david@st ives

Lauren

just seen this post , i tested pin 3 and got a reading of 12.something volts

I found out it was the white wire at pin 1 and tested at the ibnition module end while cranking the engine and did not get a reading on the led tester , then i tested with a voltmeter and got a reading of 0.03 volts , which i guess was just interference etc.

I will try your next +12 test when i have charged my battery up for an hour , it keeps going flat with all these cranking tests.

I assume this test is for continuity for the white wire and to eliminate everything after the DME.

thanks

Dave

david@st ives

Completed the test and i got a spark,

So now i think we are between the flywheel and the brain

Test for ohms on pins 47 and 48 was 524 oms

Voltage was about 4.2 v

Dave

Lorenfb

Sensor Voltage was about 4.2 v while cranking. Right?

Use these: www.systemsc.com/diagnostic.htm

and www.systemsc.com/tshoot.htm

If all tests O.K. the DME is bad.

david@st ives

Lauren

I only had one scope lead so tested pins 47 and 48 with it

Pin 47 nothing

Pin 48 got a trace , well it looked like 3 seperate traces together if you knoe what i mean, i dont fully understand the scope 2 traces had high peaks and the third was a lot shallower .

How much is a repair job on the dme if it is kaputt ? or how much for a second hand one?

Has anyone got a brain (dme) i could borrow , so i can confirm mine has died

Thanks

Dave

Indycam

Can you scope the line to the switches at the dme ?

david@st ives

Indy

I am not sure what you mean

Dave

Indycam

Well I don't know if its at all helpfull but here goes , the dme is hooked up to the switches , the dme sends a signal to the switches , the switches then turn on and off the coils , the coil sends out a spark .

If the dme is sending the signal to the switch , the signal can be lost before it gets to the switch . If the switch never seea signal it never does anything . If the dme signal to the switch is not being made or sent , thats another thing .

david@st ives

I have tested the white wire from pin 1 at the dme end and at the switches and there is no trace at all with the scope.

Apart from the input from the flywheel sensor which i am almost certain is working, can anything else stop the ecu from sending out a pulse to the ignition switches ?

Have you ever seen a grown man cry ?



I Dont know what to do next ?

Indycam

Did you disconect the wire from the dme ?

JasonAndreas

A faulty idle speed switch on the throttle valve.

Have you tried checking the DME control unit for fault codes with a Bosch Hammer or using the accelerator pedal method?

david@st ives

Indycam

Tests with wire disconnected

, sent 12 volts down pin 1 at dme connector and got a spark

Tests with wire connected

1 scoped wire from pin 1, 3 inches away from the dme connector
2 scoped same wire at coil switch
3 Tested for voltage at the same 2 points

Results no readings at all

Jason

Is there a test for the Idle switch,

I have not got access to a Bosch hammer , my nearest porsche shop is over 100 miles away , i live at the far tip of Cornwall and we have been forgotten about in the Porsche stakes.

I have just looked at the accelerater pedal method but unfortunately my car is a UK 90 model and does not have this feature

Will the tester i have seen mentioned on this forum be any use to me in my present predicament ?

Will it read codes on non starter ?

I will put all the tests done so far in one post for easy reading later.

Thanks for all your help

Dave

Indycam

Have you ever opened up the dme ?

It kinda sounds like your dme is on vacation .
Might be time to send it to california for some R&R .

What do you think of your scope ? Are you ok with the thing ?

Lorenfb

"Is there a test for the Idle switch"

Don't waste time testing the idle switch, as it has NOTHING to do with stopping the spark!

The ONLY things required are:

1. power @ pins 18 & 37
2. a signal @ pins 47 & 48
3. grd @ 2 & 19

dougn

while we're on the subject....Loren, what if someone wanted to do something crazy like use carburetors instead of the FI....but you still wanted the DME to provide the ignition. is that feasable?

david@st ives

I have never opened the DME , I am tempted to have a look inside now to see if theres anything obvious.

The scope is good , I dont realy know what i am doing with it , but i know how to detect a signal with it, I will read up a bit on how to use one correctly.

How much does a repair job cost ?

I take it grd = ground/earth

And i test with 12+ light on disconnected dme connector.

Correct me if i am wrong

Dave