Hot start relay - always on?

[PTRL HD]

I've been going down the checklists found in multiple threads related to intermittent starting issues. Today I installed the hot start relay on my '84 3.2l Carrera.

After installation when I went to try it out the starter began spnning when my ignition switch was in the "run" position and kept spinning in both the "run" and "start" positions, even after the engine was running. Has anyone else had issues with this happening after installing the relay kit?

I verified my installation several times. The only thing I can find different from the instruction sheet is instead of a red w/black stripe wire to the ignition switch the wire is yellow, which is normal on a 911, from what I can see. I removed the relay kit and the starter worked as normal. In my case that's about 4 out of 5 times it will work.

The only thing I can think of is a faulty relay? I've ordered a replacement today, but it will be a few days before that shows up to test it. What else could be causing this to happen only when the relay has been installed?

[boyt911sc]

Originally Posted by PTRL HD

I've been going down the checklists found in multiple threads related to intermittent starting issues. Today I installed the hot start relay on my '84 3.2l Carrera.

After installation when I went to try it out the starter began spnning when my ignition switch was in the "run" position and kept spinning in both the "run" and "start" positions, even after the engine was running. Has anyone else had issues with this happening after installing the relay kit?

I verified my installation several times. The only thing I can find different from the instruction sheet is instead of a red w/black stripe wire to the ignition switch the wire is yellow, which is normal on a 911, from what I can see. I removed the relay kit and the starter worked as normal. In my case that's about 4 out of 5 times it will work.

The only thing I can think of is a faulty relay? I've ordered a replacement today, but it will be a few days before that shows up to test it. What else could be causing this to happen only when the relay has been installed?

Bench test the relay. Do you know how to check and test it?

Tony

[donporfi]

What rating does that relay have ?
Like Tony said, bench test the relay.
Hella sells an 80 amp relay, Autozone has those in stock.

[jlex]

I almost got a hot start relay for my '88 due to intermittent starting, but solved the problem by replacing the braided ground strap at the transaxle. For $10, I'd give that a try first. Those starters draw lots of power, and a corroded ground will cause your symptoms.

[PTRL HD]

Originally Posted by boyt911sc

Bench test the relay. Do you know how to check and test it?

Tony

With forums and YouTube I know almost everything, right? My electrical test equipment is at my workshop and I probably won't get back there until Monday, but I'll bench test it then. Unless I get impatient. So probably earlier.

Originally Posted by donporfi

What rating does that relay have ?
Like Tony said, bench test the relay.
Hella sells an 80 amp relay, Autozone has those in stock.

The Bosch is a 30 amp. If it tests fine, I'll find a larger one that fits the application.

Originally Posted by jlex

I almost got a hot start relay for my '88 due to intermittent starting, but solved the problem by replacing the braided ground strap at the transaxle. For $10, I'd give that a try first. Those starters draw lots of power, and a corroded ground will cause your symptoms.

Ground strap to the transmission and at the battery were both replaced a couple months ago, with no change. The DME relay was replaced twice, each time seeming to resolve the issue just long enough for me to get comfortable enough to be stranded somewhere and have to push start the thing, again! Starter, electronic part of ignition switch, and battery have all been replaced. Prior to replacing the ground straps, those and other ground points were cleaned up. I decided to add the relay to put on the band-aid since nothing else seems to be helping.

I even replaced the wheel bearings, brake pads/rotors, rebuilt the calipers, and replaced the rubber brake lines just so it would be easier to push start! OK, some of that was due for replacement anyway, but it sure did push nice and easy last time I tried!

Thanks all for the feedback so far!

[timmy2]

Have you cleaned the contacts in the 14 pin connector for the engine harness at the fuse panel?
Both male and female can get pretty crusty green and cause a high resistance in the solenoid wire circuit.
D5 deoxit and a brush are what to use.
DME relay only uses the crank signal on the yellow solenoid wire to allow fuel to pump during cranking.
Has no bearing on the ability to crank the starter.

[timmy2]

Starter solenoid circuit:
1. Ignition switch applies 12vdc to the yellow wire in the ignition switch.
2. Yellow wire in ignition harness goes to 6 pin male & female connector through the dash.
3. Yellow wire exits 6 pin connector with a 3-4” wire stub that plugs into the through body harness and DME sensor wire. (and A/C if installed.)
4. Main yellow wire goes through the main body harness directly to the male 14 pin connector on the rear fuse panel.
5. Engine harness yellow wire runs directly to starter solenoid.

[PTRL HD]

Originally Posted by timmy2

Have you cleaned the contacts in the 14 pin connector for the engine harness at the fuse panel?
Both male and female can get pretty crusty green and cause a high resistance in the solenoid wire circuit.
D5 deoxit and a brush are what to use.
DME relay only uses the crank signal on the yellow solenoid wire to allow fuel to pump during cranking.
Has no bearing on the ability to crank the starter.

Forgot to mention that one - I checked it and gave it a light cleaning. The contacts looked good and the plug looked brittle so I was pretty gentle. I'll grab some D5 and follow back to that one.

Thank you for the full path - I should have some time Monday to follow it start to finish to see if there are any connections I've overlooked.

The relay seemed a long shot but I tried it based on other starting issues I read about. Afterward it started reliably... for a while. The most recent time was after I had no luck after changing the ground straps and battery. I was looking for the hot relay kit and found the extra DME relay I had and thought "what the heck". No other changes and it started right up. And kept starting probably the next 30 times I tried it. Could have been coincidence, but it seemed to help my issue for a little while, anyway.

[GH85Carrera]

I presume you installed it because your Bosch starter locks up and does not spin when the engine is hot. 50/50 odds that the relay will do anything to help. I went through that. On long road trips the starter would get hot, and not spin. I put in the relay, and it made no difference at all. When the starters get really hot, they just quit working. I tried a new starter, and those are all just really a rebuilt one. It had the same issue. I finally gave up on the Bosch giant starter, and went with the much smaller high torque starter. After many long roads trip and lots of HOT starts it has been flawless.

So if your hot start issue continues, dump the Bosch starter and get the high torque small unit. And no, I do not have any relationship with whoever makes the high torque starter, except as a satisfied customer.

[PTRL HD]

Glen, thanks for the advice but I should probably have clarified - I do not have the hot start issue. I have a true intermittent start issue. The car doesn't seem to care if its hot, cold, wet, or dry. Well, its not wet very often, so that could be worse for all I know.

The issue I was having prior to my attempt at installing the hot start relay (and other parts) was the engine not turning over but I could hear a hum of some sort when turning the key to the start position. I assume the whir is either the starter spinning without extending the bendix or its the fuel pump pumping. I am typically working on it by myself so I have been unable to 100% verify the source of the activity during the attempted starts.

[PTRL HD]

I checked the full circuit minus the 3-4" stub that connects to the body harness and all were clean. I was struggling to get both hands in to separate that one to check it out.

I did find some discoloration on the wire to the positive battery clamp so I cleaned that up. I saw recent posts that the positive clamps have had issues loosening up, so I crimped it the best I could using the largest vise-grip I had. I'll replace the clamp in the near future, too.

I didn't get the test light and clips to properly test the relay, but I'm guessing it was good. The replacement relay arrived and did the exact same thing. I'd guess this is a problem with the electrical portion of the ignition switch sending a signal that causes the relay to always engage the starter motor, but that switch has been replaced within the last 2 years because of this issue. Could it be something with the mechanical part? Or the interaction between the 2 pieces? Or do you think it would be something else completely?

At this point, without the relay, I know it will start most of the time, and will run fine after a push start, so I'm going to start driving her again to see if cleanup of the positive battery connections made a difference.