Hiow to Test for crank / sensor

[racecar866]

my 944s just stopped running. After cooling it started again, now it wont start at all. I checked fuel, seems like plenty coming out of rail. spark is there, Does anyone know how to check the sensors for cam and crank. I thought if you cranked the car over and the tach moved that confirmed they where ok, both seem to be plugged in and appear fine. Any help or other suggestions are welcome.

[mlue]

Remove the DME Relay also called Fuel Pump Relay lightly tap it a few times and replace to see if thats what causing the problem.

[SoCal Driver]

You need an oscilloscope to test the sensors. Reference puts out a plus 2 volt pulse per engine revolution. The speed puts out a continuous plus 2volts so it could be checked with an analog volt meter.

It's usually the connectors that fail. Either don't stay together (use a pull tie or two) or are cracked and have broken the wires inside.

www.clarks-garage.com

[blown 944]

I doubt it is the sensors if you have spark.

I would look at a fuel situation moreso.

[earlr85944]

I agree, if you have spark and fuel check the quality of both, also check plugs etc.

[onZedge]

I used a wide angle LED from Radio Shack p/n 276-309 with a 220ohm current limiting resistor. LED voltage range is 1.7-2.4V. Works like a champ and you can see either the ref sensor pulse or speed sensor pulses. For less than $5, I even embellished mine with female spade connectors and a chrome LED holder for better visibility. I also made another one with a 2.1V LED as a go/no-go tester. I reason that if it could fire that, the sensor to flywheel tooth clearance is "probably" OK.

Everybody needs to have one of these in their tool box to awe spectators with your electromechanical troubleshooting prowess!

[Razorback1980]

That's pretty cool idea Edik...a lot cheaper than an oscilloscope.

[SoCal Driver]

I like it when people save the jpegs I up load!

A "noid" light for the Bosch injectors will tell you if they are firing. How is the compression?

[racecar866]

I removed the DME relay, tapped it a few times and boom she fired right up. Thanks for the help.

[earlr85944]

Cool, now change it and or carry a spare.

[mlue]

Originally posted by racecar866
I removed the DME relay, tapped it a few times and boom she fired right up. Thanks for the help.

You're welcome, get a new relay ASAP.

You're the 3rd person among others since the new year started that I've told this to and it has worked, a few years ago this basic DME relay check would have been 944 "101" but now i think most people are over looking this relay and just jumping ahead thinking the problem(s) are more complex than they are.

[onZedge]

Originally posted by earlr85944
Cool, now change it and or carry a spare.

Change it AND carry a spare!