Oh no, I didnt take anything posted here in offence in any way. And I hope nobody reads my posts in that manner. I think we all just want to see david get his car running. And we all share in his frustration. I wish I didnt live an ocean away so I could just pop over to his place and give him a hand.
Sometimes I read my posts and think I am being a little blunt, but thats the nature of forums. You can read everything 10 different ways. I just like offering a little advice when I think it might help.

My thoughts are that with the hammer he can check the dme related input signals quickly and easily, WOT switch, idle switch, air flow meter, etc, etc, etc. If I remember correctly all of the input signals are there to be read, and it should be obvious if one of them isnt working. and -maybe- the DME is showing a fault that will point him in the right direction.

When I was looking for my DME fault, i couldnt use the hammer because in my case it was a dead DME.

I agree with you, that the flywheel reference sensor would look to be a prime culprit, except that in the previous posts he put a scope on it and got a 5v p-p trace from it, which should mean it is fine.

----
As I see it if the following requirements are met, regardless of all other sensors in the car, there will be spark at a spark plug when you turn over the engine:
(Note: Jason andreas also believes the throttle position switch for idle may be required)

-The DME must be functional (This he already checked)

-The DME must be getting battery power, (At DME connector Pins 24-18 have ~12 Volts with key off)

- The DME must be getting switched ignition power from the DME relay (At DME connector pins 24-37 have ~12 Volts with key on) This check ensures your DME relay ok.)

- The flywheel reference sensor must be functional (At DME connector pins 47-48 speed ref sensor input shows a signal > 3v p-p)

- The distributor must be turning

- The coils must be ok

Maybe David should run through this checklist and we can try and find the fault that way. (But i still like the idea of popping a hammer or scantool software on and seeing what it has to say. )

Kirk

 

There are several 911 owners and repair shops in Cornwall , UK .
It seems strange that this is going on for so long . Has anyone seen any of the parts ?
All very odd.

Geoff

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KS400200 , the oldest 964 on Rennlist , unless you know differently !

 

ok I had to go back through the 6 pages of replies and review what was done again:


David said:

1/, I have tested pin no 1 with a multimeter ,no voltage found
** This is fine, it should be a +12V pulse to fire the coils when turning over the engine, if everything is working correctly. ie: flywheel ref sensor sends +5v pulse to dme, which does its work and in return sends correctly timed +12v pulses to coils to fire plugs as distributor aligns withs plug wires to individual cylinders.

2/, Also i sent 12 volts up pin 1 and produced a spark at a spark plug
** great, now we know that your coils and entire output circuit work fine. But I assume you saw the spark on a coil lead and not a spark plug lead???

3/ Changed the coils
** well I guess you got some spare coils now

4/ I have got dodgy hall sensor wiring , I have had to pair the wires back due to them being split and looking like they were shorting.
** this needs some more explanation

5/ had the ecu tested came back ok
** DME is not at fault

6/ pins 18 & 37 ok 12 volts
** I assume this means the voltmeter was put between (pin 18 and pin 24 gnd) and you read +12v and then between (pin 37 and pin 24 gnd) and the meter read +12V. Any ground could be used but its better to check against the DME gnd.

7/ pins 2 & 19 ok for earth
i assume again that this means you put your meter between (pin 2 and pin 24) and read 0 ohms resistance (continuity) and between (pin 19 and pin 24) and read 0 ohms resistance. You can also check between Pin 24 and a solid vehicle ground to make sure it is has continuity as well.

and from another post he seems to have shown a good scope trace from pins 47-48 speed ref sensor. But I wasnt really positive about that after re-reading everything.


So the first thing I would like to know for sure is that when the car is turned over, is there a spark at the coils or not? I'm not really clear if this was checked or if it was spark at the spark plugs that was checked. Is the distributor turning?

----------------

From a post by Colin at 9m, the DME pins are as follows:


Pin Description
1 Ignition pulse to output stage
2 Ground - Ign Output stage shield
3 DME Relay ground (fuel pump) must switch to gnd
4 Idle speed control
5 Tank venting valve (switch at 2000 rpm ??)
6 Engine speed to Tacho
7 Signal from AFM
8 Signal from Hall Sensor
9 Unused
10 Ground - Lambda sensor shield
11 Knock sensor 1
12 Power supply to AFM (use for Motec AT Sensor)
13 Diagnostic plug, lead L
14 Ground, linked to Bosch 24
15 ti signal, cylinder 3
16 ti signal, cylinder 6
17 ti signal, cylinder 1
18 Permanent positive
19 Ground - to loom gnd point 3
20 Unused
21 Diagnostic plug, knocking yes + no
22 Check engine control
23 Resonance flap
24 Ground
25 Unused
26 Ground for AFM
27 Unused
28 La sensor signal
29 Knock sensor 2
30 Shield for Knock & Hall sensors, Ground for Knock
31 positive to hall sensor
32 Consumption gauge (fuel used?)
33 ti signal, cylinder 5
34 ti signal, cylinder 4
35 ti signal, cylinder 2
36 Unused
37 Voltage from DME Relay with ignition
38 Unused
39 Version coding
40 Air conditioning compressor clutch
41 AC switch
42 Unused
43 Unused
44 Intake Air Temperature NTC1
45 Engine Temperature NTC2
46 Altitude Potentiometer (BAP sensor)
47 Speed/reference mark positive
48 Speed/reference mark negative shield
49 Unused
50 Heating/air-conditioning regulation
51 Unused
52 Idle signal - throttle valve (use wire for TPS 5v)
53 Full load signal - throttle valve (use for TPS signal input)
54 Coding plug characteristic map
55 Diagnostic plug, lead K

 

Red

There are no recognised Porsche mechanics in Cornwall, 2 guys were recommended to me , but i quickly lost confidence in them, when i was told to replace the distributor.

My nearest opc is 100 miles away and as far as i know the independents are further away.

my biggest obsticle at the moment is money, before Sten kindly tested my dme in his car i was looking at a very big repair bill at a Porsche shop, in fact i was at there mercy, the last guy said how long is a piece of string, he could only quote on time and said it could take up tp 50 hours at £100 an hour (no thank you)

 

Thanks for the above i will spend all day on the car tommorrow and report back

Dave

 

1. Item #4 we are talking about the flywheel reference sensor or the distributor hall effect transducer?

2. Also I would like you to have someone turn the engine over with the DME connected and see if you get sparking at the coil leads. I am trying to figure out whether your spark problem is upstream of the coils in the DME/Flywheel reference sensor, or is it downstream in that your distributors are not distributing spark to your spark plugs?

3. We should also check the gap on your flywheel reference sensor to your flywheel. The closer it is to the flywheel teeth, the higher the voltage your scope will show. You will have to look up the exact gap. I believe it is supposed to be 1mm. (maybe somene else remembers)

Kirk

 

1. item 4 = hall sensor wiring at the distributor

2. no sparking at all, i have tried at the distributor lead as well as the spark plug leads.

3. will test tommorrow

Dave

 

hello dave, try this

hook everything back up.

1. put the new dme relay back in .try turning over with key and see if it starts. if no start go to step 2.

2. take each coil wire( the one that goes to coil and distributor cap center) from distibutor cap and mount near ground or hook to spark plug and ground them and turn engine over while someone looks to see if you get spark on BOTH of them. do you get spark to one or both of them? when i spoke with you, you said you only tested one coil and not both. the reason you need spark to both because lets say one coil is firing and it is hooked to the secondary distributor the one that is driven by the belt and it broke it will not start. then seeing you replaced the coils, its probably one of the coil ignition control units that went bad and the primary is not we will deal with this later. just verify if both coils are firing for sure. if only one is firing make sure that igniton lead that comes from that good coil goes to the primary cap, it is the cap closest to center of the engine and the secondary is the one close to the large blower duct. try to start again. if car runs you need to different trouble shooting. if none of them fire go to step 3.

3. disconnect the DME plug and put 12 volts to pin 1 on the harness as you did before, are BOTH COILS firing?? i believe the key must be in the on position , however you tested it before do it the same way. if so we need to be clear that both are firing so we can eliminate the both coils and both ignition control units. go to step 4.

4. while you have the DME plug still disconnected go to the engine compartment and disconnect both ignition modules. do continuity test from the harness plug at the dme pin 1 to each plug pin number 5 at the ignition module ..... we are just checking the wires only and you do not need to make any contact with the DME or the ignition modules only the harness. then check continuity from pin 2 at the DME plug( which is the shielding for pin 1) to pin 3 on both ignition modules plugs. you should have continuity for both. now you need to check for shorts at the DME plug by checking pin 1 and pin 2 there should not be any continuity. and check pin 1 to chassic ground, there should be no continuity. you can check pin 2 to chassic and i believe that there should be none also as the ground comes from the DME, do not worry but let us know what you get. i just want to make sure that the wire for pin 1 is not grounding to the shield wire or chassis. if all is good. go to step 5.

5. with the the DME plug still disconnected you need to find out where the engine flywheel sensor disconnect plug is unplug it. check for continuity at pins 47 and 48 at the dme plug and to the appropriate pin at the flywheel plug. check for continuity 47 to 48 also to make sure they are not making contact somewhere and check each wire 47 and 48 to chassis ground you should not have any. you should only have continuity from 47 at dme plug to the pin at sensor and the same for 48. but not to each other or the body ground. if it passes this test i would say that the flywheels sensor needs to be removed cleaned and inspected.



do not replace any parts till we all put our head in on this one. i not a wizard but this is the steps i would take. i do not want you to spend any money till we are sure we have narrow it down to the eact component. WORK SAFE and let me know what you come up with. if you need for me to give you a ring email me and i will call you.

 

12345

 

Could it be that no 6 just relays the signal straight away to the tacho but it is held back at no 1 until the signal is correct ie , 30 rpm and strong enough ?


I have removed the sensor and cleaned it, and put it back , still the same.

 

Did you try Norgar Engineering , 01872 275201 ? They are listed as a Cornwall Porsche expert .
Maybe they are one of the people you dont like.

I have contacted 911@ Porsche World to see if they know anyone down your way who can rapidly find/fix the problem .

Normally 2-3 hours has everything fixed , so your experience is deeply frustrating for you .

Lets see who can be found .

Geoff

--------------------------------------------------------------------------------
KS400200 , the oldest 964 on Rennlist , unless you know differently !

 

Red roooster

I tried a guy in Redruth who didnt fill me with confidence and an ex opc mechanic who made me cringe the way he was ripping my car apart in all the wrong places. I will give Norgar a ring in mid week, I think my next step is to send my sensor to Barry to see if it works on his car, I will send to him on monday if he agrees.

I still think the key is can no 6 still have a signal without no 1.

The 2 voltages and 2 grounds have been tested ok as well as the flywheel outputs, supposedly they are the only values which will stop a spark signal.

Many thanks for reminding me about Norgar , i had all but forgotten about them.

Dave

 

Dave,

Maybe mention to Nogar that 911 & Porsche World have been brought into the story !

I wasnt talking nonsense when I mentioned the appropriate time scales .

I spent many years mapping everything Porsche and finding non run problems for all kinds of people , both owners and specialists.
Armed with the knowledge of sytem operation , pick one end as the best guess and plow through till you find the problem. Have available the usual bits , so a substitute can be done and usually that it !
A 964 is 3 hours maximum for a difficult problem .

The 993s where attacked by gross DME loom disater , sometimes by small fires !! That didnt need much brain power .

It like all this stuff , working from one end to the other is the only sure way .
Spasmodic looks at bits and pieces usually leads to time wasting and you still dont know what the problem is !

Sorry if you read this as an attack the excellent guys who have been doing their best to help . The usual problem is that someone settles down to lead you through to the problem but at the same time other problem areas are being thrown at you . That leads to confusion .
The fact that your car hasnt run for 3 months underlines the point .

As a gentle approach , maybe you should PM one of the guys who have put lots of time in ,and ask him to privately lead you along.

I really hope that no one reads this as an attack on their help and input but a car that isnt running after 3 months idicates a procedure problem .

I wish you every success in correcting the problem and you understanding of how the DME works will greatly help you bring help to others .

Geoff

--------------------------------------------------------------------------------
KS400200 , the oldest 964 on Rennlist , unless you know differently !

 

At the risk of annoying everyone further, I feel this topic has more than out stayed its welcome.

But here goes last post honest.

Firstly i am getting a flywheel signal at 48 and i have been informed that it should be 47 , as 48 is the sensor ground and 48 should be the signal, so thats the first conflict.

Also that test was with the dme disconnected.

Now heres whats interesting when i plug the connector back in to the DME the signal dissappears

So nothing on 47 & 48 when DME plug connected.

 

I have just bought a new flywheel sensor and i am baffled as to how fit the connectors together.

It is a 993 part and supercedes the 964 part hence the extras

I have been sent a plastic extender plug which only seems to fit on the new sensor and not to my existing plug in the engine compartment. they have also sent me a tiny orange gromet and a thin spade connector.

I used to watch the krypton factor as a kid but this is beyond me, can anyone help ?

Thanks

Dave