No spark on cyl 2&3, tested...coil drivers?
10-30-2005, 03:36 PM
#1
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
No spark on cyl 2&3, tested...coil drivers?
Hello,
Trying to trouble shoot my VQ, I've got no combustion on cylinders 2 and 3 for some reason.
The coil pack has only 3 wires: Power, ground and signal from the ECU. I verified that the power wire was hot, and that the ground wire was grounded and that the signal wire was making a solid path to the ECU. I put in a new plug and used a known good coil off of another cylinder and still no spark.
I listened to the injectors and they are all clicking but when I pulled the spark plug from cylinder 2 it wasn't wet after a couple minutes of running. Should it have been wet after running without spark in that cylinder? Would the air being pumped around have dried it off?
I've heard that injectors can get varnished over on the tip after sitting for a long time (like this motor has). I'm also wondering if it could be the ECU's injectors drivers for those two cylinders.
Any thoughts?
thanks,
allen
Trying to trouble shoot my VQ, I've got no combustion on cylinders 2 and 3 for some reason.
The coil pack has only 3 wires: Power, ground and signal from the ECU. I verified that the power wire was hot, and that the ground wire was grounded and that the signal wire was making a solid path to the ECU. I put in a new plug and used a known good coil off of another cylinder and still no spark.
I listened to the injectors and they are all clicking but when I pulled the spark plug from cylinder 2 it wasn't wet after a couple minutes of running. Should it have been wet after running without spark in that cylinder? Would the air being pumped around have dried it off?
I've heard that injectors can get varnished over on the tip after sitting for a long time (like this motor has). I'm also wondering if it could be the ECU's injectors drivers for those two cylinders.
Any thoughts?
thanks,
allen
11-01-2005, 06:48 AM
#5
Supporting Maxima.org Member
iTrader: (3)
Join Date: Oct 2002
Location: Ontario, Canada
Posts: 1,204
It is a pulse signal that you would need a scope to measure accurately. The needle swing on an analog VM might allow you to make a comparison between the ones that are working and those that are not.
A DVM may give you a time based average of the pulses. According to the FSM, it would be ~0.2V at idle.
A DVM may give you a time based average of the pulses. According to the FSM, it would be ~0.2V at idle.
11-01-2005, 10:22 AM
#6
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
THANK YOU eng92, I forgot all about that page of the FSM! I'll use my analog meter to compare a good cylinder to one of the bad ones like you suggested.
p.s. The more I learn about engine management the easier it gets, can't wait to make the jump to a standalone.
thanks again,
allen
p.s. The more I learn about engine management the easier it gets, can't wait to make the jump to a standalone.
thanks again,
allen
11-02-2005, 06:14 PM
#7
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
Eng92,
Call me a noob but I can't seem to get a solid reading on any of my ignition wires at the ECU while idling. What should I have my analog meter set at, DC right? I got no needle movement in the V range only when I put it on 0.5mA and then only on ignition wire number 1.
any help is appreciated
allen
Call me a noob but I can't seem to get a solid reading on any of my ignition wires at the ECU while idling. What should I have my analog meter set at, DC right? I got no needle movement in the V range only when I put it on 0.5mA and then only on ignition wire number 1.
any help is appreciated
allen
11-02-2005, 10:34 PM
#8
Supporting Maxima.org Member
iTrader: (3)
Join Date: Oct 2002
Location: Ontario, Canada
Posts: 1,204
That doesn't really surprise me. At a 650 rpm idle speed, each coil would get a pulse 5.4 times every second. I kind of hoped you would get some needle "flutter". The signal change is just too fast for your meter to respond to.
Do you have a digital meter you can try and get an average value with?
Other options are renting/borrowing a scope or swapping in a known working ecu.
I have 3 good ecus here and could loan one out if you pay the freight both ways. I am up in Canada though so shipping can take some time and be more expensive.
Do you have a digital meter you can try and get an average value with?
Other options are renting/borrowing a scope or swapping in a known working ecu.
I have 3 good ecus here and could loan one out if you pay the freight both ways. I am up in Canada though so shipping can take some time and be more expensive.
11-03-2005, 05:57 AM
#9
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
I do have a digital unit and tried it but didn't get any kind of usefull response, not sure I even had it on the correct type of voltage.
I appreciate your offer and I may take you up on it if I can't find anything local.
Travis, if you're reading this, do you have any spare ECU's? I think you bought every last one we had here!
thanks,
allen
I appreciate your offer and I may take you up on it if I can't find anything local.
Travis, if you're reading this, do you have any spare ECU's? I think you bought every last one we had here!
thanks,
allen
11-03-2005, 07:03 AM
#10
Supporting Maxima.org Member
iTrader: (3)
Join Date: Oct 2002
Location: Ontario, Canada
Posts: 1,204
You would need a decent bench meter to measure pulse width, amplitude and frequency accurately.
You will not get a consistent reading because your meter sampling rate is much lower than the frequency of the signal you are trying to measure.
If your meter has a peak hold function, you can use that on the DC volt range and let it run for a while and see what kind of measurement you get. Eventually your meter will take a sample when the ecu issues its pulse signal.
Much easier to swap ecus though, then you know for sure.
You will not get a consistent reading because your meter sampling rate is much lower than the frequency of the signal you are trying to measure.
If your meter has a peak hold function, you can use that on the DC volt range and let it run for a while and see what kind of measurement you get. Eventually your meter will take a sample when the ecu issues its pulse signal.
Much easier to swap ecus though, then you know for sure.
11-05-2005, 03:21 PM
#11
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
Well, my meter isn't nice enough to have a peak hold function but I did find a spare ECU to try but the problem is still there, no spark on cyl 2 and 3.
I realigned my front crank sensor and got it closer to the signal wheel but that didn't help.
I'm really stumped on this one. They have power, they have ground and the signal wires to the ECU are not broken or shorted to ground. I swapped coil packs around again and proved the coil packs in cylinders 2 and 3 to be good.
Obviously all of the correct and necessary sensors are in place or I wouldn't have spark to the other 4 cylinders.
Any ideas?
thanks
allen
I realigned my front crank sensor and got it closer to the signal wheel but that didn't help.
I'm really stumped on this one. They have power, they have ground and the signal wires to the ECU are not broken or shorted to ground. I swapped coil packs around again and proved the coil packs in cylinders 2 and 3 to be good.
Obviously all of the correct and necessary sensors are in place or I wouldn't have spark to the other 4 cylinders.
Any ideas?
thanks
allen
11-05-2005, 05:38 PM
#12
Supporting Maxima.org Member
iTrader: (3)
Join Date: Oct 2002
Location: Ontario, Canada
Posts: 1,204
When you verified that your signal wire was "making a solid path back to the ecu", did you just check for continuity between the coil and ecu connectors?
If that is the case, you could have a short to any other non grounded wire and still get continuity.
If this was my dilemma, and I did not have access to an oscilloscope, I would cut the signal wire for one of the problem coils at both the ecu and the coil connector. Be sure you leave yourself sufficient wire at both ends for reattachment. Run a temporary separate piece of wire direct from the ecu connector to the coil connector (outside the vehicle).
If this does not work, then there may be a problem with the coil harness connector itself.
If that is the case, you could have a short to any other non grounded wire and still get continuity.
If this was my dilemma, and I did not have access to an oscilloscope, I would cut the signal wire for one of the problem coils at both the ecu and the coil connector. Be sure you leave yourself sufficient wire at both ends for reattachment. Run a temporary separate piece of wire direct from the ecu connector to the coil connector (outside the vehicle).
If this does not work, then there may be a problem with the coil harness connector itself.
11-06-2005, 06:19 PM
#14
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
Originally Posted by eng92
When you verified that your signal wire was "making a solid path back to the ecu", did you just check for continuity between the coil and ecu connectors?
If that is the case, you could have a short to any other non grounded wire and still get continuity.
If this was my dilemma, and I did not have access to an oscilloscope, I would cut the signal wire for one of the problem coils at both the ecu and the coil connector. Be sure you leave yourself sufficient wire at both ends for reattachment. Run a temporary separate piece of wire direct from the ecu connector to the coil connector (outside the vehicle).
If this does not work, then there may be a problem with the coil harness connector itself.
If that is the case, you could have a short to any other non grounded wire and still get continuity.
If this was my dilemma, and I did not have access to an oscilloscope, I would cut the signal wire for one of the problem coils at both the ecu and the coil connector. Be sure you leave yourself sufficient wire at both ends for reattachment. Run a temporary separate piece of wire direct from the ecu connector to the coil connector (outside the vehicle).
If this does not work, then there may be a problem with the coil harness connector itself.
allen
11-07-2005, 07:31 PM
#15
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
Well, I tried your suggestion and temporarily replaced the signal wire on coil 2 but it didn't make any change. I left coil 3's wiring alone. I wonder if I should replace coil 3's signal wire too.
I have a 3.5 waiting in the wings, I may just scrap this setup and put the 3.5 in and run it w/ the Megasquirt. Trying to make the stock ECU work has been nothing but problems since day one.
I'll try temporarily replacing coil 3's signal wire first though.
allen
I have a 3.5 waiting in the wings, I may just scrap this setup and put the 3.5 in and run it w/ the Megasquirt. Trying to make the stock ECU work has been nothing but problems since day one.
I'll try temporarily replacing coil 3's signal wire first though.
allen
11-07-2005, 08:37 PM
#16
Supporting Maxima.org Member
iTrader: (3)
Join Date: Oct 2002
Location: Ontario, Canada
Posts: 1,204
I wouldn't bother with #3. If you didn't get any spark on #2 with the signal wire changed, the wires are not the problem.
The only thing I can really think of now is the connectors themselves. I personally have never had issues with connectors so I thought it would be pretty unlikely that they would be a problem.
When I finally get the 3.5 in my car, if it doesn't fire up first crank, I will probably invest in a decent used scope.
The only thing I can really think of now is the connectors themselves. I personally have never had issues with connectors so I thought it would be pretty unlikely that they would be a problem.
When I finally get the 3.5 in my car, if it doesn't fire up first crank, I will probably invest in a decent used scope.
12-05-2005, 08:06 PM
#19
12-06-2005, 09:21 AM
#20
Senior Member
Thread Starter
Join Date: Jan 2004
Posts: 369
Wow, sounds like they're telling my story there! The 3.0 I was using had never been apart though as far as I know. I pulled it out of a wrecked Maxima and it never left my posession since then.
I wonder if the placement of my front crank sensor could be the problem (since I made the bracket custom), if I had it mounted slightly off (like a degree or two) then it may have the same effect as one of the pulleys being off a tooth. Hmmmm. I may never know now that I've changed the setup.
allen
I wonder if the placement of my front crank sensor could be the problem (since I made the bracket custom), if I had it mounted slightly off (like a degree or two) then it may have the same effect as one of the pulleys being off a tooth. Hmmmm. I may never know now that I've changed the setup.
allen
Thread
Thread Starter
Forum
Replies
Last Post
jmlee44
4th Generation Maxima (1995-1999)
8
10-02-2022 02:13 PM