Ya..it was sucking in fire.

If it was ON fire, it would look like a horror show in there. Melting, bubbling, popping plastic..crusty with entirely oxidized material.

 

So..get a battery charger, hook it up, and jumper the FP relay...and wait. This needs hard tested for a few hours.

 

[QUOTE= Sounds very reasonable and thought out, except there aren't any fuel lines over the intake boot. The nearest fuel lines are either on the other side of intake runners, or on the wrong side of the MAF, near the firewall. If this is a fuel fitting issue, it couldn't be a drip. It would have to be a spray to traverse a few inches horizontally, hit the backside of the MAF and run down to the bottom of the intake boot.[/QUOTE]

OK, but there are some lines just under and kind of beside the MF; and there are 5 or 6 connectors very close.

 

Dupe Post

 

 

Dumb question. Do you have silicone vacuum lines?

 

OP can you post a few engine bay pictures

 

@Speedtoys Yep, for sure, it was sucking in fire. I firmly believe the fire was on the inside of the tube and worked it's way out, not the other way 'round. There just isn't _any_ fire or heat damage in the surrounding components. Yes, I will clean it up really well in there, hook up the battery charger and let it sit with the pump jumped on, all day or overnight. This is probably not related, but it's got a brand-new fuel pump, less than 1000 miles old.

On that note- anything else I need to do to let it safely sit overnight, turned on? Do I need to disconnect the coils? Probably not, since they're fired electronically, right?

And yes, in that photo, you can see the fuel lines are nearby, but not in a place they could drip on the intake boot. If they were dripping _under_ the intake boot, and the resulting puddle caught fire, there would be a LOT more widespread damage. For one thing, the plastic vacuum lines going to the pressure regulators would have melted long before the thick rubber intake boot.

@Jerry Feather I sure wish I could see and access everything as nicely as that photo!

​@Hilton All of the vacuum lines were replaced 6 months ago, and they're all OEM. I don't think Porsche used silicone, did they? I kind of wish they were a combination of stainless steel hard lines with silicone fittings instead of plastic and (I think) Butyl rubber. For one thing, if they were stainless steel, I wouldn't have had to go through the 7 levels of hell required to change the vacuum modulator line. :-P

If I had infinite free time, I'd probably replace all the plastic vacuum lines with 3/16 Poly-Armour, and then never think about them again...

@Mrmerlin Sorry, I haven't been able to get out there to work on it more, but I'll get some more photos posted as soon as I can.

FYI, I sent out the MAF to have it rebuilt. It's supposedly all finished with a new venturi, upgraded / calibrated electronics, and a new aluminum side cover. It should be here any day now. All of the other replacement parts are sitting here in a box, waiting to go. Everything together came in under $800- thank goodness!

 

Umm dont let the car sit with anything running unless you have a supervision person in the room.

 

Ok that rules out my possible "leaking FPS/Dampener dissolving silicone vacuum line under the MAF boot" hypothesis.

Not many possibilties here - fuel, but from where?

 

Although some of the things seen are difficult to explain the only realistic possibility is a pool fire caused by fuel ponding in the throttle body downstream of the butterfly as a result of failure of a diaphragm in either the FPR or a damper. Normally such would eventually get entrained in the air stream but in this case it possibly accumulated and for whatever reason [maybe a backfire?] it ignited. The flame front managed to get into the MAF and do the damage it seemingly did. Had the fire come from external fuel leakage catching fire the damage would have been far greater than a rubber boot taking most of the hit.

It will be interesting to see what other damage emerges as the system is opened up- for starters the seals on the throttle butterfly shaft will probably be toast - the hose to the ISV is presumably toast but other than that there is not much else to damage assuming the fire did not get hot enough to melt the alloy.

 

So I got the MAF rebuilt, but decided to fix all the random leaks before I try it out.

I have it apart right now and just replaced the front crank seal.




I just noticed my harmonic balancer is cracked.



This got me thinking… maybe it’s spun and the timing marks are off? Maybe it’s been running like crap because the timing belt was installed according to an inaccurate mark? Maybe terrible valve timing caused fire to fly up into my MAF?

What’s the best way to check it? Does anyone here know what angle the woodruff key on the crank points in relation to the OT mark on the balancer?

Also, what kind of balancer should I get? Are there any options left these days besides NOS factory ones or really expensive custom ones?

 

Probly a lot of that out in the wild, the OE dampers on many (if not most) cars failed (the rubber has hardened, shrunk, and begun to crack and delaminate years ago) which results in crank vibrations that work hard to fatigue parts connected to it.

 

Eh… no such luck. I put the balancer on and used a dowel in the #1 plug hole to check tdc. The pointer points right at OT when it’s supposed to.

Taking everything apart and cleaning it up has made it evident that the oil pan gasket is leaking like a sieve. It might even be leaking more than the crank seal was- but I couldn’t tell because the pan gasket leak is directly below the crank seal leak.

This is the leakiest danged vehicle!

 

I just thought I'd come back and give everyone the final update on this thread.

• I finished up the oil pan gasket and crank seal. Everything is nice and clean and sealed up tight on the bottom now.
• I installed a new OEM harmonic damper.
• New intake boot, and all associated hoses.
• Rebuilt MAF

Started it up...and it ran like total crap. Did a bunch more exploration, found that the vacuum line on the fuel damper was leaking, but only under very heavy vacuum! @Jerry Feather you win the grand prize!
That explains the fuel source for the fire, and it also explains why it didn't appear to be leaking when I checked it before.

So, I replaced the fuel damper... and it ran better but still not very well.

I started exploring more, eventually hooking up the oscilloscope to test signals at the LH and EZK. I found a very intermittent cam position sensor signal at the EZK. When I pulled the connector off of the cam hall sensor to check it out, the plug on the sensor crumbled apart and the pieces fell out on the ground. The connector pins are corroded as heck. I don't absolutely know for sure, but I'd bet that terrible signal caused a bad spark timing event, which caused a backfire, which ignited the fuel leaking out of the fuel damper.

I've ordered a cam sensor and I'll replace it ASAP, but I think that's for a different thread.

Thanks, everyone!