Cold start system.

[AndrewWolfeUK]

Hello To all,

Ive just joined your site, very good it is too.

I have a 1973 911. It takes me about 15 mins to get the damn thing started in the morning and its becoming a pain.
So i have searched the threads about the the cold start and i have learnt quite a bit.
The main BUT being the cold start system from inside the air box seems to be missing!
I have tested the tube on top of the pump and if you suply 12v's it pumps out plenty of fuel, with nowhere to go.

I would be very greatful if anyone could help me. I need a picture of the system inside the air box or i would like to purchase the system new or used.

Even some sound advice would be cool.

Many thanks in adavance.

[AndrewWolfeUK]

Forgot to add I live in England so the cold start system is needed every day!

[Rot 911]

Andrew, welcome to the board. Do you have an early or late '73? This determines if you have MFI or CIS fuel injection.

[AndrewWolfeUK]

Pass!

How can i tell the difference?

Sorry new to the Porsche game.

[Rot 911]

MFI engines have a pump with tubes running to each injector on top of the engine and an air cleaner housing that looks like the one on this engine:


CIS engines have air cleaner housings that look like this one:

[AndrewWolfeUK]

MFI then.

Is this the begining of a big job?

[Tim Walsh]

welcome to the board. I've got the same car (73 911 w/ MFI). There is a cold start system on mine that runs from the heat exchanger (the first exhaust piece) to the airbox and there's also a 1" tube that runs from the same HE to the MFI pump (under the airbox). Are both of those hooked up?

[Rot 911]

Tim only the 1" tube is part of the MFI system and it controls the enrichment circuit once the car is started. The bigger hose that goes to the air cleaner is merely part of the early attempt at pollution control. The cold start circuit on the late MFI consists of 2 fuel lines that run to each bank of throttle bodies, they in turn connect to individual "t" fittings at the base of each individual throttle body. These plastic "t" are impossible to obtain if they are missing.

Andrew, you probably have a cheap, but tedious fix. Before you go any farther, please, please, please, read everything in this tech article and you will be a happy MFI owner!
http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

[AndrewWolfeUK]

The heat exr's are virtualy non existant!
There is a pipa about an inch in diameter going to the rear of the air box Then a smaller on coming off, also a thin maybe 1.2cm diameter coming out under the air box.

What are you thinking i should do?

[Tim Walsh]

does it fire and die or just not start?

I think if it fires and dies that it maybe the warm up thermostat on the MFI pump being stuck, that would lean the mixture out enough that it would take forever to get it to start.

but I'm still very much and amatuer, heck my car hasn't even started since I got it.

BTW here's a pic of my engine with the warm up parts on.
www.uncg.edu/~tpwalsh/911_10.jpg

[Rot 911]

Originally posted by AndrewWolfeUK
The heat exr's are virtualy non existant!
There is a pipa about an inch in diameter going to the rear of the air box Then a smaller on coming off, also a thin maybe 1.2cm diameter coming out under the air box.

What are you thinking i should do?

If the heat exchangers are rusted away do not use your heat because you will quickly die of CO poisoning! Next the "pipes" you refer to have nothing to do with the cold start system. One is a vacumn tube and the other is an oil breather line. You should also have an airbox drain line. If you had bothered to read the tech article you would have seen this diagram among others:


Further in the article you would have read this:
"Cold start enrichment hoses and connections:
Ensure these small hoses are not leaking and in good condition. Always use the proper FI hose clamps (i.e. do not use the slotted worm drive clamps as these cut into the hose over time). The tiny plastic T-junctions and elbows mounted on the sides of the throttle body trumpets should be tight and look for cracks if bent out of shape. Treat with care as these are not replaceable I believe!! (Also check your vacuum hoses and junctions periodically)."


I don't mean to lecture, but the shotgun method of trying to fix an early 911, much less any car, is a waste of both yours and my time. Read the articles, then you can ask much more knowledgeable questions.

[AndrewWolfeUK]

Ive had a look at the page its got lots of info on the MFi engine.

What i need is a picture of what i need to replace as i don't even know what any of it looks like.

Thanks again

[Rot 911]

Originally posted by AndrewWolfeUK
Ive had a look at the page its got lots of info on the MFi engine.

What i need is a picture of what i need to replace as i don't even know what any of it looks like.

Thanks again

Fortunately I took some pictures when I was working on my '72. In this pic what I circled in red are the cold start enrichment lines. What I circled in blue is the line that runs up to the fuel filter.

[Rot 911]

What I circled in green here is the hot air hose that runs to the MFI thermostat:

[Tim Walsh]

woops I'm not quick enough.. here's a pic of the front of my engine (when I got it)
www.uncg.edu/~tpwalsh/911_10.jpg

[AndrewWolfeUK]

Hi Kurt

Originally posted by Kurt V

I don't mean to lecture, but the shotgun method of trying to fix an early 911, much less any car, is a waste of both yours and my time.

I'm here to listen, so in the interest of saving both our time, this is what ive got:


I have to get a cold start system sorted out because 15mins of starter motor every morning cant be good.

Many thanks again

[Rot 911]

Andi, are we speaking two different languages here? As I previously stated THE LATE MFI SYSTEM SUCH AS YOURS DOES NOT HAVE A COLD START SYSTEM INSIDE THE AIR FILTER HOUSING. THE AIR FILTER HOUSING HAS NOTHING TO DO WITH THE COLD START SYSTEM ON YOUR CAR! IN FACT TAKING THE AIR FILTER HOUSING OFF YOUR CAR WILL HAVE ZERO EFFECT ON STARTING!

Go back and look at the pictures I posted. Do you have the cold fuel enrichment lines I circled in red? Are they and the line I circled in blue attached to anything? Do you have the hot air hose running to the MFI thermostat I circled in green? FORGET THE DAMN AIR FILTER HOUSING!

[AndrewWolfeUK]

O.K. Kirt,

I'm with you now, an English company had drilled the air box thing into my head about 6 months ago never been able to understand it, but i know why now.

There is no system like the one you circled in red.

The blue is also non existant.

The green circled bit is there and very much intacked.

Thanks again Kirt and Tim

Sorry its taken so long to begin to understand you!

[Rot 911]

Originally posted by AndrewWolfeUK

There is no system like the one you circled in red.

The blue is also non existant.

Now you know what your problem is. You have no cold start enrichment! Look at the fuel filter and the solenoid on top of it. I bet the fitting for the cold start line has been capped off. You will need to run the lines I have circled in the pictures. Look and see if you still have the "t" fittings on the throttle bodies. They are what connect the fuel lines to the throttle bodies that are circled in red. Are they there?

[tryan]

andrew , post some pictures of your motor/induction. it will be easier to determine the problem.
also, your ignition system need to be 'spot on'. have you had a tune up within the last year? how well does the car start once warm? 15 minutes seems like there might be other issues or procedure problems.

kurt, your cis motor is like a work of art ! quite elegant.