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no spark
i'm new to the 944. i got this car from a guy who daily drove it for a few years and for the past 3 yrs it has been sitting. he had broken the reference sensor off in the bell housing. i tapped the sensor out and replaced it, but still no spark. i have voltage at the injectors and and at the coil. is there anything else that would prevent spark?
he said he replaced the coil before it sat, but just to be safe i think i should check it.i just checked for voltage at the terminals of the coil. am i checking the coil wrong? matt
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" Last edited by mcguiver7; 05-29-2006 at 08:13 PM.. |
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05-29-2006, 08:11 PM
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Hey Matt, Go to Clarks-garage.com and it will explain the whole procedure. There was also a post within the last three days from SoCal Driver that goes through a five minute check to help find problems, do a search on his posts and check it out. Also make sure your grounds are all good.
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Tom 1990 944S2 Cabriolet 2002 Chevy Silverado 2500HD 2003 Maroon Ford F350 dually Last edited by Razorback1980; 05-29-2006 at 08:48 PM.. |
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05-29-2006, 08:45 PM
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Need to change the timing belt too. Sitting for three years lets the belt take a "set". When you start to run the belt around the pullies again unbending where it's sat bent causes the belt backing to break.
As to no spark; Pull a plug wire off of the dist cap and plug. Stick it in the to of the coil. Lay the plug on the body so it grounds out and crank the car. If no spark swap the connectors for the sensors and try again. If still no-go you will need to check the gap on the rear sensor. About 1/32" or 0.8mm. Do the cranking again and swap the sensor connectors again if no spark. Don't let the sensors go too close to the flywheel. The front one can break off the "pin" (setscrew) that is used for TDC.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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05-29-2006, 10:11 PM
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thanks for the info. i'm almost positive the wires aren't swapped. they still had the labels on them (dg and bg). the first thing i did when it wouldnt start was grounded a plug to the intake manifold.
is there anyway to set the clearance by the referencesensor? the speed sensor is stuck in there. matt
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" |
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05-30-2006, 03:37 AM
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If the bracket has been moved at all you need to have the rear sensor loose in the bracket to do the adjustments. Besides heat swelling and corrosion, sensors will stick in the bracket if they have been bent; "he had broken the reference sensor off in the bell housing..."
I would take off the bracket and loosen the sensors. This will allow you to inspect the TDC pin/setscrew also. Don't adjust it.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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05-30-2006, 08:19 AM
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yea he was trying to pry the sensor out. and broke it off at the head of the sensor. i think he might of tried to remove the bracket w/ the wrong size hex (locking bolt was already stripped). so i have no way of taking the bracket off. i can adjust it though. the speed sensor seems to be stuck pretty tight in there. is there any trick to getting these out? the reference sensor took me a good day or two of engineering and fighting with it.
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" |
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05-30-2006, 08:36 AM
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You have to take the bracket off. No other way. Both sensors adjust as one. Bet the other stuck sensor is broken inside too. Get a dremal like grinder and take the heads off of the stripped bolts to get the bracket out. Otherwise you have to remove the engine.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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05-30-2006, 10:07 AM
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would a bad speed sensor prevent spark as well?
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" |
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05-30-2006, 05:21 PM
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Speed sensor is used to for injector open timing. Injectors also use the TDC reference sensor to know when to open. In other words the system does not function with out both sensors.
You need to remove the bracket and check that the TDC pin is still intact besides checking both sensor to bracket settings. No short cuts here.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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05-30-2006, 07:08 PM
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thanks for the help socal. i was able to get the speed sensor out tonight but ruined it in the process. it already had a crack in the connector so probably better off i replace it anyways. i used the .8mm washer trick and reset the adjustment using the reference sensor. theyre identical sensors are they not? when i order the sensor tomorrow do i ask for a reference or speed sensor, or does it matter?
matt
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" |
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05-30-2006, 09:32 PM
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Identical. You can save a few dollars by getting the BMW sensors rather than the 944 sensors. The leads are a few inches longer but your pocket book will not be as light.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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05-30-2006, 10:32 PM
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great info. which model bmw should i ask for?
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" |
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05-31-2006, 03:55 AM
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Location: North Idaho
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More than a few have had this problem. A few archive searches here and other places will help. Electrical problems can be pesky.
Harvey
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'94 968 Coupe, 6-speed '88 928 S4, 5-speed '85 928 S, 5-speed (Sold) '02 Audi TT Turbo, 6 speed (Sold) |
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05-31-2006, 08:19 AM
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i understand that it will not run without both sensors. so i'm currently waiting on my new sensor, but i did however adjust the gap w/ the new sensor then i removed it and installed it in the front to use it as the reference sensor. still no spark. is this a sign of a bad dme or bad dme relay? where is the dme relay located? i have the manuals on the car but they dont show it.
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" |
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05-31-2006, 07:31 PM
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Back to square one:
With the key on there should be battery voltage at the coil and at one of the two pins at any injector. No voltage at the coil is usually a bad ignition switch. Voltage at the coil but not at the injectors is usually a bad DME relay. Voltage at both but no spark is usually the reference sensor and/or it's adjustment. Note that the adjusment is done with the rear speed sensor and the reference (front) sensor follows along. However no spark can also be a bad coil, coil to dist wire, a broken pin on the flywheel, a bad cable from the sensors to the DME, a bad DME, a bad or loose rotor, a bad dist cap, a broken timing belt. Putting a spark plug wire directly into the coil will eliminate the dist/rotor/timing belt from the equation. Checks the flywheel pin and sensor wiring and adjustment. Running a jumper from the battery to the coil will eliminate the ignition switch. Using the bifricated jumper to replace the DME relay will eliminate the ignition switch too. This will also run the fuel pump. Don't leave the jumper in it if it does not start.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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05-31-2006, 09:10 PM
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ok going down the list.
with key on there is voltage at both terminals on the coil and one of the pins on the injectors. therefore ignition switch and dme relay are ok. voltage at both but no spark. reference sensor was adjusted properly by a glued washer to the speed sensor(.8mm +- .05mm washer) coil, distributor cap/rotor, plug wires are all brand new. fuel pump relay is brandnew. pin on flywheel was still intact. timing belt is fine (engine was cranked manually by hand and by starter and tdc was still preserved) conclusion: 1 possibly sensor harness wiring 2 dme how would i check to see if the dme is ok? i'll check resistance between the reference sensor and the dme.
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" Last edited by mcguiver7; 06-01-2006 at 06:58 AM.. |
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06-01-2006, 05:32 AM
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You are missing one item on your check list; the pin on the flywheel.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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06-01-2006, 07:17 AM
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Quote:
Quote:
 or am i supposed to be checking the height of this pin as well?
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" Last edited by mcguiver7; 06-01-2006 at 08:16 AM.. |
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06-01-2006, 08:14 AM
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if i take the dme to porsche do you think they would check it for free?
btw. thanks for all the info guys, especially socal
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85 (early) 944 78 sc targa "The fool who wades in doubt will float like concrete" |
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06-01-2006, 08:26 AM
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SoCal knows his stuff...he's obviously BTDT and has a good memory.
Harvey
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'94 968 Coupe, 6-speed '88 928 S4, 5-speed '85 928 S, 5-speed (Sold) '02 Audi TT Turbo, 6 speed (Sold) |
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06-01-2006, 08:57 AM
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1983 Porsche 944 2.5 liter
