Hesitant to start

[dave944s]

Hi all

Just changed the hall sensor on my RS2, now it takes a few turns of the engine to start, if I try to start without pressing accelerator, it takes ages to fire up, if I turn the ignition on and off a couple of times (I can hear the fuel pump running then stops) pump the accelerator a few times, turn it over and then the engine fires up, once running if stopped and started, it runs no problem, I think it's a fuel problem, as if the fuel is not getting to the injectors on first try, but I would like your thoughts and possible fix. By the way , no error faults found after clearing the G40 fault.

Dave S

[UrS4boy]

J17 Fuel Pump Relay and the RS2 fuel pump operation

Hi all. Just changed the hall sensor on my RS2, now it takes a few turns of the engine to start, if I try to start without pressing accelerator, it takes ages to fire up, if I turn the ignition on and off a couple of times (I can hear the fuel pump running then stops) pump the accelerator a few times, turn it over and then the engine fires up, once running if stopped and started, it runs no problem, I think it's a fuel problem, as if the fuel is not getting to the injectors on first try, but I would like your thoughts and possible fix. By the way , no error faults found after clearing the G40 fault. Dave S

Congrats on successfully changing your G40 cam sensor behind the cam sprocket. However, I have to wonder if something didn't get replaced quite properly, e.g. fuel rail, fuel pressure regulator, etc.

It does sound like a fuel issue of some sort. Your opening and closing the throttle probably does nothing other than take up some time while the fuel rail re-pressurizes.

What bothers me about your story is the part where you hear the fuel pump when you turn the igntion on and off. I think what you hear is the initial "testing" cycle of the after-run pump that occurs when the ignition is first turned on. IF the fuel pump wiring is still as stock (not on VEMS), then the RS2 G6 fuel pump ONLY gets power once the J17 fuel pump relay is taken to ground (and therefore energized) by the ECU via pin 3. Pin 3 is only activated by the ECU once the ECU gets a good signal (> 13 RPM) from the G28 engine speed sensor, as a safety precaution (to stop the fuel pump in an accident that stops the engine). Power flows through the J17 to the S13 fuel pump fuse and then to the G6 fuel pump.

J17 fuel pump info: http://forums.quattroworld.com/s4s6/msgs/22583.phtml

[Rikki Kitto]

Now that is a good answer

[dave944s]

Hi UrS4boy

Thanks for the reply, the car had sat for about 8 months as I was away a lot with business, I didn't need to touch the fuel rail or the fuel regulator when changing G40 sensor, the fuel wiring is stock and I can see nothing in the information from the previous owner to say otherwise, is it possible that the relay will need replaced, maybe because it is not working properly due to sitting for a long time not being used, thanks for the help.

Dave S

[Henkjan]

... if I try to start without pressing accelerator, it takes ages to fire up, if I turn the ignition on and off a couple of times ... pump the accelerator a few times, turn it over and then the engine fires up...

another explanation for this is a poor signal from the throttle potmeter, causing the idle stabaliser to remain closed when not on the accelerator. check it's resistance (multimeter on contacts 4 and 6), it should be either infinity on depressed accelerator and near zero ohm otherwise. if it is not zero, then replace the potmeter.

[dave944s]

another explanation for this is a poor signal from the throttle potmeter, causing the idle stabaliser to remain closed when not on the accelerator. check it's resistance (multimeter on contacts 4 and 6), it should be either infinity on depressed accelerator and near zero ohm otherwise. if it is not zero, then replace the potmeter.

Hi Henkjan

Although I am mechanical inclined I'm not that great with electrics, if you could point me in the direction of potmeter or photo of the same, I can do the check you suggest, very many thanks for your help.

Dave S

[UrS4boy]

G69 / F60 Throttle valve position potentiometer /idle switch information

I am mechanical inclined I'm not that great with electrics, if you could point me in the direction of potmeter or photo of the same, I can do the check you suggest, very many thanks for your help.Dave S

G69 / F60 Throttle valve position potentiometer /idle switch information:

http://forums.quattroworld.com/s4s6/msgs/20405.phtml

Test sheet (also linked in the above):

http://12v.org/urs/G69F60ThrottlePositionSwitchTestSheet.pdf

All of this accessible by clicking on the labels in this Engine Bay Device Map:

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[Henkjan]

item 9 in the pic

[UrS4boy]

Item 2 in the right most part of this 3B/ABY/ADU intake track composite diagram.

Somebody please post a photo of the 3B/ABY/ADU throtttle switch so I can put it in my throttle potentiometer/idle switch info post (credit to you)

[dave944s]

Thanks guys

I can't do anything tonight, but if the weather is good tomorrow (car outside at the moment) I will have a go at your suggestions, great forum this, don't post much but when I do the response is great, will let you know how I get on.

Dave S