Wont start after warm up
 

This started happening last week. After driving and the engine warming up , the car won't start. Starts and runs fine after cooled down. From what I have read it could be CPS or fuel pump....or perhaps a valve near the canister up front. Would be happy to hear from anyone who has experienced this and what worked to fix the issue

Thanks

First you have to identify the issue before you can fix it.
Do you have a check engine light on?
Any codes?
You can use a digital volt meter to test the CPS and or the fuel pump.
a simple Ohms resistance test for starters..

Or watch your tachometer needle while cranking when hot (your no start condition).
The needle should pulse... if it does not then the CPS is suspect.

A fuel pressure check at the fuel rail (presta valve) with your no start condition present will tell you if you have fuel pressure or not.
Unlikely that your fuel pump stops working just because the engine is warm.
It sets in the fuel tank and is cooled by the fuel running through it.

Classic cps symptoms. Start there first.

Thanks for the replies.
I tried to get the car to recreate the issue by idling it in the driveway...now it will stall on occasion...every 15-20 minutes or so...but will start easily after it stalls
My CEL doesn't work as I believe the LED is non functional in my cluster
Only code I can see of any import is a DME code 9110...K21 instrument cluster DME control unit
Intermittent issues are the hardest to troubleshoot...going to test DME and fuel pump relays when the rain stops

Cheers!

You may want to fix your CEL issue and your 9110 code issue first.
Instrument cluster issues can causes other issues.
Instrument cluster issues are often caused by low voltage (bad ground) issues.
You could wind up chasing your tail for a very long time with instrument cluster issues and codes present.
Always fix code issues and other known issues first.
Do you have other codes besides the 9110???
What year is the car??

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.

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.

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

Jarjar

I just discovered that my fuel pump relay has the pins labeled one way on the front of the relay.
Then the pins are labeled the opposite on the back side.

So "MY INFORMATION HAS BEEN INCORRECT".

So yes position 30 is always battery voltage
position 86 is switched voltage
I get voltage at position 86 with key on.
When I turn the key off it takes about 4-5 seconds for the voltage to drop out.

So if I can send you anymore confusing information let me know.

I just tested pin position 86 again to be sure.
It is battery voltage with key on.
But the voltage drops out about 5 seconds after I switch the ignition off.
This is without starting the engine.
Just key on then key off.

Hey blue62

Well, thanks for letting me know...goodness knows Im confused enough with this thing...lol...at least now I know how the relays work...haha

Im going to keep going through things ( when its not pouring rain )...cleaning grounds etc..cluster grounds and ecu grounds first..CPS might still be the issue when warm...I wonder if that could have thrown the DME code...I do have a durametric but my laptop is a bit long in the tooth and a bit frustrating to use...might grab a new one this weekend

Cheers

Pouring rain....I am guessing your in Vancouver Wa.
I am up in Woodland...
Grounds, CPS, or the ignition switch....I know you replaced the ignition switch in the past. But it is a possibility.

Also if your CEL is not working you could have codes.
Then there are pending codes which don't set the CEL.

Up in Vancouver BC area...just north of the border

Ya, will be working on a few things today and may get out the durametric on the weekend...should have tackled this in the nice whether...lol

Thinking just to replace the cps, although I am not one to throw parts at a problem...however it won't throw a code from what I have read and they aren't that much for the peace of mind, and may cure the main issue

Might buy a fuel pressure gauge as well...will search for something decent

cheers

You could rig up a way to wire a Digital multi meter into the CPS wires.
Then run the engine tell it stalls.
Then try to start the engine and watch the meter for a CPS signal.
I think they give off a hertz range signal but not positive.

Goggle testing CPS I'm sure you will find lots of info.

I thought you may be down here in Vancouver wa.
Every time you mention rain it is raining here in Woodland just North of Vancouver.

So it stalled again,...I bypassed the fuel pump relay and it started...but when I test the relay out of circuit it works fine on the bench...thinking the relay is intermittent...and not working with a load on it

cheers

Relays do go bad.
one of the things that can happen is......
The points in them carbon up or burn.
That causes resistance ...resistance causes heat.
They get where they don't work when they get hot.
Not common but it happens.
I think that type of relay is not expensive.
Change it out and see what happens.
Keep my posted always interested in solutions.

On my 996, the issue was corroded battery Y cable in the engine, where it splits to go to the starter. I am not sure if that issue is common on the 986 as well. It is a well documented issue on the 996. When I took mine off, the side in the engine bay was very much corroded with green corrosion. It looked horrible.

It was embarrassing when my car wouldn't start on a out of town PCA drive about 2.5 hrs away from home. I was massively relieved when it started after the engine cooled down.

I did eventually get this figured for those who may encounter this problem. It turned out to be the CPS. Its not difficult to change. Cheers