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Join Date: May 2006
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Angry 83 944 wont start, near suicide- HELP

I have been "Helping" my son fix his 944 for about a year now. Started off with ballance shaft belt, got it aligned and finally went to start it after several weeks of working on it. Before it quit for good the fuel pump wouldn't start so we jumped it with 12v and it started working.
Now the car wont fire and the fuel pump don't pump. I tested the coil and got weak spark but its a new coil. We have voltage at injector on both sides of plug. Injectors dont click when motor turns. Replaced speed and position sensors but have not gapped them yet, and now we have replaced wiring harnesses and don't know which connector is the speed sensor?
Tested the dme relay and voltage kicked both circuits/ resistance good. Cheched the computer/ dme for bad foil runs and bad solder, none found, no sign of water, but water had been present from the leak that started everything. The leak claimed the fuse box and relays and the dash harness. The engine harness was also replaced attempting to narrow the search.

Any help would be extremely appreciated!

Old 05-05-2006, 04:52 PM
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Check the gap on the speed and ref sensors. The speed sensor is closest to the clutch.

0.8mm

AFJ
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Old 05-05-2006, 06:20 PM
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going to regap tomorrow but dont think the position was moved when they were replaced.
Old 05-05-2006, 06:39 PM
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Their possition is fixed radially around the flywheel. The sensors are pulse generators and have to be the correct distance from the flywheel teeth and TDC pin. Gap as Mike indicates on the rear most sensor. This is the one over the starter ring teeth. The front sensor will be gaped correctly too.

It's easy to get these plugged into the wrong cables too.

Quick check is to turn the key on and see what the voltage is at the coil and at the injectors. No voltage at the coil means the ignition switch could be bad. Voltage at the coil but not at the injectors means the DME relay could be bad.

If you have voltage at both pull the #1 plug wire, stick a spare plug in it, lay it on the intake so the injector body is grounded and see if you get a spark when you crank it. If there is no spark check and adust the sensors. Check the HV cable from the coil to the dist cap too. This can pull out inside the weather boots. The rotor could have come loose and twisted too. Check the two small screws that hold it to the end of the cam shaft. Check that the spark plug wires are in their correct locations on the cap.

Check all the connectors on the AFS, DME temp sender, throttle switch and oil pressure sender. In fact watch the oil pressure when you crank it. Make sure it comes up a bit before you fire it up.
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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?
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Old 05-05-2006, 06:50 PM
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Send a message via AIM to Razorback1980
Also visit Clarks-garage.com. It is your friend and will save you many headaches.
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Old 05-05-2006, 07:11 PM
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thanks for the reply socal, as far as the checks you listed i somehow overlooked the points and rotor, will replace them tomorrow. The spark at the plug during the coil test was weak but the plug did spark.
Old 05-05-2006, 07:27 PM
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No points. Just a rotor and cap. Points would make this too easy. The DME (electronics) does all of the work from the inputs. This is why it's very important that all be connected and properly adjusted. It's all very simple -- once you understand 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!
Old 05-05-2006, 07:32 PM
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latest update; we are gapping the sensors and when we jumped the dme relay connector for just the fuel pump we got the dripping water sound, (my son says) but i have not checked the flow yet. I suspect there is none since the regulator leaks some and it is dry. Gonna try the new rotor and cap as well and see what happens. Post later.
Old 05-06-2006, 10:39 AM
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What do you mean the regulator leaks? The first unit that the fuel sees coming into the fuel rail is a damper. Kind of a muffler for hydraulic flows. The return side is where the fuel pressure regulator sits. Has the hose that is just clamped on. No high pressure fittings.
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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!
Old 05-06-2006, 04:41 PM
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ok, this is the scoop.If we jump the dme relay we get power to fuel pump. I have voltage at injectors and coil, but no fire. Sensors are gapped to .8mm and i think we have them plugged in right. So is it the dme?
Old 05-07-2006, 11:41 AM
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Could be the DME. Need to check that the sensors are plugged in correctly. Switch the connections and see if the tach jumps when you crank it. Also you can check the pulse/voltage that the rear sensor creates when cranking. Stick a voltage meter on it set to the low scale and you should see at or a little over 2 volts when cranking. Otherwise you need to use an oscillisope to see the wave form.

0.8 mm is about the thickness of a dime. Or about 1/32". Check it again. Don't let the sensors ride the flywheel or two things will happen; you will grind the bottom of the rear sensor off and the front sensor can hit the set screw pin and break it off (which may be your problem).
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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!
Old 05-07-2006, 12:19 PM
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thanks for the help socal, we tried to check voltage for the rear sensor and we hooked one lead to ground and the other to each pin at the connecter. We got no voltage. Also the tach doen't move? Is it the sensor then?
Old 05-08-2006, 08:19 AM
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If there is restance between the center pin and one of the side pins on the sensor then it sould generate the required votage/pulse when properly set. No resistance means the windings are open/broken. Note one side is the floating shield. Should not be any resistance.
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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!
Old 05-08-2006, 03:34 PM
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Thanks socal, tested the relays and both have resistance to one side about 1.5 k. Going to regap later to .6 mm. Best i can tell they are gapped about 1.2mm. I ordered a new dme computer but it will be 2 weeks before i get it if the have one. We ordered the bosch and an extra relay, from what i can tell they are both the same?
Someone suggested we check power to the computer but i'm not sure how to do that, also haven't figured out which connector is for the speed sensor on the new wiring harness.
The other thing i have not done is test the temp sensor(ambient?)
Don't know where it is or if it is even significant for fire. Right now i have no fire at the plug and no fuel at the damper. I do have voltage everywhere except the fuel pump as far as i can tell.
This has been a 2 year endeavor and has haunted me in my sleep many nights, lol, can't wait to hear it run again.
Again i want to thank everyone who has helped identify possible causes and explain the basic procedures for us laymen. TY
Old 05-09-2006, 10:24 AM
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Fuel pump does not get voltage until you crank the car. The voltage that is sent to the starter is split off and sent to the DME. The DME then closes the second set of contacts on the DME relay. You should be able to hear the fuel pump run for a half second or so right after you stop cranking. Have to lean out of the car with your head down though. Or have someone back by the passenger side rear wheel.

If you have voltage at the injectors with the key on then the DME is getting voltage too. The injectors are powered from the DME power. The coil gets it's power from the ignition switch as does the first set of contacts in the DME.

Check and clean all of the ten gauge red wires on the positive battery terminal too.

Following a testing plan will keep you from thowing parts at 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!
Old 05-09-2006, 03:59 PM
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Good timing for this to come up........I didn't learn from the first experience with my older son and a 87 N/A, so I let my younger son by an 83 (one car with another "parts" car). The guy we bought it from had problems getting the car to start so I'm going to use y'all suggestions to get the 83 running. The 87 is still on my Mustang car trailer; trying to figure out if I should fix the body or scrap the car. Its great to be back!
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Old 05-09-2006, 09:35 PM
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Old 05-09-2006, 11:08 PM
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Pins ???

How many pins does the flywheel have??

944 1988 Automatic


(I hope you say one, I think thats all I can see)
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Old 08-28-2006, 03:49 PM
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Thank you again for the help So Cal. I ran all the tests and replaced nearly every electrical part in the car. The wiring harnesses actually cleared up some of the original problems, the cause of the bad wiring harness was holes in the tubs under the hood. Someone probably mounted something there at one time and didn't know they filled up with water. The fuel pump was also bad, may have been from sitting too long. The main fault with the no start condition was the BRAIN.
If we had a good brain to test the system with we migh have isolated that sooner. Unfortunately there is no other method of testing for the brain. Also, the wiring harness might have caused a fault in the new brain and we would be back to square 1 and out the price of the brain (non-refundable).
We still have trouble with the DME relay. Its a tempermental bastard. I am planning to run a different relay, probably ford since i have a few laying aroud, and leave the dme signal hooked to the new relay along with new power straight to the relay and then to the pump.A new ground will go to the pump as well. I think the dme relay will not give any problems as long as you only use the side that turns on the dme (brain). That circuit seems to kick with supplied voltage very consistently. I think the relay is underpowered for the fuel pump however, hence the new relay to carry all that current to the pump.
It may be a while before i have the time to complete this, but i will post when there is something done. Thank you for all you help, EVERYONE!

Last edited by robert bley; 08-28-2006 at 05:03 PM..
Old 08-28-2006, 05:01 PM
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There is nothing wrong with the DME/fuel pump relay design. It's part of the logic for the DME and has properly sized contacts. Changing it and the wiring is just asking for trouble.

This is NOT A FORD so don't try to bail wire it together like you would a Ford.

I'll give you a hint: If you have problems with the fuel pump it's not the relay. If the fuel pump is pulling too much voltage/amps the fuse should blow first.

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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!
Old 08-28-2006, 05:22 PM
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