Need help with Spec Boxster no-start issue - 986 Forum - The Community for Porsche Boxster & Cayman Owners

seningen · 09-11-2018, 10:10 AM

Need some debug help...

SPB cranks, no fire ... however let me explain further.

My first DE with it a year ago, I backed it out of my space and it died as I was putting in first and trying to pull away.
Would not retire... but cranked ok

Put it on a charger and it fired up 30min later.
I continued to charge it all weekend but figured battery was toast so I got a new one Wet Cell Acid .... 16CLB I think.

Worked fine for my club race and 6 months later she fired up coming out of the trailer. Ran 2 sessions on Friday, 3rd session would crank, no fire. Doing some debug, I realized I left my marker lights on. Tried charging, no luck, tried jump starting from my cayenne, no luck. On a whim I decided to disconnect the battery and attempted to start through the jumper cables. Slowly cranked but on about the third revolution she fired up. Remove cables, still ran (alt is putting out juice ~14.2v) Put battery back on, still ran.
Killed it, tried to refire, crank but no start.

Went home charged up the old battery, that one was dead. Bought a new gel cel, played chemist, charged it up, same story crank but no fire.

If I could get enough juice from cables, I could slow crank and fire, did this a couple times.

Went and bought an AGM battery. Same song and dance.

Looks like my kill switch is a 4 pole, 2 big with a junction box and hefty cables while the other two are 16 gauge (ie small) *** i determined that this powers my master ignition switch -- which drives a large relay.

I’m trying to figure out why the car would fire if all the batteries were bypassed but would not start with battery whether jumped or not.

It rained all today at track, so I didn’t have debug opportunity.

I have a durametruc I could hook to the dme, but not sure what to look for.

Tonite I bypassed kill switch, didn’t matter.

battery only 12.8v, cranking gives me 10.6v, 40psi of oil pressure, but no fire.

Was not able to do jump start tests as I was in my trailer

When cranking -- its a solid crank -- up to 40psi.

When I bypass the battery -- it barely cranks at all -- theres only so much I can get through the jumper cables -- but it fires.
it's like whirrrrr, pause, whirrrrr pause, whirrrrr --- FIRE. Then it idles just fine for as long as I let it.
Take the cables off its fine, put the battery back on, just don't turn it off and try to restart.

with the battery in the system -- its cranking full speed -- but that's it.

mike

rastta · 09-12-2018, 06:22 AM

These issues are tough to sort out. Have you checked the crank position sensor? Another thing to check is the cable in the engine compartment that splits to the alternator and starter. Might have corroded or come loose.

Topless · 09-12-2018, 07:02 PM

If the motor cranks ok, the battery is fine. Eliminate that from your possibilities. When the battery is toast it will not turn over with the starter. Period.

Now to the issue. Several possibilities:
1. Failed/intermittent ign switch. A very likely possibility
2. Failed crank position sensor. Maybe but usually once they die they will never start again.
3. Failed/intermittent fuel pump.
4. Failed/intermittent ECU

Change out the ign. switch first if you can't clearly isolate the problem. Cheap and reasonably easy.

seningen · 01-20-2019, 08:25 PM

4 months later still fighting this problem.

what is the bare minimum that allows boxster to fire?

i shipped off dme/immob/key ... tested good, removed the immob req (illegal, but I wanted to take that out of the equation)

Got dme back, still no joy, dme does work as I tested it in I second boxster I bought as test mule.

i have no fuel pump gnd signal
no fuel injector signal at fuel injector
no spark signal at coil pack

i have 5v and 12v at maf.

i do not have a gnd signal to engage starter on the wire that would engage the starter relay
but on this car it’s push to start, so the relay is hard wired to gnd and relay fires and starter
engages.

i have a good CPS signal

I have checked ignition switch and swapped jic, no start.

wgats the bare minimum needed dme needs to want to start the car?

running out of ideas.

thx,

mike

seningen · 01-20-2019, 08:28 PM

Quote:

Originally Posted by Topless

If the motor cranks ok, the battery is fine. Eliminate that from your possibilities. When the battery is toast it will not turn over with the starter. Period.

Now to the issue. Several possibilities:
1. Failed/intermittent ign switch. A very likely possibility
2. Failed crank position sensor. Maybe but usually once they die they will never start again.
3. Failed/intermittent fuel pump.
4. Failed/intermittent ECU

Change out the ign. switch first if you can't clearly isolate the problem. Cheap and reasonably easy.

Switch good and swapped
Cps good, scoped signsl at dme
Fuel pump works, no gnd signal from dme to relay
ECU good, starts another car all day long
No spark
No fuel injector signal

BFeller · 01-22-2019, 03:17 PM

After a period of cranking with no fire - the fuel pump shuts off. That is all I can add. Which doesn’t explain why it does not fire when cranking as you confirmed spark.

seningen · 01-23-2019, 07:47 AM

*** SOLVED ***

The rain, the battery running down, battery cables, kill switches, fuses, relays, DME, Immobilizer, Key RFID, etc

None of that had anything to do with it

Shortly after I bought the car
I installed a traqmate system, including a traqmate USB to control the cameras and data acquisition.
That system had been in the car for nearly a year prior including 2 or 3 event weekends with no symptoms whatsoever.

There was a pin on the traqmate usb labeled 5v with the input analog pins. The documentation. Is poor, so I hooked up 5v off the obdii port after having found you can get 5v off of there (I don't remember how that was determined, probably internet)

I eventually had to buy a street car to have a known good reference. She showed up late last week and was keen to success.

After checking things back and forth between the street car and the Spec Boxster, including triple checking the DME.
I decided some input to the DME must be wrong and is causing the DME not to let the car start.

So I wrote out all 88 pins and made a chart and one by one probed each signal in the street car, and then did the same in the spec boxster.
After probing all the signals between the street car and spb I noticed only a couple differences, one was the software voltage pin which only
connects to the obdii port.
Street car was 0v, spb 5v. Also the durametric could talk to both dmes, but on the spb, all live data was defaults and voltage was 0v, regardless of the DME,
while on the street car with both DMEs I got live data.

I went home and thought about where the 5v could have come from, and I remembered the traqmate usb had a 5v pin.
I also remember sourcing that 5v from the OBDII connector as that is what I had found online to do. My spidy senses
were tingling -- was I on to something?

About midnight last night, I found some documentation online on the old traqmate system. It wasn't very good, but I could see a photo of the pins labeled on the USB box
and blew up the picture. , It wasn't clear, but it looked like 5v was an output
Not an input!!! I had figured at the time that the 5v was needed for the analog data acquisition, not the other way around. Surely it couldn't be that simple.

After a sleepless night
I ran out to the shop this morning, unconnected the traqmate usb
And she fired right up
Motherf@cker!!!

I think the 5v put the dme into some sort of program mode or something, disabling its ability to start the car.

Why did jumping it work without battery?

I think once you got 14v, the 5v wasn't high enough to put it in the program mode...
I also think that once you get running, the DME just does its thing -- OR, the Boxster's alternator put out 14v, and once again
the 5v input was read as a low, not an assert.

Further complicating the matter was the small fuse box that was added for accessories that I had tapped off of for the traqmate 12v hookup
is janky, and I don't think it has a good internal connection. That's getting yanked and a new, and more accessible unit will be installed.

Just diabolical....

Now I have to put it all back together and get my medical done and sign up for NOLA.

Thank you very much to all who supported my efforts and responded to my posts -- especially Ahsai. If nothing else,
the moral support allowed me to just keep plodding along.