again G28 question

[Benquattro]

My 3B wont't start.
I have Fuel pressure at the engine.
I have spark at the engine.

Last year I replaced my G4 reference sensor.
Is it possible that my G28 does not work?

My question really is; if only the G28 would not work, what would the engine do?
Will it have spark as I have? Wil it have fuel pressure but no fueling?
Cause when I Put in pilot spray, it does start and I do not have a boost leak.

[BrianSmith_S2]

My 3B wont't start.
I have Fuel pressure at the engine.
I have spark at the engine.

Last year I replaced my G4 reference sensor.
Is it possible that my G28 does not work?

My question really is; if only the G28 would not work, what would the engine do?
Will it have spark as I have? Wil it have fuel pressure but no fueling?
Cause when I Put in pilot spray, it does start and I do not have a boost leak.

Check out my posts on this thread regarding the G4, G28 and G40 sensor. Im no expert but i was given expert guidance from forum members on what to check. As far as i know you may have fuel pressure and spark at the engine but its the G4 in conjunction with the G40 that governs whether the engine starts with fuel pump, sparks and injectors.

have you got use of an osciloscope to check your sensors? By the way the G28 is same sensor as the G4

Regards, Brian

http://www.s2forum.com/forum/showthread.php?t=48066

[S2central.net]

Sounds like faulty fuel pump relay cos if you are getting spark then you must be getting a signal from G28 and also G4 and G40 are in sync.

I have fitted an LED inside my pump relay as a handy way to check it. I posted some info and pics on that - it is only way to know unless you want to fish thru lots of wiring spaghetti or remove lots of rear trim to see if 12V is getting to the pump.

[Benquattro]

I have fuel pressure at the engine.
But no fuel injection.
So the fuel pump must be ok (and it's a new 044 pump).

I don't get this.

[BrianSmith_S2]

I have fuel pressure at the engine.
But no fuel injection.
So the fuel pump must be ok (and it's a new 044 pump).

I don't get this.

Thats what i had, the G4 and G40 pulses were out of sync due to the timing being out, i.e. the lower crank pulley had shifted

I had fuel pressure but no injector signal.

Brian

[Benquattro]

Crank pulley shifted? I bought a new steel one from this forum and the belt is rather tight.

I wil check this though, thanks

[S2central.net]

DO check the timing carefully. If G4 and G40 do not align then the ECU assumes something mechnical is wrong and it does not inject fuel.

[S2central.net]

@Brian - I have been rather focussed on the TDi woes this week - did you get yours sorted after those many hours scoping, probing & head-scratching ?

[Benquattro]

It seemed to be the fuse of the high output coil from 044 motorsport, which obviously takes a lot more current than the original coil.
Shame

[Benquattro]

Correction, it was the fuse of the bosch motorsport fuel pump. The original 5amp broke.

[BrianSmith_S2]

@Brian - I have been rather focussed on the TDi woes this week - did you get yours sorted after those many hours scoping, probing & head-scratching ?

Garage confirmed the lower pully had moved slightly as you suspected from the 2 channel scope plots of the G40 and G4. Its in being sorted at the mo..... cant wait to drive her again... its been weeks

[UrS4boy]

Procedure to Relay Fuel Pump directly to Battery

It seemed to be the fuse of the high output coil from 044 motorsport, which obviously takes a lot more current than the original coil.
Shame

You might want to consider relaying the fuel pump directly to your battery, as detailed in this DIY (for a C4 UrS 20vt but the idea will be the same for yours):

http://forums.quattroworld.com/s4s6/msgs/24327.phtml

[Benquattro]

You might want to consider relaying the fuel pump directly to your battery, as detailed in this DIY (for a C4 UrS 20vt but the idea will be the same for yours):

http://forums.quattroworld.com/s4s6/msgs/24327.phtml

Great! Thanks

[S2central.net]

@Brian - you were lucky it slipped enough for motronic to prevent it starting , but hopefully not far enough to do any valve damage.