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Discussion Starter · #1 ·
Tracking down a no start I got no spark from 2 coils so replaced all 6 and did spark plugs but to no avail. From looking on the forums here this can be caused by cam sensor, the PTU or ecu. I took my ecu out there is a little but of leaking capaciters but they are stull attached, I will supply photos for a second opinion, I have a 1993 3000gt btw.
 

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Tracking down a no start I got no spark from 2 coils so replaced all 6 and did spark plugs but to no avail. From looking on the forums here this can be caused by cam sensor, the PTU or ecu. I took my ecu out there is a little but of leaking capaciters but they are stull attached, I will supply photos for a second opinion, I have a 1993 3000gt btw.
Those capacitors have been replaced at some point, they are not the originals. I do see what looks like signs of leakage under 22 µF capacitor, but don’t know if that’s from current capacitor or left over from the original. You might just take a Q-tip wet with rubbing alcohol, scrub that area to see if will come off the board. It doesn’t look bad enough to cause a problem, but the only way to know for sure is have some service with dedicated test bench to test it.

Cam sensor is a maybe possibility, but I’d question that since the 3-6 coil is still firing. It’s hard to figure how it in conjunction with crank sensor would recognize one pair of cylinders coming to TDC but not the other four cylinders. It's main function (in conjuction with crank sensor) is to let ECU know which cylinder is ready for fuel to be injected.

Since PTU triggers firing of each coil separately, that’s a real possibility. If you have multi-meter and know how to use it you can bench test operation of transistors in PTU using test at bottom of page on the below link.

 

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Discussion Starter · #3 ·
Those capacitors have been replaced at some point, they are not the originals. I do see what looks like signs of leakage under 22 µF capacitor, but don’t know if that’s from current capacitor or left over from the original. You might just take a Q-tip wet with rubbing alcohol, scrub that area to see if will come off the board. It doesn’t look bad enough to cause a problem, but the only way to know for sure is have some service with dedicated test bench to test it.

Cam sensor is a maybe possibility, but I’d question that since the 3-6 coil is still firing. It’s hard to figure how it in conjunction with crank sensor would recognize one pair of cylinders coming to TDC but not the other four cylinders. It's main function (in conjuction with crank sensor) is to let ECU know which cylinder is ready for fuel to be injected.

Since PTU triggers firing of each coil separately, that’s a real possibility. If you have multi-meter and know how to use it you can bench test operation of transistors in PTU using test at bottom of page on the below link.

Thanks for input it did seem like the ECU was previously opened as screws were pretty stripped I will start with PTU as I too don’t think it would be a CAS as it knows two cylinders are at TDC.
 

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Discussion Starter · #4 ·
Those capacitors have been replaced at some point, they are not the originals. I do see what looks like signs of leakage under 22 µF capacitor, but don’t know if that’s from current capacitor or left over from the original. You might just take a Q-tip wet with rubbing alcohol, scrub that area to see if will come off the board. It doesn’t look bad enough to cause a problem, but the only way to know for sure is have some service with dedicated test bench to test it.

Cam sensor is a maybe possibility, but I’d question that since the 3-6 coil is still firing. It’s hard to figure how it in conjunction with crank sensor would recognize one pair of cylinders coming to TDC but not the other four cylinders. It's main function (in conjuction with crank sensor) is to let ECU know which cylinder is ready for fuel to be injected.

Since PTU triggers firing of each coil separately, that’s a real possibility. If you have multi-meter and know how to use it you can bench test operation of transistors in PTU using test at bottom of page on the below link.

So I replaced ptu and got the same problems I hooked my volt meter to my obd1 port and got a TDC sesnor code #22 (2longs 3 shorts) so I am going to perform that job and see if that solves the issue.
 

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So I replaced ptu and got the same problems I hooked my volt meter to my obd1 port and got a TDC sesnor code #22 (2longs 3 shorts) so I am going to perform that job and see if that solves the issue.
I assume you meant to type code #23 (not #22) with (2longs 3 shorts), if so that is cam sensor which service manual refers to as TDC sensor for some reason I'm not sure about.
 

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Discussion Starter · #6 ·
I assume you meant to type code #23 (not #22) with (2longs 3 shorts), if so that is cam sensor which service manual refers to as TDC sensor for some reason I'm not sure about.
Well threw on a new cam sensor and same issue kinda loosing hope here I have replaced everything having to do with ignition except the ecu. It gets real close to starting like everything is helping just getting really weak spark but now at least I have spark at all cylinders. I am thinking of just taking it to a mechanic at this point. I am also still getting same code from ecu.
 

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Well threw on a new cam sensor and same issue kinda loosing hope here I have replaced everything having to do with ignition except the ecu. It gets real close to starting like everything is helping just getting really weak spark but now at least I have spark at all cylinders. I am thinking of just taking it to a mechanic at this point. I am also still getting same code from ecu.
If you take it to a mechanic be sure it’s one that has experience with these particular cars, as there some unique things with them not found in other cars. Where are you located in general, some one here may know of mechanic near you. Is your ECU a MD190662, if so knowing your location might help with possible testing it in someone’s known working car.

If you have spark on all cylinders now and no start, you might have an additional problem. Like jumped timing belt, I haven’t heard of a code 23 when that happens, but it might be logical since out of sequence signal from crank and cam sensor might cause ECU to interrupt that as cam sensor problem. Could even be missing fuel or compression problem, only way to know is to check (test) until it’s narrowed down.
 

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Discussion Starter · #8 ·
If you take it to a mechanic be sure it’s one that has experience with these particular cars, as there some unique things with them not found in other cars. Where are you located in general, some one here may know of mechanic near you. Is your ECU a MD190662, if so knowing your location might help with possible testing it in someone’s known working car.

If you have spark on all cylinders now and no start, you might have an additional problem. Like jumped timing belt, I haven’t heard of a code 23 when that happens, but it might be logical since out of sequence signal from crank and cam sensor might cause ECU to interrupt that as cam sensor problem. Could even be missing fuel or compression problem, only way to know is to check (test) until it’s narrowed down.
Well when I test for spark with an inline spark teamster cylinder 5 and 6 light up the light fully but the other 2 coils barely light it up.
If you take it to a mechanic be sure it’s one that has experience with these particular cars, as there some unique things with them not found in other cars. Where are you located in general, some one here may know of mechanic near you. Is your ECU a MD190662, if so knowing your location might help with possible testing it in someone’s known working car.

If you have spark on all cylinders now and no start, you might have an additional problem. Like jumped timing belt, I haven’t heard of a code 23 when that happens, but it might be logical since out of sequence signal from crank and cam sensor might cause ECU to interrupt that as cam sensor problem. Could even be missing fuel or compression problem, only way to know is to check (test)
If you take it to a mechanic be sure it’s one that has experience with these particular cars, as there some unique things with them not found in other cars. Where are you located in general, some one here may know of mechanic near you. Is your ECU a MD190662, if so knowing your location might help with possible testing it in someone’s known working car.

If you have spark on all cylinders now and no start, you might have an additional problem. Like jumped timing belt, I haven’t heard of a code 23 when that happens, but it might be logical since out of sequence signal from crank and cam sensor might cause ECU to interrupt that as cam sensor problem. Could even be missing fuel or compression problem, only way to know is to check (test) until it’s narrowed down.
so I talked to a mechanic friend of mine he said to check resistances and thinks I have a bad ground I will supply images sorry I am not a good electrical guy so it doesn’t make much sense to me but I have what seems like much lest resistance on the two coils with weak spark meaning less ground but to my knowledge all 3 coils share the same ground so a little confused here . Also thanks for the help so far you a champ!



If you take it to a mechanic be sure it’s one that has experience with these particular cars, as there some unique things with them not found in other cars. Where are you located in general, some one here may know of mechanic near you. Is your ECU a MD190662, if so knowing your location might help with possible testing it in someone’s known working car.

If you have spark on all cylinders now and no start, you might have an additional problem. Like jumped timing belt, I haven’t heard of a code 23 when that happens, but it might be logical since out of sequence signal from crank and cam sensor might cause ECU to interrupt that as cam sensor problem. Could even be missing fuel or compression problem, only way to know is to check (test) until it’s narrowed down.

 

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Discussion Starter · #9 ·

If you take it to a mechanic be sure it’s one that has experience with these particular cars, as there some unique things with them not found in other cars. Where are you located in general, some one here may know of mechanic near you. Is your ECU a MD190662, if so knowing your location might help with possible testing it in someone’s known working car.

If you have spark on all cylinders now and no start, you might have an additional problem. Like jumped timing belt, I haven’t heard of a code 23 when that happens, but it might be logical since out of sequence signal from crank and cam sensor might cause ECU to interrupt that as cam sensor problem. Could even be missing fuel or compression problem, only way to know is to check (test) until it’s narrowed down.
I also verified 12.2 Volts all coils with key on. Also I found some broken grounds do you know where they go? They are on transmission housing. (MT)
 

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Well when I test for spark with an inline spark teamster cylinder 5 and 6 light up the light fully but the other 2 coils barely light it up.
Little confusion here because 5 & 6 are from 2 different coils, the coils for cylinders are as follows, one for cyl 1&4, one for cyl 2&5 and one for cyl 3&6.

so I talked to a mechanic friend of mine he said to check resistances and thinks I have a bad ground I will supply images sorry I am not a good electrical guy so it doesn’t make much sense to me but I have what seems like much lest resistance on the two coils with weak spark meaning less ground but to my knowledge all 3 coils share the same ground so a little confused here.
You're testing coil resistance at wrong spot, that’s harness connector for PTU. You want to unplug the square connector (red arrow pointing at) then take ohm reading at coil side of connector (not harness side). See procedure clip from manual below picture, first section is primary side taken from plug and second is for secondary taken from where each plug wire comes from, you also don’t want to see a “M” or “K” in front of the Ω symbol in first section but do want to see the "K" in front of the Ω symbol for second section for secondary side.
Click on image to enlarge



Also I found some broken grounds do you know where they go? They are on transmission housing. (MT)
If your talking about items circled in red in picture below, that’s not grounds. That’s coated metal bendable fingers to hold plastic wire loom protector tubes in place, to keep them secure and away from moving parts like shift linkage you see at bottom part of that picture.
Click on image to enlarge
 

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Discussion Starter · #11 · (Edited)
Little confusion here because 5 & 6 are from 2 different coils, the coils for cylinders are as follows, one for cyl 1&4, one for cyl 2&5 and one for cyl 3&6.


You're testing coil resistance at wrong spot, that’s harness connector for PTU. You want to unplug the square connector (red arrow pointing at) then take ohm reading at coil side of connector (not harness side). See procedure clip from manual below picture, first section is primary side taken from plug and second is for secondary taken from where each plug wire comes from, you also don’t want to see a “M” or “K” in front of the Ω symbol in first section but do want to see the "K" in front of the Ω symbol for second section for secondary side.
View attachment 300855 Click on image to enlarge

View attachment 300856


If your talking about items circled in red in picture below, that’s not grounds. That’s coated metal bendable fingers to hold plastic wire loom protector tubes in place, to keep them secure and away from moving parts like shift linkage you see at bottom part of that picture.
View attachment 300857 Click on image to enlarge
So I tested the connector as the coils are now and donet expect them to be bad at the connector I am getting 100k ohms which is was too much I will supply photo to know I am doing it right if it is too high resistance what does that indicate.
 

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Discussion Starter · #12 ·

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the working coil (3-5) measures 80k ohms
No you’re still testing coils wrong, you don’t test them from harness side of connector as I said above, you test them from coil side of connector!
then take ohm reading at coil side of connector (not harness side)
After reading this and considering what your mechanic friend said about check resistances for bad ground, I suspected he doesn’t understand that the primary side of coils in these engines makes the ground thru the PTU and the ECU together to make that ground. So you can’t simply test coil primary windings negative terminal to ground, because that will only show when transistor in PTU and ECU are if perfect condition for that to occur, which is unlikely to happen with engine shut down and you certainly don’t want to be taking ohm readings with circuit energized and engine running.
 

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Discussion Starter · #14 ·
No you’re still testing coils wrong, you don’t test them from harness side of connector as I said above, you test them from coil side of connector!


After reading this and considering what your mechanic friend said about check resistances for bad ground, I suspected he doesn’t understand that the primary side of coils in these engines makes the ground thru the PTU and the ECU together to make that ground. So you can’t simply test coil primary windings negative terminal to ground, because that will only show when transistor in PTU and ECU are if perfect condition for that to occur, which is unlikely to happen with engine shut down and you certainly don’t want to be taking ohm readings with circuit energized and engine running.
Okay with testing from coil side I get 1, 1 , and 1.1 ohms
 

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Okay with testing from coil side I get 1, 1 , and 1.1 ohms
OK… that’s close to being in correct range of 0.67-0.81 Ω, although a little high I don’t believe that would be a problem. It could just be some error in your meter, if you read any ohm’s when you touch meter leads together, for accuracy you need to subtract that from any readings taken of components or wiring.

Edit: You answered as I was posting :D
Edit 2: Those readings are acceptable.
 

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Since I’ve been simply replying to your questions about what you might see as the problem, and you sometimes miss questions I’ve included in sometimes long comments maybe it’s time to switch gears to troubleshooting and shorter replies.

I’m not sure what type of spark tester you have that can determine weak spark from strong spark, but considering that might be correct :unsure: and you’re getting 12.2 volts to coils with key on. I wonder if coils are still getting sufficient voltage when cranking, if that voltage fails to 10 volts or lower when cranking it could certainly affect coil output and for sure at around 9.5 volts the engine is not going to start and/or maybe not even turn from starter. If so it might be time to troubleshoot voltage supply problem.
 

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Discussion Starter · #18 ·
Since I’ve been simply replying to your questions about what you might see as the problem, and you sometimes miss questions I’ve included in sometimes long comments maybe it’s time to switch gears to troubleshooting and shorter replies.

I’m not sure what type of spark tester you have that can determine weak spark from strong spark, but considering that might be correct :unsure: and you’re getting 12.2 volts to coils with key on. I wonder if coils are still getting sufficient voltage when cranking, if that voltage fails to 10 volts or lower when cranking it could certainly affect coil output and for sure at around 9.5 volts the engine is not going to start and/or maybe not even turn from starter. If so it might be time to troubleshoot voltage supply problem.
Okay so I took a step back and just looked around engine bay for it anything weird the cam sensor connector had the ground have out and no signal so I re did the connector and now I don’t miss fire so my timing was off but I still just crank and crank. Re put on spark tester which has a light in it, I assume weak spark as it barely lights up light when on my f-150 it is very bright and it runs perfect which is why I say weak spark. So when testing primary coil resistance which says .67-.81 ohms is spec I get 1.5~ on all coils I am testing coil side. Do I replace the bracket for coils then or what. The coils are new and test very well all with in spec. I did put in new ECM no change. Thanks for continuing to help.
 

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So when testing primary coil resistance which says .67-.81 ohms is spec I get 1.5~ on all coils I am testing coil side. Do I replace the bracket for coils then or what. The coils are new and test very well all with in spec.
There’s something wrong in this explanation that may have a bearing. Are you saying the coils test in the .67-.81 ohms range when not installed to bracket and/or wired up, but test 1.5 ohms when wired and installed to the bracket and when taking reading from pins in connector?

The bracket has no bearing on coil operation; it’s simply a piece of metal for coils to mount on and is not involved with ground of coils in any way, the noise suppression capacitor on end of bracket does ground thru bracket but it’s just to keep ignition noise out of radio. So replacing the bracket would be waste of time and money.
 
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