Car Fire!!!

[Wayne 962]

Well, my luck went south yesterday. After getting the car home the night before, it started up right away the next day and drove perfectly to AAA (where I registered it). Getting back into the car, I started it up, and it was driving very poorly. It is important to note that this is a car that I am unfamiliar with, so I wasn't 100% sure whether it was just cold, or something else.

Well, it stalled driving and it felt like it was driving on 4 cylinders. Finally managed to get it home to the shop, but it was driving very poorly. I decided to let it cool down.

We took a look at it later on, and noticed that the distributor cap was in less than new condition and was actually loose on the distributor. We put a new cap and rotor on (Tom and I), and started it up again. Did the "feel the header pipe test" and found that the right side was very hot, and the left side was not so hot. Hmm, I thought it may have been a clog in the fuel supply to the left carb. Clog indeed - the entire carburetor had been on fire inside the plastic air cleaner housing, and melted the entire top of the carb, including the venturis!

This probably explained the clunking noise I heard when it was having problems - this was probably a small chunk of the venturi falling down the intake into the engine. So, my carb is toast (luckily I have spares) and the engine may possibly have some damage in the head from where the valve seats. A compression test later on will tell.

I'll have to get into the intake tomorrow with a small wire brush and dremmel tool and clean it all out (rotate the engine so that the intake valves are closed). New jets, venturis, and stacks are on their way from Richard at PMO. New Magnecors will go on the engine too. Hopefully, there will be no lasting damage.

Lessons to be learned? I made a mistake - something that I should have remembered or thought about more carefully when the car started having problems. If you're ignition system fails on a carbureted car, then raw fuel will continue to be dumped into the intake, creating a potential backfire / fire situation. It's very important to stop driving the carburetted car if you think you may have an ignition problem. It's less of a problem if you have MFI or CIS, but still dangerous. This is why so many Ferrari 308s catch on fire. The 308 engine is like two four cylinder engines combined together. It will run perfectly balanced with one bank of cylinders disabled. If one of the two CD boxes on the 308 goes out, the carbs will continue to dump raw fuel into the exhaust system, where it will ignite in the CATs. These will quickly reach 3,000 degrees and the rear of the car will burst into flames (rubber, paint, carpet in the trunk). Most 308 owners are aware of this problem.

The same is true for carb 911s. One thing that aided in the fire was the use of plastic velocity stacks (I didn't know they were in there - just had picked up the car and driven only a few miles). Although I didn't write this in the book, I wholy recommend that you stay away from these plastic stacks - the metal ones are way better and much safer (they won't crack either).

I'm not sure if the carb is salvagable - we'll have to see when I finally get around to tearing it apart. It looks like a mess on top, but the throttle body looks like it may be undamaged. I'll post pics in the near future...

The moral here? If you have an ignition problem with your car - don't just keep driving it. I only drove about 3 miles, and it basically destroyed the carb. Get out - investigate further. If you don't, you may find your entire car going up in flames. Also, make sure you carry a Halon fire extinguisher. Here's a link to the ones we sell, in case you don't happen to have one:

http://www.pelicanparts.com/catalog/Safety/H3R.htm

Because I was unfamiliar with the car, and because I wasn't thinking clearly, the damage was more than could have been. Just thought I'd pass along some of this wisdom. If you think you have an ignition problem, get out and investigate further...

-Wayne

[konish]

Wayne,
That sucks....sorry to hear...

R/
Dustin

[Joeaksa]

Wayne,

Sorry to hear about the problem and hope you can save as much as possible.

When driving a car that you are not familiar with its difficult to really have a feel for everything. Good advise you are passing along and if it does not feel right, then many times its not right and needs to be corrected and fast.

Joe A

[red-beard]

Spend the money and buy some PMOs. That is what I'm going to do with my 914/6 (2.7 RS spec engine).

Sorry to hear about the fire. You were lucky!

James

[astark]

Wayne--

Sorry to hear about your bad luck. It could have been a lot worse, you could have been on a long trip only to notice flames in the rear view mirror!

Hope the damage isn't too bad.

Alan

[rcwaldo]

Wayne, sorry to hear this, but glad you didnt lose the whole car, or worse, you!

Please excuse my ignorance, but which car is this? Did you get another 911?

Chris

[dillinger]

Wayne,

Sorry to hear about your misfortune. I just placed another parts order for my car today, so I've contributed a few $$ towards your repairs

Don

[RoninLB]

Great info.

So an ignition miss caused a backfire and started a fire ?

[concentric]

That sucks, Wayne.
Sounds like you have the carb situation under control. Good luck with the engine.

JCM

[RoninLB]

anyone have any idea about flame arresters on a 911 ?

"The operating principle of the flame arrester is to cool and quench the flame front by forcing it to pass between some closely spaced metal elements that act as a heat sink. Since the engine must take in air without too much restriction, many elements are required with many small spaces between, hence the typical arrester design of a circular shape that is six or more inches in diameter and an inch or more in height. Some form of delayed or late ignition takes place in one of the cylinders at a time when the intake valve is open and the resulting flame ignites the fuel and air vapor in the intake manifold. The pressure created has to go somewhere, and that's back out through the carburetor or intake system. With a working flame arrester, only the pressure is released and none of the flame gets out."

they are required by the CG on boats

[Wayne 962]

Originally posted by RoninLB
Great info.

So an ignition miss caused a backfire and started a fire ?

Possibly, although I can't recall it backfiring on this trip. At least it didn't backfire loudly. The 308 backfires all the time (can't seem to fix that, and some people tell me it's normal) so maybe I didn't even notice it on the 911...

-Wayne

[Wayne 962]

Another thought for those of you in this situation. Most carb fires can be put out by simply running the engine. The air will draw the flames, fumes and everything else into the carb and into the combustion chamber. Sometimes shutting off the car is *not* the best thing to do because the flames will then extend upwards. Damned if you do, damned if you don't. Then again, shutting off the car shuts off the fuel pump. I suppose if you really had your head about you, you would run to the front trunk and pull the fuel pump relay, while keeping the car running. I actually like the idea of a fuel cutoff switch somewhere in the cockpit - good in case something like this happens, and also good as a theft deterent too!

-Wayne

[Zeke]

Wayne, you seem to be taking this in a rather cavalier fashion. And beating yourself up a bit as well. I'm sure I wouldn't have done anything more than you did. After all, it was only 3 miles.

Glad to hear it wasn't worse and hope you dodge a bullet regarding the valve and seat. Just yesterday i was telling you how solid the car was supposed to be. I meant sorted as well as solid, but now, you might have reason to go over the car very carefully.

May I recommend a good book?

[Zeke]

Originally posted by Wayne at Pelican Parts
I actually like the idea of a fuel cutoff switch somewhere in the cockpit - good in case something like this happens, and also good as a theft deterent too!

-Wayne

Maybe that's why the 356 has such a thing. He heh. (Well, it's a valve, but what the hey? Does the same thing.)

[Wayne 962]

Indeed, I will be (and had planned to) go over the car very, very carefully prior to driving it any number of miles...

-Wayne

[k9handler]

glad to hear the car (and you) are ok...with the title I thought your car caught fire!

[Rufblackbird]

same here...glad you and the rest of the car is ok!

Guess I was too gutsy and went on a 8000 mile roadtrip without really examining much on the car and really lucked out.

[GrantA]

Wayne,

Sorry to hear about the fire, it sort of wrecks your confidence in the car and gets you into the "what if?" mood. Let us know if there is serious damage inside the engine.

I'll pass the tip about the Ferrari 308 on to a friend who has just bought one.

All 'ra best.

Grant
____________________________________
1978 911SC Targa (only way to go)

[RoninLB]

I've seen a lot of 4 barrel carbs start carb fires like Waynes with cracked dizzy caps. It'll pop-only when reved to 3k rpm with air cleaner or flame arrester on. It'll flame without the air cleaner or flame arrester on at 3k. WOT at idle usually sucks it in.

[dhoward]

PPI?