned/brushed every single connection, ground and fuse connector. I originally thought that my 25+ year old Bosch starter was the problem. I've been chasing my tail ever since. The relay is pretty much my last hope, other than replacing the cables.

I've read here that the "14 pin connector" in the engine compartment could pose such an issue. Is this the connector that goes into the electrical compartment where the analysis plug is located? And if so, what systems are tied in with this connector?

Signed,
Frustrated.

LOL. I feel your pain, believe me...

One time, I even flat-bedded the car to the wrench. My issues were always when cold. Even checked again before we loaded it. By the time it got there, car started 100% on the key. I was ticked...

Next time it failed (luckily on my driveway), I decided that I had time, seeing as how I wasn't going where I had wanted to go. Not to mention a solid failure to diagnose against. So I just tore into it...

The 14 pin connector is in the engine bay; comes out of the back of the relay/fuse panel and connects the motor harness to the car. Pin 1 on that plug is the infamous yellow wire that powers the solenoid (or is on mine, anyway).

You could have grown root crops on the oxidization on my connectors; I emery-clothed the pins and sockets and cinched them up tighter or spread the pins. For good measure, I also cleaned up the connections from the ignition harness at the firewall 6-pole plugs as well, although it looked fine in comparison. Because previously I'd "fixed" the problem by plugging another electrical harness/switch into the bulkhead - which bought me nearly 3 months before the problem came back.

After I did both the 14pin plug and the bulkhead connectors, it worked for the next 6 years/25,000 miles...

I'd be inclined to suspect the ignition switch a little as well. After all, I just had one die on me with exactly those symptoms. Cheap German junk only lasted 35 years and 250,000 miles, LOL.

Even eliminating it as a concern is worth the cost; and you might need the spare.

Ignition switches can do all sorts of things they're not supposed to when they get funky... I let the magic smoke out of the wiring harness on a 750-4 once; switched it on and the neutral light went out after 2 seconds - then I noticed the magic smoke escaping from under the tank...

kidrock · 10:53 AM

Thanks, Spug. Already replaced the switch. The bulkhead connector looked fine, but I'll go ahead and give her a cleaning. Thanks for confirming the location of the 14-pin connector (especially the correlation of Pin #1 with the yellow wire), I'll have a stab at it when I get some time (Thanksgiving!!!)

BTW, the 14-pin connector looks like a bit of a PITA to disconnect. I've already broken several German connectors in the recent past (I also own a 7 series BMW). Before I delve into it, do you have any suggestions or is it easier than it looks?

911pcars · 11-04-2012, 11:11 AM

Quote:

Originally Posted by kidrock

Spuggy nailed it....everything. I've done everything he's done, and I still get a loud "click" at the solenoid from time to time. It just seems as if the system isn't passing quite enough juice. 1-10 re-attempts with the key usually solves the issue. Main cables from battery to starter have no corrosion. Battery, starter, ground cables are relatively new. I've cleaned/brushed every single connection, ground and fuse connector. I originally thought that my 25+ year old Bosch starter was the problem. I've been chasing my tail ever since. The relay is pretty much my last hope, other than replacing the cables.

I've read here that the "14 pin connector" in the engine compartment could pose such an issue. Is this the connector that goes into the electrical compartment where the analysis plug is located? And if so, what systems are tied in with this connector?

Signed,
Frustrated.

There are many contact points in the circuit that energizes the starter solenoid, esp. in later models where the yellow (no. 50) wire circuit includes the engine bulkhead connector. Each connection point provides an opportunity for corrosion, oxidation and mechanical contact issues to accumulate and produce a threshold voltage drop to prevent energizing the solenoid. Cold weather and a partially discharged battery contribute to this.

In addition, the "start" contacts in the ignition switch is one of those voltage drop locations. These contacts also receive the most wear in the switch. One can minimize wear at this location by instead using a remote switch.

Here's a link to add such a switch and relay circuit to maximize the available voltage to the starter solenoid (early 911): Remote Starter

Hope this helps,
Sherwood

kidrock · 11-04-2012, 12:09 PM

Sherwood,

your post brings me back to my original problem....the installation of the low voltage relay. Your link, with diagrams, show how to install the relay. However, after closely following the directions and applying it to my high torque starter, it apparently is incorrect.

Basically, when I turn the key to Position #2, the starter activates prematurely and continues to run after starting the engine....I have to physically turn the key off to stop the starter from "throwing out", which in turn, stops the engine as well.

I have tried several wiring alternatives, all resulting in a non-activating starter.

So, although I have previously thought about installing a remote switch, it appears as if I may not be able to do so until I figure out why I am unsuccessful at installing what appeared to be a very basic relay switch.

911pcars · 11-04-2012, 12:32 PM

Quote:

Originally Posted by kidrock

Sherwood,

your post brings me back to my original problem....the installation of the low voltage relay. Your link, with diagrams, show how to install the relay. However, after closely following the directions and applying it to my high torque starter, it apparently is incorrect.

Basically, when I turn the key to Position #2, the starter activates prematurely and continues to run after starting the engine....I have to physically turn the key off to stop the starter from "throwing out", which in turn, stops the engine as well.

I have tried several wiring alternatives, all resulting in a non-activating starter.

So, although I have previously thought about installing a remote switch, it appears as if I may not be able to do so until I figure out why I am unsuccessful at installing what appeared to be a very basic relay switch.

Assuming you describe position 2 as the ON position, that is the incorrect connector to energize the starter solenoid. The correct terminal connection should be marked "50" on the switch, the spring-loaded, momentary ON position.

Try this. Remove the yellow wire from the ignition switch. Using a temporary jumper wire and momentary ON-OFF switch, connect this circuit to the + terminal of the battery. With the switch closed (ON), the starter should energize. This is basically a remote switch circuit but without a relay to shorten the current path from battery to solenoid.

With the ignition switch at position 2, this should energize the ignition and fuel system. Start engine with the above temp. circuit. Or connect the yellow wire to the number 50 terminal on the switch per the factory setup.

Sherwood

spuggy · 11-04-2012, 04:31 PM

Quote:

Originally Posted by kidrock

BTW, the 14-pin connector looks like a bit of a PITA to disconnect. I've already broken several German connectors in the recent past (I also own a 7 series BMW). Before I delve into it, do you have any suggestions or is it easier than it looks?

Hmmm, it's one of those brittle casings. Looks like bakelite to me. Be gentle with it buddy

Once you unclip the top of the plug, everything inside wants to burst out. Get a photo of it quickly, lol.

Seriously, the wires will have taken a "set", and their orientation should be pretty obvious, with at most one or two of them being ambiguous - and fairly easy to sort out with the diagram.

The connectors are actually available new if needed, pretty sure this is it Pelican Parts - Product Information: 911-612-113-05-M100

JohnJL · 11-04-2012, 04:51 PM

Quote:

Originally Posted by kidrock

Spuggy nailed it....everything. I've done everything he's done, and I still get a loud "click" at the solenoid from time to time. It just seems as if the system isn't passing quite enough juice. 1-10 re-attempts with the key usually solves the issue.

No joking, because I sympathise and know how frustrating this is, my cure to this exact situation was to give the positive and negative battery clamps an extra 1/4 turn on the terminals. Seems even a tiny bit loose and I would get the click from the solenoid but not enough to turn it over.

The original poster has something else going on though if the starter is energizing in the "run" position.