Starting Procedure - 911 MFI

[smithne]

Hi,

A slightly dumb question perhaps, but I currently own an unmodified '72 911S with MFI and would be grateful for some advice on starting procedure. No problems with cold and hot starts as the factory handbook explains what to do. However, is there a recommended technique where the engine is only slightly warm, eg after standing or 2 - 4 hours or so? I have tried various degrees of hand throttle and gas pedal and sometimes need a couple of go's until the engine fires. Just want to make sure I avoid flooding the engine, which I guess is easy to do if you don't know what you are doing.

Many thanks.

 

[Alan Woods]

Mine is only a T so on carbs but does sound similar...

Starts great from cold or hot, but does struggle sometimes if you take a short trip say just to fill up with petrol. Using no throttle doesnt seem to work and as you say too much will flood so just a matter of feathering it until it cataches but dont gas it too much!

 

[Nick Moss]

Hi Neale

Despite there being a handbook recommended way to start an MFI 911, invariably every car is different after 40 years of wear and repair. They are usually difficult when cold as there are 3 or 4 different components (temperature sensor, relay, solenoid and various pipes and fittings) that comprise the cold start mechanism (discounting the operator). When hot it's just the operator, so in between the various components can have differing effects. When "warm" I would apply 1/4 throttle and turn the key. It's very difficult to flood an MFI engine as pumping the throttle at zero or cranking speed has virtually no effect on the amount of fuel being delivered.

 

[Robin]

Starting when slightly hot, dont touch the throttle pedal, turn the key and raise the hand throttle lever about half way, when it fires adjust the tickover to about 1000 rpm with the hand throttle and drive off. Dont forget to put the hand throttle back as soon as you start moving and be prepared to lift it slightly if you have to stop at a junction or in traffic. The engine should fire easily as the cold start solenoid on top of the fuel filter dumps fuel directly into the air intakes every time you turn the key. If it still does not start easily then check and adjust the points gap and the spark plugs. Good luck and enjoy driving it.

 

[vic cohen]

Just one thought ................when the rubber pipe to/from my fuel pump[ rear wheel arch] is beginning to break down from modern petrol useage the symptoms are as u ve decribed ......Mr Moss even knows this.................
It is almost impossible to flood , when it starts happening i keep churning with my foot flat on the floor!!!!!!!Honest ,only ever failed once , Moss was there.............when pipe was totally closed up by sucking effect , pipe was a soft as mush by then .................

 

[Robin]

Didn't the good Doctor know about starting problems with what is basically a diesel fuel injection pump by putting two batteries into the car.
On the fuel hose problem, I replaced all of my fuel hoses after a holiday in France using their 95E10 petrol, it took 3 metres of 8mm ID hose.

 

[vic cohen]

Unfortunately ,Robin, my car could nt recognise we were in the middle of France the only time i failed to start it....................it was also very wet and blowing a gale on the sideof a very high beauty spot ...............young Moss and a couple of other good friends managaed to cobble up a spare piece of pipe and we all reached the Classic Lemans event ............couple of other Porsches there and Steve Winter replumbed me !

Since that time have tried several different brands of pipe , now change every year or so when symptoms appear to be coming on...............the wonders of modern science!!!!!!!!

 

[Robin]

Isn't it great to have Early 911 friends out there.

 

[oldtimer]

Where can I find out more about the need to replace fuel lines ? If you can smell petrol in the car is that a sign of impending doom ? It sounds like a big issue to me. My car only does 2000-3000 miles a year but assume deterioration of fuel line is more time dependent than mileage dependent . I have not seen any column inches in the Porsche mags related to this...is it a curry night only topic for the cognoscenti ?[]

 

[vic cohen]

Well U, Robin and I are all over 21 ,but think we cud agree its not a finite art !

The smell far more likely to be that little thing just ahead of front bulkhead on the LHS ..............even with my Hooter never smelt it ,just pipe goes mushy and atrats closing up under suction .......litterally faster u go more it close off supply!

Steve Winter at Jaz has tried most pipes ...........good man to ask ............

ps curry always a good idea!

 

[38F3E1]

ORIGINAL: oldtimer

Where can I find out more about the need to replace fuel lines ? If you can smell petrol in the car is that a sign of impending doom ? It sounds like a big issue to me. My car only does 2000-3000 miles a year but assume deterioration of fuel line is more time dependent than mileage dependent . I have not seen any column inches in the Porsche mags related to this...is it a curry night only topic for the cognoscenti ?[]

I have put something in PP this month as Porsche Classic are quite clear now on what petrol you can and cannot use these days. In the UK it basically means super unleaded only as this is restricted to 5% ethanol (E5).

Regarding when to replace - waiting to smell petrol is chancing it as the first time you may know your fuel pipes have failed is as your engine bay is engulfed in flames. I would say time dependent rather than mileage dependent. Regular inspection or preventative replacement is the best approach plus never put E10 petrol in your tank.

If anyone gets to speak to Steve Winter before I do post the answer up here.

Ian.

 

[38F3E1]

ORIGINAL: Robin

...I replaced all of my fuel hoses after a holiday in France using their 95E10 petrol...

Sensible as this is now explicitly forbidden to be used in our cars as per post above.

Ian.

 

[Melv]

I generally find a quarter throttle and a juggle with the hand throttle works in all circumstances, hot, cold and luke warm.
Some cars seem to respond to a few pumps on the throttle before cranking when cold....

 

[smithne]

Dear All,

Many thanks for the feedback on my original post, much appreciated. I can now proceed with a lot more confidence!

The impact of modern unleaded on the fuel system is a separate concern and I suppose not just for early 911 owners. However, I assume that Porsche after-market component suppliers are already aware of this and will develop parts made of more resilient materials in due course.

Cheers

 

[vic cohen]

on reflection , ..'.replaced after French trip Robin '..............mine went right off on French trip ,while at Classic Lemans one of Steves other customer cars same and the race car all went off............may not be sciemtific[ i know my pipes were there for a given period etc , but not the others]

 

[jamescharnley]

Ian, interesting stuff about E10 fuel.

I've tried a google search & as far as I can tell at the moment, most branded normal unleaded is still E5 , although it will be e10 soon ??? Anyone know a way of confirming this is the case ?

 

[Robin]

ORIGINAL: jamescharnley

Ian, interesting stuff about E10 fuel.

I've tried a google search & as far as I can tell at the moment, most branded normal unleaded is still E5 , although it will be e10 soon ??? Anyone know a way of confirming this is the case ?

Probably when your fuel hoses start to melt !

 

[Lightweight_911]

ORIGINAL: jamescharnley

I've tried a google search & as far as I can tell at the moment, most branded normal unleaded is still E5 , although it will be e10 soon ??? Anyone know a way of confirming this is the case ?

As I understand it, the percentage of ethanol in fuel will rise to 10% in 2013 - until then there will be a committment to offer fuel with 5% ethanol.

After 2013 there is some talk that the Govt will mandate Super Unleaded as the 'protection grade' and as such it will continue to be available with a max of 5% ethanol.

To get round the problem of swelling fuel hoses (& any rubber seals in the fuel system) in older cars, they will need to be replaced with Teflon-lined hoses (& Teflon seals) - the only other drawbacks to using it in older vehicles seem to be (slightly) greater fuel consumption &, possibly, a greater susceptibility to vapour locks in the fuel system (probably of more relevance in carburetted engines).

There are a number of states in the US that have had E10 petrol for ~ 20 years so there should be solutions available to resolve these problems for our cars.