77 911 CIS fire

[edc153]

Started working on a 77 CIS 911 the other day that had not run for 2 to the 4th power years, or more. After getting the fuel distributor main plunger released from it's stuck condition, and could see the fuel seemed to flow normally from the injectors as they dumped into a catch can, we decided to try to start it up.

The starter is really SAD(, so we pushed it down the street for about 50 feet, and it fired and ran for the first time in "x" to the 4th years.

The owner was elated :)

Then it back fired( blowing the center injectors out of their ports on each side of the engine.

The engine stalled and quit. My wife called out to us from across the street, "It's Burning!"

We quickly pushed it close to the house, and along with the Mummies fire engine service; began putting the fire out with the hose. The 911 fire trucks arrived in about 5 minutes just after we stopped the burning.

As I was still dumping 20 gallons a minute from the garden hose onto the engine, a fireman told me I did a good job putting it out. Then I looked at the owner, he got singed by the flames when we pushed it, the paramedics then began putting the mummy wrappings on him where he was injured, and took him to see the emergency docs.

He is ok, the sight of seeing his car catch fire and burn for a few minutes really traumatized him. When he came back from the E room, I explained what happened:

For some reason, the right center injector kept spraying fuel after the engine quit. The engine ran for a few seconds after the back fire pressure blew it out the hole, the two or three seconds run time before shut down (due to two large vacuum leaks), a spark from the stainless shrouded plug wires ignited the vaporizing fuel which continued to flow from the injector while we pushed it the 50 feet to the curb.

At the curb the flame had spread around the engine, making it difficult to put out. We lost the injector lines, a right rear tire, relatively minor burns to the exterior, and perhaps the oil lines from the dry sump tank. Considering the car desperately needed paint and body work long before this fire, we considered ourselves lucky we had the courage to push it to the hose before losing the whole care to the flames.

This car does not have the blow off valve in the airbox. As many times as I have read about the exploding airbox on these cars, I just could not believe it would happen to me so seemingly easily. And what's with those injectors coming out of the ports? All of the injectors and seals are new.

We gotta fix that guys, where's the clips to hold them in. VWs don't have such a shoddy arrangement with their CIS injectors.

Ed

[timmy2]

Wow! That is crazy, you are lucky you didn't get burnt too. it's good to know the owner of the car is ok.

I just bought a new set of fuel lines for my car because the old rubber covering had come off on most of them but I was going to wait a while before I installed them. I am now inspired to change them out sooner rather than later.

I recently had a similar backfire that blew the pop off valve right out and started the air filter on fire. I was lucky compared to your story. Pulled it out and stomped on it.

I bought a used stainless airbox as a result of that event as the seam on my airbox blew apart as well. I'm really thankful the injectors stayed in place when it happened after reading your story.

[M.D. Holloway]

Well, sounds like you guys were lucky that God! The chances are that he prolly wont want to get near the car again. Once burnt, twice shy...

So, maybe he is interested in parting it out?

[manbridge 74]

A somewhat painful learning experience. Glad no one was seriously injured.

I looked at several mid-years and all of them had a fire extinguisher behind the seats.

[E Sully]

I hope the owners injuries are minor and heal quickly. Let the shock wear off and take a calm look at the situation. The excitement of starting up a long sitting Porsche can sometimes lead to skipping a few checks to make sure things go smoothly. Don't blame a 35 year old injection system that had been sitting 2 to the 4th power years, or more for this. The injectors were blown out by the force of the excess gas igniting. Retaining clips on the injectors would not have stopped excess fuel being dumped in the engine from exploding.
A complete used cis system can be purchased on the Used Parts forum for a very reasonable price, along with any other parts that were burned. Test the injectors with a set of gages to make sure they open at the correct pressure and have a good pattern with out leaking. Flush the fuel tank, new filters, replace old hoses, check vapor recovery system, replace old ignition components and wires, valve adjust and cylinder stud check. Fresh oil. No mouse nests on the engine.
Also make sure the brakes and tires are in good order. Old rubber lines can look good externally, but be deteriorating internally. No point in a running engine if it can't stop. Of course having safety equipment like a fire extinguisher, eye protection, and a first aid kit is always important. And start the car outside away from the garage and house.
Hopefully the next story we will get to read is how the car was returned to good running condition.

[manbridge 74]

^^ What Ed said.

I have seen a 911 with hoses marked "not for fuel injection use" right there on the hose.

Soft and spongy. Just waiting to burst.

[fanaudical]

It's good that everybody will heal well.

I hope you don't mind, but this is a great warning for others: Resurrecting an older vehicle often entails more than changing liquids and getting out the starting fluid. Careful inspection of the integrity of critical components is necessary and warranted.

[szyzygy]

As a fellow 1977 911 owner, I'm sad to hear this

[edc153]

The fire would never have happened if the injectors had stayed in place.
So what is with that?

I worked on VeeDubs for years before graduating to Porsche. The VW CIS injectors could in no way get blown out of their ports. So aside from the obvious, it makes no sense how they could be pushed out so easily.

What is the solution to this problem? I cannot put them back in place now and expect them to hold. That would be foolish. Perhaps the new orings used to hold them in place are the wrong ones. There are no clips to hold them in place. There should be something else.

I generally only do 65-73 and 993 911s'. Also worked on 944 turbos for 10 years. If there is a known method for holding these CIS things in place, I wanna know.

Thanks Gents!
Ed

[timmy2]

I changed out both the injector O-rings and the inner sleeve o-rings on my 3.0. had the airbox blow out and no loose injectors so maybe you just need to replace the o-rings? There are 2 types out there, one is the "German" version. (Green)

The injectors should be pretty hard to pull out if seated correctly. Perhaps when you had them out for the flow testing you performed one was not seated fully when re-installed before you fired it up. (shouldn't have kept flowing fuel after shut down either)

If you install a pop off valve there will be a path for the inevitable backfire gasses to escape through instead of forcing out the injectors.

[edc153]

Originally Posted by E Sully

I hope the owners injuries are minor and heal quickly. Let the shock wear off and take a calm look at the situation. The excitement of starting up a long sitting Porsche can sometimes lead to skipping a few checks to make sure things go smoothly. Don't blame a 35 year old injection system that had been sitting 2 to the 4th power years, or more for this. The injectors were blown out by the force of the excess gas igniting. Retaining clips on the injectors would not have stopped excess fuel being dumped in the engine from exploding.
A complete used cis system can be purchased on the Used Parts forum for a very reasonable price, along with any other parts that were burned. Test the injectors with a set of gages to make sure they open at the correct pressure and have a good pattern with out leaking. Flush the fuel tank, new filters, replace old hoses, check vapor recovery system, replace old ignition components and wires, valve adjust and cylinder stud check. Fresh oil. No mouse nests on the engine.
Also make sure the brakes and tires are in good order. Old rubber lines can look good externally, but be deteriorating internally. No point in a running engine if it can't stop. Of course having safety equipment like a fire extinguisher, eye protection, and a first aid kit is always important. And start the car outside away from the garage and house.
Hopefully the next story we will get to read is how the car was returned to good running condition.

Thanks for your reply Ed,
The injectors, the plastic sleeves, and the orings are new. Virtually any type of retainer would be better than what it there now. It is such a simple thing. Why is it that no one has created some sort of hold down for these things? All of the later electronic injection systems use bolts to hold the injectors and rails down. The early mechanical systems screw into the heads!

It is a really weak link in the safety chain. Especially when dealing with volatile fuels. If the back fire had been forced to vent out the airbox, it would not have caused such a fire. Plus, the force would have mostly been stopped by the throttle plate.

I'm just amazed that for as long as these cars have had this problem, no one has fessed up to the real nature of it and corrected it. I build aircraft on the side, and this kind of thing would be entirely unacceptable in that arena, where you often do not get even ONE mistake! Yes! You must be right every time! Especially with fuels.

Oddly enough, I have seen K Jet on aircraft in the past. But only once.

Ed

[E Sully]

The best way to have minimized this would have been to shut off the ignition switch right away, and have a fire extinguisher on hand.
Even a carburated engine can have a fire similar to this if excess fuel due to a stuck float caused the back-fire. The problem isn't with the injector holder, but the electric fuel pump.
Could the design have been built safer? Sure, the earlier fuel systems did not have anything to stop the fuel pump from running with the ignition switch on, unlike later models. When properly installed it takes a lot of force to blow an injector out of the holder. If it had a retaining clip, perhaps the fire would have taken a different path, but after the back-fire it still would have kept burning till the fuel and or oxygen source was cut off. The air box and filter would have probably caught fire, injection lines would then melt and spray fuel.

Yes, aircraft like my brothers have multiple redundant safety features. It is neccesary because unlike a car you can't just pull onto the shoulder, kill the ignition and get out to put out the fire. But even with all the safety features, things still fail in aircraft with even worse consequences.

The bottom line is the best way to keep safe is to make sure components are tested before they are put in service, especialy when this old, and have the proper safety equipment. The main culprit here was an old injection system that could have been checked over in a more thorough manner considering it's age.

[racer_X]

Wow, it sounds like it could have been way worse. I know it is hard to remember to shut the fuel pump off in the heat of the moment.

I keep a class B fire extinguisher in the car at all times when driving and out of the car when I am working on it. I had a close call with a lose blow off valve.

Do you call 911 for a fire or is it you need a 911 for a fire?

[edc153]

I will be lobbying for the install of a main battery cut off near the decklid. Aircraft have them, as well race cars. I had to disconnect the battery with a wrench to get the pump to shut off. Very disappointing. The key did not do the job!!!?

Ed

[boyt911sc]

Originally Posted by edc153

I will be lobbying for the install of a main battery cut off near the decklid. Aircraft have them, as well race cars. I had to disconnect the battery with a wrench to get the pump to shut off. Very disappointing. The key did not do the job!!!?

Ed

Ed,

Understand what caused the problem/s. Instituting other preventive measures is a good idea if you know and understand the root cause of the fire incident. The dislodged injectors spraying fuel caused the fire. But what caused the injector/s to pop-out from its mounting? A very lean condition could have contributed to the back firing or an improperly mounted injector/s could be the reason. Whatever caused it could be debated for a long time.

If I were do another start-up for this engine, I would consider the following:
1). Install a pop-off valve. This would entail probably a $30 investment.
2). Check for vacuum/air leaks. Pressurize the system with low pressure air. This test takes only a couple of minutes to do. Do not guess.
3). Do a fuel pressure test for several minutes and inspect. Make certain that the fuel delivery system is leak-free.

Then proceed to do another start-up run. Good luck and keep us posted.

Tony

[azasadny]

This is one of the reasons I converted my '74 911 2.7L CIS to Weber carbs. Lower pressure in the fuel lines = less risk of leaks and fires...

[E Sully]

You seem to have a faulty electrical system if the key did not shut off the pump, as well as the starter issue and possible wiring issues in the engine compartment from the fire. The air box most likely is damaged from the backfire at this point. As I posted above, all the parts can be had for a reasonable price in the Used Parts Forum. Complete cis systems are commonly sold by people switching to carbs or parting cars. I have been able to get almost everything I needed for my 1973.5 cis by patiently searching. I even have a complete back up cis which cost less than $200. I wish you and the owner a lot of luck with the car. I would definitely suggest going through the checks listed in this thread.
Resurrect 73.5T after 10 yrs of storage - Need Your Help with laundry list

[GradyM]

+1 on the electrical not shutting off the fuel supply.When is a fuel pump ever supposed to run in normal service without the ignition in On position.

[edc153]

A burnt wire somewhere caused the ignition to stay on. Now when I connect the battery, the ignition turns on and the back up lights come on. Gotta do some wire repair.

The owner badly wanted to start his car, but consistent starter problems meant he did not want to pay for a starter again before hearing it run, so we pushed it. I think the starter had been rebuilt too many times. It never wanted to work well under load even after a new battery and cleaned up cable terminals. I replaced the tranny ground strap with a new one as well.

The fellow simply does'nt have the funds to do Webbers, or a much cheaper megasquirt sys. So I could'nt talk him into it.
There is no visible damage to the airbox internally.

I'm just amazed that for as long as these cars have had this problem, no one has fessed up to the real nature of it and corrected it. I build aircraft on the side, and this kind of thing would be entirely unacceptable in that arena, where you often do not get even ONE mistake! Yes! You must be right every time! Especially with fuels.

Ed