Car stalled and will not restart HELP!

[UrS4boy]

just checked for a spark in the dark with the plug out and earthed and there appears to be nothing, is there a sensor which will stop fulling and the spark?

Yes. Like the AAN, the 3B fuel pump is controlled by the fuel pump relay which, in turn, is controlled by the ECU and only energized via ECU pin 3/55 if the ECU receives a good G40 cam position Hall sender signal. To get this G40 signal (on pin 8/55), the cam sender needs to be working properly AND cranking speed needs to be higher than 25 RPM, i.e. a weak battery or bad starter that don't get you to 25 RPM while cranking = no Cam sensor signal = no energized FP relay = no fuel = no start). If everything works properly, the FP relay also energizes the fuel injectors with 12v, which wait patiently for a ground signal from the ECU to function. Here are some 3B Motronic diagrams for a 200 20vt (might have different fuse numbers, etc. than a 3B in a B3 S2)



and

[montez]

also distributor was replaced 12 months ago, I will double check tomorrow in the light

[s2_bo]

That's good to know.
That fuel pump relay is pretty important then!

Good luck, hopefully it's something simple.

[UrS4boy]

That's good to know.
That fuel pump relay is pretty important then!

Yep. And more importantly, the fact that without a good Hall sender Cam position signal, the FP relay will never be activated and the car will never start.

[montez]

is there an easy way to test the hall sender or the fuel relay

[S2central.net]

@UrS4boy - I am not sure you are completely correct here.

When I bench tested an ABY ECU - the FP relay was activated ONLY when the RPM sensor (G28 on the crank) was giving something more than 25rpm. I was doing this without a G40 (hall sensor) input from the camshaft/dissy... Maybe 3B and AAN is different on this but it would seem odd.

AFAIK - G28 is the gate for activating the fuel pump while G40 is the gate to determine ignition on cranking... If ECU cannot see both G4 and G40 arrive in the expected way - it has no way to know where #1 cylinder is... without that it cannot start.

So - if you have no sparks then either G4 or G40 is faulty (could be mechanical/dissy problem on the 3B as per broken cog suggestion already).

If you have no fuel pump activation then a faulty G28 is most likely (assuming the relay is good).

Remember - ECUs are pretty stupid when it comes to fault codes sometimes... You really need an oscilloscope to see WTF is going on sometimes - at the sensor and the ECU ideally to rule out a potential loom fault / crusty pin / bad joint.

This is why I internally modified a fuel pump relay a while back for easy testing... posted a thread with pics and such ages ago. It is also why I created the plug and play hall effect tester... Available for loan if it helps you root cause it.

[montez]

I will try the fuel relay mod tomorrow, I don't understand that if I check the voltage going to the fuel pump when the ignition is on it is seeing 10v but not running? is it because it is not sending enough amps over?

[BrianSmith_S2]

@UrS4boy - Remember - ECUs are pretty stupid when it comes to fault codes sometimes... You really need an oscilloscope to see WTF is going on sometimes - at the sensor and the ECU ideally to rule out a potential loom fault / crusty pin / bad joint.

.

Is it just me or is this stalling and non starting issue seems to be occuring more frequently to forum members. I feel a 2 channel oscilloscope group buy coming on to do a bit of sensor probing

[S2central.net]

You get NO volts to the fuel pump until the FP relay activates it... Sure you can hotwire with a jumper around it to prove the pump runs, but you should place the voltmeter at the fuel pump while cranking to see it go from nothing to something approaching 12V (nominal).

If you are jumping 12V directly onto the fuel pump and you cannot hear it run then it is faulty for sure.

[montez]

I am seeing 10v at pre-ignition and it drops to 8v when it cranks, but pump does not work. pump works with 12v directly from the battery

[newsh]

Have you got an alarm immobiliser on the car?

[S2central.net]

There's a damn good question Mr Newsh.

If pump runs when its jumpered then either the FP relay is faulty (not activating the pump) or the ECU is not enabling the relay - maybe because of immo / security wiring or that G28 (RPM) signal is missing.

[montez]

Yes, I have a meta immobiliser with a push in key fob under the dash. If I test the voltage to the fuel pump before the imobiliser has been dis-activated I get nothing at the fuel pump with the ignition turned on, if I deactivate the immobiliser it shows the 10v constant, but it does not run the fuel pump or any others I have tried and this drops to 8v on crank.

I am just going to check the voltages across the FP relay which you use to put the diode onto and see if I get anything.

[newsh]

We had this same problem a few weeks ago with a member's car, the car had an aftermarket alarm/immob unit which had a multipin connector on the alarm unit. The pins carrying the fuel pump voltage had overheated from the current and burnt out, they were passing about 10v to the pump but there was not enough current flowing to run it. Have a look down by the ECU for a green wire with a stripe (the same wire that appears at the pump terminal) find the place where it's broken into and bypass the immob circuit at that point by re-joining the wire.

[montez]

Ill trace that wire tomorrow, the alarm is a pretty complex system and has been fitted correctly with all black wires so it is not easy to follow but i will get into contact with meta tomorrow and ask them if it cuts fuel and spark