CT944

What next, the crank position sensor? The car has been sitting for 2 years. I had it running for 1 day (after a few hours of cranking and plug wire changes). Parked it overnight, and it won't start. Thought is was the DME replay, but replaced it with a new one today, no luck. What to do? 28,000 mile car. Not my daily driver, so not a big deal.

Shawn944

Ignition switch ?

Shawn
87 944na
automatic

Cyrus951

Gas loses octane over time, try getting some new gas. Was it driving hard when you had it running that one day? It's hard for me to imagine a car driving fine one day, and losing spark the next. Are you sure there is no spark?

SoCal Driver

How was the car stored? Outside?

CT944

Outside for the last 18 months. Motor turns over but won't start. When it ran, it ran good. The gas seemed fine.

Luis de Prat

This sounds like your crank sensor is shot. The rubber plug may have dry rotted from the summer heat, since it's 20 years old despite the 28K. Check the connections and try wiggling them. They're located on a bracket at the back of the intake manifold.

SoCal Driver

CT944

You need to go step by step through a DME testing plan. Yes even over some of the tests you may have done.

There are 16 test points on the one Porsche has for the early 944's. Thirteen of these will cause a no start situation.

A quick test is to see if there is 12 volts at the injectors and at the coil with the key on. This will tell you two things. One is that the ignition key switch is working when the coil has voltage. Second that the DME relay has closed it's first set of contacts sending 12 volts to the injectors and the DME.

Also check and clean all the grounds from the battery to the chassis and the engine to the chassis. Check the positive cable too. The cluster of 10 gauge wires going to the positive terminal tend to loosen on the stock connector.

After this you have to look at the speed and reference sensors and the fuel pump.

The 12 volts for the fuel pump comes off of the second set of contacts in the DME relay. If you open the drivers door and bend down the crank the engine, the fuel pump will run for a half second after you let off the key/cranking. The trigger voltage for running the fuel pump comes off of the solenoid side of the starter.

This is not the same signal that the DME uses for running the fuel pump with a running engine -- plus 200 rpm. This is the speed sensor.

Sensors can be checked with an ohm meter to see if their circuit has opened up -- broken wires. From the center pin to one of the out side pins should be 0.6 to 1.6 k-ohms. The other side pin is an isolated shield for the cable. If you have an oscilloscope then the total peek to peek voltage should be 2.5 or greater. If not then the sensor to flywheel distance needs to be adjusted.

Another item often overlooked is the spark cable between the coil and the dist. This corrodes in the weather boots and will pull loose from the end connectors.

You did do the timing belt on the car before you started driving it?

SidViscous

Swap the coil. Worth a try.

CT944

How do I check those sensors. Do I need to undo the bracket first then undo the connectors? Where to the other ends go to? If they go into the motor, is it OK to pull them out to clean them?

Thanks.

Luis de Prat

Be very careful with the sensor connectors. I suggested the sensors because for one thing, your car ran a full day, didn't it? I had the same problem of turning but not starting on my 83 when I accidentally leaned on the connector and the rubber plug cracked. Someone else here found that wiggling the connector without taking it apart allowed them to start the car.

At any rate, you may have to replace one of the sensors. They're 2 identical units on the 83. Unfortunately over $100 apiece!

The other ends go to the clutch bellhousing. You'll need an elbow extension and a ratchet to get down there. I suggest presoaking overnight them with some WD-40 beforehand. Not sure whether cleaning them will help, but whatever you do, don't crack the connectors or you'll definitely need a new sensor.

SoCal Driver

I take it you have checked for the voltage at the coil and the injectors?

Pull the sensor plugs one at a time and use an ohm meter to see if the internal sensor wiring is intake -- no broken wires.

If they check out to have the proper resistance AND they have not been moved recently (clutch job) then most likely they are OK.

Check the spark at a plug. Get any used plug and check the gap. Set it to about .025. Pull the number one plug wire and stick the extra spark plug into it. Lay it across the intake to ground it and crank the engine. If you have spark then the rotor is turning (timing belt), the coil is working and the reference sensor is working.

If you have spark then it's on to the fuel delivery and intake air sensor.

Terry Jamison

I recently had the same problem on my '84 after it had been parked outside for a while. It however died on the freeway after I had a new catalytic converter welded in place.

I second checking out the coil wire. The boot on mine at the coil had cracked and allowed moisture in. The connector corroded away at the coil. I didn't find it 'til after checking many other things. I ended up replacing the coil and trying to fix the coil wire. I tried to plice-on a new connector. But it didn't work. The little brass spring plug that's part of the coil wire was all corroded as well. So, I ordered a new coil wire from the dealer at $32. It was cheaper than a whole set of wires.