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[Snapper]

A while back my 3.0V6 "S" Reg started to give problems starting. I even managed to use all the battery trying to get it to fire. There is no indicator on the dash to suggest engine management warning ...and so far it has recently had new plugs, filters, etc. The fuel pump relay has been replaced as has the pump.  Yet the old sod continues to play up, sometimes starting OK and other times needing jumping after dropping the battery to below turnover.

It has never been a problem once up and running and this makes me ask.......  is t possible that a dud battery will posses enough to turn the engine over but not enough to fire the system up ?
After several tries t fire her up and running the battery down the AA man has turned up, connected his battery thing and it fires right off. I have then driven it to the garage and it has been there overnight, starting OK every time they try and again without problems in the morning !

Any ideas of where I should look next ?

[Grumpy]

The fact that someone changed the Fuel Pump and Relay suggests that
some checks were done that pointed to no output from the pump.

If this is the case it's possible that the ECU was not issuing a command to energise
the pump, ie a faulty Crank Sensor.
Do a paperclip test and post results iaw this link.

http://www.omegaowners.com/forum/YaBB.pl?num=1189022687

If this is ok, you may have an intermittent wiring fault in the pump/relay/ ecu
circuit.
You will need to isolate each circuit and test for faults.
A) Ecu to relay.
b) Power supply through the Relay to the Pump Fuse if the relay is working.
c) Fuse to fuel pump.
d) Fuel pump Earth Return.

For a quick check if the relay is working, check for a 12V supply at the pump fuse
with ignition switched on.

For the battery, stick a Voltmeter across it and check for a reading of approx 12.5
to 12.6 Volts.

If ok, start engine and stabilise the voltage reading across the battery.
You're looking for a higher reading circa 13 Volts.
If ok, load the circuit by switching on headlights and heated rear window and
recheck. You're looking now for between approx 13 and 14 volts.

That little lot should keep you going for a little while.  

[Snapper]

Thank you for your reply and the suggestions .... just to make clear the error process in the Omega, is it possible to have error codes stored without the engine management light staying on to indicate that an error has been stored ? Mine remains off at all times other than initial start-up.

[VXL V6]

Possible Crank Sensor failing?

[Snapper]

OK I have done the Paperclip test and all I got was 2-1  and 3 -1  which I presume are reporting that the game had begun and that the engine revs were "0" . All it did was repeat these sequences x 3 and then return. Checked with my cheepo volt meter the voltage cross the battery when off and it reported 12.5  to 13 volts  ( see told you it was a crappy meter.) (rapitest) .

[Grumpy]

I got was 2-1  and 3 -1

Can I assume that was a typo and was 1-2 (Initiation of Diagnosis) and
not 2-1 (Throttle Position Sensor High Voltage) ?

3-1(31) is not conclusive with Engine not running. But if genuine would
be the reason why your Fuel Pump is sometimes not energizing, as the ECU
would be not receiving a Crank Sensor signal and would not send a signal
to the Fuel Pump Relay to energize.

Change the Crank Sensor would be my advice. They are a known common
problem.

[Snapper]

Because of the uncertainty of the 3-1 result, and the comments in the instructions for the clip test which state that 3 -1 is common on V6 when the engine is not running ..... I popped the car over to the local garage and they fixed it up to their tester . They confirmed that no engine management light would suggest no error , and on their screen the received no errors ! So , where on earth does this leave us, sure I can change the Crank Sensor but it makes me wonder why there is no error on their tester and why no management light is illuminated .

Any ideas about these queries ?

[Grumpy]

Because your fault is intermittent. The light will only be on when the fault is present.
When your fault is present, your engine doesn't start, the light is on, and you
don't go anywhere.

When you start ok and run round to the garage, you haven't got the fault and
they test a fully working system.

What were symptoms and checks they carried out when they diagnosed
the Fuel Pump Relay and Fuel Pump as faulty?

[Snapper]

Thanks for that , it amazes me that the ECU is not designed to recognise and record ignition faults ..... and having stored them spew out warning at the next successful start. Oh well GM foods are banned perhaps their logic should be too


SO guess I better find out how much this little wonder circuit is going to cost

[VXL V6]

The problem is that until the engine is running a lot of codes will not occur, Crank Sensor is an awkward one because if you have a problem with it then you will not be able to start the engine, the intermitent code that you might find stored is 19 I believe.

Not sure of the price for the 3.0 but I bought one for a 3.2 from VX for £57.00

The fault is intermittent because it tends to be a breakdown of the cable due to heat from the exhuast, the guide on here details an alternative route that keeps the cable as far away from the exhaust as possible.

[Grumpy]

SO guess I better find out how much this little wonder circuit is going to cost

It's only held in with 1 bolt and 1 electric connector. The trick is in the routing
of the cable on which 'Marks DTM Calib' has given a good write up.

Get down and get dirty, do it yourself and save some loot.  

[hotel21]

Its my understanding that fault codes are stored albeit that the management light may/does not light.  IIRC it takes a number of (20??) clean starts for a fault to clear but they are viewable historically via Tech2.  It can then wipe the system 'clean' thereafter.....

Someone will no doubt confirm later....

[Markie]

Its my understanding that fault codes are stored albeit that the management light may/does not light.  IIRC it takes a number of (20??) clean starts for a fault to clear but they are viewable historically via Tech2.  It can then wipe the system 'clean' thereafter.....

Someone will no doubt confirm later....

Spot on..

Jamie was able to tell at lakes that i ( some 8 months previously) had an issue with drivers window,

[VXL V6]

....and MDTM was able to tell from the Headlamp ECU that the car had a low battery just before I bought it!!!!

Yes I seem to remember the 20 start clear from other Vauxhalls, however if it's in the circuits for Airbags etc then the airbag light will not clear even when you fix the problem, it has to be Tech II'd which is fair enough for a safety circuit I guess.

[lee4206]

This might sound silly but have you checked the engine earth strap as i had the same intermitant problem on my 2.0  the bolt that the cable connects to was loose. And when i jumped it it started first time because i connected the leads to the positive side of the battery and the engine (therefore.  bypassing the fault).   Worth a try you never know..

P.s the way i found out was getting someone to start it while i looked under the bonnet at night and i noticed the spark