Thanks Ernest,

I just check by grounding the pin 17 of the LH control plug, the pump relay clicks and pump hummmms.

Roberto

 

Shane, many thanks,

I call Porsche agent today here in Guatemala asking part number giving by Rich, they don't has the sensor in stock, they can import it for me but need 30 days for delively and cash in advance amount $280, how much it cost you ?

Roberto

 

Sorry, I should have said between EZF connector pin 7 and 19. Try that and let us know the voltage, even if you have to go to the lowest meter setting.

The fuel pump will only be turned on if the LH gets the signal from the EZF and the engine is cranking. The pump does not run with the ignition on and the engine not running.

 

Rich,

Just test it out, there are only about 200 mV DC and up to 2.0 Volt AC.

I give you the reading in both DC and AC as don't know which one you prefer, I always think of DC as the car battery is DC, but however, AC give me more consistence reading, it give out 2 VAC in my analog and also in my digital multimeter, but in DC mode the digital multimeter give out a false reading of 0.00-0.08 mVDC.

Also, how can I know if the EZF is ON or Activated ?

Roberto

 

Roberto

The voltage output of an inductive sensor varies with RPM, the lower the RPM the lower the voltage. You should see at least 1.4V (AC). Some non-Porsche ECU-s need much more (20V) to recognize the inductive signal. The signal from the EZF or EZK to the LH must be at least 7V [alternates between 0 and 7V in relation to engine RPM].

It is best to use an oscilloscope to test these type of signals. There are some inexpensive add-on oscilloscopes for laptop PCs.

If you don't have access to an oscilloscope, testing on the DC scale of a volt meter isn't accurate but you may see some needle twitch. If you have an AC scale, use it.

When testing the sensor by cranking the engine, switch the volt meter to AC if you have it ... set it at the 20V scale to begin with and then decrease the scale if necessary. If testing when engine is running switch it to the 200V scale. The inductive sensor can output a total voltage of 120 Volts when triggered at high rpm.

You said the car last ran 3 years ago. Did you drain all the old fuel and flush the pipes? Old fuel can cause a lot of problems.

Hope this helps.

 

Rich,

I already tested the sensor last night and got 2.0 V (AC) between pin 19 and 7 at the EZF plug while cranking, it is higher than the minima of 1.4 V (AC), so I think my sensor is OK, right ? (I tested with EZF plug un-plug to the EZF unit).

As I still has no spark, please tell me what is the next step I should test with the EZF, as in your website recommend to fix the EZF before the LH control.

I don't have an oscilloscope. I will drain the old fuel and flush the pipe tomorrow, and maybe the oil also.



Roberto

 

Do you have schematics of the underhood wiring?

I suggest starting with all the connetctions, including ground points. A very important ground is the wire between the engine and chassis. Other important grounds are those behind the fuse panel (look for brown wires, they are ground wires). Disconnect them, clean them, reconnect them. Many times no start problems are caused by bad connections. If that doesn't work you then check the circuits to be sure they are good. In 3 years some little animal may have eaten a wire or insultation so there could be an open or shorted circuit. Next, you test the major elements of the system.

 

Rich,

First of all, please let me know if my Position Sensor is good or bad with all the volts data I gave you before, because if it’s bad then I need to import the sensor at once due that more than 30 days is need for the arrival.

I do have the 928 Workshop Manual schematics of the under hood wiring and will perform the following as per your instruction.

a) Perform all the ground point check on page 28.53 of the Workshop Manual including those ground point at the back of the Central Board, by disconnect them, clean them and reconnect them.
b) Perform the entire step from pages 24.112 to 24.120 of the Workshop Manual.
c) Drain the old fuel and flush the pipe.
d) Replace the old oil with flesh one.
e) Test cranks the engine and posts the result.

It maybe possible to do the entire test in this weekend, but for the while please let know if I should order the Sensor.


Roberto

 

I already tested the sensor last night and got 2.0 V (AC) between pin 19 and 7 at the EZF plug while cranking, it is higher than the minima of 1.4 V (AC), so I think my sensor is OK, right ? (I tested with EZF plug un-plug to the EZF unit).

Roberto, based upon the voltage you see, the sensor is functioning properly.

¡Buena suerte!

 

Roberto,

Also check the plug and connection to the two modules just behind the front bumper under the hood (in front of the engine). Another shop had a no start problem and found that those connections were corroded. After they cleaned them, the 928 ran like new!

 

Also, if you haven't changed the engine oil and filter in 3 years, I would suggest changing that too.

I guess your local Porsche agent doesn't stock many 928 parts. I know you can get them from the big 3 here in the US, probably faster and less expensive.

 

OK Rich, I will do it tomorrow, today I only can clean all those ground contacs, because some of the screws are quite difficult to accesses.

 

Rich,

After drain and refill the old fuel and old oil as your recommendation, I perform the follow (from page 28-53 to 28-64 of the Workshop Manual):

TEST POINT 1 (Checking Ground and Plug Connections)
From steps 1 to 2.7, all done (remove and clean with sand paper).

TEST POINT 2 (Power Supply for Electronic Ignition Control Unit)
From steps 1 to 2, all done, between terminal 25 and 12 has battery voltage.

TEST POINT 3 (Speed – Reference Mark Sensor)
Not tested, because I don’t have an oscilloscope, but between terminals 7 and 19 has 1.055 k-ohms and produce 2.034 volts AC while cranking the engine.

TEST POINT 4 (Pressure Sensor)
Not tested, because this needs the motor running.

TEST POINT 5 (Temperature Sensor I)
From steps 1 to 2, all done, between terminals 10 and 22, have 2.35 k-ohms.

TEST POINT 6 (Temperature Sensor II)
From steps 1 to 2, all done, between terminals 23 and 12, have 2.28 k-ohms.

TEST POINT 7 (Throttle Switch)
Idle Speed Contact: Between terminals 4 and 12.
Throttle closed = 0 ohm
Throttle at half opened = 1.46 k-ohms
Throttle full opened = 1.30 k-ohms

Full Load Contact: Between terminals 17 and 12.
Throttle closed = 1.33 k-ohms
Throttle at half opened = 1.49 k-ohms
Throttle is full load pos. = 0 ohm

TEST POINT 8 (Ignition System)
Not tested, don’t have oscilloscope.

TEST POINT 9 (Octane Loop)
Not tested, because need motor running.

TEST POINT 10 (Alternator, Regulator)
Not tested, because need motor running.

Bad luck! I couldn’t found any corrode contact or voltages or ohms out of specification, almost all the terminal are clean and fit, but I still can’t see any SPARK, I am really desperate now, what I could do next, please help to save this 928.

Roberto

 

What about checking the coil/s to see if it/they are in spec?

Regards,

 

Roberto,

You've tested all the easy things. Now comes the hard work.

Have you bridged the main relays to see if that makes a difference? Try bridging the EZK and LH relays (between 30 [should always have 12V] and 87 and then crank the engine. Test for the spark from both coils (be careful, if it comes to life the spark can be very strong!). If there is spark from one coil, you know the EZF is probably OK and you have a circuits to test.

If you had a friend with another 928 you could swap some modules and parts and hopefully find the bad part. Do you know any Porsche 928 owner nearby? The key elements to test are the LH module (not an issue until you see spark), EZF module, ignition control modules (two) and coils (two).

Otherwise, you could box everything up and ship it to me and I could test it for you. If everything tests OK then you have to hunt for broken wires and open circuits.