'72 Hose from engine tin to MFI WUR - what material?

[LeeH]

What was the original hose made of? Is it still available? What's a reasonable substitute?

And while you're here...

I've got a feeling the PO had the car tuned by someone who wasn't fully familiar with the MFI system. The car runs great hot, but is a real pain to start cold. Is if fair to assume that if the car runs great hot and the hose between the engine tin and WUR was disconntected that it's going to run rough once it is connected?

[Formerly Steve Wilkinson]

Forget the original material unless you're a concours junkie. It was made of cigarette-package tinfoil. Get, from an aircraft-materials supply house such as Aircraft Spruce or Wicks Aircraft--both big companies with websites--CAT or SCAT ducting.

Stephan

[Oldporsche]

S.C.A.T tubing

Silicone Air Tubing. diameters -XX

Such as SCAT tubing dash 10.

Very often the FBO at your local airport has some for sale.

David Duffield

[Formerly Steve Wilkinson]

Now wait a minnit! SCAT stands for Silicone Air Tubing? I don't think so. If it does, explain to me CAT and SCEET, which are two other common varieties...

Stephan

[LeeH]

Definitely not a concours junkie, but does it come in a color other than red?

Is there a disadvantage to using any other material - radiator hose, for example?

[Bobboloo]

I bought mine at a VW autoparts store. Black cardboard over foil. Cheap, fits and works.

There's no reason to assume that it will run bad with the hose hooked up. It should run leaner when warm however. If it does run bad when warm then it's probably adjusted too lean.

A cold starting problem has nothing to do with the hose. The cold start valve is probably not functioning. It could be malfunctioning for mechanical and or electrical reasons. I would first make sure that it's getting current.

Get a voltage meter and connect the hot lead to the wire that goes to the cold start valve atop the filter assembly and the neg. to ground. Then have someone crank the ignition while the motor is cold. You should see voltage on the meter of 9 to 12 volts. (only when cranking) If you don't then there is an electrical problem.

Report your findings and we can take it from there.

[Grady Clay]

Lee,

Is there any hose now between the tin and the thermostat on the MFI pump? If not there is probably a series of problems to deal with. If there is a hose, what condition? What is the (rust) condition of the left heat exchanger?

Use the original hoses. There are actually two concentric hoses with an insulating air space in between. Our host has them and they are not expensive. Large heavy hose won’t pass hot to the thermostat as soon and single thin hose has more heat loss.

I agree that possibly the cold start is not working. After you have confirmed proper electrical operation, take the hose off that goes to the stacks. Test to see if fuel flows when cranking and doesn’t flow or drip when the engine is running.

If your MFI has been molested by someone who had good intensions but didn’t know all the subtle details, you need to fix the issues asap.

Please report back what you find.

Best,
Grady

[LeeH]

Originally posted by Grady Clay
If your MFI has been molested by someone who had good intensions ...

What a nice way to put that! I know the PO took it to the same shop several times - one I've never heard of for Porsche repair in Phoenix. The receipts are hand written and hard to decipher. I know one says adjust FI for emmissions. It also has new injectors. I've been studying the MFI documents on Pelican, which is what got me looking at the hose from the tin. BTW, I will confess to being light on tools and without a lot of experience with this stuff, but am willing to learn.

The car is hard to start cold. Lots of cranking, but it always starts and with a predictable number of near starts. When finally started it runs fine, but will occasionally stall at a stop sign. Once good and hot, it runs great through the entire RPM range and idles well. I had a little backfire on deceleration and found the cut off micro switch out of adjustment. I havent' driven it since making that adjustment last night.

The hose from the tin to the thermostat was not connected. It was crimped in a few spots and someone used some sort of pipe to make a union and it was completely disconnected there. The heat exchangers are stainless so they're fine.

[Grady Clay]

Lee,

A not uncommon problem is for the MFI thermostat to not be turning off at all or turning off too slowly for a variety of reasons. Chief are the thermostat hose is broken or restricted and the other is if the thermostat elements are covered with oil and dirt. Others can include improper shimming of the elements, removing some of the bi-metal discs, restrictions or air leaks in the heat exchanger, and more.

Too many times someone will only treat the symptoms (too rich mixture) and not the cause (mal-functioning thermostat system.) They lean the main mixture to get the engine to run semi-correctly when warm and then it doesn’t want to start and run properly when cold.

The difficulty comes when you repair the thermostat system so it turns off the cold enrichment properly. Now you have the situation where the repair of one problem causes another problem to manifest itself – sometimes difficult to diagnose. You can go from a running engine to one that will hardly run at all, even though you have repaired a problem. This is the situation Bobby noted.


What to do?

As you posted you are willing to learn, there are many on this Forum who are very skilled with MFI and will lead you through the process. Yes, you will need some tools. The labor you save DIY will more than pay for the tools and you get the satisfaction of becoming your own MFI expert.

First I recommend you get all the MFI information in one place and study it several times, asking questions here. Today, I think the best way is to maintain a digital folder and also a paper print out.

Since the engine runs properly hot, I would refrain from making any more repairs or adjustments until you have done the Check & Measure portions of the CMA procedure.

I assume you have downloaded a pdf copy of CMA.
Check Measure Adjust (CMA)
http://www.scatliff.mb.ca/pelican/MFI_Check_Measure_Adjust.pdf

Some is a little hard to understand because it was originally a translation from the German. Study it and ask questions.

This is a good thread about the thermostat and some worthwhile extensions to CMA.
“MFI thermostat spacers”
p. 1 end has CMA extension, p. 3 has nozzle, fuel flow, and fuel pressure.
MFI thermostat spacers

The basic philosophy of CMA is to make sure all of the various sub-systems of your engine system are in proper condition PRIOR to making any adjustments. It is not uncommon for a simple defective part (cracked cap, loose thermostat hose, etc.) to fool the unwary into making all sorts of unnecessary replacements, changes, and adjustments causing much more work and expense.

I recommend you search the Phoenix area shops and dealers and find their skills and resources. Every DIY needs backup in a predicament and access to skilled eyes. Go to your local PCA region. Ask if there any retirees who are knowledgeable. Get together with other local MFI owners. Besides, you can get the prior invoices interpreted.

For tools you will need some basics. Many can be inexpensive equivalents to Factory P-tools. Many can be “of local manufacture” as Porsche euphuistically puts it – i.e. homemade.


There is a great deal of satisfaction owning a MFI 911 when, at a Porsche event or playing golf, someone asks you who tunes your Mechanical Fuel Injection and you answer “I do it all myself.”

Tell us what you want.

Best,
Grady

[DonDavis]

This is a great thread. It goes into my MFI bookmark folder.

Lee, we need to spend a day together at my house. I've got plenty of tools and am in the process of getting a few other items. I have the MFI adjustment kit from Pelican, but as Grady says, the rest of the system needs to be debugged first.

[LeeH]

What does the kit consist of?