911sc Auxiliary Air Regulator full of petrol

[DoMeister]

Hi all, first post!

I’m an avid reader of this great forum, now I’m jumping in…

I’m starting an engine rebuild project on a 911 SC 1982 targa. Engine is up on the stand and I’m in the teardown process. First thing I came across today was when I took the air hoses off the back of the airbox I noticed some petrol lying in the houses. Moving on to the auxiliary air regulator, when I remove that and turned it upsidedown a good half a cup of petrol poured out of it!

Two questions I guess, the first question is will I be able to use it again, I see there is a electrical connection, with all of this petrol inside the regulator is it now damaged beyond repair?

Second question, what should I be looking out for as the root cause for this? I noticed when removing the air hose to the right of the airbox where the connector is red into the hose at the flap connection, the airbox above this is badly damaged. I will need to replace the airbox and suspect that was the root cause of the problem but honestly not sure.

Thanks everyone for your input
Dom

[Walt Fricke]

Dom - petrol not a good sign, as you recognize. Some pictures would be helpful, as not everyone uses the same terms for the bits and pieces.

The thing with an electrical connection I tend to call the auxiliary air slide - the thing you bench test by looking through it at room temperature, and after applying power to its heater, then putting in a freezer for a while and looking again to see if moves from open to closed and back again. I am dubious that the heater would ignite petrol, but best not to test that, and it shouldn't be there anyway.

A bit hard to see how petrol from the air box would get into the air plumbing. The cold start valve would be about the only source unless you have an intake valve which doesn't close, so compression could cause the continuously injected petrol to move backward?

Does the thermo-time switch, which controls to an extent the cold start valve, work as it should?

Did (or can you) you do a leakdown test on each cylinder? Or just do a compression test (might be hard to do on the engine stand, though).

[DoMeister]

Walt, thanks for the reply

I agree there are many terms for the same things which adds even more complexity. I referred to the throttle body as flap connection from reading the PET.

I’ve added some pics of the auxiliary air regulator and PET diagram. Thanks for the tip on how to test it. I will test using the freezer tomorrow.

The cold start valve which I guess is the warm up valve in the PET has 2 fuel lines to the K-jet head and 2 vacuum hoses but I can’t see how fuel would transfer to the auxiliary air regulator?

A tip on how to test the warm up valve off the engine would also be great

So where the air flow hose meets the throttle body (red) there were signs of fuel. Directly above the throttle body there is damage to the air box. Could that be causing fuel to back through hose#63 and the through #46 and into the AAR being the lowest point?

Thanks Dom

[boyt911sc]

Dom,

You get oil in Auxiliary Air Regulator (AAR) due to excessive oil in the crankcase. Your CIS air box could have also some oil deposits too. Check the crankcase breather hose going to the oil tank. I have seen AAR’s with oil deposits inside them and that is not normal.

Tony

[DoMeister]

Tony,
How does oil get into the AAR?
Could it be fumes from oil burning on the outside of the case or through the inlet pipes? What would cause it to come through the inlets?

My half cup of petrol in the AAR finished black indicating oil but I didn’t get the full 13 litres out of the engine when I drained the oil. Too many leaks...

Thanks this all helps
Dom

[pmax]

Welcome.

Oil in the intake Is usually due to an overfill and the AAR is down low with tubes going to it from the air box. Gas, the only scenario I can think of is from the CSV leaking into the intake ‘claw’ the bunch of tubes behind the air box.

Might wanna post in the tech forum as well, this topic being better suited over there since I don’t think an engine rebuild is in the works for you, thankfully!

[Walt Fricke]

Dom - parts listed as 63 and 32 should have petrol (gasoline) in them, as they are part of the cold start valve system, which sprays a bit of fuel into the airbox when the starter is engaged on a cold engine.

Does petrol include both gasoline and lubricating oil?

Part 47 (AAR) can get oil into it via part 47's connection the the big air boot 18. Because the oil tank is vented into the boot, and if the oil is overfilled for the cornering loads you induce driving (racing, for instance, sloshes the oil around a lot more than ordinary driving), some of it gets into the intake. Porsche preferred some oil in the intake to having it dribble out onto the ground, which happened with the 2.7s system. Not apt to be a problem to have a film of oil in the AAR.

But a half cup of any fluid in the AAR is way off the charts - something is badly wrong there, but at least it is oil.

What you call the cold start valve isn't - it is the warmup regulator or WUR, also known as the control pressure regulator. The two vacuum type lines are not fuel lines, and ought not to have any fuel (or even oil traces) in them. The lower one applies vacuum to the WUR lower chamber, and the upper one - I am pretty sure, for a ROW '82 SC, just provides filtered atmospheric air to the upper chambeer. The two WUR fuel lines (51 & 61) could only let fuel get into the upper vacuum type hose if the pressure setting diaphragm were ruptured, in which case one might expect the engine wouldn't run, as the control pressures would be way way too low, and the mixture way too rich to ignite.

So be careful about terms - there is the WUR, which controls the fuel counter pressure in the fuel distributor, and thus the air/fuel ratio of the fuel injected into the intake ports, and the cold start valve - which gives an extra squirt of fuel into the distribution manifold (air box underside) when the engine is being started cold. Not the same at all.

To test the WUR you need the fuel pump connected, and a gauge and some plumbing. But it doesn't leak fuel (or oil). There are scads of posts (many on the general 911 forum) on how to test a WUR, how it works, what to do, etc.

The cold start valve is controlled in a couple of ways - it only gets power when the starter is engaged, and then only when the thermo-time switch (upper left corner of the left hand chain box cover) is cold. The TTS has an internal heater - when electrical power is applied it heats up a bimetal strip, which opens. When that is open, the CSV doesn't squirt. When the engine is hot, the same strip is open, so no extra fuel.

You test the TTS by figuring out its circuitry, and testing to see if a) it is open or closed when it should be - an ohmmeter or just a test light or buzzer or other continuity tester. And b) checking the resistance of the heater coil - should be some small number of ohms if good, and an open circuit if the coil is broken.

You might find it helpful to describe how the engine ran before you removed it from the car. If it ran fine, all that might have been wrong was a substantial overfill of oil at some point. Easiest thing for a new 911 owner to do is to check the oil level with the engine cold after sitting overnight, get alarmed, and add enough quarts to bring the level on the stick up to snuff - not realizing that that amount of oil had simply leaked into the engine sump - which is normal.

If it was hard to start, or wouldn't start, or ran poorly, those would be other issues.

Why is it out of the car?

[DoMeister]

Walt,

Thanks for all that information, it’s really helpful and helps me track down root causes.

I’ll give some context on the engine but don’t laugh! And then I’ll give you my findings on the AAR.

The engine is out for a full gasket replacement, today I found a broken head stud and tomorrow I will check the rest to see what the state of play is. Down the hole I go…

I recently bought the car as an unfinished project. To say it was unloved is an understatement. Lots to do replacing full brake system and lines and pretty much everything else, tackling rust, you name it!

The car wasn’t running when I bought it and the previous owner said that he thought it was related to the CIS head. When I took the fuel tank out to have a look it was full of sludge/oil and damaged underneath so I just decided to replace it and therefore replacing fuel pump fuel lines fuel filter made sense, that should then bring me to the airbox, C.I.S. head and fuel injection/air system.

When I saw the state of the AAR I thought that couldn’t be right and if that is the case then there’s a problem somewhere that has created this puddle in the AAR. I’m contemplating a rebuild kit for the C.I.S. head, I think at the moment the WUR is okay but when I get the system back together I’ll be better able to test it. I’m on the hunt for a replacement ROW airbox, the one I have is just falling apart and has been stuck together with silicone!

Results for the AAR, there is some movement in the gate although I thought it would be more but the again my temp test is probably only in the mid range. First picture is room temperature on spring day in Ireland so not that hot, second picture is after being in the freezer for 60 minutes.

Any thoughts, it appears to be working but is it working well enough? Can the electrical connection be tested? I guess it’s sending a signal to something base on the reading of the AAR?

Thanks
Dom

[DoMeister]

Pmax/ Walt
I honestly didn’t know what a CSV was. I’m going to spend a bit more time looking at this in more detail. eBay is always a good source of information for photographs and when I saw the CSV and the blue connector I now know where this valve is located.

Interestingly when I dropped the engine and began the teardown that blue connector was not connected! So with no power to it I’m guessing it had no function, have we just found the cause of the puddle in the AAR? ��

[Walt Fricke]

I figured you hadn't yet become conversant with how CIS works in some detail, and what the many and varied parts do. Your car has parts I don't have memorized, as it is the last US model. Other parts are the same, or at least similar.

There are a variety of Bosch and other manuals for the CIS available on line - they are very helpful with most basic function questions. Less so as, say, a how to on fuel distributor disassembly and reassembly. But at least you learn the functions. The two halves of the FD are separated by a thin stainless steel (I think it is stainless) plate or diaphragm. Most of the holes in it are obvious - for bolts, or for the central fuel control plunger assembly. However, it has one very small hole, which one might even overlook. The otherwise pretty symmetrical diaphragm can only be installed with that tiny hole in one position, as it is critical in the control pressure system. Lots to figure out, but it isn't like understanding quantum mechanics.

You can get, on line, a wiring diagram. The AAR circuitry is, I believe, the same from at least '77 through '83. Its resistance heater, and the resistance heater inside the WUR, are both on the same circuit, and controlled by the fuel pump relay - they should receive 12V whenever the fuel pump is running. You can check the heater in both with an ohmmeter or continuity tester - an open circuit seems the most likely failure.

That AAR isn't working right - putting it in the freezer should open it all the way up, if I recall the test I once did. I don't know what temperature closes it all the way, but I suspect it is well above room temperature - the engine operates at 190-210 degrees F, and a room temperature engine is basically cold. Hook up 12 volts to the AAR, and watch what it does. Won't hurt it. The moving part can get sticky, and can be cleaned.

The WUR can be pretty easily opened and inspected. When open, apply 12V to the heater element, and observe how the bimetal arm moves. (my memory of how hard it is to open the AAR is dim, but most of this stuff can be opened up).

These heaters, by the way, don't care about polarity - two electrical prongs, either can be plus or minus. And good to check the car's wiring. With the engine out of the car, unless you have pulled the relay or something, if you turn the ignition switch to on, the fuel pump should run - which you probably don't want - never good to run it dry, and you don't want to pump fuel. But you can figure out a way to see if you have continuity from the fuel pump relay to the plugs which go into the AAR and WUR heaters. However, chances of the wires being bad aren't awfully high unless the previous owner busied himself with cutting up wiring. Not connecting them, that's an other matter. Somewhere you can find some kind of specs on the AAR, even pictures of it as far open as it should get when cold, and of it shut when hot. Am I right that your pictures show almost no movement?

Opening the fuel distributor isn't all that hard. Putting it back together so it doesn't leak is trickier - I've failed twice, but others have succeeded, and thankfully there are aftermarket repair kits. If you Google around you can find ugly looking pictures of crud in these, and others where they look fine. The most straight forward way to deal with the FD is to test its function without taking it apart, but that calls for a test rig. If the engine were in the car, where you have a working fuel supply system, you can pull the injectors and squirt them into bottles, observing gross deviations in the flow patterns and whatnot. Making your own bench test rig is possible, but a fair amount of what probably is one time work. If you lived in the US, you'd be referred to Tony for a rebuild, but the pond complicates the financial and time part of that. Maybe someone in GB does this kind of stuff?

I'd start searching CIS repair, and similar subjects. You will find Jim's Garage, which is a site with a lot of documentary and diagram resources. And here lots of information - did you search for AAR, for instance, or AAR stuck or AAR test? Lots of good information, and not a whole lot which is wrong.

[Walt Fricke]

Oh - the AAR and WUR don't send electrical signals to anything. They are valves, if you will, not sensors. The WUR does control the control pressure at the FD, but that is hydraulic. The thermo-time sensor does send a sort of signal - it either keeps a circuit closed (current flowing), or open - it is a switch, and keeps the CSV from flooding the engine.