Turbo

Car is driving me nuts....

Went for a drive a month ago ...and car ran perfect then.

Yesterday tried to start, engine turns strong but won't start
Checked the plugs and seems that I have no spark?


This is what already has been done:

-Swapped the DME relay (first guess) with new one: still no start/ spark
-Shortened the DME relay in the socket: 87-87b-30:still no start/ spark
-Checked the speed & reference sensor ohms and both seem ok
-Checked coil, on both terminals I have 12V towards ground so this should also be ok
-Coil Primary: 0.7 ohms
-Coil Secondary: 5.62 K ohms
wire to distributor: 0.1 ohms
-Ignition rotor (inside distributor/ Center to tip measurement): 1.08k ohms
-Battery in the car is brand new (almost 1 month old) and its a Bosch

-I've read about a topic here at rennlist forum that the DME ECU can also have cracked solder joints on the transistors for the ignition; checked these also, and all look ok

-Distributor cap and rotor are also checked and had minor carbon on the contacts....cleaned them ...but still no result

Anyone has some suggestions what else to do / check

Regards
Turbo

r911

how about the thin wires going into the distributor?

Turbo

Do you mean the the wire from the coil (center of the coil) to the distributor?

This one has 0.1 ohm

Steve Weiner-Rennsport Systems

If you have fuel pressure at the rails, but no spark, its ignition related.

Bridge the DME relay and check fuel pressure to make sure the pump is running. See if it starts.

Check crank reference and position sensors with an oscilloscope.

Do you have the original ignition coil?

Turbo

Hi Steve


If you have fuel pressure at the rails, but no spark, its ignition related.
Indeed it's ignition related

Bridge the DME relay and check fuel pressure to make sure the pump is running. See if it starts.
Bridged the DME relay - didn't checked the fuel pressure (just because I don't have the tools for it) but still won't start


Check crank reference and position sensors with an oscilloscope.
Also don't have a oscilloscope (did do the ohms check and seem ok with this method

Do you have the original ignition coil?
Yes it is still the original coil, ohms measurement s are within spec

scarceller

Can you first simply test if the DME is alive following this procedure:

Turn the key to 'RUN'
Then in the engine bay is the idle control valve vibrating and humming?

If the ICV is not vibrating and humming with key in 'RUN' then the DME is not booted up.
Let's start by verifying DME is actually running.

If the valve is vibrating then test for spark directly at the coil (eliminated the dizzy). Just connect a spark plug to the coil wire directly, remove the coil wire from the center post of the dizzy and put a test spark plug on the end of that wire and then ground the plug, do you get spark at the test plug?

Report back.

One last thing: when you jumpered DME relay pins 30, 87 and 87b did the fuel pump start running the minute you jumpered those? Pump MUST run when 30 & 87b are jumpered, did it run?

Turbo

Hello Scarceller

Turn the key to 'RUN'
Done
Then in the engine bay is the idle control valve vibrating and humming?
Yes this is humming
If the ICV is not vibrating and humming with key in 'RUN' then the DME is not booted up. So this is not the case, ICV is ok
Let's start by verifying DME is actually running.

If the valve is vibrating then test for spark directly at the coil (eliminated the dizzy). Just connect a spark plug to the coil wire directly, remove the coil wire from the center post of the dizzy and put a test spark plug on the end of that wire and then ground the plug, do you get spark at the test plug?
NOPE no spark there
Report back.

One last thing: when you jumpered DME relay pins 30, 87 and 87b did the fuel pump start running the minute you jumpered those? Pump MUST run when 30 & 87b are jumpered, did it run? Yes pump is running

scarceller

Is it possible that you may have swapped the speed and ref sensor harnesses? If you had them both unplugged at the same time you could easily have swap them.

Just swap them on purpose now to see if that helps. You will not harm anything if they are swapped.

If swapping them does not help put them back as they are now.

You can also test them with a LED test light, but it must be a LED 12v test light. Walmart usually has a LED test light in the automotive section.
Just put the test light across the 2 sensor pins that read 900ohms and then crank the motor, the speed sensor will flicker brightly while the ref sensor will be dim but also flicker.
This is a poor mans approach to testing the sensors without a o-scope.
You can also place the LED test light across the coil's '+' and '-' post and it will also flicker if the coil is getting ground pulses.
LED test light is very handy quick test tool.

SiberianDVM

When my '84 3.2 failed to start (at the track, no less) and there was no spark, it was either the speed or reference sensor, can't remember which.

I know you said you checked ohmage, but I would change them out before I went much further.

Turbo

Is it possible that you may have swapped the speed and ref sensor harnesses? If you had them both unplugged at the same time you can easily swap them.
No, i'm 100% sure they are connected correct. With ohms measurement I only removed one at a time; just to be sure that I don't mix up them

Just swap them on purpose now to see if that helps. You will not harm anything if they are swapped.

scarceller

OK, in that case you really need to see if they are generating pulses. Get a LED test light.

In the past month was anything else done to the car? Even the smallest thing, would be good to know what if anything changed between it's last start 1 month ago and now.

Turbo

Also checked the ignition rotor
This one is also ok; 1.08 k ohms from tip to center

Strange thing is that the car just drove fine a month ago???


What I forgot to mention is that there is also an aftermarket car alarm in the car (as far as I know always has been in the car.....I have the car now for ± 18 years)
It's a gemine alarm

Could this one also influence the ignition?? Seems to me that is works as before ...it has also the central locking option on it.

Turbo

Only thing that was done before the last drive was replace the check valve after the fuel pump and of course fresh gasoline. (hot start was harder....took few seconds longer then with cold start.... thought I had the beginning of vapor lock).

So not something that can influence the ignition

scarceller

You can also make a simple LED test light with a basic standard LED and a 10,000 ohm resistor.

Turbo

Today's update


Checked the pin assignments from the DME ECU (the connector for the DME ECU)

All grounds are ok
All ohm measurements are ok

12V on pin 18 & 35