Need MFI help or advice...PLEASE

[Shuie]

The car is with my wrench right now. Its been there for over a month and no progress. The guy is really good, but I honestly dont think he or anyone else has worked on MFI car around here for years. They are just not that common.

Heres a summary of the problems:
Very hard to start - It takes a long time of cranking, pumping the gas pedal, cursing, and whining to get it to start. I can smell fuel, so its really rich and probably real close to flooding if its not. Once its started, it idles with the handthrottle engaged.

Once the hand throttle is released and the RPMs drop below 2k, it dies. It will not idle at all when its warmed up and the hand throttle is down.

No restart after it dies until it cools off. It doesnt matter what I do, it will not restart until it cools down. If I try to start it when its warm, it backfires.

Things I know or have tried.
-Checked the airbox and filter, both are clean
-Disconnected the cold start solenoid, no impact
-Disconnected the idle circuit wire on the front of the MFI pump, no impact
-The Permatune is new

Something Ive noticed:
The tube that runs from the heat exchanger to the front of the pump (thermostat device that leans out the mixture once everything is warm) is not supplying any warm air even after the car has idled for a few minutes. Its connected and I did not see any obstructions or pinch points in the tub. I should be able to feel warm or hot air coming out of this thing right?

P-Thomas helped me check a few things when I first got the car. when the easy stuff didnt fix the problem, I brought it to my wrench since he is the pro and I didnt want to screw anything up.

Anybody have any thoughts? What about the tube going to front of the pump thermostat thats not supplying any hot air?

Thanks again guys!

[Tim Walsh]

Shuie,
A few things I've noticed when my car was running (last summer ).
1. ALL three hoses needed to hooked up to the MFI pump thermostat otherwise you won't create any movement of air (there is a hose that should connect to your airbox to pull the air)
2. Run through check measure adjust. There's no substitute for it. I would have wasted hours and hours on a bad engine if it wasn't for it. Start from the begining and work your way through without skipping anything. It turned out I had no compression on 1 cylinder which makes everything else mute.

[Luke Hudson]

Tim

When you say "(there is a hose that should connect to your airbox to pull the air)" where does this hose attach? Not sure If my car has this.

Luke

[Rot 911]

Originally posted by Shuie
Heres a summary of the problems:
Very hard to start - It takes a long time of cranking, pumping the gas pedal, cursing, and whining to get it to start. I can smell fuel, so its really rich and probably real close to flooding if its not. Once its started, it idles with the handthrottle engaged.

Quit pumping the gas pedal. Hold it down about 1" while starting

Once the hand throttle is released and the RPMs drop below 2k, it dies. It will not idle at all when its warmed up and the hand throttle is down.

Appears that the warm air thermostat is not working.

No restart after it dies until it cools off. It doesnt matter what I do, it will not restart until it cools down. If I try to start it when its warm, it backfires.

Again this may be the warm air thermostat problem.

Things I know or have tried.
-Checked the airbox and filter, both are clean
-Disconnected the cold start solenoid, no impact
-Disconnected the idle circuit wire on the front of the MFI pump, no impact
-The Permatune is new

Something Ive noticed:
The tube that runs from the heat exchanger to the front of the pump (thermostat device that leans out the mixture once everything is warm) is not supplying any warm air even after the car has idled for a few minutes. Its connected and I did not see any obstructions or pinch points in the tub. I should be able to feel warm or hot air coming out of this thing right?

Yes you should be feeling warm, if not hot air coming out of the pipe on the opposite side of the thermostat housing where the hose connects. At 2000 rpm you should really feel some hot air

Shuie, most people have no idea how the MFI works, even Porsche mechanics. When I got my '72E I read everything in the MFI Check, Measure and Adjust tech articles and then I went out and bought a Gunson Gas Tester for about $120.00 and became somewhat of my own expert. In the end you will do a much better job than your mechanic. But first I would address the warm air thermostat problem. I would also take apart the warm air thermostat and make sure that the disks inside are not stuck together. The Check, measure, adjust shows a picture of the disks. Take your time and make sure you keep them in the correct order. Give them a good spraying with brake cleaner or B-12 Chemtool.

[Shuie]

The lack of warm air being supplied to the t-stat was not noticed until right before I dropped the car off. I dont remember if I saw a hose from the air box that would pull the air from the heat exchanger through the t-stat. Anybody have a pic of this hose.

Im re-reading C-M-A right now and pricing gunson gas and compression testers. Compression was good when I did the PPI (128-135 on all 6 cylinders), so unless I lost it on the 700+ mile home it should still be OK. It wont hurt to check it though and the tester is cheap.

Thanks again guys! I appreciate the help.

[targa911S]

Listen to Kurt. He is 100% on the mark. If you are unsure that your wrench knows anything about MFI, DO NOT LET HIM TOUCH IT! He will get it so far out of whack it will take forever to get it back. if the car was running right to start with it is most likely something simple that he is overlooking. Reinstall all the wires to the sensors. When you clean out the thermostat washers, make sure you pay attention to how they came apart. There is an order to them. I mean don't even flip them over. There is a top an bottom to them and they are different. You do not have to remove the entire unit either. Just remove the two end screws and draw the washers out. Then clean them one at a time and stack them in order of removal on a screwdriver. When they are all clean, replace them on the thermo stick in the same order, the last one you cleaned first. Also check inside the termo itself for cr*p an clean with carb cleaner. Also check to see that the idle cut off switch is connected and working properly. Just my opinion ...but Permatunes are junk. Find a good used Bosch. I saw one on ebay yesterday, about $200. Also..and I know this sounds stupid, but, have you checked those ignition points and timing? Keep us posted.

[Shuie]

My wrench is great, he just hasnt messed with one of these in a while. He admitted it when I dropped the car off and didnt promise a quick turn around or anything. It will be done right, just dont know when. It will be done in my garage in the future, no question. Right now Ive got two cars that I cant drive and its killing me. I caught myself looking at a 914 the otherday

Ive got a Bosch CDI from my '73 I could use if the permatune is bad. When ignition points and timing came up on the check list, I decided to hand the car off. Honestly, I dont think I know how to check that stuff. The Bosch distributor, coil, and permatune were all bascially new according to the PPI.

Is there a guide or a walkthrough on how to check the points and the timing somewhere (I dont have my 101 or my haynes handy)?

Keep the suggestions coming.

Thanks again!

[Rot 911]

Schuie, you need to stay methodical and patient. Even though permatunes get a bad rap, most times they either work or they don't the fact that your car runs indicates the permatune is working. Here is what I would do first: Like Targa said, hook back up all the hoses and other connections. Clean and then set your points for .018 and your plug gap at .028. Next, pull off the thermostat housing and clean the disks as explained by me and Targa. Now, make sure the hose from the left side heat exchanger is connected at the exchanger and the thermostat. Next check to see if your cold start solenoid works. You can connect a hot lead to the solenoid and listen for a click or pull one of the cold start injection lines and look for gas to come out of the line. Be careful and don't set yourself on fire. If your cold start injection is separate lines to the MFI throttle body bases, be careful that you don't break those plastic fittings! If the injection is in the air cleaner housing just look to see if it is spraying gas. Once you have done all these things, see if you can get the car started. Once started, check to see if you have warm air coming out the exhaust side of the warm air thermostat. Report results back to us.

[Shuie]

Thanks Kurt! I'll try that.

[Zeke]

What if some bozo got the thermostat discs mixed up in the past. How would Shuie get them back in order? Is the correct order in the CMA?

To disable the cold start solenoid, remove the center fuse under the rear electrical cover. This is handy if you are starting to flood the engine while sorting things out.

Lastly, is the engine dying after hand throttle released and after warm up period due to over rich or too lean conditions. I'm just getting started with MFI systems, but the over rich could mean the eight second timer is stuck. I THINK the 8 second timer is by passed over 1300-1400 RPM and when the micro switch is open on the linkage which would rescue the motor from too much fuel. Can anyone verify this?

[Rot 911]

Originally posted by Zeke
What if some bozo got the thermostat discs mixed up in the past. How would Shuie get them back in order? Is the correct order in the CMA?

Yes there is a diagram.

[Paul Thomas]

Since it runs with the throttle open but wont idle when it is closed i would say that it is WAY rich. When you let off of the throttle it is choking on gas.

Do you have the MFI tools? The first thing i would do (just to get it to idle so, you can futhur diagnose the problem) is lean it out a click or 2 at a time until it will idle. Make sure and write down any and all adjustments you make so you can get back to square one if needed. Once it runs at idle, you can figure out why your thermostat isnt working. Even if the thermostat isnt working properly, i would still look elsewhere for the problem. It would be helpful if you can get someone to check the CO output to see just how rich it is. Hal Michaels car was right at 3 times the norm when we adjusted it.

The best thing you can do is become your own MFI expert. As you are aware, not many Porsche mechanics work on this stuff any more and the ones that learned it in school are gonna retire soon anyway.

Paul

[Shuie]

Milt, I removed the center fuse after disconnecting the lead to the cold start didnt work the first time. The car acted the same way.

The thing that really bugged me is that the PPI on this car was great. Everything was right and all the parts were there. After running one tank of gas through it on the way home it started dying and idling poorly. Halfway through the trip, it had to be pushstarted. I made the 2nd half of the trip with the handthrottle in place to keep the engine running while I refueled it.

When I get it back, Im going to start at the beginning of C-M-A and go through everything you all have suggetsed. Im really a newbie at this stuff, but I have a slightly better understanding of the system right now than I did last month when I put it in the shop.

[Rot 911]

Originally posted by P-THOMAS
Since it runs with the throttle open but wont idle when it is closed i would say that it is WAY rich. When you let off of the throttle it is choking on gas.

Do you have the MFI tools? The first thing i would do (just to get it to idle so, you can futhur diagnose the problem) is lean it out a click or 2 at a time until it will idle. Make sure and write down any and all adjustments you make so you can get back to square one if needed. Once it runs at idle, you can figure out why your thermostat isnt working.

Sorry Paul, but this is just bad advice! The last thing you want to do is start adjusting the main and idle circuits BEFORE you make sure your warm air thermostat is working. Keep in mind that the thermostat insures the mixture is RICH when the engine is cold. As the engine warms up the warm air thermostat disks expand and adjust a rod that LEANS the mixture out. The last thing any person new to MFI should do is start playing with the idle and main circuit screws!!!!!!!!

[tobluforu]

Is the rod that connects the rack to the pump the right length. If it is not, your car will not idle. Check all rods to make sure they are not binding. What about the idle adjustment screws (ports). Are they clogged? Don't forget the ports that the vucuum advance, retard connects to. Make sure these are not clogged as well. Check the rod length!

[Grady Clay]

Shuie,
Kurt, Zeke, and Targa911S are giving you great advice and you are right on in approaching the problem from CMA. First order of business is to measure cylinder leakage and cranking compression. Next is proper ignition function, followed with measuring fuel pressure and fuel flow quantity.

Some thoughts;
You said the problem developed after the first tank and you were on the road driving the ‘T’ home. A car that sits can get fine brown rust powder in the fuel tank that doesn’t manifest as a problem until driven extended on the highway or on the track. It is possible that someone removed the fuel screen in the tank and the fuel filter at the engine is compromised so you got dirt/rust into the FI system? Contamination at the pump and nozzles effect idle first.
Yes, the points could have closed up on your trip home. Pull the side cover off the pump. All the parts should be clean, rust is bad. The oil in the pump should appear the same as in the engine.
You said you weren’t getting any hot air to the thermostat. How is the condition of the left heat exchanger? The large rubber hose from the heat exchanger can fail and close off the air flow. The two concentric upper air hoses to the thermostat need to be new. Follow the good advice as to the condition of the thermostat (cleanliness and set-up.) Farther down the road you can make yourself a little tool that you can put in place of the thermostat and turn it all the way off for diagnostics (in to the stop is off.)
These guys are right, it’s best for you to become your own best expert on MFI. Since you have two MFI cars (thus far) I would recommend that you invest in all the tools and diagnostic equipment. Besides, when you turn your “hooligan” into a MFI 2.8S twin plug street/DE car, you can make it really run right. Think of the ‘T’ as practice for fun things to come and hang in there.

Best,
Grady

[Paul Thomas]

Kurt,
I am not suggesting that he start "playing" with the adjustments. I also did not suggest that he even touch the idle adjuster. This adjust does very little and should only be set AFTER the main adjustment. I am suggesting that he get the car to a point where he can work on it without it idling at 2500rpm. If you keep track of the adjustments you have made, it is easy to get back to where you were. I have had great success setting up and tuning my own custom MFI set-up.

If his car is hard to start, has a strong gas smell, and will run with the throttle plates open but not closed, what is your diagnosis of the problem? Overly rich is a good place to start.

Paul

[Early_S_Man]

Schuie,

The 'Blue Book' [C, M, A] isn't the only document you need to be reading. All of the articles, FAQ, and diagrams at the Pelican MFI page are important, and I strongly suggest that you download and print them. An MFI reference and 'study' binder can be very useful when learning, and helpful later when actually working actively on the car!

Additional documents from Pelican that are, or can be very important:

1. Two-page 1971 color schematics of the electrical system ... best if printed on 11" x 17" page, but useful even at 8.5" x 11". The engine and MFI-related portion of the schematics are identical to the '72-'73 schematics and can replace the factory service manual data if you don't plan to get one.

2. Distributor advance curve and timing info from this thread ... all of the individual images should be saved as JPG files and printed separately.

distributor lube...

3. Search and print all of the threads related to MFI speed switch, rpm transducer & speed relay problems over the past 3 years ...

microswitch... which is terminal 30b?

MFI microswitch-- Warren?

I suggest a permanent warning lamp panel to monitor the following signals ... plenum-rated CAT 5E network cable has enough leads for the task, and is readily available:

1. ThermoTime Switch heater element
2. ThermoTime Switch contact closure
3. Cold-Start Solenoid operating signal
4. Speed Switch [RPM Tranducer, Speed Relay] output signal
5. Cut-off Solenoid operate signal

Finally ... take both lower rubber and upper foil/plastic 25 mm warm-up thermostat ducts off the engine, carefully, and run a broomstick or large dowel throughthem to get any leaves, dirt, rodent nest material, etc. out! If your heater is working, the thermostat should be getting hot air, too!

[Grady Clay]

Shuie,
After re-reading your posts, another possibility is that the thermostat isn’t turning off (for any of several reasons) and someone adjusted the main mixture lean to have it run. That leaves the idle too lean to run at all, even at full rich idle setting. Once the engine is up to temperature, the hot engine oil may tend to turn the thermostat off. This might lead to the inability to restart until everything (thermostat) cools off.

If this were the case you would first fix the thermostat situation. If, when the thermostat is “off” (in) and the engine is very rich on main, only then should you be prepared to address the main mixture. Don’t worry about the idle until you are sure the main mixture is in the ball park. It won’t idle if it’s way too rich or even slightly too lean. Too lean tends to cause popping on deceleration when all the way off the gas (assuming no intake air leaks, holes in the muffler, defective exhaust gasket, etc.) Too rich, it will idle (perhaps OK) when cold but not idle correctly or at all when hot.

BTW, you should measure the thermostat rod position in both cold conditions and hot conditions. All you have to do is remove the two screws that hold the assembly to the pump and measure the protruding rod with some calipers. Most important, it should move out (longer) with increasing temperature. Try putting it in your deep freezer overnight for cold conditions.

When going thru this process it may be necessary to have several sets of “hot’ sparkplugs. Gasoline fowled plugs will fool you.

A MFI 911 must have EVERYTHING working correctly or it doesn’t work well (or work at all.) MFI 911s have some of the best horsepower and absolutely the best throttle response of any 911 made. I also have a 2.8S MFI 914-6 and my passengers would have broken the rear window many times if not for the headrest.

Best,
Grady

PS: Where is CMA for MFI available on-line for all to see?

[Grady Clay]

Shuie,

Warren is RIGHT ON! Look for an obstruction in the hot air tubes.

I’ll e-mail you the “Electric wiring diagram (Part I) and (Part II) Type 911T, 911E, 911S, Model 72” if you want. I have the originals. It is slightly different from the ’69, '70-’71 MFI system (the ’69-’71 MFI has two solenoids on the front of the pump and ’72-3 has one.)

Yes, making a remote indicator for the MFI electrical system will allow you to diagnose problems forever. I have done several. The best was one that just piggy-back clipped on the connections and included fuel pressure. It went out of the ajar deck lid, through the quarter window, to the driver’s seat. I modified a CO2 fire extinguisher to cool off the sensors.

Warren, Add your advice for other MFI publications for all to see. Your Pelican references are great.

Best,
Grady
gradyclay@hotmail.com