No spark diagnosis - running out of options
01-28-2010, 08:37 PM
#17
Race Car
Thread Starter
In addition the KLR takes the ignition from the DME, massages when needed, then passes it back to the DME. My earlier message shows how you can bypass the KLR and run ignition timing as a loop-back.
note: if you have been trying to start the car for some time (multiple tries), with the absence of ignition, you could flood the engine and render the plugs useless. (of course for this to happen you have fuel but no spark).
note: if you have been trying to start the car for some time (multiple tries), with the absence of ignition, you could flood the engine and render the plugs useless. (of course for this to happen you have fuel but no spark).
I actually found out that my DME on the 89 is wierd, and presumably not delivering fuel, because of this. I meant to put the good car's DME back in, and crank it to burn up the fuel, but left the bad car's DME in. Regardless, I'm not gettinng any fuel in the bad car, so I don't have to worry about it. Once I get the fire, I'll take care of the fuel.
John, this thread has reminded me that I owe you an e-mail from a couple of months ago about valve sizing. Hope to get on that this weekend - sorry for the delay!
01-28-2010, 08:39 PM
#18
Race Car
Thread Starter
That's a very good point, but yes, I've moved the wires back and forth, and the good car runs with either, the bad car with neither. Had that go bad on my GTO when I was in high school, and it took me weeks to find it. SO yeah, I always check that! 
01-28-2010, 10:09 PM
#19
Burning Brakes
I had a similar problem, 12v at the coil. I could induce a spark by lifting the ground wire and grounding it. but wouldn't fire with the ground connected. Turned out it was a ground fault on the ground wire back from the coil to the DME. Found it fixed it and bingo.
Last edited by samluke; 01-28-2010 at 10:47 PM.
01-28-2010, 10:32 PM
#20
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01-29-2010, 12:09 AM
#21
Race Car
Thread Starter
KLR bypass did not fix it, either. I'll take another look at the ground circuit mentioned by samluke. However, the wierd thing is that I have not been able to induce a spark by grounding it. When you were able to do that, did you disconnect the negative terminal, and manually ground it? Or did you ground it still fully wired?
01-29-2010, 12:39 AM
#22
I think this may be the test samluke is referring to.
Here's another checklist I found a long time ago, unsure of where...
and.... another simple test
Ignition Coil Test (From Clarks Garage, IGN-04)
1. Disconnect the ignition coil output wire at the distributor cap.
2. Connect a spark plug to the end of the ignition coil output wire which you just disconnected.
3. Connect a ground wire to the threaded portion of the spark plug.
4. Disconnect the ignition coil ground wire from the negative terminal on the coil (Green Wire).
5. Connect one end of a ground wire to the ignition coil negative terminal.
6. Turn the ignition switch to the ON position.
7. Tap the other end of the ignition coil ground wire jumper on an good grounding point (for example the battery negative terminal) and look for sparks at the spark plug that correspond to the frequency of your tapping of the ground wire.
8. If you have a good spark at the spark plug, the ignition coil is good.
9. If you don't get a good spark, check for approximately 12 VDC from the coil positive terminal (black wire) to ground with the ignition switch in the ON position. You should also get approximately 12 VDC from the coil negative terminal (Green wire) to ground.
1. Disconnect the ignition coil output wire at the distributor cap.
2. Connect a spark plug to the end of the ignition coil output wire which you just disconnected.
3. Connect a ground wire to the threaded portion of the spark plug.
4. Disconnect the ignition coil ground wire from the negative terminal on the coil (Green Wire).
5. Connect one end of a ground wire to the ignition coil negative terminal.
6. Turn the ignition switch to the ON position.
7. Tap the other end of the ignition coil ground wire jumper on an good grounding point (for example the battery negative terminal) and look for sparks at the spark plug that correspond to the frequency of your tapping of the ground wire.
8. If you have a good spark at the spark plug, the ignition coil is good.
9. If you don't get a good spark, check for approximately 12 VDC from the coil positive terminal (black wire) to ground with the ignition switch in the ON position. You should also get approximately 12 VDC from the coil negative terminal (Green wire) to ground.
Coil Check
There are two small wires to the coil, a black and green one (per Haynes & a visual of my coil). The black one supplies the 12V when the key is on. The green one goes to the DME and is used to control the coil and time when the spark voltage is created.
Step 1 - With your meter set to DC Volts and the key in the run position check the black wire for 11-13V.
If Bad 0 Volts- check ignition switch and wiring from it to the coil.
If Bad - less than 11 Volts - charge/change battery
If OK - Step 2 - Check the green wire, it should also have the same voltage as step 1.
If Bad - remove the green wire and re-check the coil terminal, not the wire, if still bad the coil has an open in the primary side - replace coil.
If OK - re-attach green wire if you removed it, now you will need the test lamp (the meter is not fast enough to register the chnges in voltage on the green wire) Connect the test lamp to the green wire (the other side of the test lamp can go to any convienient ground, ie neg battery terminal) and crank the engine. It should flicker not just dim.
If bad (no flicker just dims) I would put the test lamp on the black wire and check for the same result - if so - something in your DME circuit is bad and I have no experience there but I would try cleaning the DME connectors with electrical cleaner before I went to much further.
If you see a flickering light then check the coil output by putting a spark plug on the coil high voltage wire, holding the threads of the plug against some metal engine part, crank the engine and look for spark across the end of the plug.
If no spark then the secondary of the coil is open - replace the coil.
If OK re-attach the coil high voltage wire to the cap, move the plug to the end of one of the plug wire and repeat crank the engine and look for spark.
If bad - change rotor, cap and wires.
There are two small wires to the coil, a black and green one (per Haynes & a visual of my coil). The black one supplies the 12V when the key is on. The green one goes to the DME and is used to control the coil and time when the spark voltage is created.
Step 1 - With your meter set to DC Volts and the key in the run position check the black wire for 11-13V.
If Bad 0 Volts- check ignition switch and wiring from it to the coil.
If Bad - less than 11 Volts - charge/change battery
If OK - Step 2 - Check the green wire, it should also have the same voltage as step 1.
If Bad - remove the green wire and re-check the coil terminal, not the wire, if still bad the coil has an open in the primary side - replace coil.
If OK - re-attach green wire if you removed it, now you will need the test lamp (the meter is not fast enough to register the chnges in voltage on the green wire) Connect the test lamp to the green wire (the other side of the test lamp can go to any convienient ground, ie neg battery terminal) and crank the engine. It should flicker not just dim.
If bad (no flicker just dims) I would put the test lamp on the black wire and check for the same result - if so - something in your DME circuit is bad and I have no experience there but I would try cleaning the DME connectors with electrical cleaner before I went to much further.
If you see a flickering light then check the coil output by putting a spark plug on the coil high voltage wire, holding the threads of the plug against some metal engine part, crank the engine and look for spark across the end of the plug.
If no spark then the secondary of the coil is open - replace the coil.
If OK re-attach the coil high voltage wire to the cap, move the plug to the end of one of the plug wire and repeat crank the engine and look for spark.
If bad - change rotor, cap and wires.
Unplug one injector
A bad FPR can shut down the (ground) pulsing to BOTH the coil and the 4 injectors. Disconnecting 1 injector connection might give a clue...see if it fires on just 3 cylinders. When we checked the voltage for flucuations the fuel pump was not connected so it didn't overpressurize the system. Maybe that is why it did seem to work.
One of the most common failure modes for the FPR is to fail closed to the point that fuel rail pressure is extremely high. The high differential pressure across the injectors causes them to draw excessive current. The excessive current is seen by the injector drivers which subsequently shutdown. If you have a condition where the car will not start or starts and almost immediately dies, try disconnecting the wire for one (1) injector. Attempt to start the engine. If it starts and continues to run, the fuel pressure regulator is likely bad. Bear in mind that running on only three cylinders, the car will run very rough. By disconnecting one injector, it reduces the current enough to keep the injector drivers from shutting down.
Turn the key on and check for battery voltage at the injectors. This will tell you that the DME relay is good through the first contacts that provide power to the DME.
A bad FPR can shut down the (ground) pulsing to BOTH the coil and the 4 injectors. Disconnecting 1 injector connection might give a clue...see if it fires on just 3 cylinders. When we checked the voltage for flucuations the fuel pump was not connected so it didn't overpressurize the system. Maybe that is why it did seem to work.
One of the most common failure modes for the FPR is to fail closed to the point that fuel rail pressure is extremely high. The high differential pressure across the injectors causes them to draw excessive current. The excessive current is seen by the injector drivers which subsequently shutdown. If you have a condition where the car will not start or starts and almost immediately dies, try disconnecting the wire for one (1) injector. Attempt to start the engine. If it starts and continues to run, the fuel pressure regulator is likely bad. Bear in mind that running on only three cylinders, the car will run very rough. By disconnecting one injector, it reduces the current enough to keep the injector drivers from shutting down.
Turn the key on and check for battery voltage at the injectors. This will tell you that the DME relay is good through the first contacts that provide power to the DME.
01-29-2010, 12:57 AM
#23
Race Car
Thread Starter
I just tried to do the second test you mentioned. And I would say that teh test ligth dimmed, rather than flickered. But, that coil is from the running car, so I know that it is good. I may need to run a continuity test to ground to see if it ever tries to beep.
I'm about to call it a night. I'm afraid I may be about to swap wiring harnesses, which I am NOT looking forward to. I do have a lead on another one, though it is rough.
Thanks MUCH for all of the replies, guys. I didn't exepct so many thoughts so soon. Hope I get it figured out.
Oh.....anyone know where any good schematics are? I've got the service manuals, but those are too small, hard to read, and at times ambiguous (such as the "connection with field data" things they put there.
01-29-2010, 08:20 AM
#24
Burning Brakes
By disconnecting the ground wire from the coil, and then with the key on you will be able to induce a spark by briefyly touching and removing a new ground wire to ground. You have to test for spark by using the coil to distributor wire. Otherwise you don't know which wire will be sparking plus the roror has to be close enough to a pin. If 12v is available and no spark then there is a problem in the supply side or the coil.
If you can get a spark then check the ground wire continuity to ground with the wire disconnected, low resistance will indicate a ground fault. If there is a ground fault it doesn't matter what the DME/KLR is trying to do. The same problem can also occur if the circuit is open back from the coil to the DME.
If you can get a spark then check the ground wire continuity to ground with the wire disconnected, low resistance will indicate a ground fault. If there is a ground fault it doesn't matter what the DME/KLR is trying to do. The same problem can also occur if the circuit is open back from the coil to the DME.
Last edited by samluke; 01-29-2010 at 09:01 AM.
01-29-2010, 08:45 AM
#26
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Another easy test. Disconnect the ground wire from the coil. This wire is from DME pin #1.
Attach a LED to the ground wire, second leg of LED to +12V from battery. Crank the car, LED should flash.
Now instead of +12V from the battery, picjk +12V from the positive side of the coil. If LED is flashing, DME/KLR/wiring are fine. You need a second person to watch the LED or you can route it inside the car.
If you suspect the wiring, you can verify this by running the same test as above, just attach the LED at the DME connector (you will open the connector to get access to the wires).
note: Some LED lights come prewired with a resistor. Some you have to add one).
Ideally you want to check the signals via a scope, but most do not have one. So the LED will have to do.
Attach a LED to the ground wire, second leg of LED to +12V from battery. Crank the car, LED should flash.
Now instead of +12V from the battery, picjk +12V from the positive side of the coil. If LED is flashing, DME/KLR/wiring are fine. You need a second person to watch the LED or you can route it inside the car.
If you suspect the wiring, you can verify this by running the same test as above, just attach the LED at the DME connector (you will open the connector to get access to the wires).
note: Some LED lights come prewired with a resistor. Some you have to add one).
Ideally you want to check the signals via a scope, but most do not have one. So the LED will have to do.
01-29-2010, 09:06 AM
#27
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01-29-2010, 09:41 AM
#28
Race Car
Thread Starter
Trust me, I freaking HATE that swing-door contraption of an air meter. On my XR, I picked up GOBS of power when I converted to a MAF - about 5#/minute of airflow (I had done so much that that was obviously a cork), not to mention a faster spool. I am thinking about getting rid of all of the Porsche stuff, and making a trigger wheel that will allow me to use my Ford stuff to run the engine. If not that, a Megasquirt or something along those lines.But, I'm not sure what I want to do with this car. I had planned for a while to turn it into my track car. But, I'm not sure I am going to keep it. It is a low mileage (64,000), very good condition car. it also is pretty rare - I've been told that there were only about 12 Glacier Blue turbos made. If I can sell it for enough money to get my other one upgraded a lot, I may just go that route. If I do, I would prefer to keep it stock.
samluke, I have tried that method, and for some reason, I can't get it to induce a spark. Funny thing, I can't do it on either car. SO I am wondering if I may be grounding the wrong terminal (the negative one). A little later today, I'll just isolate the coil from the car trying it directly connected to the battery. Attached is the setup I'm using to check for spark - as you can see, I am running directly off of the coil wire.
John, good call on the LED. Will definately be doing that. Note that I've got a remote starter switch running under the hood, so I can do it without an assistant to turn the key.
Chris, thanks for that link!!!! That is awesome - I hadn't found another for under $200. Will definately be picking up that, regardless of whether or not I can figure it out using LED's.
mclarreno9 - I missed the FPR point. Thanks for posting that! Very interesting, I'll be trying that today, as well.
Again, guys, thanks so much for all of the help on this! If I ever meet y'all in person, first round is definately on me.
Last edited by 67King; 01-29-2010 at 10:02 AM. Reason: Attachment
01-29-2010, 11:16 AM
#30
Burning Brakes
If you can't induce a spark then its a supply side problem or your not testing it right. If that's not right you can foget the control side.
Be careful, but a test could be to put 12 v direct on the coil +ve and try the touch test. No spark means bad coil. If you can get it to spark that way, then you may be able to get it to run by connecting back just the coil negative back to the DME, and keeping the hot on the positive. That would at least prove out the control side.
Be careful, but a test could be to put 12 v direct on the coil +ve and try the touch test. No spark means bad coil. If you can get it to spark that way, then you may be able to get it to run by connecting back just the coil negative back to the DME, and keeping the hot on the positive. That would at least prove out the control side.