AFM Adjustment, etc.
12-29-2010, 02:42 PM
#76
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Thanks Loren - You are correct.
This morning I decided to go step by step through ignition, fuel and then electronics. I started with the ignition per the Bentley manual and, basically, I am not getting spark. I swear my timing light was triggering a couple of days ago, but this morning - nada. I verified the light was working on my jeep. I also repeated the spark plug test using an autolite 35 and an autolite 46. I got nothing. These plugs are new and should be good. I have 12 volts at the + post on the coil. It also failed the spray carb cleaner in the intake test. The plugs, cap and rotor are all new.
I then moved on to Loren's tests per above. All checked out except that I do have the silver coil (brand new). Previously, I tried swapping in my old (black, working) coil, but nothing changed. I verfied the speed and position sensors using the LED trick from the 944 guys. I'm not quite sure what Loren means by "check for flashing signal on one of the two coil pins", but as stated before, I have tried two different coils.
Basically, I think it's the DME. I have pulled the DME and now need to find another 911 owner or shop that is willing to let me swap it in to test whether or not it works.
If anyone is reading this and is near Road Atlanta and is willing to give this a go, let me know. I can come to you and compensate you for your trouble. Even if you are in the metro area let me know.
You guys have been a really big help.
This morning I decided to go step by step through ignition, fuel and then electronics. I started with the ignition per the Bentley manual and, basically, I am not getting spark. I swear my timing light was triggering a couple of days ago, but this morning - nada. I verified the light was working on my jeep. I also repeated the spark plug test using an autolite 35 and an autolite 46. I got nothing. These plugs are new and should be good. I have 12 volts at the + post on the coil. It also failed the spray carb cleaner in the intake test. The plugs, cap and rotor are all new.
I then moved on to Loren's tests per above. All checked out except that I do have the silver coil (brand new). Previously, I tried swapping in my old (black, working) coil, but nothing changed. I verfied the speed and position sensors using the LED trick from the 944 guys. I'm not quite sure what Loren means by "check for flashing signal on one of the two coil pins", but as stated before, I have tried two different coils.
Basically, I think it's the DME. I have pulled the DME and now need to find another 911 owner or shop that is willing to let me swap it in to test whether or not it works.
If anyone is reading this and is near Road Atlanta and is willing to give this a go, let me know. I can come to you and compensate you for your trouble. Even if you are in the metro area let me know.
You guys have been a really big help.
12-29-2010, 09:04 PM
#77
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Update - we have ignition. I called around to a couple of shops, but for some reason everyone that could help me was out (holiday week I guess). So, I did a search and read up on looking for cracked solder joints in a DME. I cracked the thing open and ding..ding..ding. I found one. The infamous T504 transistor. I thought surely it couldn't be that simple. It was.
However, I thought I had really screwed something up because after it started, it started spewing acrid white smoke. I forgot about all the carb cleaner I had sprayed in there trying to start it earler. Oh well, I guess my intake runners, valves and cylinders are nice and clean.
Again, thanks to everyone for all the help and support.
However, I thought I had really screwed something up because after it started, it started spewing acrid white smoke. I forgot about all the carb cleaner I had sprayed in there trying to start it earler. Oh well, I guess my intake runners, valves and cylinders are nice and clean.
Again, thanks to everyone for all the help and support.
12-30-2010, 03:41 AM
#80
Great that it's resolved! Need to refer all future DME ECM problems/repairs
to you, as you are now the 3.2 expert based on all your experience from
this thread.
"I'm not quite sure what Loren means by "check for flashing signal on one of the two coil pins"
Yes, should have been clearer and stated; "using a test light".
to you, as you are now the 3.2 expert based on all your experience from
this thread.
"I'm not quite sure what Loren means by "check for flashing signal on one of the two coil pins"
Yes, should have been clearer and stated; "using a test light".
12-30-2010, 01:44 PM
#81
Addict
Great that it's resolved! Need to refer all future DME ECM problems/repairs
to you, as you are now the 3.2 expert based on all your experience from
this thread.
"I'm not quite sure what Loren means by "check for flashing signal on one of the two coil pins"
Yes, should have been clearer and stated; "using a test light".
to you, as you are now the 3.2 expert based on all your experience from
this thread.
"I'm not quite sure what Loren means by "check for flashing signal on one of the two coil pins"
Yes, should have been clearer and stated; "using a test light".
12-30-2010, 10:27 PM
#82
Three Wheelin'
Joe,
Glad you found the issue, this is a pretty common one. What he meant by flashing signal is to use a test light on the negative terminal of the coil while someone cranks the engine. If the light flashes on and off, that means that the transistor in the ignition driver circuit of the DME is working and switching the coil on and off, just like the ignition points would in an older car. If the light stays on continuously while cranking, then you know that you have a problem with that circuit, and of course no spark being generated.
You learned a valuable lesson in troubleshooting and hopefully it'll help you out next time.
Glad you found the issue, this is a pretty common one. What he meant by flashing signal is to use a test light on the negative terminal of the coil while someone cranks the engine. If the light flashes on and off, that means that the transistor in the ignition driver circuit of the DME is working and switching the coil on and off, just like the ignition points would in an older car. If the light stays on continuously while cranking, then you know that you have a problem with that circuit, and of course no spark being generated.
You learned a valuable lesson in troubleshooting and hopefully it'll help you out next time.
