86 Roadster - Ck engine light - no codes???
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
86 Roadster - Ck engine light - no codes???
Well I was on the Interstate this morning in the cool morning breeze clipping along at about 80 mph with the top down and really enjoying myself. My L98 was running very strong without a stumble, miss or hesitation and it just flat cut off. It was like someone turned off a light switch. I coasted over to the shoulder and as I slowed down the Check Engine Soon light went on. I had lights and full electrical power in all areas of the cockpit. The starter cranked the engine just fine, but to start. I thought it was a fuel problem, but the fuel pump was working and I had pressure and fuel at the rails, just apparantly no spark. I looked all over for a loose or disconnected wire - nothing. I had to flatbed the car 20 miles home.
I hooked up my computer and WinALDL software to read the trouble codes and got nothing. I have attached a few screen shots of the raw data, flag data, sensor data and error codes. I'm puzzled that there is a check engine light, but no error codes. WHAT THINK ?
I hooked up my computer and WinALDL software to read the trouble codes and got nothing. I have attached a few screen shots of the raw data, flag data, sensor data and error codes. I'm puzzled that there is a check engine light, but no error codes. WHAT THINK ?
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
If the datalogging works then the ECM must still be alive. Does the manual say you can get a 'check engine" light without a code? I will have a look at my book and see.
The code is not displayed as a number but by a series of flashes and pauses of the "check engine" message.
For example a code 13 (oxygen sensor) is 1 flash, pause, 3 flashes.
The code is not displayed as a number but by a series of flashes and pauses of the "check engine" message.
For example a code 13 (oxygen sensor) is 1 flash, pause, 3 flashes.
Last edited by Lemme; Sep 25, 2010 at 07:43 PM.
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Nope, not flashing, just constantly on. Car cranks, but won't start, has fuel pressure at the rails and no spark. I'm thinking a fried coil or ECM which I'll check out tomorrow. I'm just puzzled as to why the check engine light is on and there are no codes???????
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
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Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Today I jumped ALDL terminals A & B and got a code 12. No other codes were flashed. Additionally, when I jumped A & B the OD unit light went on and the main fan ran. This is exactly the same configuration that was shown in my WinALDL software. So at lease the WinALDL software and the jumped terminal flashing are saying the same thing.
I also checked to confirm that there is no spark at the plugs - no spark. I also looked closely around the distributor to see if I could see any loose, broken or disconnected wires - nothing.
Next I'll check to see if there is power coming into the distributor. I assume that the red B wire coming in should read 12 volts (correct ?).
I'm suspecting a fried coil, but I don't know why this would make the fan run; puzzling....
I also checked to confirm that there is no spark at the plugs - no spark. I also looked closely around the distributor to see if I could see any loose, broken or disconnected wires - nothing.
Next I'll check to see if there is power coming into the distributor. I assume that the red B wire coming in should read 12 volts (correct ?).
I'm suspecting a fried coil, but I don't know why this would make the fan run; puzzling....
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Today I jumped ALDL terminals A & B and got a code 12. No other codes were flashed. Additionally, when I jumped A & B the OD unit light went on and the main fan ran. This is exactly the same configuration that was shown in my WinALDL software. So at lease the WinALDL software and the jumped terminal flashing are saying the same thing.
I also checked to confirm that there is no spark at the plugs - no spark. I also looked closely around the distributor to see if I could see any loose, broken or disconnected wires - nothing.
Next I'll check to see if there is power coming into the distributor. I assume that the red B wire coming in should read 12 volts (correct ?).
I'm suspecting a fried coil, but I don't know why this would make the fan run; puzzling....
I also checked to confirm that there is no spark at the plugs - no spark. I also looked closely around the distributor to see if I could see any loose, broken or disconnected wires - nothing.
Next I'll check to see if there is power coming into the distributor. I assume that the red B wire coming in should read 12 volts (correct ?).
I'm suspecting a fried coil, but I don't know why this would make the fan run; puzzling....
Yes, there should be 12V to the distributor at the BAT terminal (pink wire).
Last edited by Lemme; Sep 26, 2010 at 09:23 PM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Some guys think it may be the coil or the spark control module. How can you test the control module without taking it out of the distributor? I assume I can pick up a spark module at NAPA, Advanced Auto or any of the brand parts stores?
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Funny you say that. I installed a new chip a few weeks ago which I thought I had successfully burned. Suddenly fan came on, ran like a dog etc. Put the old chip in and away she went.
What I worked out was I didn't quite get the chip burning process done correctly. To be specific I forgot to load the new tune into the buffer of the burner first before burning to chip.
:o
What I worked out was I didn't quite get the chip burning process done correctly. To be specific I forgot to load the new tune into the buffer of the burner first before burning to chip.
:o
Last edited by Lemme; Sep 27, 2010 at 08:48 AM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
I have had several were it has indicated successful upload to emulator but obviously something out of wack ; wrong check sum or something because fan ran as soon as key turned on
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Chip has been in there for several years now and I have not uploaded any changes to the prom programming.
Some guys think it may be the coil or the spark control module. How can you test the control module without taking it out of the distributor? I assume I can pick up a spark module at NAPA, Advanced Auto or any of the brand parts stores?
Some guys think it may be the coil or the spark control module. How can you test the control module without taking it out of the distributor? I assume I can pick up a spark module at NAPA, Advanced Auto or any of the brand parts stores?
Last edited by Lemme; Sep 27, 2010 at 09:17 AM.
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
My understanding is that there should be a pulse coming from the distributor on the purple and white wire. This feeds into the ecm for timing purposes. Should be able to connect a dwell meter, tacho or analog volt meter between this wire and ground to see if it is working while you crank the engine..
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Voltage to ECM on purple and white wire may be a 5V DC signal but will be pulsed as the engine is cranked. Like the points opening and closing in the old days.
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
I'm getting nothing on the pink BAT in wire. Maybe I am not getting a good ground. Will check it again....
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Got a better ground and tested positive for 12v into the distributor. So, it looks like the problem IS in the distributor and you guys are right - coil or ignition module. Tomorrow I'll dig into the distributor and check out the ignition module which is the prime suspect now.