SoCal Driver

You have to eliminate all of the inputs first.

Are the sensors pulsing 2.5 volts?

Is there the correct voltage going to the AFS?

Is the AFS showing the correct range of resistance as the flap is moved?

Is the temp sensor in the AFS ranging correctly?

Is the engine DME temp sensor ranging correctly?

Is the throttle switch working correctly?

Me thinks its the sensors and the fly wheel. The speed sensor comes off of the starter ring teeth. The reference sensor the pins. The sensors are adjusted to the starter ring 0.8mm and the pins will have to be addjusted to the sensors.

Mike Pancheri

Hey guys-

I'm the mechanic currently working on the car. Thanks for all the help so far!

As an update:

Injectors have 12v with Key-On

Coil + has 12v with Key-on and while cranking

At this point, I'm assuming the DME is not at fault, correct?

The Ref/Speed sensor adjustment bracket is basically rusted/frozen to the engine, so it could not have moved.

The new Fidanza flywheel had the pin installed. We doubled checked the depth and distance to the sensors with a .8mm washer, and also used some plastigage to confirm. All is ok on that front.

We swapped the sensor positions on numerous occasions, even though the labels on the wires makes them impossible to confuse.

The condition is manifesting itself as follows: We crank the vehicle, and there is no spark present at the plugs. However, as soon the key is released, we are getting two quick sparks.

We are now backprobing the sensors to establish the 2.5v fluctation while cranking. Is it safe to assume that if the 2.5v is not present that one and/or both of the sensors are inoperable??

Thanks again. I look forward to any input you all might have.

Michael Pancheri
TyrolSport

SoCal Driver

Michael,

Nothing like taking the bull by the horns!!!

Single pin? There are two consecutive pins on my 83 944 flywheel. The single pin at the forward rim is for the factory TDC test sensor. But if this matched the flywheel you took off...

At this point I would have to use a scope and see what the speed and reference sensors are indicating. Also check that the injectors are firing.

Getting spark letting off the ignition key is possibly from the power being removed from the coil and the DME discharging. The DME takes the coil to ground to fire it.

Never used one but others say you can use a "noid" light to check the injector pulse.

As a test of the DME relay you can jump across the pins to run the fuel pump and power the DME.

Pins 30 to 87 will power the DME and the injectors. Pins 30 to 87b will run the fuel pump.

Rather than pin 30 which is direct to the battery I would use pin 86 which is from the ignition switch.

There have been a rash of bad sensors lately with wires fracturing in the connectors. The whole sensor has to be replaced as the cable has a specific impedence.

I've never had a starting problem with the two clutch jobs I've done, one with an engine swap. Have had a bad sensor that was a real PITA to figure out with just an ohm meter.

Mike Pancheri

Thanks for the response, SoCalDriver.

I backprobed the Reference and Speed sensors using a Voltmeter(No oscilloscope)

Reference sensor: 1.85v spike

Speed sensor: 2.15v spike


Any ideas?

SoCal Driver

Spec.

Speed is > 2.5 volts total sine. This is a constant input and should not have any spike or fluctuations.

Reference is > 2.0 volts positive.

So I would say you are a little shy. Need to check the clearence and set it at 0.8 mm on the back (speed) sensor. The reference sensor should follow along.

Also should have almost 2 ohms resistence between the center and one of the outer pins on the sensors.