Coupe 20V Starting

Audi Nut Joined: Jan 03, 2007 Posts: 77 Location: Cork

I am nealy finished a major rebuild on my 1990 20V (7A) Coupe quattro, I noticed on another post on here that the G62 Coolent Sensor plays a part in the timing of the engine, the original connecter on this was missing when I bought the car, the connector pins are still there, I just pushed them on the pins on the G62, if the wires are not connected to the right pins on the G62 Sensor would the engine fail to start. Would this apply to the Main Temperature Sender under the Inlet Manifold and the another sensor (not Knock sensors) lower down on side of the block under the MTS.

Needs to get out more Joined: Dec 03, 2010 Posts: 180

i dont know for sure but i think one sensor is for the temp gauge on the dash and overheat warning, and one is for the ecu temp signal and one for cold start or coolant fan after run. i think only one sensor is used by the engine management . have you tried the 20v.org site? you may get more help there.

Posted: Fri Jan 06, 2012 11:55 pm

G62 is the temperature sender for the ecu. It's located at the rear of the head and has a 2 pin connector.

Is this the sender you're referring to ?

Posted: Sat Jan 07, 2012 8:24 pm

You may well already know this, but probably the biggest 20v no start issue, is ignition timing. You must get flywheel '0' mark lined up with the 'flat' edge in the bellhousing window, the cam sprocket must line up with it's index mark at the top of the cam cover and the rotor index mark (and therefore rotor arm) must be lined up with the notch on the distributor housing.
The front pulley also has a tdc mark but cannot always be trusted, the vibration damping rubber can allow it to slip out of synch, best to use the flywheel mark, which will be accurate.
Other than that does it throw a fault code at all?

Audi Nut Joined: Jan 03, 2007 Posts: 77 Location: Cork

Thanks for the replies, its the G62 Sensor on the back of the Head, this could be wired incorrectly, what colours are 2 wire going into the sensor, and which should be on the top and Bottom pins.
The Cam Shaft Sprokets marks is lined up with timing marks on the Cam Cover and the Fly Wheel 0 is lined up with the Bell Housing, there is no spark at the Plugs, if the G62 Sensor wires were crossed on the sensor pins, would the engine fail to start.

Posted: Mon Jan 09, 2012 2:08 pm

The G62 sensor can be connected either way round - it doesn't matter.

I doubt that this is causing your 'no start' problem. A disconnected sensor just looks like a very, very cold one.

Most likely, the no start is caused by the distributor not being lined up exactly correctly.

To quote Scotty: "... and the rotor index mark (and therefore rotor arm) must be lined up with the notch on the distributor housing. "

I speak from experience: the rotor/distributor need to be aligned with each other almost exactly, before you get sparks.

Ian.

Posted: Mon Jan 09, 2012 6:44 pm

A temp sensor issue will not cause a no spark scenario, a timing issue will.
If you are sure the distributor is set right, I suggest you pull fault codes?

dizzy with dustcover removed. Align the '-' on the hall effect rotor with the notch on the edge of distributor body

Posted: Mon Jan 09, 2012 7:46 pm

have you inspected the hall sender and coil?

Posted: Mon Jan 09, 2012 9:16 pm

As Scotty has indicated, if the flywheel mark is lined up and the cam pulley dot lines up with the V, you should remove the distributor cap and confirm that the rotor arm points to the HT lead for #1 cylinder.

If you have no spark, there are some tests in the workshop manuals you can run to eliminate certain components.

Are you getting a spark from the coil ? Easy to test by grounding the main HT lead from the ignition amplifier.

I've had this a couple of times. First time was a broken flywheel pin. 2nd time was a broken wire inside the connector for the distributor.

Audi Nut Joined: Jan 03, 2007 Posts: 77 Location: Cork

Thanks for all the replies, Dizzy marks are lined up with rotor pointing to Cylinder No. 1 HT terminal post on Dizzy. I will check Coil and other checks as indicated in Haynes Manual, prior to the strip down, the engine was firing, there was a problem with a leaking Injector which was causing a misfire, car has not been started for a few years, could any of the critical items failed since last started. There is an alarm system with immobiliser on the car, maybe this could have went faulty when the car was laid up.