Turbo

I don't have a spare coil

Turbo

Did this also in the meanwhile....but no wave form on the scope.
The 12V is not pulsed

scarceller

Can you put a 1000ohm resistor in place of the coil and then scope the resistor?

It will at least show us if the darlington transistor that drives the coil is working. The resistor is needed to serve as a pullup resistor on the darlington.

Or you can try and scope the base of the darlington transistor directly in the DME.
The base of that large transistor is driven through resistor R521, locate that resistor and scope it to see if you have any pulse.

Turbo

Will try that tomorrow or day after ....have to get one first

Thanks for the support already

scarceller

Here's another quick coil test:
- Unplug the DME from the harness. DME CAN NOT be connected!
- Put a test spark plug on the coils high voltage side, no distributor being used, and ground the plug to the main ground screw on intake runner #1, clamp the test plug to that screw with vise grips.
- Turn Key to 'RUN' and insure that the coil's '+' has 12vdc
- At the DME harness connector quickly jumper pin 1 & 19 with a paper clip, just jumper it very quickly and remove the jumper. Basically tap the two pins (1&19) together quickly, no more than 1/2 second. Did the plug spark?

What you are doing is applying ground from pin 19 directly to the coil's '-' via pin 1 this instantly charges the coil and the plug will spark the minute you remove the jumper.

Do NOT leave that jumper in more than 1/2 second as you'll super heat the coil, that coil charges in 4milliseconds! If you get no spark you may have a bad coil or you have bad wiring. If she does not spark Then repeat the test by jumpering grnd directly at the coil's '-' post.

This is a poor mans coil test but be aware that it will super heat the coil if you leave grnd on that post.

You can also bench test the coil the same way with a 12v source.

Turbo

Did this test just a minute ago with a sparkplug.
And YES :-) we finaly got a spark on the sparkplug
So this leaves us to a dead DME ECU unit....

Checked already at ebay but no units at this moment offered

upier

Try this page.
http://www.ftech9.com/new-products/

Turbo

They only offer them for the 944 models

scarceller

At this point it's best to have the DME tested/verified and repaired if need be. Far cheaper to fix what you have than find a new one.

PM me I may be able to help you with the DME.

Turbo

You have mail ;-)

Lorenfb

Since you have the DME ECM out, re-solder the three pins of the ignition power transistor driver.
These pins will be obvious once the circuit boards are removed from the bottom aluminum plate.

Turbo

Hi I opened the DME ECU box and checked every soldering. I did a touch up on all suspicious solder points.

Did got last week some parts from a friend:
-DME ECU unit
-cyl. tem sensor
-used coil

Put in the DME unit and after long cranking the engine started...
Let it run for few minutes and tried again...No start
Swapped the coil and the temp sensor .... No start

Waited till next day. engine was cold. Started again with the borrowed DME ECU unit...again started after few cranks. Shut it down and tried immediately again...started again. Immediately after this I connected back my own DME ECU unit and yes car started.....let it run for few minutes ...shut it down and tried again ...No start


For this moment I was sure the coil and DME unit should be ok?

Last week I suspected the alarm could also be the cause (it is an aftermarket Gemini alarm; module 1160 and 1320)

Took me a day to remove it all properly...but unfortunately no luck on the starting issue

Today is decided to put everything back together.... complete car is getting parted (stuff loose in engine compartment, dash partly removed for the alarm, ....)

Decided to give it a shot, started the car ...and with the first crank the car started strong.... huh what the f#! .... and this with my original DME ECU

I let the engine run for ±5min.... rev up the rpm of the engine with the gas pedal and engine reacts immediately

then I shut down the engine and tried immediately to start again .....hhmmmm.... NOTHING

engine turns but won't start ...its driving me nuts

Even after 2h it won't start again?
Even shorted the DME relais and let the fuel pump run for 1 min before cranking...No start


Removed the plug from the DME ECU unit and checked this time the impedances after this short engine run:

Here is what I have
•Air temp sensor: 250 ohm
•Idle speed control valve: 42 ohm
•Crankshaft speed rpm sensor: 1.105k ohm
•reference sensor (tdc): 1.105 ohm
•cylinder head temp sensor: 791 ohm (after ± 10 min the engine didn't start measured)

Also checked the coil with the engine warmed up (5 min of run)
prim and second measure: 0.5-0.7 ohm and 5.6k ohm


Has it something to do with the temperature or not ?

Other thing I noticed is that there is a clicking/ ticking noise in the area of the coil/ Left fuel injectors....could be normal ...but didn't notice this before...all things are getting suspicious for me for the moment

I also read on a forum that a coil can get in fail mode when an engine gets hot...could this be the case?
Also did read an other point on the fuel pressure regulator that this can fail and cause a no start?

Open for any other recommendations


Grts
Turbo

scarceller

From the sound of things I strongly suspect you may have a ref/seed sensor acting up with heat and/or vibration. At this time if you are 100% that the no start is a result of no spark replace both those sensors.
If the CHT sensor is old you may also change it out since it routes along the same path as the ref/speed sensors. But the CHT sensor has nothing to do with no spark. A no spark at the coil's high voltage output usually is the result of:
- Ref/speed sensors
- DME
- Coil
- Bad wiring
In that priority order.
You already tested 2 DMEs and 2 coils, next is the speed ref sensors.

Turbo

Some update after a weekend:

Changed all sensors this weekend !!
What a pain in the a#!$ job is this.....not much room ....or my hands are just too big 😊

A lot of time took removing 1 sensor from it's housing (had to cut it to remove it) and also the temp sensor was quite a job to get loose..

After I removed the clamp (located on the backside of the heat shielding of the engine) that keeps the 2 sensor cables together... the cables (black outside) isolation just came loose and cracked on both sensors....very strange...?

After I changed all 3 sensors; Finally started the car .. and car started immediately!

Let it run for few minutes so that the engine was a bit of warm...and started again...and again started right up.

Did a test-drive today and the car is running and starting perfect now !

Big for all the help I got from scarceller !!


Strange that this had influence on my starting problem...
I managed to keep one senor intact ....and also without this black isolation on the outside it still has it ohm readings within target...I think the shielding of both wires where touching each other on the location of the clamp ...causing interruption for the startup. And even worse when engine is hot??

A tip that I can give everyone here: If your sensors on your engine are also still original -> replace them to prevent a no start as my car had

Here are some pictures of the cracked isolation:

scarceller

That black insulation is cracked from the heat over years on heat cycle. If you have the insulation cracked like this then they need to be replaced. These sensors are likely the originals that came with the car. I bet you'll be all set, enjoy the car!