Boxster refuses to start whenever he feels like it!!

[Javi Cooper]

OK I'm stumped on this one. My '99 Boxster sometimes decides randomly not to start. Power goes on normally when key is turned but starter won't crank. This is completely random - haven't seen anything close to a pattern yet. Sometimes car starts fine for days. Sometimes it happens many times a day. When it happens it could take one or two tries to start or it could take literally 100+ tries and I have to walk away and come back hours later to try again. It may or may not happen first thing in the morning, and it may or may not happen right after it's turned off. Engine hot or cold. Rain or shine. Night or day. Short or long drives. Totally random.

I know what most of you are thinking but it's not the ignition switch. Neither is the starter nor the clutch safety switch. Ignition switch and starter were replaced and clutch switch was bypassed and problem persisted exactly the same. I'm thinking maybe immobilizer but I would think that either works or doesn't work full time, not back and forth.

I hate intermittent electrical problems Such a pain to diagnose. Any ideas?

[blue62]

Make sure your battery cable connections at the battery are clean and tight.
Check the ground cable connection at the body make sure it is clean and tight.
There is a connection in a little box next to your power steering res. make sure it is clean and tight.

Change your starter relay out for a new one. it is located in the rear trunk.
Relay panel #2 relay #7 (I think.)

You may want to change out the DME relay as well.
Relay panel #2 Relay #1

Relays have a little set of contact points in them that can burn or carbon up over time.
It is possible that that could be your issue.
Cost is around $10.00-$20.00 each and you can get them at any auto parts store.

[Javi Cooper]

Thanks. Is the DME relay the same as the starter relay?

My local stores only have this one in stock. It shows up when I search for DME relay but not for starter relay. The prongs and their numbers seem to be the same as the Porsche relays (though the 85 and 86 are inverted in the diagram):

https://www.autozone.com/electrical-and-lighting/dme-main-relay/p/duralast-relay-19208/12845_0_0

Here's the OEM starter relay:

https://www.pelicanparts.com/More_Info/99661511000.htm?pn=996-615-110-00-OEM&SVSVSI=1043&fs=0

And the OEM DME relay:

https://www.autozone.com/electrical-and-lighting/dme-main-relay/p/duralast-relay-19208/12845_0_0

All three look the same, correct? I'd like to buy the local ones today. Thanks

[Stl-986]

these are a pain to troubleshoot since they are random. But I doubt your issue is either of the above.


Need more information when it does it. Does it try to crank over and no start or does it not even crank over?
Do you have cruise control?
If it does crank over, does the tach move (even just a little bit)?

If it does crank over and tach does move, it's fuel pump or fuel relay
If it cranks but tach doesn't move, its the CPS
If it doesnt even crank, it could be the starter, starter relay, battery or terminals

cruise & brake switches are known to go bad and are cheap & easy to replace. Ignition is cheap but a pain to replace and another known item to cause issues like this, even random. Last thing I would think is the issue is the starter, but you already replaced that and the switch.

Answering the above when it happens will help. It isn't common that the relays would go bad in these unlike a 944 that the DME relays are very well known to go bad and almost anyone keeps a spare in the glovebox.

[Javi Cooper]

Need more information when it does it.
Does it try to crank over and no start or does it not even crank over?
No cranking at all when it does it. No clicks, no turning, nothing. As if the starter, fuse or relay were removed completely.

Do you have cruise control?
Yes

If it does crank over, does the tach move (even just a little bit)?
If it does crank over and tach does move, it's fuel pump or fuel relay
If it cranks but tach doesn't move, its the CPS
N/A to these three questions since it doesn't crank at all. Good to know about the CPS for future reference though

If it doesnt even crank, it could be the starter, starter relay, battery or terminals
New starter was just installed. Putting in a new relay and cleaning the terminals and ground today. Will report back in a few days (since it's an intermittent issue I have to wait a couple of days to make sure the problem doesn't come back).

I don't think it matters, but my car is a base Boxster with a 996 3.4 swap and 996 ECU, just for reference (or showing off )

Thanks for the help

[blue62]

Originally Posted by Javi Cooper

Thanks. Is the DME relay the same as the starter relay?

My local stores only have this one in stock. It shows up when I search for DME relay but not for starter relay. The prongs and their numbers seem to be the same as the Porsche relays (though the 85 and 86 are inverted in the diagram):

https://www.autozone.com/electrical-and-lighting/dme-main-relay/p/duralast-relay-19208/12845_0_0

Here's the OEM starter relay:

https://www.pelicanparts.com/More_Info/99661511000.htm?pn=996-615-110-00-OEM&SVSVSI=1043&fs=0

And the OEM DME relay:

https://www.autozone.com/electrical-and-lighting/dme-main-relay/p/duralast-relay-19208/12845_0_0

All three look the same, correct? I'd like to buy the local ones today. Thanks

Pull both relays from your Porsche.
Take them to auto Zone.
They should be able to cross reference the numbers and get you what you need.
If they can't cross reference the numbers find an auto parts store that can.

[Javi Cooper]

Thank you all for the help. After replacing the starter relay and driving around for a day and a half it looks like the problem has been solved When I removed the relay the plastic cap was loose and the circuit board slightly exposed. Maybe moisture was getting in and messing with the contacts or something. I'm not out of the woods yet but I don't remember going a whole day without the issue happening at least once.

Learned a few new tips for changing the ignition switch too. Going through the A/C vent is way, waaaay easier than from under the dash.

Sometimes I wonder why I do the things I do Someone told me that the relay was integrated in the starter, so I went with that and replaced the starter first (it was dying anyway) then the clutch and ignition switches. A simple Google search or forum question would've told me in two minutes that the relay was separate and to start there...

But hey, at least I also fixed that broken A/C vent too

[blue62]

Originally Posted by Javi Cooper

Thank you all for the help. After replacing the starter relay and driving around for a day and a half it looks like the problem has been solved When I removed the relay the plastic cap was loose and the circuit board slightly exposed. Maybe moisture was getting in and messing with the contacts or something. I'm not out of the woods yet but I don't remember going a whole day without the issue happening at least once.

Learned a few new tips for changing the ignition switch too. Going through the A/C vent is way, waaaay easier than from under the dash.

Sometimes I wonder why I do the things I do Someone told me that the relay was integrated in the starter, so I went with that and replaced the starter first (it was dying anyway) then the clutch and ignition switches. A simple Google search or forum question would've told me in two minutes that the relay was separate and to start there...

But hey, at least I also fixed that broken A/C vent too

Simple but important rule when working on automobiles.
Always start with the simplest thing first then work your way up to the most complex one step at a time.
Relays don't fail very often but they are simple to change and cheap.
And you had already done the more obvious things.

Please get back to us in say a week I would like to know for sure the relay was the issue