MFI, 1972 warm-up issues (combined)

[wahoofan]

OK - I'm about to take the thing off (I'm assuming it is the mfi thermostat?) , but 2 questions. What do I clean it with, and is there supposed to be a hose connected to the underside off the thing(thermostat?)?

[jstobo]

The idle on a MFI engine is adjusted with the air screws below each stack. You need an air sync. tool to do it right. If you have use the screw at the microswitch to adjust your idle, you have messed up the shutoff solenoid and rpm transducer circuit. If you are idling at 500 rpm when warm you need to adjust the air screws. If no effect, spray with Chemtool B-12(I get mine at walmart). I never had to use the mixture screw to adjust the idle. Also, your hand throttle has a plastic arm that slips over the throttle cable. If the hand throttle isn't working either it has slipped off or broke. New ones are available from Stoddards.

[wahoofan]

Here's what it currently looks like

[Grady Clay]

So long as you are patient and don’t have 10 thumbs – you can do this. Slow is good. No one will do it as patently as you. Most don’t want to pay $100/hr for an expert to go slowly. If nothing else, you gain the knowledge and experience to properly communicate with the pros (if you can find one).



This above is well intentioned and knowledgeable advice from good guys. Stop, don’t do anything. Your 911 is running, abet with a few hiccups, just change the oil, go drive and leave it alone – for now.

The slippery slope you could go down is as follows: You clean the grime out of the thermostat (the device that Milt is talking about) and get it working properly. Now the engine hardly runs at all. You then think the plugs were fowled from the dirty thermostat and do a tune-up on the ignition system uncovering some “while you are there” issue. And so on with the engine not running well. All the time it turns out that the PO had adjusted the main mixture to compensate for the dirty thermostat. There are many possible scenarios but they lead to the same result – you get lost in the system. Many professional mechanics have been bit by this also.

What to do?

Porsche developed a system for addressing MFI; it is called Check, Measure, Adjust (CMA). The emphasis is on Check and Measure before you Adjust.

The original CMA covers this sequence:
Porsche lists the Check Sequence as:
1) Air cleaner cartridge
2) Compression loss
3) Spark plugs (spark plug connectors)
4) Dwell angle
5) Ignition timing
6) Fuel pressure and flow
7) Injection nozzles
8) Injection timing
9) Correlation
10) Exhaust emission test
a) at part load
b) at idle speed

You should study the CMA document and ask questions. It is designed for the professional mechanic who is already familiar with the system. CMA was written in about ’68 and assumes all the parts are new. While we have the benefit of 20-20 almost 40-year hindsight; none of the parts are new any longer. You are about to practice geriatric mechanic.

While CMA gives you most of the steps, it doesn’t tell you exactly how to do them. These few cryptic words are chapters in a 300 page book.

In fact it is so much more I call it CMA2. Following is an outline; 1 to 14. I’m going to address each one separately as an individual project. In practice there is considerable overlap. In chasing an elusive problem, you may go through the complete sequence many times.

CMA2
1) Research, read, ask, plan, and make your own personal notebook/workshop/parts manual. Collect tools and equipment or access to them. Know your starting point; check the oil sump & change the oil, go drive, measure the mileage, and take notes.

2) Air cleaner cartridge. Almost all is done with the air cleaner system in place as it will be used. Have an OE exhaust available. Make it easy to remove sump tank breather and fuel evaporative emissions hose.

3) Compression tests include both cranking compression and cylinder leak test.

4) Ignition: Spark plugs, spark plug connectors, wires, cap, rotor and general proper condition of the ignition system. Check electrical connections and grounds. Check distributor bearing, springs weights condition. Run distributor on tester. Dwell angle, points condition, condition of cam and lubricant. Ignition timing, proper advance curve, and vacuum operation. When complete and timing is set at 6000 RPM, note the timing at idle (with & without vacuum retard if applicable) and static timing.

5) Fuel pressure and flow, new fuel filter and clean the screen in the bottom of the fuel tank. Clean the tank if suspect.

6) Injection nozzles; inspect, test, clean, or replace.

7) Injection timing: If you need to adjust the MFI pump timing, use the opportunity to replace the Gilmer belt and both toothed pulleys. You can save the old ones as road spares. This is also an opportunity to replace the seals at the left cam and injection pump.

8) Camshaft timing and valve clearance. Use this opportunity to torque the cylinder head nuts and rocker arm shaft bolts.

9) Correlation and includes the condition of the throttle bodies. One of the important issues is that all the linkage moves off idle simultaneously. Check air flow at idle and just off idle for each cylinder.

10) Confirm the cold start solenoid doesn’t leak and turns on & off sharply.
Cold start thermo-time switch proper function.
’69-’71 cold start solenoid on MFI pump.

11) Over-run fuel shut-off checked for function. RPM transducer and microswitch.

12) The cold running thermostat must be clean, getting hot air, and functioning properly. When hot, it must be completely shut off.

13) Exhaust emission test; at part load, at idle speed.

14) Road testing, dyno testing and repeat entire sequence.


I’ll go through the sequence one step at a time and everyone can chime in and keep it on the straight and narrow.

For now, your mission is to gather information, change oil and go drive.
Pelican and some others are full of good archival material. Do some searching and download the relevant stuff. Start yourself a “Personal Car Specific Manual”
notebook.
Your first oil change on a dry sump 911 will be an enlightening experience – read up.
Aside from the fun, this driving has an actual purpose. You want to get everything “settled in” with highway and spirited driving. This is the only way to get good accurate compression and cylinder leak tests. You also want to carefully measure your fuel and oil consumption under controlled circumstances. Note the color inside the exhaust tip.


Don’t let this seem like it can overwhelm you. Mere mortals can do this.

Automotives 101:
An engine has three basic systems; air/fuel, electrical, and mechanical. For our purposes the air/fuel system can be divided as fuel supply, high pressure mechanical fuel injection, cold start/run enrichment, and air metering. The electrical can be divided as 12VDC supply, high voltage ignition, and low voltage control circuits. The mechanical system has three basic functions; power generation, power transmission and the necessaries. Power generation has to do with the sealing of the combustion process, getting the air/fuel into the combustion chamber, and getting the combustion products out. Power transmission gets the power to where you can use it and includes the piston, rod, bearings, crankshaft, etc. The necessaries let everything happen and include valve actuation, oil system, engine cooling, etc.

The bell rang – end of class.

Best,
Grady

EDIT for content (many times more I'm sure.)

[wahoofan]

Do any of these pics help?

[Grady Clay]

Why don’t we see if the Moderators can combine these two threads into one.

Best,
Grady

[Zeke]

No, there is not a hose that is supposed to be connected to the "bottom" side. That is the exit for the warm air from the heat exchanger under the engine. Though Grady is right, at least take a hair dryer to the thing after disconnecting the upper hose and see if it will move with heat applied. Don't worry, it is built to take heat, but you don't need to fry it to see if it works.

What this "themostat" does is expand and push the main rod in on the fuel mixture adjustment and lean the mixture out when things are at operating temps. So, the default mixture is for cold and is too rich for warmed-up operation. What is being suggested above is that someone may have adjusted the main, or part load, mixture for the best mixture with the thermostat frozen. This would make the idling very difficult when cold. Grady is saying that if this is the case and you fix the t-stat (assuming it IS frozen), then the car will run rough when warm.
Fix one problem only to have another is what he wants you to avoid. You can still test the thing w/o doing any cleaning, removal or adjustment.

The 500 rpm thing may very well be a different set of issues. Again, that's why Grady wants you to familiarize yourself with all the perameters. It's not complicated in the sense of electronics and sending units, but it can be daunting to work on MFI for the first time.

The bottom line here is, it isn't that easy to find someone who is all that good on MFI and you may throw away some more money. Better to take baby steps and report back here.

God, am I becoming some kind of MFI expert? I don't think so, but I have been throught the CMA steps and see the realtionships of the components.

Get the hair dryer out and let us know. At least look at thediscs inside the housing for dirt and corrosion. Report your findings. These threads serve to help many others in the future, so even if this is repetitious, it is beneficial as each case takes a slight different perspective. Even if it all boils down to the same thing. Stay with us here and we'll stay with you.

[Zeke]

Originally posted by Grady Clay
Why don’t we see if the Moderators can combine these two threads into one.

Best,
Grady

I 2nd that. Just shoot a message to them.

[wahoofan]

Wow, you guys are a true fountain of knowledge!! Unfortunately, I took the t-stat apart before I read grady's post, but it didn't seem to be too dirty. Also, since Zeke warned me not to scramble the discs, of course I dropped about 10 of them on the ground!! I don't have 10 thumbs, but I seem to have at least 5 or 6 I tried to put them back to match the others, but the last four don't have the little bevels and are all different thicknesses. Will this make a difference?

[Zeke]

Well, now you can do a search because I remember a thread from recent that had all the info you'd ever want to know about the discs. You will get that back together in short order. Not to worry.

I'm surprised that it wasn't real dirty and malfunctioning. I would have bet the house on it. Goes to show you what I know.

BTW, we have a small chain of restaurants here in SoCal, especially in Orange County, called Wahoo's Fish Taco. Excellent food. Just thought I'd pass that along because of your screen name.

[wahoofan]

OK - I put it all back together and she runs exactly as she did before, so nothing fixed but no harm done!! That doesn't mean the t-stat is working right, just that it's not dirty.

BTW, I'm a huge Cleveland Indians fan, and their very politically incorrect mascot is Chief Wahoo, hence the screenname

[wahoofan]

Jeff Higgins Is the warm up solenoid still in place and operational?


Where is it and how do I know if it is working?

[targa911S]

Wahoo..you are getting some of the best free info on the planet from guys who really know this stuff. PAY ATTENTION! You are on the right track. Now you CAN put a Home Depot washer / spacer in there and it will lean it out more. Being that it never gets less than 40 degrees here, mine ran rich all the time like yours, until it got to opps temp. I added another spcer on a tip from a P wrench friend and viola! No probs. Now it may get a little colder in Canton Ohio than 40 degrees, so think about it if you are going to be driving it in "normal" Ohio temps. Not like it has been the last few weeks. That alone may be giving your car fits as it is just is not use to that kind of temp. Also are your cold start injectors shutting off? just a thought. Now I will give you back to the guys who REALLY know about this stuff. Just my .02

[Grady Clay]

CMA2 – Step 1)
1) Research, read, ask, plan, and make your own personal notebook/workshop/parts manual. Collect tools and equipment or access to them. Know your starting point; check the oil sump & change the oil, go drive, measure the mileage, and take notes.


Information gathering: Here are some links:

Check Measure Adjust (CMA)
http://www.scatliff.mb.ca/pelican/MFI_Check_Measure_Adjust.pdf

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

“MFI thermostat spacers”
p. 1 end has CMA extension, p. 3 has nozzle, fuel flow, and fuel pressure.
MFI thermostat spacers

“More Fun with MFI and LM1”
How to use protractors for correlation.
More fun with MFI and LM-1

“More MFI”
More MFI

“MFI Problems”
MFI Problems

“MFI Speed Switch”
MFI Fuel Shut off solenoid questions

MFI tools
MFI tools for DIY'er

“MFI electrical”
A different MFI thread - electrical

“'72 Hose from engine tin to MFI WUR - what material?”
http://forums.pelicanparts.com/porsche-911-technical-forum/201734-72-hose-engine-tin-mfi-wur-what-material.html#post1715584

trouble shooting “Grady/ Sherman(72 Guys) Ok now what?”
http://forums.pelicanparts.com/porsche-911-technical-forum/203301-grady-sherman-72-guys-ok-now-what-post1729700.html#post1729700

“Mechanical Fuel Injection” site with OK stuff:
http://www.my930.com/MFI/TipMFI.htm
“What is a complete MFI system worth?” Good stuff on the differences and what is necessary to convert to MFI. Whats a complete MFI system worth.
“MFI Size Chart”
MFI Induction Chart

Early_S_Man posted this” Here are several threads on the subject ...
Changes in Pelican's server have invalidated several links ... I suppose I need to go back and chart all of them, then edit and revise the links ...
Several people posted multiple threads on one problem, and that unnecessarily complicated keeping track of the various threads!
http://forums.pelicanparts.com/show...ght=mfi+warning
http://forums.pelicanparts.com/show...fi+speed+switch
http://forums.pelicanparts.com/show...=rpm+transducer
http://forums.pelicanparts.com/show...&threadid=78685
http://forums.pelicanparts.com/show...mfi+speed+relay
http://forums.pelicanparts.com/show...tch+replacement
Good luck! Warren Hall
Good thread on fuel pump, filter, tank on Early S Forum
http://d240157.u39.zeonhost.com/forum/showthread.php?t=4147&page=1&pp=15

List of MFI rebuild/experts:
http://www.early911sregistry.org/Resource-MFI.html

“Any good MFI people out there” on EarlyS
Hot starting issues.
http://early911sregistry.org/forum/showthread.php?t=4355

The Search function is your best friend.


I can’t tell you how important I feel a Personal Car Specific Manual is to owning, maintaining, and passing to the next caretaker.

First is it fun to use for show-‘n-tell
It is very instructive to you in gathering and assembling all the history and knowledge in one place.
It serves as an incredible resource when tinkering.
It enhances the value of the car.
A copy is a life-long memento.


Some tools and equipment are absolutely necessary to work on MFI. Most can be “Of local manufacture” as Porsche euphemistically puts it. Some are only useful if they are Factory original. Many are available from our host. If you don’t find them at Pelican Parts, Baum is the next source. Some are still available through the PCNA parts system.

Tool sharing is a great solution. Have several MFI owners each own some of the tools and have group tune sessions. Several could get together and form a LLC that owns all the tools and equipment. The collection could be lent to a shop in return for its care and maintenance.

Of course there is satisfaction in having your own private factory tool collection on display.

I’ll work on a tool list.


Driving for long distance on the highway, spirited driving, and DE events are necessary to get really accurate cranking compression and cylinder leak measurements. It also puts a lot of fuel and energy through the engine – getting the cobwebs out, so to speak.

Knowing your starting point is very important. You want to document every symptom and condition. This helps in diagnosis and eventually in a successful outcome.
Record every change. Many times you will need to retreat a few steps. You need to know what you did and how much you adjusted.

Needless to say if there is debris in the sump, you are flogging a dead horse. You want to know that all the machinery is in good condition before you light into the MFI. Fresh oil is necessary regularly because one of the issues with MFI is diluting the oil with gasoline. Gasoline isn’t a good lubricant. If seriously diluted, the gas can evaporate leaving insufficient lubricating oil. In tuning, the gasoline vapors fool the exhaust gas readings.

Your highway mileage will be a good indication of the MFI mixture setting. You will be able to gain insight comparing highway mileage to normal commute mileage.

If your memory is like mine, note taking is indispensable.


Best,
Grady

[wahoofan]

I know this has been covered before, probably in response to one of my own posts, but I still have a concern or two. Here's the problem:

Car runs great when it is warm - seems smooth with lots of power and idles around 800-900......fuel odor when you stop at light if you've been on it hard, no strong fuel odor at idle.

When cold, car is a bear to get started and runs awful for 3-5 minutes. The car turns right over and catches right away, but it won't stay running unless you hold the pedal about halfway down. During this period of sputtering and clunking it will stall if you try to give it too much gas. Then suddenly, after a few minutes, it seems like it will catch and rev freely and smoothly and will idle at a real low rpm. Once it warms a little more idle will rise and the engine will run smoothly.

Now, here's the questions:

1) Am I hurting anything on the engine by forcing it to run so poorly in the cold with cold oil, etc.?

2) Since I won't be able to get into much hard-core analysis of the MFI 'til spring, is there any quick-fix or "smoking gun" to chase for this problem? I have already cleaned the thermostat and checked the hoses, new fuel filter, new oilfilter and change, new air filter, new plugs and wires, new cap/rotor/points, new battery.

Thanks to all for the help - despite some drivability issues, I LOVE this car and can't wait for Spring!

[SandyI]

The MFI system in my 911E runs rough for the first 3-5 minutes when it's cold. That's perfectly normal.

Are you using the hand throttle between the seats on start-up? It should be in its full up position and then you don't use the gas pedal at all to start the car.

[wahoofan]

Sorry, forgot to add that hand throttle came disconnected and I haven't had a chance to hook it back up yet!

[Spud]

That's contributing to the problem. You need the hand throttle to hold the pedal down for you, trying to do it without the hand throttle is possibly making things seem to run rougher, since your foot is moving the pedal small amounts.

Get the hand throttle connected, if I recall correctly it should hold the idle at 3K RPM when pulled all the way up.

[304065]

Might be a slightly too rich mixture on startup, which is why giving it more air (opening throttle) helps.

When you change the oil is there gasoline in it? This will kill your engine if the gas evaporates, leaving the oil tank dry.

You say you've cleaned the thermostat. How many pairs of discs? Any spacers? Paper gasket at the end of the thermostat housing? This could be the problem.

[SandyI]

Fix the hand throttle. Your starting problems will be solved.

On a cold start up, the hand throttle fully up will keep your car idling at about 900-1100. Then in about three minutes, the car will begin to warm and the RPM's will head past 3,000. That's when you lower the hand throttle slightly and drive off, never revving past 4000 until the car's in the operating temp zone.