Baffling starter problem

[BBShriver]

Last night I took my car out to get gas and put air in the tires.. filled up the tank and got back in, and no-start. I could hear the fuel pumps come on, headlights worked fine, but started didn't even try to turn over.. completely dead.

Called AAA, guy came and gave me a push start. I drove home, got it in the garage, and turned it off... tried to re start it twice and it started fine both times.

Today I thought I'd check for a loose ground or anything obvious, which I did not find. Started it up and went to visit a friend... got home, and turned it off in my driveway while I went around to open the garage door... got back in and no start again.

When it does start, the starter doesn't struggle or act like there's any problem.

I'm thinking a faulty solonoid, but wanted to see what others thought.

1973 911T

Thanks!

[mkc1962]

Lotsa talk here about this topic.....Same happend to me a few months back, for me it was a bad ignition switch. I spent days with a multi meter, cleaning grounds, greasing connections etc..Finally to find that the Switch was internally shot. Suggest that regardless what you find to be the problem, you install a hot start switch setup in the engine bay for future any such misfortunes.

[acapella8]

I wouldn't go the switch route yet. Mine 78 had a hart-start issue. John Walker's advice was to wrap it, which I did, on the few hot days we've had here in Chitown it has resolved the issue. Solenoid gets gummed after 35+ years, go figure. They can be cleaned, but is a pain to get to. Thankfully, I did not have to remove mine, the heat shield blanket worked.

Search starter + heat soak, and you will get about 1000 results...

[mkc1962]

I agree...trouble shoot and find the problem....dont just throw parts at it.

[psalt]

You wouldn't be the B Shriver with an E Type engined XK Jaguar ?

Ok, the 911 starter is a different kettle of fish. Intermittent starter problems are common. The fact that the battery is at the other end of the car should not be overlooked. The first thing to do is put a volt meter on the yellow wire at the starter and see if you are getting 12 volts when the key is in crank. Then check all the ground connections at the battery, chassis, gearbox, etc. OK , if you are smart , by pass the whole lot with a jumper cable to the block. The starter switch is another usual suspect and the electric part is available separately if you test it and it is bad. My experience is that the Bosch starter fails on the ground circuit. The factory "rebuilt " Bosch starters all use cores over 20 years old and can last 3 years or 6 months, because the rebuild does not touch the effected area. After many years of failed factory rebuilds, I have given up and switched to the Japanese hi torque starters that are half the price. At least there are no SU carbs. Good Luck.

[BBShriver]

Originally Posted by acapella8

I wouldn't go the switch route yet. Mine 78 had a hart-start issue. John Walker's advice was to wrap it, which I did, on the few hot days we've had here in Chitown it has resolved the issue. Solenoid gets gummed after 35+ years, go figure. They can be cleaned, but is a pain to get to. Thankfully, I did not have to remove mine, the heat shield blanket worked.

Search starter + heat soak, and you will get about 1000 results...

Thanks I'll try the search.. it has only happened when hot, but sometimes has not been a problem when hot either.. but short stops seem worse. This only just popped up recently.

Do you have any pictures of the heat wrap? I might look into cleaning the solonoid as well.

Originally Posted by psalt

You wouldn't be the B Shriver with an E Type engined XK Jaguar ?

Ok, the 911 starter is a different kettle of fish. Intermittent starter problems are common. The fact that the battery is at the other end of the car should not be overlooked. The first thing to do is put a volt meter on the yellow wire at the starter and see if you are getting 12 volts when the key is in crank. Then check all the ground connections at the battery, chassis, gearbox, etc. OK , if you are smart , by pass the whole lot with a jumper cable to the block. The starter switch is another usual suspect and the electric part is available separately if you test it and it is bad. My experience is that the Bosch starter fails on the ground circuit. The factory "rebuilt " Bosch starters all use cores over 20 years old and can last 3 years or 6 months, because the rebuild does not touch the effected area. After many years of failed factory rebuilds, I have given up and switched to the Japanese hi torque starters that are half the price. At least there are no SU carbs. Good Luck.

Yep, I'm that B-Shriver. Technically the XK140 is with my dad these days, I was in high school when we rebuilt it. I take it you're from the Jag-Lovers group as well?

Forgive me, but I'm a mechanical engineer, and electronics never really were my thing. When you say bypass the whole thing with a jumper, can you explain that a bit more?

[911pcars]

My suggestion is to begin checking the easy and obvious things first.

Check all battery cable and ground connections. They should be tight and clean with no corrosion between the posts and the cable connectors.

Check the battery to make sure it's fully charged. If you have voltmeter, connect to the + and – terminals. Should read ~12.7 volts or better with no load and 9+ volts when the ignition switch is in the crank position.

If the battery stays at the no-load voltage level during cranking, there's no connection to the starter (cranking should normally produce a voltage drop at the battery. While cranking, source voltage to the entire vehicle normally drops to about 9+ volts, including the yellow solenoid wire.

If the yellow starter solenoid wire shows 12 volts while cranking, the ignition switch is okay, but no current is reaching the starter (maybe bad solenoid).

If the yellow starter solenoid wire shows less voltage than the above, but the starter doesn't move, there could be an internal short in the motor. See bench test below.

Does the solenoid produce any sounds? You should hear it click as it becomes energized in the crank position.

At this point, remove the starter assy. from the engine, then bench test it by connecting battery jumper cables to the solenoid. Clamp the ground jumper wire to the starter motor frame.

If it still doesn't work, you can attempt to disassemble and troubleshoot it yourself or trade it in for a rebuilt starter assy.

There's a chance only the solenoid is malfunctioning. Bypass the solenoid by firmly contacting the + jumper cable directly onto the starter motor post. If the motor now spins, replace the solenoid. However, it's probably more convenient to purchase a complete starter motor assy. than to find just a replacement solenoid; maybe not.

Hope this helps,
Sherwood

[1990C4S]

Originally Posted by 911pcars

If the yellow starter solenoid wire shows 12 volts while cranking, the ignition switch is okay, but no current is reaching the starter (maybe bad solenoid).

If the yellow starter solenoid wire shows less voltage than the above, but the starter doesn't move, there could be an internal short in the motor. See bench test below.

There's a chance only the solenoid is malfunctioning. Bypass the solenoid by firmly contacting the + jumper cable directly onto the starter motor post. If the motor now spins, replace the solenoid. However, it's probably more convenient to purchase a complete starter motor assy. than to find just a replacement solenoid; maybe not.

Hope this helps,
Sherwood

Excellent advice here. I am guessing it's not the battery or the cables, it's possibly your key switch, but I think it's a flakey solenoid.

[psalt]

Yep, I'm that B-Shriver. Technically the XK140 is with my dad these days, I was in high school when we rebuilt it. Forgive me, but I'm a mechanical engineer, and electronics never really were my thing. When you say bypass the whole thing with a jumper, can you explain that a bit more?

Hi Brandon,

Yes, I think we met at one of Mike Eck's Jaguar meets years ago. You will find lots of posts about intermittent starter problems on this list. The starter circuit draws a hugh amount of current compared to any other circuit in the car and the distance from the battery to starter can be an issue on the 911. On a well designed front engined car, there is a short positive cable to the starter and a short negative cable directly to the engine block, but this is not true for the rear engined 911. The starter switch wiring also goes through several connectors that can be bad all the way to the back of the car and if the car has A/C a relay that can cause problems. Many will tell you to start by disconnecting and cleaning the ground cable at the battery, the chassis ground post(s), the ground strap at the gearbox which is good advice. I usually use a single jumper cable from the battery terminal under the car directly to the starter body to see if this is the problem. Many times it is not. My experience is that when ever you have a starter problem, suspect the battery first. Only after you have the problem with a fully charged, known good battery, move on to the other parts. An intermittent problem is tough to diagnose, you really need to be ready to test it when it is failing. This presents another problem with the 911 because you can't get at the starter and jump it with a screw driver like front engined cars. I always advise installing an $8 remote starter button in the engine compartment on 911s, so that if you have an intermittent problem, you can get out and fire it up on the button. Many times the extra juice to the solenoid is enough to get it to spin. I do not recommend attempting to clean or replace the solenoid. You have to unsolder very large lugs and the replacement solenoids are from Mexico or China and do not last long. If you read all the posts on starter problems you will find several people that have had Bosch factory rebuilds fail within a year. This is also my experience, and it is more frequent today then 10 years ago. My advice if you need a replacement is a hi torque starter, you can find them in many places and on E bay. By the way, if your car has CIS and an intermitent starter, be aware that the CSV will be spraying fuel everytime you hold the key down and the TTS wil not close it before the engine is flooded.

[acapella8]

Originally Posted by psalt

By the way, if your car has CIS and an intermitent starter, be aware that the CSV will be spraying fuel everytime you hold the key down and the TTS wil not close it before the engine is flooded.

That is good advice and explains the issues I had while (after) wrapping my starter as John Walker suggested. CSV is still working as intended. I did not account for that variable.

[brads911sc]

For me it was ignition switch as well...

[911pcars]

Originally Posted by psalt

...........When you say bypass the whole thing with a jumper, can you explain that a bit more? ..................

You answered your own question:
"I usually use a single jumper cable from the battery terminal under the car directly to the starter body to see if this is the problem."

However, as you know, sometimes it's easier said than done. The jumper cable in question is a jumper size cable, preferably long enough to span the distance from the battery to the starter motor area (e.g. join pos. and neg. cables to span the distance).

Be careful not to ground this voltage source (hot) cable against any metal portion of the chassis, firmly contact it against the large starter motor lug at the base of the solenoid. See illustration.



Since the solenoid is not energized with this connection, the motor, if okay, will simply spin w/o cranking the engine.

You'll notice the battery connection right above the suggested contact point. On other vehicles with solenoids more conveniently located, you can use a stout screwdriver blade or equivalent to electrically contact the two lugs to bypass the solenoid and energize the motor. This maneuver is space-limited on a 911.

Be careful. The battery cable can carry the full current output of the battery.

Sherwood

[BBShriver]

Originally Posted by 911pcars

My suggestion is to begin checking the easy and obvious things first.

Check all battery cable and ground connections. They should be tight and clean with no corrosion between the posts and the cable connectors.

Check the battery to make sure it's fully charged. If you have voltmeter, connect to the + and – terminals. Should read ~12.7 volts or better with no load and 9+ volts when the ignition switch is in the crank position.

If the battery stays at the no-load voltage level during cranking, there's no connection to the starter (cranking should normally produce a voltage drop at the battery. While cranking, source voltage to the entire vehicle normally drops to about 9+ volts, including the yellow solenoid wire.

If the yellow starter solenoid wire shows 12 volts while cranking, the ignition switch is okay, but no current is reaching the starter (maybe bad solenoid).

If the yellow starter solenoid wire shows less voltage than the above, but the starter doesn't move, there could be an internal short in the motor. See bench test below.

Does the solenoid produce any sounds? You should hear it click as it becomes energized in the crank position.

At this point, remove the starter assy. from the engine, then bench test it by connecting battery jumper cables to the solenoid. Clamp the ground jumper wire to the starter motor frame.

If it still doesn't work, you can attempt to disassemble and troubleshoot it yourself or trade it in for a rebuilt starter assy.

There's a chance only the solenoid is malfunctioning. Bypass the solenoid by firmly contacting the + jumper cable directly onto the starter motor post. If the motor now spins, replace the solenoid. However, it's probably more convenient to purchase a complete starter motor assy. than to find just a replacement solenoid; maybe not.

Hope this helps,
Sherwood

The battery is less than 6 months old, and when the starter does work, there's no hesitation or symptoms of a weak battery. When it works, it works perfectly.

I'm thinking the ignition switch itself is a likely culprit, so I might give that a try, and see if I can't diagnose that.

The weird thing to me is that, for instance last night I got it home, and then it wouldn't start in my driveway. I roll-started it and pulled it into the garage, at which point it started flawlessly 3 more times.

Originally Posted by 1990C4S

Excellent advice here. I am guessing it's not the battery or the cables, it's possibly your key switch, but I think it's a flakey solenoid.

Seems like solenoid or switch is a likely candidate.

Originally Posted by psalt

Hi Brandon,

Yes, I think we met at one of Mike Eck's Jaguar meets years ago. You will find lots of posts about intermittent starter problems on this list. The starter circuit draws a hugh amount of current compared to any other circuit in the car and the distance from the battery to starter can be an issue on the 911. On a well designed front engined car, there is a short positive cable to the starter and a short negative cable directly to the engine block, but this is not true for the rear engined 911. The starter switch wiring also goes through several connectors that can be bad all the way to the back of the car and if the car has A/C a relay that can cause problems. Many will tell you to start by disconnecting and cleaning the ground cable at the battery, the chassis ground post(s), the ground strap at the gearbox which is good advice. I usually use a single jumper cable from the battery terminal under the car directly to the starter body to see if this is the problem. Many times it is not. My experience is that when ever you have a starter problem, suspect the battery first. Only after you have the problem with a fully charged, known good battery, move on to the other parts. An intermittent problem is tough to diagnose, you really need to be ready to test it when it is failing. This presents another problem with the 911 because you can't get at the starter and jump it with a screw driver like front engined cars. I always advise installing an $8 remote starter button in the engine compartment on 911s, so that if you have an intermittent problem, you can get out and fire it up on the button. Many times the extra juice to the solenoid is enough to get it to spin. I do not recommend attempting to clean or replace the solenoid. You have to unsolder very large lugs and the replacement solenoids are from Mexico or China and do not last long. If you read all the posts on starter problems you will find several people that have had Bosch factory rebuilds fail within a year. This is also my experience, and it is more frequent today then 10 years ago. My advice if you need a replacement is a hi torque starter, you can find them in many places and on E bay. By the way, if your car has CIS and an intermitent starter, be aware that the CSV will be spraying fuel everytime you hold the key down and the TTS wil not close it before the engine is flooded.

I do not have A/C, I do have CIS.

Do you have pictures/wiring diagram of the proposed engine bay mounted ignition switch?

[BBShriver]

I'm considering replacing the starter assembly just as a bit of preventive maintenance even if it's not the problem... What are some of the better modern "hi torque" versions?
I found one on Ebay, but I'm always a little hesitant with Ebay stuff

PORSCHE 911 MINI STARTER IMI PORSCHE 912 / 914 / 930: eBay Motors (item 250695319003 end time Oct-11-10 06:42:13 PDT)

Thanks for the help!

[RWebb]

Pelican

[911pcars]

Originally Posted by BBShriver

....
Do you have pictures/wiring diagram of the proposed engine bay mounted ignition switch?

After you get this sorted out and back to factory specs, I'd also suggest adding a remote switch to relieve the ignition switch from the wear and tear of energizing the starter. An additional switch in the engine compartment is also convenient.

Here's what I did. The early ign. switches are NLA, hard to get and very expensive, thus this installation. Most 911s adhere to the same ign. wiring and numbering convention:
Remote Starter

Hope this helps,
Sherwood

[spuggy]

Originally Posted by psalt

CSV will be spraying fuel everytime you hold the key down and the TTS wil not close it before the engine is flooded.

Thermo time switch doesn't even come activate the CSV above the threshold temperature and has a heater built-in - so the TTS should reach the cut-off temp within a few seconds of cranking.

[BBShriver]

Thanks for the diagram. From that though it looks like you're effectively bypassing the ignition switch altogether and would not require a key at all. Is that correct?

[psalt]

Thermo time switch doesn't even come activate the CSV above the threshold temperature and has a heater built-in - so the TTS should reach the cut-off temp within a few seconds of cranking.

This is not my experience. A CIS 911 with an intermittent starter will spray fuel on each attempt and if it finally catches, blow out black smoke. I have had this happen several times with different 911's over 20 years. Are you say "you think it should'", or do you have some actual experience with failed starters to share ?

[spuggy]

Originally Posted by BBShriver

The battery is less than 6 months old, and when the starter does work, there's no hesitation or symptoms of a weak battery. When it works, it works perfectly.

Yah, this can seem like a nightmare when it's happening... I had this happen twice about 6,000 miles apart, which then turned into sometimes happening on cold mornings (usually when I wanted to drive somewhere, rather than work on the car). Like you, when it worked, it worked perfectly. When it didn't work, I usually couldn't even hear the solenoid click...

It's fairly easy to diagnose when it doesn't work, but when it's intermittent it can be hard work. I flat-bedded it to the wrench once - but it fired up perfectly when it got there... Finally it got to "almost always won't start" and I had to fix it myself - took 30 minutes or so in the end.

Having previously fitted a hi-torque starter (weight saving), ignition switch (since reverted to original) and ground straps (needed anyway), it turned out to be the connectors on the ignition harness and/or the 14-pin plug in the engine bay (this last was heavily oxidized).

Cleaned the pins and sockets up inside and out with a fiberglass pen & fine grit wet'n'dry paper, spread the pins slightly - good to go. No issues since in 2 years of daily driving. Key thing there was that you need both voltage and current to operate the solenoid, don't rule out connection quality just because a connectivity tester beeps..

For me, re-making the ignition harness connector into the bulkhead (by fitting the new one) improved the end-to-end connection enough that it cleared the problem for a couple of months and I thought it was fixed.. You can test another ignition switch without removing the original simply by plugging in the harness on the spare and see if it helps, BTW.

If you suspect the solenoid itself, either banging it (a la VW bug) or jumping the terminal to the permanent 12V starter feed (as per Sherwood's diagram) should help you narrow down whether it's sticking mechanically (e.g. cooked grease or worn out) or a bad electrical connection.

I seriously considered a remote starter more than once, but was glad I fixed the real issue in the end.