At 05:24 PM 2/7/03, Brendan Campion wrote:
>Car died turning a corner. I thought it was the ignition box. Got one from a 79 - working (99% sure at least).
>Symptoms: Car starts for a split second, and then stops. Classic symptoms of a car starting on a cold start valve, but having no fuel from the injectors.
>If you unplug the AFC relay, and jumper the 30 and (two) 87 terminals, you get the same. When its totally open (no relay, no jumper), it is the same.
>Starts, dies, Starts, Dies. If you do this enough, it will just crank the starter with no catch.
>Voltmeter gets 12V when put on terminal 30 and first 87. If this is done with second 87 term on panel, you get nothing. One goes to one set of injectors, obviously the other goes to the other set.
>I have a second computer. This changes nothing.
>At the injector plug, I can get 12V on EITHER wire by grounding to engine. If you take off the plug, and check resistance on the two pins, it has continuity. Is this SUPPOSED to happen? Meaning the wires going into the
>injector are connected when the car is off, and the key of off.

If you look at Page 97-89 in Volume VI of the Factory Workshop Manual, you can see that the injectors are fed 12 vdc from Relay XVI, the AFC Relay thru two terminals on Plug W. There are eight wires, four from W2 and four
from W3. The injectors are grounded to fire by the AFC Control Unit thru four terminals, so the injectors are grounded in groups of two.

This means that if you pull the connector from injector 1, power can flow from W2 to one side of the plug, and power can flow from W2 to injector 5, to the common terminal (15) on the Control Unit, and back up the ground wire to the other side of the plug for injector 1.

So, yes, you will see 12 vdc on both sides of the plug on one injector, if you only have one plug off.

Study of this wiring diagram will also show that a shorted injector wiring harness can kill up to four injectors, but no single short circuit or wire break in the injector harness (after the Central Power Panel) can kill the entire system.

If your entire injection system is dead, it has to be either in the power supply from Relay XVI, or the injectors are not being grounded by the Control Unit. Since you are showing 12 vdc at the injectors, the problem must be in the Control Unit or its sensors or power supply.

One test that I would strongly recommend is using a stethoscope to listen for injector clicking while the engine is cranking. Open headers won't matter much if the engine isn't firing ....

If you are not getting any clicking injectors, then it is time to look at the Control Unit and its inputs.

The oxygen sensor should not be able to kill the Control Unit, but you can unplug it to be sure. Lack of input from the oxygen sensor just means that the Control Unit runs "open loop".

The throttle switches should not be able to kill the Control Unit.

The temp sensor can keep the engine from cranking hot, by making the mixture too rich. Since the engine just stopped, I doubt if the temp sensor is at fault.

Check the four brown wires (5, 16, 17, 35) at the plug to be sure that they have a good ground.

Check the red/blue (29) and red (10) wires to be sure that they have 12 vdc with the ignition switch on.

Check the black/gray (1) wire with an analog meter (that is one with a needle, not a digital meter) for pulsing voltage when the starter is operating.

Check the black/green wire (4) for 12 vdc while the starter is operating.

Unplug the Air Flow Sensor and see if the engine will run.

Wally Plumley
928 Specialists


...if it has fuel , spark , and is "turning over" has compression it should be running ! So it is back to the basics . Do a compression test to see if it does have compression this also checks somewhat the camshaft timing . Try spraying some fuel into the intake (remove mass air sensor) see if it fires tries to run , this will confirm that it does have a good spark and compression . Test the injectors to see if they are being triggered .
Depending on the results of the above there is more to "test" . for example ; The timing impulse sensor on the top of the bellhousing may have a faulty plug connection and the engine does not know when to fire and so will not.
The oxygen sensor ( heated version )if the wires short can prevent the LH box from running . Also check near the LH brain box green and white wire coming through the firewall two prong connector is it plugged in ? .

Jim Bailey
928 International


At 09:47 PM 1/8/2005, Dan Brindle wrote:
>Here is what I have so far in attempting to get the S4 hybrid to run.
> I checked the spark and found one side not firing when cranking.
>Inspecting the coil, I found a very corroded coil wire. Thinking I had  the problem licked I changed the coil and coil wire on the left side of the engine. Restored spark but the car still would not run. Oh well.
> Next I put the charger on the car and cranked it until it started.
>Only half the engine is running. I put in a spark plug and see a spark  from both sides of the engine with it running - so I have spark on all eight.
> Once running the engine will cycle in and out of four cylinder mode.
>I tried changing the ignition computer - no change. I changed out the  FI computer and the thing pops into 8 cylinder mode and then immediately goes back to 4 cylinder. So probably I have eliminated the  computers - although I will put them in another car just to be sure.
> When running on all 8 cylinders disconnecting the connection to the resistor pack on the front of the car will stop the left side of the motor from running. When only running on four cylinders  disconnecting the cable has no impact. I swapped out the resistor pack. What does that thing do anyway?
> So I have to assume it is the injection which is shutting down  on one side although it sure is puffing out a lot of smoke when running only on four cylinders. While running the engine will cut in and out of 8 cylinder mode so it sure acts like a poor connection.
>The damn thing is a bear to start. I checked the resistance on the temperature II sensor. Both sides are equal and right in range. I checked the continuity to the plug and that is good too. The motor is a 91 and has the relay for the four cylinder. At one point I had it jumpered. No difference so I can probably eliminate the sensors on the back of the block.
>Any ideas of where next to look?
>Thanks and please e-mail me direct as I am in digest mode.
>Dan the Pod Guy
>Portia's Parts
Of course, we have no idea at all of what you might have, but here are some comments about the standard systems...

The left coil actually fires cylinders 3, 8, 5, 2.
The right coil fires cylinders 1, 4, 6, 7.

On the power side, all injectors are powered by Relay XXV thru W13 and then the ignition circuit control (the monitoring relay). The relay supplies power thru two wires, one from A1 to hard connection 1, and from there to injectors 2, 3, 5, and 8, and the other from A2 to hard connection 4, and from there to injectors 1, 4, 6 and 7. Note that these are divided into the same groups as those served by the two coils and ignition amplifier units (which you called "resistor packs").

The injectors have 12 vdc on them thru these wires any time that the engine is running, and the injectors are fired when the ECU supplies a ground to the other side of the injectors. This ground is supplied by the ECU thru terminal 18 to hard connection 2, and from there to all eight injectors.

It sounds as if your problem is in the monitoring relay or in one of the wiring harnesses between the monitoring relay and the injectors. You can determine which harness by finding which ignition amplifier has no effect on the running of the engine when it is four-cylinder mode. If jumpering A1, A2 and 87 together at the relay has no effect, the problem is probably in the harness.

Wally Plumley
928 Specialists