944S not getting spark
08-03-2023, 11:55 PM
#1
Track Day
Thread Starter
944S not getting spark
Hey everyone
Me and my brother are nearing the end of my 944S engine rebuild and am having trouble getting it started. Turning the key to ignition wakes up the dashboard and I can do most things like interact with the headlights and radio as well as turn on the HVAC fan. I have just replaced the battery and the engine cranks at a good rate (or what I think is a good rate, it doesn't slow down when cranking for 20 seconds or so.) I checked compression and am getting about 160 PSI in each cylinder. We haven't checked the fuel system but it was working before we took the engine (Running but knocking, spun cylinder 2 bearing) out originally (about a year ago) and we have been using starter fluid for most starting attempts after the rebuilt engine didn't start the first time. The ignition coil is getting 12v from both wires when the key is turned to ignition. I have the Hanes manual (the one for the base 944 as there is none I could find for the 944S, but the ignition coil is the same part number so I assumed it doesn't matter in this scenario) and I checked the ignition coils resistance across both parts, the primary only had about 0.0-0.1 ohms and I couldn't ever get continuity across the secondary. I tried to get an oem replacement for this but every place I tried to buy it from said it was on backorder till 2024. What I ended up getting one called the "flame thrower" (http://www.autoatlanta.com/Porsche-P...PN-R40111.html) I measured the primary resistance on this one and it was above the recommended in the manual, there was no place to measure the secondary. I'm a bit weary of it. When we installed this, the car still did not start (note: we ran out of starter fluid and did not use it for this test). After this I took off the distributer and noticed some blackened buildup on the contacts and rotating assembly, this would explain why we would sometimes get a cylinder or two to fire every now and then in some earlier attempts. I used some sandpaper to try and clean it off, then using brake fluid to make sure the surface was free of dirt. After doing this the car still did not start and did not have any combustion. When taking out the new spark plugs and holding them to a ground I could not see a spark and even when I used one of those inline lightbulbs it didn't light up. This is about as far as I have gotten, at this point I think it must either be the ignition coil, the distributor, or one of the wires that are in-between the ignition coil and the spark plugs. Some final things that I don't think have any affect on the car starting but might and I just don't know: I have been unable to get any oil pressure. This is a bit unnerving considering that what killed the engine was a spun bearing, even though cylinder 2 is familiar with oil starvation (we are reusing the same oil pump.) Lack of oil pressure could be also accounted to the oil pressure sensor had one of the bolts break off on removal and the connection is now being held on in a weird way that I think should still be sending power. Oil pressure gage needle bounces when cranking, but below one bar. the Halifax sensor is also not connected to the wiring harness the best way, the previous owner had broken the 3pin connecter and just had the bare wires shoved into the wiring harnesses side. I made sure to attached them to the correct connections but other than that it is still attached in this way. I have also gone through the entire dme wiring harness and made sure that every wire does have continuity to its correct place. I believe the timing is correct.
Thank you for your time and knowledge
Me and my brother are nearing the end of my 944S engine rebuild and am having trouble getting it started. Turning the key to ignition wakes up the dashboard and I can do most things like interact with the headlights and radio as well as turn on the HVAC fan. I have just replaced the battery and the engine cranks at a good rate (or what I think is a good rate, it doesn't slow down when cranking for 20 seconds or so.) I checked compression and am getting about 160 PSI in each cylinder. We haven't checked the fuel system but it was working before we took the engine (Running but knocking, spun cylinder 2 bearing) out originally (about a year ago) and we have been using starter fluid for most starting attempts after the rebuilt engine didn't start the first time. The ignition coil is getting 12v from both wires when the key is turned to ignition. I have the Hanes manual (the one for the base 944 as there is none I could find for the 944S, but the ignition coil is the same part number so I assumed it doesn't matter in this scenario) and I checked the ignition coils resistance across both parts, the primary only had about 0.0-0.1 ohms and I couldn't ever get continuity across the secondary. I tried to get an oem replacement for this but every place I tried to buy it from said it was on backorder till 2024. What I ended up getting one called the "flame thrower" (http://www.autoatlanta.com/Porsche-P...PN-R40111.html) I measured the primary resistance on this one and it was above the recommended in the manual, there was no place to measure the secondary. I'm a bit weary of it. When we installed this, the car still did not start (note: we ran out of starter fluid and did not use it for this test). After this I took off the distributer and noticed some blackened buildup on the contacts and rotating assembly, this would explain why we would sometimes get a cylinder or two to fire every now and then in some earlier attempts. I used some sandpaper to try and clean it off, then using brake fluid to make sure the surface was free of dirt. After doing this the car still did not start and did not have any combustion. When taking out the new spark plugs and holding them to a ground I could not see a spark and even when I used one of those inline lightbulbs it didn't light up. This is about as far as I have gotten, at this point I think it must either be the ignition coil, the distributor, or one of the wires that are in-between the ignition coil and the spark plugs. Some final things that I don't think have any affect on the car starting but might and I just don't know: I have been unable to get any oil pressure. This is a bit unnerving considering that what killed the engine was a spun bearing, even though cylinder 2 is familiar with oil starvation (we are reusing the same oil pump.) Lack of oil pressure could be also accounted to the oil pressure sensor had one of the bolts break off on removal and the connection is now being held on in a weird way that I think should still be sending power. Oil pressure gage needle bounces when cranking, but below one bar. the Halifax sensor is also not connected to the wiring harness the best way, the previous owner had broken the 3pin connecter and just had the bare wires shoved into the wiring harnesses side. I made sure to attached them to the correct connections but other than that it is still attached in this way. I have also gone through the entire dme wiring harness and made sure that every wire does have continuity to its correct place. I believe the timing is correct.
Thank you for your time and knowledge
08-04-2023, 08:53 AM
#2
RL Community Team
Rennlist Member
Rennlist Member
Does the S have a crank position sensor? If so, does the tach needle bounce up and down slightly with engine rotation when cranking or does it just sit dead at the bottom?
08-04-2023, 10:29 AM
#3
Three Wheelin'
Join Date: Oct 2021
Location: Southern WI - 89S2 Megasquirt PNP
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First off, why are you using a Haynes manual (for an engine rebuild no less) when the Factory Service Manuals are available for free? The Haynes manual is a steaming piece of garbage that should never ever be used by anyone in this day and age who spends any time working on these cars. Why? It doesnt accurately convey all the differences in the various 944 models (turbo, S, S2, 8V 2.5, 8V 2.7) not to mention it doesnt cover the procedures for an engine rebuild such as tolerances and torque specs... Did you even attempt to find the factory service manual? Its perplexing why anyone would embark on an engine rebuild without the FSM (for any car, not just a 944)
http://p914-6info.net/944%20Manuals.html
Secondly, the 16v cars have an external ignition control module (igniter) which sends the signal to the coil, so you should also test that (again, likely not covered in the Haynes manual).
Lastly, while you are at it, you should also bookmark Clarks garage and read through the engine troubleshooting guide and run through each step testing as you go. An engine needs 4 basic things to run, compression, spark, fuel and proper timing. Hopefully you rebuilt the engine correctly and have timing and compression, which you should verify (and if in doubt refer to the factory FSM or Clarks for guidance). From there the Engine Troubleshooting Section (link below) should be followed methodically, with the first step being verification of spark and verification of fuel. Determine which of those you lack, and then follow the steps provided. Keep in mind that Clarks doesn't have a testing procedure for the external Ignition Control Module so refer again to the FSM on information for that.
https://www.clarks-garage.com/shop-manual/ts-01.htm
https://www.clarks-garage.com/shop-manual/ign-04.htm
http://p914-6info.net/944%20Manuals.html
Secondly, the 16v cars have an external ignition control module (igniter) which sends the signal to the coil, so you should also test that (again, likely not covered in the Haynes manual).
Lastly, while you are at it, you should also bookmark Clarks garage and read through the engine troubleshooting guide and run through each step testing as you go. An engine needs 4 basic things to run, compression, spark, fuel and proper timing. Hopefully you rebuilt the engine correctly and have timing and compression, which you should verify (and if in doubt refer to the factory FSM or Clarks for guidance). From there the Engine Troubleshooting Section (link below) should be followed methodically, with the first step being verification of spark and verification of fuel. Determine which of those you lack, and then follow the steps provided. Keep in mind that Clarks doesn't have a testing procedure for the external Ignition Control Module so refer again to the FSM on information for that.
https://www.clarks-garage.com/shop-manual/ts-01.htm
https://www.clarks-garage.com/shop-manual/ign-04.htm
Testing for Lack of Fuel
As I mentioned before when testing for lack of fuel is is almost essential to have a fuel pressure gauge. You may test for fuel supply by removing the end cap from the fuel rail, installing a hose, and direct the open end of the hose to a catch pan. However, even if you get fuel from the rail during testing there is no guarantee that the fuel pressure is adequate to start the car. In lieu of a pressure test, fuel pump delivery rate test will at least give you an idea of the condition of the fuel pump.
Procedure
Disconnect one of the plug wires and connect the spark tester in series with the spark plug. Crank the engine and look for spark. You'll see the spark pulsing inside the tester as the engine turns over.
If there is no spark at the spark plug, disconnect the main lead from the ignition coil to the distributor cap and connect a spark tester in series with the coil wire. Crank the vehicle and check the tester for spark to the distributor.
If you get good spark at the main lead to the distributor and no spark at the spark plug, the distributor cap and/or rotor is bad and should be replaced. If there is no spark at the distributor main lead, proceed with ignition troubleshooting using IGN-04, Ignition System Troubleshooting.
As I mentioned before when testing for lack of fuel is is almost essential to have a fuel pressure gauge. You may test for fuel supply by removing the end cap from the fuel rail, installing a hose, and direct the open end of the hose to a catch pan. However, even if you get fuel from the rail during testing there is no guarantee that the fuel pressure is adequate to start the car. In lieu of a pressure test, fuel pump delivery rate test will at least give you an idea of the condition of the fuel pump.
Procedure
- Connect a fuel pressure gauge to the end of the fuel rail.
- Attempt to start the vehicle while checking the fuel pressure gauge.
- If the fuel pressure rises on the gauge indicating the fuel pump has started, compare the maximum fuel pressure reading to the specifications in FUEL-01.
- If there is no increase in fuel pressure, and you suspect that that the fuel pump is not starting, refer to FUEL-16 for fuel pump troubleshooting.
- If your fuel pressure is low, or increases very slowly during cranking, refer to FUEL-16 for troubleshooting other fuel related problems.
Disconnect one of the plug wires and connect the spark tester in series with the spark plug. Crank the engine and look for spark. You'll see the spark pulsing inside the tester as the engine turns over.
If there is no spark at the spark plug, disconnect the main lead from the ignition coil to the distributor cap and connect a spark tester in series with the coil wire. Crank the vehicle and check the tester for spark to the distributor.
If you get good spark at the main lead to the distributor and no spark at the spark plug, the distributor cap and/or rotor is bad and should be replaced. If there is no spark at the distributor main lead, proceed with ignition troubleshooting using IGN-04, Ignition System Troubleshooting.
Last edited by walfreyydo; 08-04-2023 at 10:39 AM.
08-04-2023, 10:37 AM
#4
Three Wheelin'
Join Date: Oct 2021
Location: Southern WI - 89S2 Megasquirt PNP
Posts: 1,343
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Regarding your lack of oil pressure - there is an oil pressure relief valve (that I am sure you are aware of if you rebuilt the engine right?) - so you might want to do some checking on that - google is your friend, friend
http://944foot2thefloor.blogspot.com...-oprv-oil.html
http://www.clarks-garage.com/shop-manual/lube-03.htm
http://944foot2thefloor.blogspot.com...-oprv-oil.html
http://www.clarks-garage.com/shop-manual/lube-03.htm
08-05-2023, 12:43 PM
#5
Keeping it simple, and yes, we have all been where you are - so much support. First, do read up on Clark’s garage. Huge information in a manner that is digestible. But assuming engine is built correct, timed correct, start with these procedures. I wouldn’t worry about the ignition module(behind drivers side headlight) until you have checked spark with a noid light (you can rent this cheap), checked your reference sensor ( that connector right center in the firewall that leads down to what looks like a spark plug on the top of the clutch housing), and finally putting on an OEM -quality coil. I bet if you ask the community someone will even offer to send you a used one that is probably good.
Get through these three things, read Clark garage and I’ll bet you get her fired up, assuming my assumptions above are true.
Get through these three things, read Clark garage and I’ll bet you get her fired up, assuming my assumptions above are true.
