Wont start after warm up

[jarjar]

Yes, ideally all codes will be cleared eventually...I have the LEDs for the cluster just need to find time to solder them in
The car is a 2001 2.7 986
No other fault codes except airbag passenger side and AC codes and a seat buckle
I verified that the DME and fuel pump relays both work.
Jumpered the fuel pump relay socket and could hear the fuel pump...cant hear the pump with the relay in
Measured the voltage at the fuel pump relay socket and is only around 8V with the ignition turned on....should be 12V I believe to actuate the relay
Fuel pump fuse is good...measures 12.5 V on bottom side and OV on top side when fuse removed
I agree there is likely a ground issue somewhere...just have to find it...open to suggestions

cheers

[blue62]

Originally Posted by jarjar

Yes, ideally all codes will be cleared eventually...I have the LEDs for the cluster just need to find time to solder them in
The car is a 2001 2.7 986
No other fault codes except airbag passenger side and AC codes and a seat buckle
I verified that the DME and fuel pump relays both work.
Jumpered the fuel pump relay socket and could hear the fuel pump...cant hear the pump with the relay in
Measured the voltage at the fuel pump relay socket and is only around 8V with the ignition turned on....should be 12V I believe to actuate the relay
Fuel pump fuse is good...measures 12.5 V on bottom side and OV on top side when fuse removed
I agree there is likely a ground issue somewhere...just have to find it...open to suggestions

cheers

How old is your battery?
What voltage does it show?

Fuel pump relay
pole 30 is power from the fuse at C4 key on. this power source actuates the relay.
pole 86 is constant "battery" voltage KEY ON OR OFF in or out so it should show 12+ volts if your battery is good
pole 85 is ground at the ECU always shows ground
Pole 87 power to the fuel pump when relay contacts close

Any work done before the issue started?
like in the last say six months?
There is a list of ground points in the Bentley book

The power from pole 30 which comes from the C4 is what actuates the relay.
If you need to know that voltage I can test mine and let you know.
I don't think a relay needs 12 volts to close the contacts but I could be wrong.

[jarjar]

Thanks so much for the info..
Battery is newer and tests about 12.5 and 14.4 running

Did some quick tests all from front of relay panel
pole 30 and 86 both show 12V key off OR on

87 is zero volts too ground

85 is 3.5 volts...I think this explains the 8 volt reading between 85 and 86 which I think needs 12 volts to actuate the relay...so need to find why pole 85 is at 3 or so volts

Funny thing is that the car actually starts ...just stalls every so often

replaced the ignition switch in the spring of this year with a vw replacement...havent had any running issues since then...other than that just the window regulator that I just replaced

Cheers

[blue62]

Originally Posted by jarjar

Thanks so much for the info..
Battery is newer and tests about 12.5 and 14.4 running

Did some quick tests all from front of relay panel
pole 30 and 86 both show 12V key off OR on

87 is zero volts too ground

85 is 3.5 volts...I think this explains the 8 volt reading between 85 and 86 which I think needs 12 volts to actuate the relay...so need to find why pole 85 is at 3 or so volts

Funny thing is that the car actually starts ...just stalls every so often

replaced the ignition switch in the spring of this year with a vw replacement...havent had any running issues since then...other than that just the window regulator that I just replaced

Cheers

Pole 30 position at the relay panel..... or lets call it the "relay socket".
Should "only show voltage with the key on". There should be "no voltage with key off"
That voltage is coming from fuse C4 the fuel pump relay fuse.
It is switched power. It is what activates or switches the relay.
If it is showing voltage at relay socket 30 with key off you have some wiring issues.

[jarjar]

Voltage is still there at pin 30 with the key off, but car seems to be running fine yesterday with no stalling issues, although I didn't drive it anywhere. Looking at the Bentley book it looks as though fuse C4 runs to a hi current fuse that comes from the battery and I don't see where it switches with the ignition on or off. C1 -C4 are all tied together so I pulled C1-C3 to see if the 12 V would go away at pin 30 but no dice. I tested the relay again with a lower voltage applied and it actuates at 8 volts so the 3.5 volts coming from the ecu shouldn't be a problem. I also pulled the ecu cables off and cleaned the pins. One strange thing is that my brake wear sensor light on the cluster has now gone out...the pads are fine but I thought one of the sensor wires was shorted causing the light to be on. Im going to keep investigating as I don't see what could be causing the no start issue and I don't really trust it to drive it any distance. Going to start looking further at grounds and the cluster...try to clear up some codes as you suggested...thanks again for the help!...cheers