944 Starting Problems

[PortiasDad]

Can anyone help? I have a Series 2 3 litre 944, starts when cold, runs perfectly, but if I switch it off and try to start when it is warm. it will not start again until it is cold.
I have changed the fuel check valve to no avail.

[smn159]

PortiasDad said:

Can anyone help? I have a Series 2 3 litre 944, starts when cold, runs perfectly, but if I switch it off and try to start when it is warm. it will not start again until it is cold.
I have changed the fuel check valve to no avail.

Try changing the DME relay - about £25. A lot of starting problems seem to originate here due to cracked solder joints I think.

[tr7v8]

Yup DME relay is first. Does the revcounter bounce off its stop when you crank it.

[PortiasDad]

Thanks I will have a look at that option

[Ian_UK1]

PortiasDad said:

Can anyone help? I have a Series 2 3 litre 944, starts when cold, runs perfectly, but if I switch it off and try to start when it is warm. it will not start again until it is cold.
I have changed the fuel check valve to no avail.

I'm sure I've read somewhere that a failing crank sensor can cause these symtoms.

[Conian]

DME isnt a bad as a problem as it used to be, theyve only been supplying the later 993 DMEs for sometime now, so the old bad ones are probably all gone

do you have any immobs on the car?
do you hear the fuel pump buzz when you turn the ignition key? (its down by the back wheel)

as a real outside chance, check ya dizzy cap, i had a tiny crack in mine, barely noticable but it wouldnt start cos of it

[pauljmcnulty]

[quote=Conian]DME isnt a bad as a problem as it used to be, theyve only been supplying the later 993 DMEs for sometime now, so the old bad ones are probably all gone
/quote]

Things do seem to go in phases; when I first joined the old Titanic forum about 8 years ago, the DME came up almost daily. It's now a rare thing to hear of a car having one that's not been replaced!

Well worth looking there first, though, as well as the condition of the leads, diz cap and rotor arm. Some alternative part details & cheaper options here:

http://www.porscheclubgbforum.com/tm.asp?m=467365

[Conian]

can you copy n paste the info for us who arent members on that forum? it wont let me see

[PortiasDad]

Thanks again for all the help, waiting for shops to open in the morning

Conian I have just signed up to the forum, you don't need to be a member of PCGB, just leave out the membership details on the form

Cheers

[porkyspecialist]

Head temp sensor or crank reference sensor (as already mentioned).

Good luck.

[stratfordshark]

You also describe classic symptoms of leaky injectors (cylinders flood with fuel which evaporates by time engine cold).

If it's leaky injectors you will be able to start immediately after shutdown when hot, but not if you wait 10 mins or so.

Test is to put pressure gauge on rail and see if fuel pressure drops beyond spec on shutdown (should hardly lose any pressure in 30 mins)

[nsa]

When mine had the hot start problem it was the thermo time switch. About £300 to diagnose and £75 for the switch (from memory). Any Porsche specialist should be able to diagnose and fix for you.