won't start...advise?
06-30-2008, 02:11 AM
#1
Three Wheelin'
Thread Starter
won't start...advise?
We made it from Houston to Maryland after a single stall event in Houston. Before the trip. we went through some water deep enough to spray up through the fender wells and the car died shortly there after. I suspected water issues at the time, but the next morning we found the positive battery cable loose and tightened it. The car started up and we launched our trip.
After making the 1800 mile trip Maryland, my son was washing the car and it failed to start afterwards. I'm beginning to sense a water connection. Here is what we know:
1) the tank was filled up yesterday and run most of the day on that tank.
2)The DME relay guts/components look "good". No scorched diodes, resistors or cold solders evident.
3) The distributor cap insides seemed dry.
4) Removing the DME relay and cranking produces no power to the fuel pump fuse when cranking
5) Installing the DME relay and cranking produces a) power to the fuel pump fuse and b) spark visible via a timing light
6) But the engine does not catch and start up after cranking
7) I can smell gas while cranking, but can't tell much about fuel delivery beyond that.
What should we check going forward?
Is there a convenient way to attach a fuel pressure gauge to the output side of the fuel pump?
I noticed that the DME relay had 2 poles. One was for the fuel pump. What is the other pole for?
Are the schematics on line?
After making the 1800 mile trip Maryland, my son was washing the car and it failed to start afterwards. I'm beginning to sense a water connection. Here is what we know:
1) the tank was filled up yesterday and run most of the day on that tank.
2)The DME relay guts/components look "good". No scorched diodes, resistors or cold solders evident.
3) The distributor cap insides seemed dry.
4) Removing the DME relay and cranking produces no power to the fuel pump fuse when cranking
5) Installing the DME relay and cranking produces a) power to the fuel pump fuse and b) spark visible via a timing light
6) But the engine does not catch and start up after cranking
7) I can smell gas while cranking, but can't tell much about fuel delivery beyond that.
What should we check going forward?
Is there a convenient way to attach a fuel pressure gauge to the output side of the fuel pump?
I noticed that the DME relay had 2 poles. One was for the fuel pump. What is the other pole for?
Are the schematics on line?
Last edited by mj1pate; 06-30-2008 at 09:57 AM.
06-30-2008, 11:56 AM
#2
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If there is a water problem, maybe you could isolate it to the front or the back. This idea may not work but it is not too time intensive. Place a large fan blowing into the engine area, hood up, and take the carpet out and another fan into the front trunk area. If it fires up in 24 hours or so, I would wet down the rear only --(maybe while running), shut it down and see it it fires up. If it does not start, I would dry that area again and see what happens. If the rear seems OK after the dryout and re-wetting, you could wet the front again and see what happens. If this works, at least you will know if it is water, and if it is front or back. I suppose there could be a water problem in the windscreen leaking into the dash??
06-30-2008, 07:11 PM
#3
Wont start
This may sound silly but recheck the fuel tank level. It is possible that you are having a fuel pick up problem or the that the tank level is lower than indicated by the guage. Does the pump come on ( fuse) , yes - then is it moving gas and building pressure? . Check for a strong bluish/ yellow spark from the coil to ground. Has any of the wiring for the ignition been mooved or bumped. The cap may be clean but may have a hair line crack in it, a very dark room and a flash lite for this one. Good luck.
06-30-2008, 08:44 PM
#5
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Location: Houston, TX
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Distributor Cap "seems" dry isnt good enough. It must be dry. 
I had one that seemed dry... Hesitation, bad pick up and go, stuttering... changed the cap.. and problem solved... Just one thing to look at...
I had one that seemed dry... Hesitation, bad pick up and go, stuttering... changed the cap.. and problem solved... Just one thing to look at...
07-01-2008, 12:20 AM
#6
Three Wheelin'
Thread Starter
I've ordered the distr cap, rotor and fuel filter overnight. The shop manual will arrive next week. Where are the fuel filter and pump located? Does anyone have a picture? Is there a tap for connecting a pressure gauge?
07-01-2008, 01:07 AM
#7
Addict
Fuel filter is on the upper left hand (driver's side) corner of the engine compartment.
Fuel pump is in the fuel tank.
the tap is on the drivers side fuel rail towards the rear of the car above cyl. #1.
Fuel pump is in the fuel tank.
the tap is on the drivers side fuel rail towards the rear of the car above cyl. #1.
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07-02-2008, 11:36 AM
#8
Tests:
1. Remove the coil wire from the distributor and place about a 1/2" from the fan housing.
Sparks should occur while cranking. Make sure that the coil has power with the ignition "on".
2. Use an injector tester (Pep Boys/Autozone - <$5.00) to check for injector signal (flashing)
while cranking.
3. Use a test light to check for power at pins 1,18,35 of the DME ECM with the key "on".
Also, check for power on the injectors.
4. Check for ground at pins 5,16,17.
5. Use an ohmmeter to check for 1000 ohms between pins 8&27 and pins 25&26.
Then check for 1.0 volts AC at pins 8&27 while cranking and .10 volts AC at pins 25/26
while cranking.
Results:
If #1 fails but not #2, then the DME ECM is bad or the coil is bad.
If #3 fails, then it's a DME relay or battery wire connection to the
relay or an ignition switch problem, or an alarm problem.
If #5 fails, then it's a pickup sensor problem.
Check here for further help:
www.systemsc.com/diagnostic.htm
1. Remove the coil wire from the distributor and place about a 1/2" from the fan housing.
Sparks should occur while cranking. Make sure that the coil has power with the ignition "on".
2. Use an injector tester (Pep Boys/Autozone - <$5.00) to check for injector signal (flashing)
while cranking.
3. Use a test light to check for power at pins 1,18,35 of the DME ECM with the key "on".
Also, check for power on the injectors.
4. Check for ground at pins 5,16,17.
5. Use an ohmmeter to check for 1000 ohms between pins 8&27 and pins 25&26.
Then check for 1.0 volts AC at pins 8&27 while cranking and .10 volts AC at pins 25/26
while cranking.
Results:
If #1 fails but not #2, then the DME ECM is bad or the coil is bad.
If #3 fails, then it's a DME relay or battery wire connection to the
relay or an ignition switch problem, or an alarm problem.
If #5 fails, then it's a pickup sensor problem.
Check here for further help:
www.systemsc.com/diagnostic.htm
07-02-2008, 01:10 PM
#9
Three Wheelin'
Thread Starter
Tests:
1. Remove the coil wire from the distributor and place about a 1/2" from the fan housing.
Sparks should occur while cranking. Make sure that the coil has power with the ignition "on".
2. Use an injector tester (Pep Boys/Autozone - <$5.00) to check for injector signal (flashing)
while cranking.
3. Use a test light to check for power at pins 1,18,35 of the DME ECM with the key "on".
Also, check for power on the injectors.
4. Check for ground at pins 5,16,17.
5. Use an ohmmeter to check for 1000 ohms between pins 8&27 and pins 25&26.
Then check for 1.0 volts AC at pins 8&27 while cranking and .10 volts AC at pins 25/26
while cranking.
Results:
If #1 fails but not #2, then the DME ECM is bad or the coil is bad.
If #3 fails, then it's a DME relay or battery wire connection to the
relay or an ignition switch problem, or an alarm problem.
If #5 fails, then it's a pickup sensor problem.
Check here for further help:
www.systemsc.com/diagnostic.htm
1. Remove the coil wire from the distributor and place about a 1/2" from the fan housing.
Sparks should occur while cranking. Make sure that the coil has power with the ignition "on".
2. Use an injector tester (Pep Boys/Autozone - <$5.00) to check for injector signal (flashing)
while cranking.
3. Use a test light to check for power at pins 1,18,35 of the DME ECM with the key "on".
Also, check for power on the injectors.
4. Check for ground at pins 5,16,17.
5. Use an ohmmeter to check for 1000 ohms between pins 8&27 and pins 25&26.
Then check for 1.0 volts AC at pins 8&27 while cranking and .10 volts AC at pins 25/26
while cranking.
Results:
If #1 fails but not #2, then the DME ECM is bad or the coil is bad.
If #3 fails, then it's a DME relay or battery wire connection to the
relay or an ignition switch problem, or an alarm problem.
If #5 fails, then it's a pickup sensor problem.
Check here for further help:
www.systemsc.com/diagnostic.htm
Very nice. Thanks Loren....I can do this.
07-03-2008, 09:48 AM
#10
Three Wheelin'
Thread Starter
Changed the distr cap and rotor and it fired right up. Wasn't a detectable drop of moisture in the old cap, but this happened twice in the 2 weeks of ownership after the car was exposed to either a drenching rain, or washed. I have to admit the old cap contacts looked like hell. This is a really fine example of a 911 in otherwise spendid condition, that PPI'd well.. Regardless, after what we have experienced and based on testimony of others, I would suggest to new owners of cars with unknown tune-up history to change the cap and rotor in the dealer lot, before driving it home.