Engine fire

[Otter74]

I was not careful enough and did something dumb that has me really bummed out. Now I’m thinking through my next steps and coming here for some questions and advice.

I had diagnosed a bad #4 injector on my car - it’s an SC with a Megasquirt - and was finally getting to replacing it. I unbolted the rail and wiggled the injectors off their seats far enough to get #4 out. #4 and #6 came off at the intake port, but #5 came out at the rail. I replaced the bad injector and seated it. I started wiggling the rail down, paying particular attention to #5 because it needed to be seated at the head. I got it down and tightened it using the rail mounting bolts, then inspected. The head of #5 wasn’t quite seated fully, so I undid everything, pulled the rail back off, and did it again, paying more attention to #5. Looked OK this time, but I wasn’t completely satisfied that #6 was on right so I did it again. Third time, everything looked OK. I turned the ignition on, no apparent leaks. Everything looked right, but crucially, I did not pay enough attention to the fuel pressure gauge on the rail. Thinking everything was OK, I started the car. It ran normally…for a few seconds, when the rail caught fire. I shut it off, jumped out, got the extinguisher out of the back seat, and put it out. Total time of fire was probably ten seconds.

Looking at it, it’s clear that the #5 injector was not seated at the rail, and that’s where it was leaking. My first thought was that the fuel lit when it ran down the valve covers and hit the heat exchanger, but I’m not sure exactly how it started, since the car hadn’t been driven in weeks and was dead cold.

So now I have to assess the fire damage and cleanup. Extinguisher was a dry chemical type, so there’s the usual white residue. How do I clean this up, and what effects from its use can I expect?

Obviously I have to replace the #5 injector, and re-seat the fuel rail. I need to assess the injector wiring harness for continuity. Ditto the two breather lines from the oil tank. I’m sure there’s more. I need to calm down and focus on other things a bit and sleep on this, and I’ll reassess everything tomorrow.

general advice on dealing with a small engine fire is much appreciated.

[Matt Monson]

Oh man, I’m sorry to read this. I remember when you found that car.

If it were me, I’d drop the engine. I’d want to check anything rubber that could have melted, even if it didn’t get hit directly by fire.

[Otter74]

Yeah, it’s been a great car - really reliable, and lots of fun for close to eight years now. It’s intermittently warm enough now for me to work on cars, so I was taking care of the injector, re-shimming the fan belt, and re-adjusting the shift coupler.

First I need to clean up the engine bay. Then inspect everything. The fire was localized to the right rail area. Most of it was on the top side of the apron, but fuel ran down past it to the lower valve cover area and garage floor, so there was some fire there too. The two breather hoses were obviously affected, as was the insulation mat. Obviously the harness, which is partly the BitzRacing EFI harness and partly the factory harness. The IAC valve was next to it, too. Down below there’s an oil line.

A friend of mine who knows what he’s talking about said the singed harness could fail with time and heat cycles even if it tests OK now. I trust him.

[Walt Fricke]

I'd get that white stuff off right now. Start with vacuuming to get anything loose. Then I'd wipe with wet rags, followed with more water, on the notion that the soda will dissolve in water. When it is all gone, dry everything. Compressed air would help a lot if you have a compressor.

Someone with more knowledge of the chemistry should have better ideas (or maybe will say water is bad, though usually it is a pretty neutral solvent).

You should do a general internet search, as this issue is not at all Porsche specific, but based on your very common type of extinguisher and extinguishant.

Cleaning up ought to let you assess what else is melted and decide what you want to do about it. This fire sounds like it was localized and short in duration. I've had engine fires which singed wires, but didn't compromise them, leaving an aesthetic issue only. The fuel rail didn't melt, so any rubber hoses may have escaped the heat. Should be easy to check relevant O rings and the like.

[fanaudical]

Yikes! I'm glad it was small and contained quickly.

I'm with Matt on this: It will be easier to inspect, clean, and repair with the engine out.

Here's the guidance I've heard for dry chemical extinguisher clean-up:

- Vacuum up what you can.

- Fill a spray bottle with 1/2 warm water and 1/2 isopropyl alcohol. Spray on the foam, let it soak a bit, then gently remove with a damp rag. Repeat as needed.

[Dpmulvan]

Dry extinguishers are corrosive to metal, I believe they contain phosphate which is acidic. Don’t use water unless you have to otherwise you’ll be smearing acidic paste all over when wiping it up.

[Otter74]

The part I’m still scratching my head about is how it started. Fuel needs some kind of concentrated energy input to catch fire - a spark, a flame, or a high heat surface. Fuel hitting the heat exchanger when it’s hot would do it, I imagine. But the car hadn’t been started in weeks and was stone cold.

[manbridge 74]

Sorry to hear. Good on you for having extinguisher ready.

Dead cold engine? Cause was almost certainly lack of ignition integrity. Spark leaked out to ground and lit it up. Check all wiring while car is running when you get it going again.

[917_Langheck]

It caught fire because the fuel pump pumped fuel, and the distributor sent electrical impulses down the plug wires. Two leaks, one at the fuel rail, and one at the lead - the fuel acting as a short to ground path - equal a fire.

(Ugg, beaten to the post again...)

[Otter74]

Plug wires are only a few thousand miles old, so I wouldn’t have though of them as being an electrical leak path, but it’s the obvious candidate. I’ll add new wires to my list - they’re not expensive. Megasquirt is controlling ignition too, using Ford EDIS module and Crown Vic plug wires.

I just commented on this to my sweetie, who has MS; she laughed and said “you car has MS!’”

[fanaudical]

Look for a stained area on a plug wire. It's possible the fuel (a solvent) saturated the covering on a plug wire and then you get insulation breakdown, errant spark, and fire.

[trond]

same happened to me but happened after the MS had a seizure up and filled the cylinders until unable to crank even. I was in a hurry and removed plugs and cranked it to get the fuel out. And poof ! As you can expect. Thankfully I did not use the powder extinguisher but the nearby garden hose. Some minor soot stain and damage to the AFR connector only.
Powder extinguishers should be AVOIDED. Use foam instead. Or as the fireman said at last course I attended; better to let the car burn down then spray that toxic powder all over. Take it apart I think and neutralize somehow. Meanwhile get rid of any powder extinguishers and replace with foam ones

[EC900]

As for cleaning, a Baking soda solution will neutralize acids found in phosphoric compounds. It would be important to know the active ingredient content of the fire extinguisher so there’s no mistaking what to use to clean the residue off.

[manbridge 74]

Originally Posted by Otter74

Plug wires are only a few thousand miles old, so I wouldn’t have though of them as being an electrical leak path, but it’s the obvious candidate. I’ll add new wires to my list - they’re not expensive. Megasquirt is controlling ignition too, using Ford EDIS module and Crown Vic plug wires.

I just commented on this to my sweetie, who has MS; she laughed and said “you car has MS!’”

You can test them with water spray while running, even new wires can be faulty.

[H-viken]

Not sure how best to clean it other than to do it asap. Can ugly otherwise

Friend of mine used a lot of water but like I said, not sure which is the best way

[EC900]

I agree, plain water will do as well.
It’s not a China Sydrome melt down situation. Sooner the better. The acidic levels might not be as bad but consider how longs it takes old battery acid leaks to compromise a front trunk floor.

[fanaudical]

I found this:

https://firesystems.net/2018/09/14/how-to-clean-up-fire-extinguisher-residue/

It looks like cleaning method is determined by the agent in the fire extinguisher.

[florio]

Hi, well done in keeping your cool and putting out the fire. As a chemist, I would suggest that you quickly vacuum up as much powder as possible. Then clean up the rest with moist towels or rags. Avoid trying to neutralise the base with acid or vice versa, it will be impossible to get things neutralised and you will be left with acid or base residues which can accelerate corrosion.
Good luck, and keep us posted!

[Otter74]

Florio and others, thanks for that. Going to load the shop vac into the wagon (I live in the city, and keep two of my old cars at another garage a few miles away) and go start cleaning it up. Didn’t have time today until now.

[dannobee]

It'll clean up with a pressure washer and some engine cleaner, too. Just don't spray it directly on things like the distributor. Put the car in a place where it's ok to sit for a few hours to dry.

This is why most shops that I've worked in had CO2 fire extinguishers in the service bays. If they didn't, I'd complain enough to get them. Dry chemical extinguishers should only be used as a last resort in a shop environment. Mostly to appease the local fire inspectors and hang on the wall as decorations.