996 won't start after 4 months in garage

I rebuilt my 2002 Targa motor after it was involved in a fire with the PO. I turned the key to on and left it there for over one minute before my first attempt to start to program the DME. Is that all it takes to do that? It turns over very strong and fast. Fuel is there -- I can smell it. Fuel pump fuse and relay are good. I can hear the pump energizing at key on. Plugs looked fairly recent. I changed the CPS with a known good used one after the first several attempts, with no change. All grounds are solid, no corrosion. Today it caught and ran for two seconds, then died. It sounded smooth for that brief moment, i.e. no chain noise, no clunks. The half tank of old fuel has been treated with anti-moisture fluid and topped up with four fresh gallons of premium fuel. Could this be the computer? Or, should I try throwing a brand new CPS on it?

Define "rebuilt".

In 4 months, the fuel shouldn't go bad... If you're positive there's fuel in the cylinders, then that leaves spark as the culprit. Since you've already replaced the cps, are you sure the rest of your wiring is ok? Is it possible that rodents have torn things up? I'd do a thorough once over of all the engine wiring before cranking it up again - especially considering you can smell fuel. If your not careful, you may wind up reliving the PO's experience...

The fire damaged much of the wiring and rubber hoses on the right side and the intakes were roasted. I didn�t rebuild internals. I did replace the IMS, RMS, AOS, clutch, pressure plate and resurfaced flywheel. All wiring was from another Targa or Cab which I installed personally. The rear harness under the carpet was from the other Targa so I know everything is connected correctly. The coils and O2 sensors were not damaged. It sounds like spark to me too. But where to start?

A few questions. How did the fire start? How was it put out? I ask because you state "the intakes were roasted". Is it possible what ever was used to put out the fire (water, fire extinguisher) got into the combustion chamber? We just had a car 2017 Ram 1500 towed in that someone put 4 gallons of water in the fuel tank. Even after removing all traces of the water (tank dropped, fuel lines flushed, fuel rail and injectors cleaned) the thing was still a huge pain in the butt to get to fire over. We did get several 3 to 5 second coughs. Then after multiple attempts she was happy again. Just a thought.

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To broad of a question. Why not post some pictures of the damage and the current state of the burned area? I mean no disrespect, but there are two types of cars I'd never purchase as salvage - that's flood cars or burned cars. Trying to sort out all of the electrical issues is a fool's errand. Most of the guys that I've known that have attempted it, usually end up in defeat and then they can't get rid of the cars or break even with parts. I would imagine a burn car would need to be completely gutted, with every wire, sensor, module, etc checked. But of course, it's all depending on the extent of the damage. Are we talking about a localized fire in the engine compartment?

Yes to localized burn. I would not have purchased it if it was a total loss. Origin of fire is unknown to me. Most severe damage was on right top side of engine. Interior was only slightly smoke damaged at rear, and only the rear deck carpet and soundproofing had to be replaced. No sensors were damaged. Only paint to be scorched was around the hatch and inside engine bay. I only had to replace plastic parts and rubber hoses on top of the engine. I did replace the two rear wiring harnesses - the one on the engine and the one under the rear carpet. I was able to use the original CPU and relays on the shelf at the rear. But, I need to admit an electrical error on my part. When the engine was out, I forgot that I had temporarily hooked up the battery to pop open the rear hatch, before I found the manual release. The positive cable briefly touched the body and began to smoke. No sparks, and I moved it after a couple of seconds and disconnected the battery. At that time the rear harness had been replaced, so maybe the DME was shorted out. I found 6 fuses that were fried, either from my error or from the fire fusing things together with the battery connected. All other electrics work fine, except the interior lights won't turn off, and they drain the battery unless I disconnect it. Do I need to re-calibrate the DME every time I disconnect the battery? I'll check for a short at the overhead light panel soon. It's still in the mid-nineties in North Texas, so I can only work inside the car for so long.

any codes present?

I'll check for codes tonight right after I buy an OBDII code reader, but I expect that there are going to be some. I'm looking for before and after photos so everyone has a point of reference.

Here are the before and after photos of the engine. Before pic. After pic. I have added 200 cell cat pipes, since the PO had a straight pipe setup.

Found some codes, as expected. 1139: O2 sensors 1141: Secondary Air Pump (Took it out and bench tested with 12v supply - runs fine. Could valves be clogged inside? 1120 & 0121: Throttle Position Sensor or MAF code? 0117: Coolant temp sensor. This was replace with Porsche OEM part before attempting to start. 2135: Throttle Position Sensor. If this one is bad that could be the problem. I assume that some of the above is due to the engine being removed/reinstalled, prior to actually starting and running at operating temps. Do you guys know how to test the TPS to determine whether or not to replace it?

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Since you have these codes now documented, clear them and see what returns with KOEO. If coolant temp sensor returns start there, it is the most simplest wiring/curcuit..

I cleared the codes and all six DTCs returned. Can you give me a DIY on testing the coolant temp sensor circuit? The throttle position sensor on there now is from a high mileage '04 cab, that came with the throttle body. I normally don't buy used sensors. New Bosch sensors are inexpensive, so it might be worth it if you think that is what's triggering the TPS code.

Update. It really wants to start. It does "run" for 2 seconds, but shuts down each time it fires up. New codes have come up. 1120 - no description on my reader 1139 - OS2 range - cylinders 4-6 2135 - throttle pedal position sensor/switch A/B voltage correlation 0122 - throttle pedal position sensor A - low voltage input 1141 & 0418 - Secondary Air Pump - relay A control circuit 0117 - Coolant temperature circuit - low input 0203 - Injection circuit open - cylinder 3 0342 - Cam position sensor A circuit low input bank 1 I would appreciate your input on how to test each of these circuits. Do any of these sensor trouble codes translate to a broken cam sensor or TPS, or just a relay or connection issue? When I'm cranking, before it fires, I see the tach move from below zero rpms to right at zero. It does not bump up while cranking. Is the "throttle pedal position sensor" in the code description the same thing as a TPS, or does that point to the sensor connected to the accelerator pedal? I found several TPSs for sale online, but my throttle body does not have the two-screw sensor on it anywhere. I know I have the correct TB, as I compared my part number to others for sale for 02-04 Carreras. I may be that the TPSs I find online are for earlier cars or Boxsters. I know that search engines don't always lead you to the right part. Thanks for any help you guys can give.

You are probably going to need the correct wiring diagram for this car, also you will need a DVOM ect for testing. With so many codes, I would start by checking the X59 connector for proper connection. It is the two big round connectors on the left of the engine compartment. Then check all fuses with a test light, and all grounds for proper connection. After you have done these basic and preliminary operations, then going to the more specific tests, test the coolant temp circuit first, it is the most simple. Disconnect the coolant temp sensor (two wire plug) , with key on engine off ,pin 1 (blu/org)should have 5v,,, pin 2 (brn/pnk) should have continuity to ground. With sensor connected and backprobing the connector, on pin 1 there should be about 2.5-3.0v... Pin 1 blu/org goes from the coolant temp sensor through X59 connector, then to pin 22 of the DME. Pin 2 brn/pnk comes from the coolant sensor and goes to a splice for all sensor grounds, then through x59 connector, then to pin 17 of the DME.

I'd like to know what would cause a fire on the top right of the engine. Power steering line leak?

That's my guess, but a leaking fuel rail or hose is another possibility. The flashpoint of PS fluid is around 350-400 degrees. The muffler pipe is below the drip area, and they get hot enough to ignite the Pentosin if covered in the fluid. I know the drip pattern well now, because unfortunately my "successful" p/s return line repair is still leaking, and all I've done so far is crank the engine. I'm at a loss as to why it leaks with a good snug o-ring. I tightened the connection as tight as I could, but I could try to get it tighter. I know there is danger of stripping the brass nut.

Tight as you could should be plenty. Maybe try a thicker O-ring? Did you replace both ends of the power steering couplings?

No, I actually transplanted them from a 2004 cabriolet. Actually the entire rear section is from that car, meaning all p/s hoses, pipes, fittings, pump, & reservoir. The high side went back together using the old o-ring, and it doesn't leak. It has the teflon ring and rubber o-ring fitted together in the compression fitting. The low side did not look like it has room for the teflon ring and the o-ring together. I tried a thicker o-ring and it would not slide all the way back to the ferrule. I'll try another one from the kit I purchased at Harbor Freight. Update on the electrical issue. I found that the 40A fuse under the rear shelf had fried, probably due to my unintended grounding of the battery pos cable on the engine bay frame. I replaced it with a spare I had, and now the air pump runs constantly with the key on. It shuts off a few seconds after I remove the key. Is that normal? the coolant temp sensor terminal connection is still dead when tested with a light or with the multi-meter. And I still have the top row of the front fuse block that is dead. Any ideas?

Another discovery. The PO removed the transmitter from the key fob. So, I have been trying to start the car without a circuit board in the fob! Can you start a Porsche with a dummy key? If not, then I'll need to buy a new transmitter and have it reprogrammed. Unless I can find a used one and take it to the dealer with my VIN. At least the metal part works to turn the ignition.

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As long as the RFID pill is still inside the FOB, you're ok. But if it's not there, then of course the ECU will not allow the car to start properly. The secondary electronics, if I'm not mistaken, just work to lock and unlock the car. RFID primary function is to provide certification that the rightful owner is attempting to start the car. It uses a rolling code procedure to handshake with the ECU.

Thanks. My friendly parts guy at the dealership near me said the same thing about 10 minutes ago. So, if I want to unlock the car using the key fob I'll need a new transmitter. They can cut a new blade and reprogram a new fob all for $400 at my shop discount. But as you said, that just gets me in and out of the car. I'm still trying to figure out why it starts then dies after 2 seconds. And I should amend my original title of this post series. It actually had the engine fire in February. So, the gas in the tank is 7 months old. Still it should start and run rough if gas is varnished. I put moisture removal treatment in the tank with 4 gallons of premium to help with the fuel issue. But I suspect the issue I'm having is all electrical.

Have you checked to see if the fuel pump is actually pumping fuel? Will it start and run on starting fluid? The fundamentals are air, fuel and spark. Air is simple. Sounds like you have spark since it runs (and then dies after 2 seconds). So it must be fuel related. You can rent a fuel pressure gauge at the local auto parts store and check your fuel rail pressure.

I smell fuel in the exhaust pipes after a no start. I think I may try the old fuel inlet into a clear hose/water bottle trick to see if I have proper fuel flow. If I have less than normal, say about 8 ounces with 30 seconds of cranking (my 1996 Audi did that much), then I'll try a pressure gauge.

I was curious and did a little research on the P0342 cam position sensor code. From what I read, the sensor itself could cause the code, but it is typically due to low voltage (bad battery or bad connection) or a bad ground. Can you swap out the sensor from the other engine? That would eliminate the sensor itself, unless they are both bad of course.

A bad ground can be the devils work.. The starts and dies thing sounds like the anti theft may be kicking in,, its how my 2006 BMW behaved when one of the keys died... Some folks put the RFID chip against the ring for the VATS on the ignition switch when they lose a key to save paying the key-ransom to the dealer, then your just using mechanical security..

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Weak batteries have been known to cause al kinds of strange things with these cars. Same with a failing ignition switch...Could a failing clutch switch also be something to look at, does the ignition lock switch allow the car to start if it fails or will it just start with out depressing the clutch?

The battery is only 2 years old. It's an Interstate, so I had it tested at an official Interstate dealer. His Interstate branded tester showed higher amps and volts than the label on the battery. I have the printout in case anyone wants to review the image. As for fuel pressure... I disconnected the line and ran a hose down to a 17 ounce bottle. It filled it to overflowing in less than 20 seconds of cranking. I tried cranking without pushing in the clutch and it would not turn over, but I did hear the fuel pump engage. The clutch switch is new, so no surprise there. After I found that the 40 amp fuse on the rear shelf was blown, the SAP now runs constantly without the key in, so I pulled the relay and replaced it with a used OEM relay from a 2004 parts engine I had. Same result. This may be unrelated to the no start, but I thought I'd mention it. So, I have fuel, air and spark. This must be the immobilizer. As I pointed out way up above in this long post the key that came with the car is an empty case. It has the pill identifier, so it recognizes the car, but without any circuit board inside the fob, I wonder if the immobilizer is thinking that the car is being hot wired. That's a $400 fix at my dealer. Worth it to me if it gets the car going. And I'd have a spare key for unlocking, but not starting.

For whatever it's worth j had symptoms similar to what your describing on my TTS trying to pull it out of storage this spring. I suspected bad fuel but it turns out it was the MAF and it wasn't giving any codes. Would start for a few seconds and die.