Won't start/DME relay (revised and corrected)
#1
Cruisin'
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Won't start/DME relay (revised and corrected)
My 1987 Carrera would start great and then just stop running after about 30 seconds to a minute.
I replaced the DME relay and then she would only crank and never start. I put the original DMe relay back in and same problem - lots of crank and no fire.
I just need a few ideas of what to pursue but I am not at all mechanically inclined so i apologize in advance.
(I had my car year wrong and signature wrong - it has always been an '87)
Many thanks
Rick
I replaced the DME relay and then she would only crank and never start. I put the original DMe relay back in and same problem - lots of crank and no fire.
I just need a few ideas of what to pursue but I am not at all mechanically inclined so i apologize in advance.
(I had my car year wrong and signature wrong - it has always been an '87)
Many thanks
Rick
#2
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Join Date: Jun 2004
Location: Virginia Beach, VA
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I know this is going to sound primative but try smacking the top of your computer under your drivers seat to see if it will then start. My car had the same problem a couple of years ago and I had to have the computer module rebuilt to fix it since replacements are no longer available. The mechanic did the same thing to my car and it started right up after i had the car towed to the local mechanic.
#3
Former Vendor
"gbailey"'s is a good test.
Also check your reference sensors: http://www.ecudoctors.com/home-porsc...nsor-test.html
We have a youtube video on how to it yourself using a multimeter.
Also check your reference sensors: http://www.ecudoctors.com/home-porsc...nsor-test.html
We have a youtube video on how to it yourself using a multimeter.
#4
Team Owner
"gbailey"'s is a good test.
Also check your reference sensors: http://www.ecudoctors.com/home-porsc...nsor-test.html
We have a youtube video on how to it yourself using a multimeter.
Also check your reference sensors: http://www.ecudoctors.com/home-porsc...nsor-test.html
We have a youtube video on how to it yourself using a multimeter.
#7
I haddah Google dat
Rennlist Member
Rennlist Member
"gbailey"'s is a good test.
Also check your reference sensors: http://www.ecudoctors.com/home-porsc...nsor-test.html
We have a youtube video on how to it yourself using a multimeter.
Also check your reference sensors: http://www.ecudoctors.com/home-porsc...nsor-test.html
We have a youtube video on how to it yourself using a multimeter.
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#8
""gbailey"'s is a good test."
Not really! Sounds like what gets posted over on the 'Dark Side'.
Read here under 'No-Start';
http://www.systemsc.com/diagnostic.htm
Not really! Sounds like what gets posted over on the 'Dark Side'.
Read here under 'No-Start';
http://www.systemsc.com/diagnostic.htm
#9
Team Owner
Really Loren ? .. coz this is what is published on your own site ...
Lastly, it's always possible that the fuel injection unit or the ignition control unit may be the problem.
Again, a light taping on each unit may help determine if either is the source of the poor running
condition, i.e. because of possible intermittent connections internally. Given the complexity of most
control units, determining a poor running problem the result of a control unit, even by use of a scanner,
is difficult. Usually, the control unit must be replaced temporarily with another unit.
Sounds like you are in fact " the dark side " figure it wouldnt be long before you were sticking your nose in where other peole were trying to help .. personally i think most would rather deal with ECU doctors .. kind of like help without the arrogance..
Lastly, it's always possible that the fuel injection unit or the ignition control unit may be the problem.
Again, a light taping on each unit may help determine if either is the source of the poor running
condition, i.e. because of possible intermittent connections internally. Given the complexity of most
control units, determining a poor running problem the result of a control unit, even by use of a scanner,
is difficult. Usually, the control unit must be replaced temporarily with another unit.
Sounds like you are in fact " the dark side " figure it wouldnt be long before you were sticking your nose in where other peole were trying to help .. personally i think most would rather deal with ECU doctors .. kind of like help without the arrogance..
#10
Instructor
Join Date: Jun 2004
Location: Virginia Beach, VA
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The "Dark Side" or the "Other Side", I don't really care what side it came from. This is what my highly respected certified Porsche mechanic did as soon as my car was rolled off of the flatbed and it started right up. It made the diagnostics pretty easy to interpret and the fix was clearly in the ECU. My post was just a simple way to possibly diagnose the problem without the complicated multimeter testing that not everyone on these boards is capable of doing.
Just trying to share my experience andhoped it helped someone else.
Just trying to share my experience andhoped it helped someone else.
#11
I haddah Google dat
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we need a sticky in this forum for 3.2 911 "no start" conditions. I have the dme test plan on a hard drive somewhere, but it's full of multimeter and ocilliscope test procedures...
#12
As stated in this thread:
"I know this is going to sound primative but try smacking the top of your computer"
As stated on the website:
"a light taping on each unit may help determine if either is the source of the poor running condition,"
Since the DME relay is near the DME ECM and the DME ECM connector, with
its pins that may make a weak connection, is attached to the DME ECM,
"smacking" the DME ECM may also affect the DME relay and/or the
DME ECM connector connections. So "a light taping" "may help" but is
never conclusive and may lead to unnecessary repairs. It's one test that
may help localize a problem along with other tests.
Here's a more complete test plan:
Simple tests to localize a 911 3.2 no start problem:
1. Remove the coil wire from the distributor cap and
place the end about 10mm from the engine case.
2. Remove the #1 injector connector and insert a noid light,
buy one at AutoZone/Reillys or Pep Boys.
3. Have someone crank the engine while you monitor both
the coil wire & noid light.
Tests results:
A. Both immediate spark and noid upon cranking then;
Both speed & ref sensors, powers/grounds O.K., and
DME ECM O.K. - Check for fuel pressure and/or spray
carb cleaner into air filter and re-do steps 1-3 above.
Check distributor cap next. The temp sensor can be
bypassed by jumping the temp connector (white)
with a paper clip, which simulates a warm engine.
B. If neither noid nor spark then; check sensors
(1k ohms, >1.0VAC speed, >.10VAC ref), DME ECM,
or powers (1/18/35) & grds (5/16/17), or DME relay
C. If noid but no spark then; DME ECM a problem,
or power to coil from ignition switch (if already
replaced the coil), also check coil wire for resistance.
Once it starts, remove the ref sensor connector, the
engine should keep running and accel perfectly (if
not then a bad speed sensor). Next, try reversing the
speed & ref sensors on the engine and then the two
connectors on top, i.e. check for possible weak sensor.
D. If spark but no noid then; power connection to
injectors & ECM (pins 14/15) or bad DME Relay.
Note: The temp sensor, AFM, and altitude sensor
affect the fuel and are essentially eliminated as
problem sources for basic starting by using carb
cleaner (A above).
The above is a starting point and NOT an exhaustive/in-detail
troubleshooting guide.
"I know this is going to sound primative but try smacking the top of your computer"
As stated on the website:
"a light taping on each unit may help determine if either is the source of the poor running condition,"
Since the DME relay is near the DME ECM and the DME ECM connector, with
its pins that may make a weak connection, is attached to the DME ECM,
"smacking" the DME ECM may also affect the DME relay and/or the
DME ECM connector connections. So "a light taping" "may help" but is
never conclusive and may lead to unnecessary repairs. It's one test that
may help localize a problem along with other tests.
Here's a more complete test plan:
Simple tests to localize a 911 3.2 no start problem:
1. Remove the coil wire from the distributor cap and
place the end about 10mm from the engine case.
2. Remove the #1 injector connector and insert a noid light,
buy one at AutoZone/Reillys or Pep Boys.
3. Have someone crank the engine while you monitor both
the coil wire & noid light.
Tests results:
A. Both immediate spark and noid upon cranking then;
Both speed & ref sensors, powers/grounds O.K., and
DME ECM O.K. - Check for fuel pressure and/or spray
carb cleaner into air filter and re-do steps 1-3 above.
Check distributor cap next. The temp sensor can be
bypassed by jumping the temp connector (white)
with a paper clip, which simulates a warm engine.
B. If neither noid nor spark then; check sensors
(1k ohms, >1.0VAC speed, >.10VAC ref), DME ECM,
or powers (1/18/35) & grds (5/16/17), or DME relay
C. If noid but no spark then; DME ECM a problem,
or power to coil from ignition switch (if already
replaced the coil), also check coil wire for resistance.
Once it starts, remove the ref sensor connector, the
engine should keep running and accel perfectly (if
not then a bad speed sensor). Next, try reversing the
speed & ref sensors on the engine and then the two
connectors on top, i.e. check for possible weak sensor.
D. If spark but no noid then; power connection to
injectors & ECM (pins 14/15) or bad DME Relay.
Note: The temp sensor, AFM, and altitude sensor
affect the fuel and are essentially eliminated as
problem sources for basic starting by using carb
cleaner (A above).
The above is a starting point and NOT an exhaustive/in-detail
troubleshooting guide.
#13
I haddah Google dat
Rennlist Member
Rennlist Member
I would add that more often than not, no start is a bad dme relay. Instead of tapping on the DME relay, I would just change it out with a known good one that you should always carry in the trunk.
I'm not clear on why you'd bother to check the #1 cyl injector and also spray carb cleaner (or starting fluid, which works probably better, upstream of the filter element). Usually a quick spray into the air box will let you know that you have a fuel delivery problem or a lean condition.
nevermind...I know I just summoned the Kraken...(sigh)
I'm not clear on why you'd bother to check the #1 cyl injector and also spray carb cleaner (or starting fluid, which works probably better, upstream of the filter element). Usually a quick spray into the air box will let you know that you have a fuel delivery problem or a lean condition.
nevermind...I know I just summoned the Kraken...(sigh)