What is this?

In the Ferrari documentation, it is called an "electrovalve" (it is a solenoid operated pneumatic valve). That particular one controls the diverter valve of your air injection system. In the stock configuration, the hose that "rotted off" the fitting on the right side would be connected to the intake manifold (i.e., a vacuum source that varies with engine load); there is no hose on the left side fitting (i.e., it is connected/vented to the atmosphere). Try a search on "air injection electrovalve" for other threads.

The diverter valve "diverts" the air injection air to atmosphere when the engine is at low load (i.e., high manifold vacuum) and high RPM.

The red wire is always at +12V and the white wire is "controlled" by the special ECU under the passenger footwell (or I might have those colors reversed, but I'm not going to look it up ).

At low RPM (something like less than 4400 RPM IIRC), the white wire is not ground -- so the electrovalve is "off" which, pneumatically, connects the blue hose going to the diverter valve to the bare "atmosphere" port (and the port with the black hose is blocked closed) -- which leaves the diverter valve unactivated, and the air injection air is delivered to the check valves and on to the air injection nozzles.

At high RPM, the special ECU puts the white wire to ground, this turns the elctrovalve "on" and, pneumatically, connects the black hose to the blue hose going to the diverter valve (and blocks the bare port closed). If the engine is at low load (i.e., there is a high vacuum in the intake manifold), this high vacuum is conveyed to the diverter valve (via the blue hose), which "opens" the diverter valve and the pressurized air coming from the air injection pump is dumped to the atmosphere. If the engine is under heavy load (i.e., low vacuum in the intake manifold), the electrovalve still pneumatically connects the blue hose to the black hose, but since the vacuum level in the black hose is low, the diverter valve does not open and the pressurized air from the air injection pump is delivered to the check valves and on to the air injection nozzles.

In the diagram that I sent you in the other thread (http://ferrarichat.com/forum/showthread.php?t=193587), I used a constant high vacuum source for the black hose -- so in that non-stock configuration, the air injection air always gets "diverted" (to atmoshpere) at high RPM (regardless of engine load).

 

It connects to the tube on the underside of the airbox. After shutoff, the small rotary air pump draws the fuel vapors out of the airbox and pumps them into the charcoal canister.
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Yes, having this fitting "open" (to allow air in) could easily cause runability problems for that cylinder. As I indicated in the other post, the fitting on the #8 intake manifold should be connected to a completely "closed" system (the vacuum sphere that operates the flap on the airbox snout via an electrovalve) -- i.e., there should be no net airflow into the fitting on #8.
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No hose -- it is "connected" to the atmosphere

And here's the hose routing for the electrovalve controlling the airbox airflap (which is the opposite logic from the electrovalve controlling the diverter valve so it seems a little weird hose connection-wise -- i.e., a hose is placed on the metal fitting and one of the plastic fittings is left open to atmosphere). Of course, if you restore this system you need to make sure that:

1. the actuator + airflap mechanism works well -- i.e., vacuum applied to the actuator = closes the flap, and no vacuum = the flap moves to the fully open position (I had to clean and relube the pivot bearings on mine), and

2. the electrics running the electrovalve works -- when the key is "on" = the voltage between the two terminals on the electrovalve should be +12V. This actuates the electrovalve which connects the hose going to flap actuator to the open fitting vented to atmosphere -- i.e., no vacuum on actuator = flap open. When the key is "off" (and some vacuum is stored in the sphere from recent engine running) = the voltage between the two terminals on the electrovalve should be 0V. This de-actuates the electrovalve which connects the hose going to flap actuator to the hose connected to the sphere -- i.e., vacuum is present on actuator (at least for a while -- mine would hold vacuum for several days) = flap closed.
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+1

 

Geno -- let me respond to the text in your PM:

You must have made a small typo because you use "front bank of carb(s)" with the two different status descriptions for the small tubes (unless I misunderstand). The bottom line is that the small tubes on the intake manifold allow about 0.5 Kg/hr of air into each cylinder at idle if they are "open" (whereas the airflow entering the main choke of the carb at idle is on the order of 3~4 Kg/hr) -- so, if some of these small tubes were blocked, but they are now "open" (by being connected to the charcoal canister system), you would need to make a mixture adjustment (more than being resynced), but with such a bastardized prior situation, it certainly wouldn't hurt to check the airflow synchronization IMO. Also, if the fitting on cyl#8 was "open", that would've been letting a lot of (undesired) air into that cylinder #8. Consequently, you may need to increase the airflow a bit into all of the other cylinders to make up for the (correct) airflow reduction into cyl #8 (and hold the 1000 RPM idle speed). Additionally, if cyl #8 had a lot of extra air entering, it would also have a lot of extra fuel entering (if it was adjusted to actually run at idle) -- so it might need to be leaned out now.

If the fitting on the #8 cylinder is hooked up correctly, it is already "closed", so blocking this off directly should have no effect.

If you did block off all of the small tubes, you would have the same situation as described above, but in reverse -- if you block off the small tubes on cylinders where they were previously "open", the airflow entering the cylinder will be decreased by 0.5 Kg/hr at idle so that cylinder will be running richer than it was before. Generally, this direction (going richer) is more forgiving (i.e., a properly adjusted mixture made richer usually still works OK -- unless your cats catch on fire -- whereas, a properly adjusted mixture made leaner has running trouble), but you can make the same compensation by just opening the mixture screw a little on those cylinders where the small tubes have gone from closed to open. The usual "manual" method is to fully close the mixture screw (so the cylinder misses at idle) and then slowly open the mixture screw until the cylinder starts contributing again and then open it another 3/8~1/2 turn. Of course, this assumes that the airflow has already been properly synchronized (and your prior "condition" doesn't give me a lot of confidence yours was/is perfect ). Alternatively, as an experiment, you could just try opening the mixture screws another 1/2 turn on those cylinders where the small tubes have gone from closed to open and see if that has any effect on the runability (although the mixture screw on #8 may need to go "in" as described before).

The key to mucking with the mixture screws is to keep track of where they were so you can "go back", if necessary -- i.e., if you open some 1/2 turn, make note of which ones. Or, if you do the full blown adjustment of "fully closed and then open to run at idle + 1/2 turn", count (and note) the # of turns from the original position to the fully closed position -- that way you can always repeat the original position.

PS Does your airbox flap now function correctly?

 

Sure, generally -- a Weber DCNF is not an uber-exotic carb (and I'd be glad to email you a copy of the Haynes Weber Manual Chapter 13 covering the Weber DCNF that you could share with your friend if he already isn't familiar with them). Birdman wrote a good tutorial you should check out:

http://www.birdmanferrari.com/service/sync/carb_synch_tutorial.htm

If your friend has a Syncrometer, you should ask to borrow it.

 

I've never had this problem, but the great step-by-step advice with photos that have come out of this question are an example of why FChat is brilliant. I dare say this site can save thousands of dollars per year for even an average mechanic.

 

The diverter valve procedure in the WSM is to directly apply a vacuum onto the nipple on the diverter valve to make sure that the diaphragm doesn't leak (i.e., it will hold a certain vacuum level) and that the diverter valve opens at that vacuum level (i.e., if you blow into the port connected to the air pump, the air goes out to the atmosphere port rather than to the ports connected to the check valves) -- so it really isn't talking about how it is hooked up to the engine (i.e. this only checks the diverter valve operation itself). If the electrovalve is "bad", or, if the ECU in the passenger footwell isn't turning the electrovalve "on" at high RPM, these would also cause the diverter valve to not open at high RPM -- even if the diverter valve itself is OK.

My advice (for a test) would be to remove the large rubber air supply line from the air pump outlet and block the free end of this large rubber hose that goes to the diverter valve (i.e., the air pump air would always just be blowing air out the steel outlet tube into the atmosphere):

If the high RPM deceleration backfire goes away, then you should dig deeper and check:
1. the diverter valve itself per the WSM
2. confirm that the electrovalve works -- i.e., when no voltage is applied, port 1 is closed and port 2 is connected to port 3; when +12V is applied between the two terminals, port 1 is connected to port 2 and port 3 is closed:
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and
3. confirm the voltage between the two wires in the harness connected to the electrovalve is 0V below ~4400 RPM and is +12V above 4400 RPM.

If the high RPM deceleration backfire is still present, then I'd still be more suspicious of some sort of "leak" in the exhaust system (still including the air injection system hardware) or something else.

 

Agreed!!

 

Yes, but at whose expense?

 

The expense of those who we would pay to do something we otherwise wouldn't have the knowledge to do. It's our money, after all ...

 

Glad to hear that you are getting closer to "OK".

Please let us know what you find is messing up the diverter valve operation -- the "cork" is OK for a few days use, but it's not really a good long-term fix