obd2 vr non starter

[Lee1873 0]

My mates Golf vr obd2 currently wont start, no fuel getting to the rail when cranking, unsure if theres spark. Im led to believe on an obd2 engine the pump doesnt actually prime & only runs when the engines cranking, tried the fuel pump relay with a known good one & no change, when scanned with vag.com it does show a maf fault(short to ground) but Ive had this fault before on VRs & the car still runs allbeit roughly

 

I tried giving the pump a separate 12v feed when cranking(or even not) the engine & the pump ran & delivered fuel to the rail.

 

So my question basically is, what component/sensor triggers the fuel pump /injectors & ignition system when you turn the key? am I right in thinking along the lines of the crank sensor being faulty & this being the trigger to start the pump/injectors & ignition circuits?

 

blown ecu also crossed my mind but would the diagnostics still communicate properly if this was the case?

 

any tips appreciated

 

cheers

 

Lee

[fla 9]

ecu relay 109

[Lee1873 0]

ecu relay 109

 

cheers for replying mate, I didnt think the obd2 cars have an ecu relay? certainly doesnt have one in the fusebox with a 109 on it? As i said I already tried the fuel pump relay no.167 but no difference.

 

If your sure this relay is indeed on an obd2 I will check again, could you by any chance tell me what position it is in the fusebox?

 

cheers

 

Lee

[fla 9]

you're right the crank sensor shuts down the injectors and spark - i dont really know anything about the OBD2 setup tbh. Sorry :( I would see that the crank sensor is still connected and there is a good contact between the sensor and the block (which provides the -ve)

[CorradoVR6-Turbo 0]

there is one signal wire to the fuel pump realy,once the relay is active it sends a feed to injectors,carbon canistor valve etc to name a few,so check this feed to the relay,you need to find out if injectors are working,either with a noide light or multimeter,this will tell you straight away if there if feed from the relay as Fla siad.

 

http://www.a2resource.com/electrical/CE2.html

 

G01/03

 

 

not bad for a few bears me thinks :lol:

[Lee1873 0]

there is one signal wire to the fuel pump realy,once the relay is active it sends a feed to injectors,carbon canistor valve etc to name a few,so check this feed to the relay,you need to find out if injectors are working,either with a noide light or multimeter,this will tell you straight away if there if feed from the relay as Fla siad.

 

http://www.a2resource.com/electrical/CE2.html

 

G01/03

 

 

not bad for a few bears me thinks :lol:

 

Cheers mate :thumb right:

So I take it Im looking for battery voltage from G01/03? & only when cranking the engine over?

If theres no feed there where should I be looking? ecu? crank sensor?

 

Also have a multi meter to check injectors, do i just unplug one & check for power (when cranking over)?

 

cheers again

 

Lee

[CorradoVR6-Turbo 0]

there is one signal wire to the fuel pump realy,once the relay is active it sends a feed to injectors,carbon canistor valve etc to name a few,so check this feed to the relay,you need to find out if injectors are working,either with a noide light or multimeter,this will tell you straight away if there if feed from the relay as Fla siad.

 

http://www.a2resource.com/electrical/CE2.html

 

G01/03

 

 

not bad for a few bears me thinks :lol:

 

Cheers mate :thumb right:

So I take it Im looking for battery voltage from G01/03? & only when cranking the engine over?

If theres no feed there where should I be looking? ecu? crank sensor?

 

Also have a multi meter to check injectors, do i just unplug one & check for power (when cranking over)?

 

cheers again

 

Lee

 

 

The siganl wire from the ecu is a earth switch,that controls the relay,you could just try bridging the relay across,this will let you know if you have a working signal wire from the ECU,but yes you should see battery voltage when cranking.

 

Do you still have the imobolizer or has this been removed?

 

As for injectors the multimeter needs to be switched to continuity,you should see it fluctuate when cranking,if nothing but a steady reading then its dead,

[Lee1873 0]

 

The siganl wire from the ecu is a earth switch,that controls the relay,you could just try bridging the relay across,this will let you know if you have a working signal wire from the ECU,but yes you should see battery voltage when cranking.

 

Do you still have the imobolizer or has this been removed?

 

As for injectors the multimeter needs to be switched to continuity,you should see it fluctuate when cranking,if nothing but a steady reading then its dead,

 

The car still has the factory immobiliser along with an aftermarket one that i switched off before trying to sort the problem, going by what you say then can I just unplug the relay from the front of the fusebox & stick the multimeter in the terminals there to check for the ecu trigger signal or do i have to drop the fusebox & take the plug out the back & test it this way?

 

Ive had issues in the past with the factory immobiliser on these myself but normally they run for a sec. or 2 then die?

 

Also tried the ususal dodgy ignition switch & have done the wiggling the key thing with no joy either.

 

Will have another look this afternoon & see how I get on

 

cheers again

[CorradoVR6-Turbo 0]

yea they will fire and then die if the immobiliser is active and yes you just have to pull the relay out and check the feeds,thin small terminal should go to ground when you switch the ignition on(ecu trigger),then one earth and one battery live,the last terminal is the feed to injectors,coilpack etc. you could just breech these tow across and see if it fires?

[Lee1873 0]

Thanks for your help mate much appreciated,

 

I ran all the tests you suggested & it appears the ecu trigger must be dead, either that or the aftermarket immobiliser is in the circuit & stopping the feed, no ground signal from the thin pin socket for the fuel pump relay & no fluctuation @ the injectors :(

 

Thing puzzling me now is that the wire G01/03 is black in colour & runs to what looks like an aftermarket relay thats fitted to the top of the fusebox, Im thinking this may be part of the aftermarket alarm/immobiliser, is this logical thinking?

 

Presumably under normal circumstances this wire would come directly from a certain pin(pin 6 i think?) on the ecu plug?

 

If that is the case before trying to cut out the aftermarket alarm sys. would it be plausible that i run a temporary wire from the correct wire/pin on the ecu plug loom to the pin G01/03 to see if it triggers?

 

Any other tips/help you could give would be great

 

cheers

[CorradoVR6-Turbo 0]

It should be direct from ecu that trigger wir,e i doubt an alarm fitter would have picked that wire to disarm the ca,r more likely he would have just picked a random ignition wire under the cowls,have you just tried to earth that trigger wire to see if the car runs? as ive seen theses feeds dead before as allot of folk try to send a 12v feed down the line and pops a little diode in the ecu,so ive just used a toggle switch to activate the relay,only down side is when your on your roof in a ditch and the engine stalls but still is spraying you with fuel......you get the idea :lol:

 

Ive sent you a PM regarding sending you the OBD2 wiring diagram :wink: