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Hi guys,

 

I'm new to the site so please be patient with me? (Also grammar isn't my strong point)

 

So, I've owned my 2003 996 carrera for the past 2 years and for the most part its been trouble free. I got it with 110,000 miles its now got 130,000.

 

Maybe 5-6 times over the last year it's  started misfiring as I come to a stop, it starts up after maybe 2 minutes and misfires for 30-40seconds, then runs fine.

 

The last two times this has happened the display has said low oil pressure as it's been misfiring, but then starts running normally with no message?

 

Any how just before Christmas I started the car as normal and left it ticking over but got held up,so it was probably idling for 40mins. I heard a loud misfiring sound and it cut out. I thought it had run out of fuel so I put a gallon in and it went up to a quarter. I tried starting it but it turns over but won't start. I have since had it towed in to a garage and they have plugged the computer into it and no faults are showing. Can anyone help as the garage isn't to sure?

 

Thanks in advance 

Mileet

 

P.S. it's a triptronic

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Welcome to RennTech.  :welcomeani: 

 

Two quick things come to mind: Have them check the fuel pressure and delivery rates, and have them also check the crank position sensor.

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Thanks so much JFP,  

 

I van here the fuel pump prime when ignition is turned on, I've read on here that the DME relay can cause simular symptoms would you agree? I'm not to sure as I don't really understand. 

 

Thanks 

Mileet

 

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1 hour ago, mileet38 said:

Thanks so much JFP,  

 

I van here the fuel pump prime when ignition is turned on, I've read on here that the DME relay can cause simular symptoms would you agree? I'm not to sure as I don't really understand. 

 

Thanks 

Mileet

 

 

OK, from your description, the car sounds like it has a fuel issue, which means either the pump is going south, or the CPS is defective and preventing the fuel pump from running correctly.  Just because the pump makes noise does not mean it is delivering the correct pressure or volume of fuel to run the injectors, the pump and CPS need to be tested, as CPS problems are often intermittent.

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Thanks again 

 

What is the CPS? Also how do we find out what correct fuel volume and pressure are?

 

Thanks 

Mileet 

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26 minutes ago, mileet38 said:

Thanks again 

 

What is the CPS? Also how do we find out what correct fuel volume and pressure are?

 

Thanks 

Mileet 

 

CPS is the Crank Position Sensor, which is mounted on the side of the bell housing.

 

You should had a decent technical reference source like the Bentley service manual for the 996.  Your fuel system should retain 3.8+/- 0.2 bar (around 55 psig) with the engine off, and sow 3.3 +/- 0.2 bar (48 psig) running at an idle.  With the engine off, your fuel pump should deliver 850 ml of fuel in 30 seconds.

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Hi can any one tell me if theres any way of testing the fuel system( diy) maybe removing a pipe and measuring volume of fuel?

also does the 996(2003) suffer with dme relay problems as of the old 993s?

 

thanks 

Mileet

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The info shown above by Joe is good. Since you have an '03, there's a fuel line quick connect around the top of the coolant reservoir. Just squeeze the grey tab in (you may not see it since it's behind facing the front of the car) and disconnect. Then you can measure the flow. You can also make an adapter to measure the pressure. There are also two brass caps on the fuel rail that you can remove to do the same but I do not recommend removing those as I had a bad experience getting them resealed when reinstalled.

Edited by Ahsai

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Can you tell me if the pump should pump whilst cranking the car?

 

I've disconnected the pipe from behind coolant res tried cranking,  no fuel is coming?

 

Thanks 

Mileet 

On 07/01/2018 at 9:15 PM, JFP in PA said:

 

CPS is the Crank Position Sensor, which is mounted on the side of the bell housing.

 

You should had a decent technical reference source like the Bentley service manual for the 996.  Your fuel system should retain 3.8+/- 0.2 bar (around 55 psig) with the engine off, and sow 3.3 +/- 0.2 bar (48 psig) running at an idle.  With the engine off, your fuel pump should deliver 850 ml of fuel in 30 

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1 hour ago, mileet38 said:

 

 

Can you tell me if the pump should pump whilst cranking the car?

 

I've disconnected the pipe from behind coolant res tried cranking,  no fuel is coming?

 

Thanks 

Mileet 

 

Yes, it should be running anytime the key is switched on.

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Brill is that with the relay in or do I have to use a jumper over middle two terminals?  

 

Gonna try and get pump out and check on Monday.

 

Thanks so much for the help

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On my '02 and '03, I need to remove the relay and jump the power contacts for the pump to run. Figure #2 here https://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/22-FUEL-Replacing_the_Fuel_Pump/22-FUEL-Replacing_the_Fuel_Pump.htm

 

No need to even put the key in. Have you checked for sparks also?

Edited by Ahsai

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Hi Guys,

 

Sorry for the late update. Hope this helps anyone with similar symptoms. I thought to try the cps first as it was only £40 and as i thought at the time an easy fix. Unfortunately mine was stuck in the housing and after lots of pulling and prying it snapped in. due to the location this was quite a nightmare. I ended up buying some hex shank 3.5mm drill bits, hex shank extenders, and carefully drilled around the outer plastic edge of the CPS as many times as I could, then chiselled, pried and picked it out the magnet out of the middle came out first. this took me about 4 hrs. I also had use of a ramp. after installing the new one the car still did not start.

 

Next I tried the fuel pump relay, that didn't work either.

 

Lastly I tried the fuel line (the one behind the expansion bottle in the engine bay. why I didn't try this first I'll never know? oh well at least now I have experience in removing stuck parts from an engine. he he.

any way once i undid the fuel line turned on the ignition no fuel came out eureka a definite problem to sort.

 

after doing some asking around and searching the web i found out that here in my own town (Doncaster UK) we have a Porsche breakers i rang up and sourced a second hand fuel pump for£70 fitted it a it started straight away.

The Breakers details are Porsche Haven 07553 875543 ask to speak to Mike very very fair and helpful. Mention Mike with the silver 996, he 'll maybe give some discount

 

Anyway i Just wanted to say a MASSIVE thanks for all your help as I really couldn't of done it with out you all.

 

Gonna try to add a picture of my old fuel pump?

Thanks Mike

 

Sorry my picture is 6.7 MB so wont let me add it.

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