resistance check

[red9444]

my car wont start,im trying to test the ignition coil and the ignition coil wire...i put the digital multimeter on 200k im getting 06.5,from the out put to the negative....and im getting 1.0 out of the coil wire. is this normal??

[red9444]

and one more thing..from the positive 15 to negative 1 i get 00.0...i think it should be 0.4 to 0.6?

[Makis]

Yes, probably normal. The coil is a single input transformer with the input sharing the coils with the output. As is a step up transformer the input-output resistance will be quite high compared to the resistance of the input terminals alone. I would say <1ohm input terminal and more then 5K input-output. Use the low ohm setting (<200 ohm) on the multimeter for the input terminals readings and 200K for the input-output readings.

[alantica]

This is from Clarks http://www.clarks-garage.com/shop-manual/ign-04.htm

Ignition Coil Test

1. Disconnect the ignition coil output wire at the distributor cap.
2. Connect a spark plug to the end of the ignition coil output wire which you just disconnected.
3. Connect a ground wire to the threaded portion of the spark plug.
4. Disconnect the ignition coil ground wire from the negative terminal on the coil (Green Wire).
5. Connect one end of a ground wire to the ignition coil negative terminal.
6. Turn the ignition switch to the ON position.
7. Tap the other end of the ignition coil ground wire jumper on an good grounding point (for example the battery negative terminal) and look for sparks at the spark plug that correspond to the frequency of your tapping of the ground wire.
8. If you have a good spark at the spark plug, the ignition coil is good.
9. If you don't get a good spark, check for approximately 12 VDC from the coil positive terminal (black wire) to ground with the ignition switch in the ON position. You should also get approximately 12 VDC from the coil negative terminal (Green wire) to ground

Ignition Coil Resistance Check
In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.

1. Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
2. Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.

Also check out the DME Relay at http://www.the944.com/

[red9444]

problem is im not sure im doing it right..but im not getting a spark how ever i am doing it..i wish i had a picture...

[alantica]

Here are some diagrams http://dcauto.gotdns.com/section/index/3585451/901

[red9444]

let me explain what i did....i took the coil wire off from the dis cap..then i put a spark plug in it...i took a wire connected to the engine for ground,i took that wire and put it on spark plug threads..removed the green wire on the coil,hooked up another wire to that,took that wire and tapped it on the battery negative..no spark,coil heats up...did i do it right? if someone understands me...also if it matters its a 944S i dont think it dose..thanks if no one is getting me,ill draw a picture..

[alantica]

Tried uploading my pics and it keeps timing out. There are pics in the Haynes Manual Porsche 944 {83-89} (ISBN 1 85010 657 6) pg. 116. They are actual but generic pics since Haynes doesn't do a good quality breakdown like one would find in an OEM shop breakdown book. What you see in the DC diagram is just as good.

Year model of your car would be nice [signature line].

Is the engine turning over repeatably or not cranking at all such as a "dead battery"?

With the key in the forward start position (not complete forward cranking position) are you seeing approx. 12V at the end of the wire that comes from the coil and plugs into the rotor cap?

[alantica]

Originally Posted by red9444

let me explain what i did....i took the coil wire off from the dis cap..then i put a spark plug in it...i took a wire connected to the engine for ground,i took that wire and put it on spark plug threads..removed the green wire on the coil,hooked up another wire to that,took that wire and tapped it on the battery negative..no spark,coil heats up...did i do it right? if someone understands me...also if it matters its a 944S i dont think it dose..thanks if no one is getting me,ill draw a picture..

Sorry, you posted before I finished my last post. No experience here with the S model.

Looking at the diagram http://dcauto.gotdns.com/illustration/index/195376964 , your problem may be the Ignition switch unit.

[red9444]

engine turns over fine..yes i have 12v at the 2 wires green and black on ignition coil..

[alantica]

Your coil is most likely working correctly. I am assuming that your rotor cap; rotor button; plug wires; plugs; fuses are working correctly. On most new vehicles with ignition switch units you are given trouble codes to help troubleshoot problems (Exp: check engine light flashing codes). I don't know about the S model and hopefully somebody else with more knowledge will kick in some info and help you in this area.
With the S model out of my experience range, I would look at these items in the following order based on troubleshooting time. These are common items in most basic 944 & S models.

1. DME Relay. Can be bypassed. http://www.clarks-garage.com/shop-manual/fuel-05.htm

2. Alarm System. Can be bypassed. http://www.clarks-garage.com/shop-manual/elect-23.htm #4 can be done at this same time since it is in the local area depending upon what you think of your capabilities with electronics.

3. Speed & Reference Sensors. Please make sure that you read through the entire procedure before you try to check these sensors. Mark the cables that run back to the DME before beginning or it could turn into a PIA trying to figure out the correct wire. The switch connectors are VERY easily cracked and broken. Take you time.
http://www.clarks-garage.com/shop-manual/ign-02.htm

4. DME Control Unit. This can be pulled out and you can reheat the solder joints and re-seat the chip. Cold solder joints are a constant problem on the boards. http://www.clarks-garage.com/shop-manual/dme-01.htm If you want more info PM me your e-mail and I'll send you pics and how I fixed mine to get my car back on the road.

Best of Luck!

[Makis]

Originally Posted by red9444

let me explain what i did....i took the coil wire off from the dis cap..then i put a spark plug in it...i took a wire connected to the engine for ground,i took that wire and put it on spark plug threads..removed the green wire on the coil,hooked up another wire to that,took that wire and tapped it on the battery negative..no spark,coil heats up...did i do it right? if someone understands me...also if it matters its a 944S i dont think it dose..thanks if no one is getting me,ill draw a picture..

You don't get a spark if you just connect the coil to 12V. You need to pulse it. If you just touch the battery the way you setup your experiment you should get a spark.

[red9444]

Originally Posted by alantica

Your coil is most likely working correctly. I am assuming that your rotor cap; rotor button; plug wires; plugs; fuses are working correctly. On most new vehicles with ignition switch units you are given trouble codes to help troubleshoot problems (Exp: check engine light flashing codes). I don't know about the S model and hopefully somebody else with more knowledge will kick in some info and help you in this area.
With the S model out of my experience range, I would look at these items in the following order based on troubleshooting time. These are common items in most basic 944 & S models.

1. DME Relay. Can be bypassed. http://www.clarks-garage.com/shop-manual/fuel-05.htm

2. Alarm System. Can be bypassed. http://www.clarks-garage.com/shop-manual/elect-23.htm #4 can be done at this same time since it is in the local area depending upon what you think of your capabilities with electronics.

3. Speed & Reference Sensors. Please make sure that you read through the entire procedure before you try to check these sensors. Mark the cables that run back to the DME before beginning or it could turn into a PIA trying to figure out the correct wire. The switch connectors are VERY easily cracked and broken. Take you time.
http://www.clarks-garage.com/shop-manual/ign-02.htm

4. DME Control Unit. This can be pulled out and you can reheat the solder joints and re-seat the chip. Cold solder joints are a constant problem on the boards. http://www.clarks-garage.com/shop-manual/dme-01.htm If you want more info PM me your e-mail and I'll send you pics and how I fixed mine to get my car back on the road.

Best of Luck!

i tried all 4 of those things already...if theres power at the black and green wire on the coil dose that mean the ignition switch is ok?

[alantica]

Originally Posted by red9444

engine turns over fine..yes i have 12v at the 2 wires green and black on ignition coil..

Originally Posted by red9444

also if it matters its a 944S i dont think it dose..

It does matter. The DME's have separate Bosch/Porsche part numbers and the electrical engineering of engine timing & fuel injection are different.

The Haynes manual does have a schematic that gives a breakdown of the ignition switch. If the engine is turning over and you have 12V on each side of the coil, I wouldn't suspect the ignition switch. The switch is allowing current to flow through the fuse board and the rest of the ignition system. If your problem is not the ignition switch unit at the rotor I would swap out the DME.

When the ignition key is turned 12V+ arrives at the coil {BLACK WIRE} from the battery. A trigger {PULSE VOLTAGE} is applied from the DME {GREEN WIRE} which makes the coil generate 15,000V through the coil wire to the center of the rotor cap. It is rotated around the plug wires with the rotor button. The voltage travels through the wires to the bottom of the plug where it is grounded creating a spark, thereby igniting the fuel.

Coil operation: Inside the coil current from the battery flows through the thicker primary windings and a magnetic field builds in strength thanks to the help of the iron core. When the switching device opens (or is triggered - DME), the flow of current is broken and its magnetic field collapses over to the thousands of secondary windings. During this collapse, the voltage is stepped up, creating the higher voltage 15KV that is required to jump the spark plug gap and ignite the air/fuel mixture.

So, in your case if you are seeing 12V at either side in the forward (not turning the starter) switch of the ignition, it would be normal because voltage is coming from the DME and the battery. In the start position (starter turning) the voltage changes from the DME as a trigger making the coil rotate in milliseconds the outgoing coil current 15,000V plus out the coil wire to the rotor cap. You may not be getting that trigger from the DME.

In my 88 944 I changed all parts in the ignition to my car. Coil, rotor & cap, rotor button, wires, plugs, DME relay & bypassed the alarm module. I was still seeing 12V at either side of the coil with no start. I put the same parts in my 87 944 and it started with no problem. I used a light and noticed it was dim on the 88 but bright on the 87 during starting. I swapped out the DME's and the 88 cranked and ran.

The problem was the DME. I took the DME apart and used a soldering iron to reheat the soldering joints and I also reset the plug in chip. I put the DME back in the car and it started with no problem. In my opinion the $500.00 plus cost of a used DME that I saved was well worth the effort. It took about 6 weeks to go through that process and was extremely frustrating because the 88 is a daily driver.

Reference: http://www.the944.com/ ...at the bottom of the page is "Workshop Manuals and PET". Select that link and all of the manuals are listed. You need Vol5-electrical.pdf, this covers the S model. Direct link: http://www.cannell.co.uk/944_workshop_Manual/Vol5-electrical.pdf

[red9444]

Originally Posted by alantica

It does matter. The DME's have separate Bosch/Porsche part numbers and the electrical engineering of engine timing & fuel injection are different.

The Haynes manual does have a schematic that gives a breakdown of the ignition switch. If the engine is turning over and you have 12V on each side of the coil, I wouldn't suspect the ignition switch. The switch is allowing current to flow through the fuse board and the rest of the ignition system. If your problem is not the ignition switch unit at the rotor I would swap out the DME.

When the ignition key is turned 12V+ arrives at the coil {BLACK WIRE} from the battery. A trigger {PULSE VOLTAGE} is applied from the DME {GREEN WIRE} which makes the coil generate 15,000V through the coil wire to the center of the rotor cap. It is rotated around the plug wires with the rotor button. The voltage travels through the wires to the bottom of the plug where it is grounded creating a spark, thereby igniting the fuel.

Coil operation: Inside the coil current from the battery flows through the thicker primary windings and a magnetic field builds in strength thanks to the help of the iron core. When the switching device opens (or is triggered - DME), the flow of current is broken and its magnetic field collapses over to the thousands of secondary windings. During this collapse, the voltage is stepped up, creating the higher voltage 15KV that is required to jump the spark plug gap and ignite the air/fuel mixture.

So, in your case if you are seeing 12V at either side in the forward (not turning the starter) switch of the ignition, it would be normal because voltage is coming from the DME and the battery. In the start position (starter turning) the voltage changes from the DME as a trigger making the coil rotate in milliseconds the outgoing coil current 15,000V plus out the coil wire to the rotor cap. You may not be getting that trigger from the DME.

In my 88 944 I changed all parts in the ignition to my car. Coil, rotor & cap, rotor button, wires, plugs, DME relay & bypassed the alarm module. I was still seeing 12V at either side of the coil with no start. I put the same parts in my 87 944 and it started with no problem. I used a light and noticed it was dim on the 88 but bright on the 87 during starting. I swapped out the DME's and the 88 cranked and ran.

The problem was the DME. I took the DME apart and used a soldering iron to reheat the soldering joints and I also reset the plug in chip. I put the DME back in the car and it started with no problem. In my opinion the $500.00 plus cost of a used DME that I saved was well worth the effort. It took about 6 weeks to go through that process and was extremely frustrating because the 88 is a daily driver.

Reference: http://www.the944.com/ ...at the bottom of the page is "Workshop Manuals and PET". Select that link and all of the manuals are listed. You need Vol5-electrical.pdf, this covers the S model. Direct link: http://www.cannell.co.uk/944_workshop_Manual/Vol5-electrical.pdf

yeah,but I ALREADY REPLACED THE DME WITH ANOTHER USED ONE,this one has not sings of ever being opened..i should find someone and test both dmes maybe this one is bad too? how unlucky would that be..

[red9444]

the rpms dont jump at all when i crank the car..and yes u replaced the reference sensor,and the 944S dont have a speed sensor...

[red9444]

i dont know what to check anymore,if the ignition switch is good and theres power at the coil...i checked or replaced everything..

[alantica]

I don't know what else to point you towards besides checking each wire in all the wiring for corrosion, cracking, poor connections & grounds. If each DME is the same Bosch part number you could swap out the plug-in chips in the DME's to see if one of the chips is bad and works with the boards in the other DME. You could also trade the boards. Take out DME 1 upper board and put in DME 2 upper board.

Just to clarify since I am troubleshooting off of electronic theory & schematics. Did you swap out the ignition switch unit { part #9 http://dcauto.gotdns.com/illustration/index/195376964 } at the rotor? Not to be mistaken for the ignition switch. I ask because this is a common failure on engines that have an electronic control unit. Most ISU's are fried when people try to jump start a car from another running vehicle.

No jump in the RPM's would point towards a sensor which is shown on the PET schematic and from what others have stated on the boards while troubleshooting the same problem. If yours does not have a sensor I could only theorize that the jump would be caused by a signal from the ISU or from the DME. I don't know what else would provide the feedback to the tachometer. Can you post your VIN?

[944 Ecology]

The final ignition stage of the 944S is a separate module located near the driver side headlight. Make sure it's plugged in.

[red9444]

Originally Posted by alantica

I don't know what else to point you towards besides checking each wire in all the wiring for corrosion, cracking, poor connections & grounds. If each DME is the same Bosch part number you could swap out the plug-in chips in the DME's to see if one of the chips is bad and works with the boards in the other DME. You could also trade the boards. Take out DME 1 upper board and put in DME 2 upper board.

Just to clarify since I am troubleshooting off of electronic theory & schematics. Did you swap out the ignition switch unit { part #9 http://dcauto.gotdns.com/illustration/index/195376964 } at the rotor? Not to be mistaken for the ignition switch. I ask because this is a common failure on engines that have an electronic control unit. Most ISU's are fried when people try to jump start a car from another running vehicle.

No jump in the RPM's would point towards a sensor which is shown on the PET schematic and from what others have stated on the boards while troubleshooting the same problem. If yours does not have a sensor I could only theorize that the jump would be caused by a signal from the ISU or from the DME. I don't know what else would provide the feedback to the tachometer. Can you post your VIN?

i did not change the #9 part,because i have power at the coil wires..heres my vin i dotn knwo how that helps..WP0AA0949HN451756 ..thanks for the write up thought,im taking the car to a shop in harrisburg..he said he will mess with it and see if he finds the problem,i just dont have the exp...