Speed and ref sensors.

[calmchaos944]

Hello.
Recently I had the retaining bracket for my 1986 944 n/a auto trans break and take my sensors out with it.
With the old sensors the car would start but misfire above 20mph.

I got a set of sensors and a bracket from a 86 n/a manual and tried to hook them up tonight.

I gapped them with the rear sensor that hovers over the ring gear, and tried to start the car. And no go.
The tach didnt bounce or anything.

So I gapped them again. Still no bounce on the tach, or start.
The back sensor (above the ring gear) is properly gapped, but I stuck my finger in the TDC inspection hole and found that I could slide my finger under the front sensor (above the flywheel).
So the back sensor is all fine but I cannot get the front one to go down enough to get a proper reading to the DME.

The part numbers on the sensors are the same as my old ones.

Does anyone have any idea why this would happen? Is the retaining bracket different for the manual and auto trans flywheels?
Does the auto flywheel have a smaller diameter?

Any ideas on how I could remedy this?

Thanks for any help.
~Brett

[SoCal Driver]

If your old sensors had a collision with the flywheel then the pin (set screw) for the reference (front sensor) could have broken off. Also note that this pin is not at TDC as the line on the flywheel is.

You could also have the sensors plugged into the wrong leads.

[calmchaos944]

I made sure they were plugged in correctly.
What could be done if a pin has broken off?

[calmchaos944]

if it is only one pin. it is still there and looks unharmed.
The back sensor is the one that took the beating.

[calmchaos944]

I got the sensors professionally checked and they're ok.
I'm not getting spark and the tach isn't bouncing.

What could it be? Could the sensors have blown the DME?

[SoCal Driver]

Where does one get the sensors professionally checked?

Do the five minute test.

[Brando]

Only way to "check" to see if your pin is broken is to have a borescope and look through the hole of one of the sensors for the pin as you rotate the engine. Or separate the bellhousing, move the drivetrain back and check the flywheel.

[calmchaos944]

I took the sensors to a shop that works on German cars. Most of which are 944 or 951 around here.
What is the five minute test?

And Brando, why can't I check the pin by just looking through the TDC hole? I don't even see any scratch marks on it.

Thanks

[calmchaos944]

And as of right now I'm sitting on a no spark condition. I checked the coil and that is holding a charge and can spark. I checked the ignition X and DME relays. I hooked up a timing light to a plug and I'm just getting no spark. The cap and rotor are good. Wires are good.
The only thing I could think of is maybe the DME itself?

The sensors are gapped and bolted in and it seems they were checked to be OK.

Any other ideas?

[SoCal Driver]

See if you are getting an injector pulse. Both the coil and injector logic come off of the reference sensor. If there is an injector pulse then the coil circuit in the DME is bad. Usually a "loose" transistor. Solder connections have cracked. Can be re soldered.

[calmchaos944]

This is going to sound dumb, but how do I do that?
Just stick a volt meter into one of the injector connectors and try to crank the engine?

[SoCal Driver]

Go to a good autoparts store and buy a 'noid' light for Bosch injectors. Goes between the injector and the connector. Flashes when the injector is pulsed.

[tnporsche]

Get a oscilloscope to see if a pulse is really being sent.

No pulse nothing will work.

[calmchaos944]

Originally posted by tnporsche
Get a oscilloscope to see if a pulse is really being sent.

No pulse nothing will work.

I could go to a mechanic for the cost of an oscilloscope.

Also, there is no auto parts store around me that has noid lights. Is there any way to check the injectors with just a volt meter or am I going to have to get one online?

thanks

[Brando]

To test the injectors in the system you need something that goes between them and their connection to the DME. Hence the noid light. If you have spare connectors of male and female type you might be able to make something. But why do that when you could buy the light?

[SoCal Driver]

Please put your "location" into your profile. Even PepBoys has noid lights. Might try asking for injection tester light.

eBay No. 290115145509

[SoCal Driver]

Another eBay 140118176028

[calmchaos944]

hmm... OK thanks.
I'll try pep boys even though it's an hour away.
I have an advance and a Napa near me, but both told me that they don't have them anymore. No idea why.

Thanks though. I'll let you know what I find out.

[calmchaos944]

FOUND IT!
Ok, I replaced the reference sensor wires with Lindsey racing ones, and it works now. Must have just been bad wires.
Funny thing is I wasn't even going to do that, but I figured since the noid light and other things were taking so long to get here I would replace the wires.

At least now I have a noid light kit if I ever need it again.

Thanks for the help!