Intermittent No Start

[brshap]

Looking through the Bentley manual, I'm thinking maybe the ignitions switch is bad? According to page 970-36 the yellow wire should only show voltage when the switch is turned.

[old man neri]

Originally Posted by brshap

When the key is turned the voltage would shoot up to 16 or 17 and then back down.

Not sure what to make of this. Any ideas?

You had your multi-meter on the correct setting with the leads in the right spots? The reason I ask is it would be very very strange to get anything more than 12V (14V with the engine running) on almost all wires on the car.

[Superman]

Originally Posted by old man neri

You had your multi-meter on the correct setting with the leads in the right spots? The reason I ask is it would be very very strange to get anything more than 12V (14V with the engine running) on almost all wires on the car.

Right you are. With the engine off, voltage should be 12.5-ish. Engine on, maybe 14 volts. These, with lights and other accessories off.

[brshap]

Originally Posted by old man neri

You had your multi-meter on the correct setting with the leads in the right spots? The reason I ask is it would be very very strange to get anything more than 12V (14V with the engine running) on almost all wires on the car.

I had one lead on the ring end of the yellow wire and the other lead on the tranny ground strap. Voltmeter set to 12V. Its a quality meter, not a harbor freight cheapie. I agree it is strange so I will test again.

Originally Posted by Superman

Right you are. With the engine off, voltage should be 12.5-ish. Engine on, maybe 14 volts. These, with lights and other accessories off.

According to the Bentley voltage should be more than 7 volts. Would this lead you to believe its an ignition switch issue or maybe some corrosion along the wire somewhere thats creating high resistance and inconsistent voltage reading?


Thanks for you help guys.

[Quicksilver]

You need to test basic systems. Get a long lead with clips to hook on under the car and use a multimeter on it. Take notes and where the issue is will make itself apparent.
- Connect to the starter switch lead on the solenoid and make sure that you are getting power when you try to crank. There will be a voltage drop but it should show some level of consistency that will be a clue.
- Connect to the battery and see if you get a consistent voltage drop when the starter engages vs when it doesn't crank. An automotive starter is an overloaded device. It draws a huge quantity of current and can't be run for long before the starter, cables, and battery will melt down.
- Connect to the solenoid's battery connection and check for voltage drop cranking vs non cranking.
- Connect to the starter's connection to the solenoid and check voltage cranking vs non cranking.
Because of this you can easily see if the starter is actually being engaged because it will cause a noticeable drop of voltage.

With those four things you can troubleshoot most all of this. Assuming that the battery voltage doesn't show an obvious battery problem those four voltages are all you need.
You should see a reduced voltage drop when the car doesn't crank because the needed power isn't getting to the starter and we need to follow the chain of the other tests to see where it is going wrong.
- If the voltage drop at the solenoid's battery connection is noticeably higher then at the battery then you have a battery cabling/connection issue. Otherwise look farther down the chain.
- If you don't have voltage or only very reduced voltage at the starter switch's connection to the solenoid then you have a switch or wiring issue. (Compare voltage at the ignition switch to determine which.)
- If you have a reduction in voltage from the solenoid's battery connection to its connection to the starter here is a problem with the solenoid contactors. (Thank you Porsche for making a solenoid that can't easily be rebuilt.)
- If you have full voltage to the starter but it doesn't crank it means the starter isn't trying to crank and you have a brush, commutator, or winding issue.
or the starter isn't drawing current because of a brush/commutator or winding issue.

[brshap]

Originally Posted by Quicksilver

You need to test basic systems. Get a long lead with clips to hook on under the car and use a multimeter on it. Take notes and where the issue is will make itself apparent.
- Connect to the starter switch lead on the solenoid and make sure that you are getting power when you try to crank. There will be a voltage drop but it should show some level of consistency that will be a clue.
- Connect to the battery and see if you get a consistent voltage drop when the starter engages vs when it doesn't crank. An automotive starter is an overloaded device. It draws a huge quantity of current and can't be run for long before the starter, cables, and battery will melt down.
- Connect to the solenoid's battery connection and check for voltage drop cranking vs non cranking.
- Connect to the starter's connection to the solenoid and check voltage cranking vs non cranking.
Because of this you can easily see if the starter is actually being engaged because it will cause a noticeable drop of voltage.

With those four things you can troubleshoot most all of this. Assuming that the battery voltage doesn't show an obvious battery problem those four voltages are all you need.
You should see a reduced voltage drop when the car doesn't crank because the needed power isn't getting to the starter and we need to follow the chain of the other tests to see where it is going wrong.
- If the voltage drop at the solenoid's battery connection is noticeably higher then at the battery then you have a battery cabling/connection issue. Otherwise look farther down the chain.
- If you don't have voltage or only very reduced voltage at the starter switch's connection to the solenoid then you have a switch or wiring issue. (Compare voltage at the ignition switch to determine which.)
- If you have a reduction in voltage from the solenoid's battery connection to its connection to the starter here is a problem with the solenoid contactors. (Thank you Porsche for making a solenoid that can't easily be rebuilt.)
- If you have full voltage to the starter but it doesn't crank it means the starter isn't trying to crank and you have a brush, commutator, or winding issue.
or the starter isn't drawing current because of a brush/commutator or winding issue.

Wayne, thank you for this. Here are my results:

First I reran the previous test- remove yellow wire, connect to MM lead, other lead to ground strap. 20mV no cranking (essentially 0) 12.5 cranking (ok)

Then I check voltage drop on the negative side- neg bat terminal to MM lead, other lead to bolt on top of starter- 0V no crank/ nominal voltage drop cranking (ok)

Next was voltage drop on positive side- pos bat terminal to MM lead, other lead to post on solenoid (red/ black wires)-0V no crank/ nominal voltage drop cranking (ok)

Last was MM lead to pos bat terminal, other lead to yellow wire- 0v no crank, 12.5 cranking (ok)

I believe all of these results are normal. Is it time to replace the starter?

[david.avrahami@]

Have a look at #3 on this thread...

[brshap]

Originally Posted by david.avrahami@

Have a look at #3 on this thread...

If there was a short at the yellow wire wouldn't I have seen low (or no) voltage while cranking?

[Quicksilver]

Originally Posted by brshap

Wayne, thank you for this. Here are my results:

First I reran the previous test- remove yellow wire, connect to MM lead, other lead to ground strap. 20mV no cranking (essentially 0) 12.5 cranking (ok)
. . .

Am I reading this correctly? You put the multimeter inline with the yellow wire from the starter switch? The multimeter won't pass the current needed to kick the solenoid.
- If the yellow wire was through the multimeter then lack of voltage elsewhere would be expected.

The wire for the solenoid should just be clipped to where it wire connects so you can get the voltages while the system is operating.

[brshap]

Just to circle back on this thread in case it can help someone in the future, the culprit was.... the battery positive cable (at the starter)!

Despite cleaning it with a wire brush and no visible corrosion it must have had enough resistance to not deliver enough amperage to the starter. This is explains the inconsistent voltage drops. A clean up with some fine grit sand paper did the trick.

Thanks to everyone for your help.

[SoCalSK8r]

OK...so I'm having random no start issues. When it starts it runs great, voltage while running is 13.7V and it cranks up with no issues. Randomly it won't start...and then if I crank it a few times it can sometimes crank over.

Right now it won't crank over at all, but luckily is parked at home so I'm not stranded. So now that it won't crank over I began measuring the electrical connections to see what's going on...here's what I got so far:


The battery reads 12.7V no cranking, 11.2V after cranking
I'm getting full 12.7 volts to the big wire on the starter when not cranking (didn't measure this while cranking)
for the yellow wire, its 0V when ignition is off, and then only 9 volts when cranking. (other end of MM is connected to the battery)

I've read that you only need 7V while cranking so I'm not sure 9V is a problem although I wouldn't expect a 2V+ drop from the battery to the yellow wire but then again my ground lead is a small wire going all the way back to the battery.

I guess next I'll compare the voltage I get at the ignition switch with what I found at the yellow wire.

Any other thoughts please chime in....

[Targalid]

The yellow wire provides the power for the starter solenoid. It is the switch that turns on the starter. When you turn the key to the start position the solenoid should be energized and close the circuit to the starter motor. If the voltage is too low the solenoid will not work. When you turn the key and there is no sound at all, the solenoid is not operating. If you hear a click, the solenoid has been activated but the starter motor has not engaged. I would think that at 9 volts the solenoid would not activate for its full travel and operate the starter motor. Low voltage is most often due to a bad ground. There is the connection of the battery negative ground cable to the car body and the car body to the transmission ground strap...and, don't forget, the battery cable connections at the battery. These connections should be sanded until they are shiny, then reassembled with protective grease to prevent oxidation.

[brshap]

Originally Posted by SoCalSK8r

OK...so I'm having random no start issues. When it starts it runs great, voltage while running is 13.7V and it cranks up with no issues. Randomly it won't start...and then if I crank it a few times it can sometimes crank over.

Right now it won't crank over at all, but luckily is parked at home so I'm not stranded. So now that it won't crank over I began measuring the electrical connections to see what's going on...here's what I got so far:


The battery reads 12.7V no cranking, 11.2V after cranking
I'm getting full 12.7 volts to the big wire on the starter when not cranking (didn't measure this while cranking)
for the yellow wire, its 0V when ignition is off, and then only 9 volts when cranking. (other end of MM is connected to the battery)

I've read that you only need 7V while cranking so I'm not sure 9V is a problem although I wouldn't expect a 2V+ drop from the battery to the yellow wire but then again my ground lead is a small wire going all the way back to the battery.

I guess next I'll compare the voltage I get at the ignition switch with what I found at the yellow wire.

Any other thoughts please chime in....

I went INSANE figuring this out so just be patient and realize that this part of the system is relatively simple. All of your results so far sound fine but you haven't learned much yet. As the poster Targalid said first check that you get a solid click from the soleniod when you turn the key. Its loud so you will hear it.

Next you need to check voltage at the large wire at the starter motor post while cranking. Its good that you're showing battery voltage at the post when not cranking but that doesn't give you what your're looking for.

That said, you are probably dealing with a resistance problem so the very first thing you should do is THOROUGHLY clean all of your grounds, ground strap, battery posts, and battery connections. Even if it looks clean, clean it anyway. after that clean the spade or ring terminals on all of the starter wires. Then clean the posts on the starter itself.

If none of that works then do voltage drop tests on the positive and negative sides of the circuit. Feel free to PM me if you have any questions. I'm not an expert but I must have read and tried everything I read on every thread on Pelican.

[SoCalSK8r]

Thanks guys... I had cleaned up a bunch of grounds a while back (2 months ago?) to try and sort out a low voltage issue at the battery and it solved that problem and also any of the start up issues seemed to be gone up until now. I may have missed one so I'll just go back and clean all those up for good measure.

I did some more troubleshooting:
I can hear a click when I turn the key along with a buzzing noise (fuel pump). So assuming that the only sounds I should hear are the fuel pump buzzing and solenoid clicking....if not I need to dig further.

With the ignition off I get 12.9V at the big starter wire (ground hooked up to battery)
With the ignition switch in the start position, the voltage drops to 0.6 V. (ground hooked up to battery)

[kidrock]

Haven't logged on for many moons and was just lurking, couldn't resist chiming in here on this topic.

SK8r, if you have an aftermarket alarm system, this could possibly be your issue.

IIRC, installers will tie the new system into the ignition wiring loom that runs from the ignition switch into the bulkhead connector, essentially creating a "weak link" that results in enough of a voltage drop to cause a no-start issue. This is the wiring that Mr. Avrahami is referring to in post #3 of this thread.

Before I figured this out, a jump start would temporarily remedy the no-start. I got frustrated one day and started pressing wires under my dash and, voila, found the culprit. There was a lot of ugly hacking and I was not a happy camper.

Installed a new system after pulling 5 lbs of crud wiring, and *soldered* the main wires (also yellow, IIRC). Problem solved.

Good luck!!

[sc]

Similar fix to David's here...

Chased this intermittent issue for years.... problem isolated to either the 11 wire plug in the Engine compartment or the actual harness that runs on top of the engine to the solenoid. I ran a new yellow wire from ignition switch directly to solenoid...increased its size to 10 GA. using high temp GXL automotive grade wire and ran through tunnel.
On my switch one yellow wire sends 12v to the solenoid. Although its the only function for this wire it has a few connections via the engine compartment connection plug before getting to the solenoid. The original wire is still in the system....just disconnected and capped at the switch and solenoid.

Good luck
SC

Originally Posted by david.avrahami@

1987 carrera....I had a similar issue and was found to be the yellow start wire between the ignition switch and the engine compartment connection 11 wire plug. a short that could not be identified. We disconnected the yellow wire on both sides and added a new wire and welded it on both sides. This was a much cheaper way then replacing the whole 11 wires strand.

[SoCalSK8r]

Originally Posted by sc

Similar fix to David's here...

Chased this intermittent issue for years.... problem isolated to either the 11 wire plug in the Engine compartment or the actual harness that runs on top of the engine to the solenoid. I ran a new yellow wire from ignition switch directly to solenoid...increased its size to 10 GA. using high temp GXL automotive grade wire and ran through tunnel.
On my switch one yellow wire sends 12v to the solenoid. Although its the only function for this wire it has a few connections via the engine compartment connection plug before getting to the solenoid. The original wire is still in the system....just disconnected and capped at the switch and solenoid.

Good luck
SC

Good input - I haven't toyed with the 11 wire plug in the engine so I'll check that out next.

I'm wondering if the fact that I'm only getting 9V to the yellow wire is my main issue. I'll try doing some measurements at the ignition switch, and then run a new yellow wire to see if that resolves the issue.

Chasing down electrical issues is about as much fun as having a wet fart in a snow suit.

[sc]

I'm no expert....so others can chime in...but 9v to any 12v automotive actuated device is not good....you may have found the source of the issue.
Starting at the switch and working back to the solenoid should provide results on where a problem could be.
The switch should have around 12-14v going to the solenoid. So at every connection point until you get to the solenoid you should be able to verify voltage.
Correction.....its actually the 14 pin connector near the rear fuse panel that needs voltage verification.

Originally Posted by SoCalSK8r

Good input - I haven't toyed with the 11 wire plug in the engine so I'll check that out next.

I'm wondering if the fact that I'm only getting 9V to the yellow wire is my main issue. I'll try doing some measurements at the ignition switch, and then run a new yellow wire to see if that resolves the issue.

Chasing down electrical issues is about as much fun as having a wet fart in a snow suit.

[SoCalSK8r]

Originally Posted by sc

I'm no expert....so others can chime in...but 9v to any 12v automotive actuated device is not good....you may have found the source of the issue.
Starting at the switch and working back to the solenoid should provide results on where a problem could be.
The switch should have around 12-14v going to the solenoid. So at every connection point until you get to the solenoid you should be able to verify voltage.
Correction.....its actually the 14 pin connector near the rear fuse panel that needs voltage verification.

I'm with you.... Bentley says as long as you have over 7V you are fine. I'm using a high quality DMM so there's no doubt in my measurement BUT I do agree that it should be very close to the same as the battery voltage so that's what I'm zoning in on at the moment (well, tonight anyway)

[SoCalSK8r]

Narrowing in here....I've got 9.2V while cranking when I measure the yellow wire in the starter (referenced to chassis ground)

I get 12V at the #1 pin on the 11 pin connector in the engine bay when cranking (references to chassis ground)

I’ve cleaned the contacts on both ends of the yellow wore and that did nothing. Maybe I need to be more aggressive in my cleaning or I need to put in a new yellow wire from the starter up to the 11 pin connector.


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