MFI hose goes where?....

[Flying Toaster]

This weekend, I removed the air cleaner shroud to find yet another hose missing from the Injector pump. In the picture below, the arrow is pointing to where there is a hose missing from the pump. Where is it supposed to go? As it is, the PO must have run the car for some time this way as there is quite a bit of grime in the pump holes. (is there any maintenace / cleaning I should do?)
I posted a topic recently about the hose that runs down to the exchanger (hence the red check marks showing its supposed path) Thanks for those who answered that question for me.

My last question is, can I remove the piece that is marked with the red X? My car seems to start & run fine without the hose running from the air cleaner to this "restrictive" component. I dont plan on running the car in the winter. TIA for any help or advice, so far everyones responses have been very helpful in other areas that I am learning in. -John

[Zeke]

Well, you got the small hose part right. Make sure the bottom part under the engine time is there and hooked up. As for the other gizmo, you should be fine w/o it. I'm not an expert and my '71 is a bit different as the snorkel goes to the right and gets it's hot air from the heater box.

The ones I see with the short snorkel like yours have nothing else. Your deal looks to supply warm air for idling. It's a smog thing.

[Rot 911]

Zeke gave you some good info. You are missing a very important hose to you warm up thermostat. I am surprised you car is running very well. You need the hose that runs between the two check marks. Now get under the car and look for the hose that should be running from the sheet metal under the lower check mark hose fitting to another hose fitting at the front of the heat exchanger housing towards the front of the car.

[Flying Toaster]

I do appear to have the lower hose intact. I am however about to remove the exchangers in place of a set of headers (great price, couldnt refuse). What have others done in the past to protect the MFI pump after removing the exchangers?

Where does the hose go that the arrow is pointing two. i didnt even notice it missing until after I pulled the air cleaner box.

[DonDavis]

My car is running kind of crappy and this past weekend I took off the warmup thermostat, disassembled, cleaned and put it back on. Made some other adjustments and it runs much better. Wonder if your car would run even better than now if you do the same. There are a bunch of discs inside and you need to keep them together. It's really easy to do.

BTW, if you do go with the headers, I would be interested in your old heat exchangers.

PM me with details, Please. Thanks and good luck.

[Early_S_Man]

John,

Best to check that large 6-ply reinforced hose for obstructions, and be certain hot air is getting to the thermostat housing when you install the missing hose at the check marks.

There is no hose attached to the thermostat outlet port you marked with the arrow. The hot air is vented into the engine compartment, though I have wondered about running a hose outside ...

Be sure to download all 23 MB of documents on this Pelican page, print them out, and put in a special MFI binder:

http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

Did the previous owner plug or tape [aluminum tape from a heating/air conditioning supply store works well] up the hole in the sheet metal where the 2" hose to the intake flapper valve hose passes through -- the large hose missing from your 'X' device you want to remove??? it is very important not to have any misc holes that hot air from surrounding the muffler can be drawn through up into the engine compartment!

[Grady Clay]

John wrote [edited],

Hi Grady. Sorry to bother you. I recently picked up my first 911 & it is equipped with a 2.4L MFI engine. I am worried about how to maintain this unit. I KNOW the previous owner did nothing with the car as far as maintenance. Can you recommend a website or a forum thread that would supply me with info on the MFI system & how to clean/maintain it? As it is, I am missing two hoses that run off the front of the MFI unit. Keep in mind, I know nothing about the MFI unit & how it functions. My first priority is to make sure it continues to work properly & stays clean/lubricated. Thank you for any advice or help. -John C


Grady wrote [edited]

The Pelican Forum is the best place I have found. Do some careful searching using "MFI" and "CMA". There is lots of stuff, most good. You should download CMA manual. I recommend you start yourself a personal car-specific service-workshop-parts manual. Copy the Factory manual parts and relevant parts of all the commercial books. A loose-leaf binder will do just fine. With a photocopier, scanner, camera, etc. you can make yourself an invaluable personal information tool.

MFI system is a mechanical computer - sort of like the WWII Norton Bomb Sight. It also includes much more than what most consider the "Injection" - everything has to be working at top form for the engine to run properly. That includes compression, ignition, cam timing, etc. even the condition of the engine oil and air filter is important.

I think I saw your thread yesterday where there wasn't any heat hose going to the thermostat. Check your oil for dilution with fuel. I'll post on your thread. Best, Grady

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John,

Once you get the thermostat hot air hose working properly, that may significantly lean out the mixture. You can get the thermostat hot with a hair dryer as a test. The engine may go to running very poorly, dying at idle, popping, etc. Someone may have leaned the main mixture as an attempt to compensate for the thermostat not shutting off. If there is no change in the running of the engine, someone may have disabled the thermostat. In any case you should change oil immediately. If the engine was always running very rich there is the possibility of serious dilution of the oil with gasoline.

What type engine (T, E, S)? What year?
How does it start cold?
How does it run when cold?
How does it run when hot?

Best,
Grady

[Flying Toaster]

Originally posted by Grady Clay
What type engine (T, E, S)? What year?
How does it start cold?
How does it run when cold?
How does it run when hot?

The engine is a 2.4L T out of a '73. It seems to start fine with a slight touch of the gas pedal while cranking for no more than 2 seconds. It runs ok. After it fires up it runs rough for no more than 4-5 seconds, then smooths out. When its hot it idles smoothly as well. I did notice that it ALWAYS seems to run rich. I havent had the car long enough to diagnose beyond what little I've mentioned above. When I test drove the car, it did exactly as I mentioned above. I havent driven it since as I found som many other problems once getting it home that required immediate attention (i.e. burnt fuse panel, leaking gas tank, leaky fuel lines in the front, etc....)
When you say "change the oil, your referring to the 12 quarts of engine oil correct? I assume there isnt a separate reservoir of oil for the MFI pump?
In the meantime, I will try & read up on the MFI info PP has listed as I am not sure where the "thermostat" that others have mentioned is located.
Thanks again, its greatly appreciated. -John

[Grady Clay]

John,

Yes, change all the engine oil. When the MFI is running too rich, it still performs OK. In cold, cool weather or if just not warmed up fully each time, it will dilute the oil with gasoline. Because the oil/gas mixture in thinner than just the oil, it will be consumed by the engine at a faster rate with the mixture being replaced with just fuel. It can become so diluted that it is almost pure gasoline. In this condition, one trip up to temperature can evaporate all the gas leaving nothing in the oil tank. Of course the cams, bearings, etc. don’t take kindly to poor lubrication. A common symptom is that the engine appears not to use any oil or is constantly over full of “oil”.

BTW, this is a common problem in little shops and body shops if they drive your 911 in, out, and around daily for many days without it ever being warmed up.

The MFI pump holds about 0.5 liter of engine oil that is supplied via a small pressure hose from a banjo fitting under the oil pressure sender on top of the engine. It is an “overflow” system where there is a constant small flow of oil into the pump and is returned to the engine via a hose to a pipe on the breather.

The MFI thermostat is the cylindrical device with tubular openings, in your first image. It is between the check and arrow. It is the part that is missing the hot air hoses.

See if you can find some local Pelicans to help you look over the 911 and prioritize your projects.

Best,
Grady