Big Problem, Involves The Fuel Injector Harnesses
03-27-2006, 05:51 PM
#1
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Thread Starter
Join Date: Dec 2005
Posts: 33
Big Problem, Involves The Fuel Injector Harnesses
I was replacing the fuel injector harnesses on my 91, when i was finished i checked all the connections, everything checked out ok. So I went ahead and started it up, its now only running on three cylinders.
The only possible thing i can think of is the mistake i made of not unhooking the battery before doing this procedure and im not sure but i think two wires might have been crossed and this made a spark. I have no idea what to do now im out of a car and i cannot drive it to a shop.
I am in serious need of help from anyone who knows exactly what they are talking about.
P.S. I thought it might have been a blown ecu chip so i took it out and had my dad check it ( hes a certified tech ) and it all checked out too.
HELP
The only possible thing i can think of is the mistake i made of not unhooking the battery before doing this procedure and im not sure but i think two wires might have been crossed and this made a spark. I have no idea what to do now im out of a car and i cannot drive it to a shop.
I am in serious need of help from anyone who knows exactly what they are talking about.
P.S. I thought it might have been a blown ecu chip so i took it out and had my dad check it ( hes a certified tech ) and it all checked out too.
HELP
03-28-2006, 04:54 AM
#2
Jack Of All Trades
Join Date: Jun 2004
Location: Acton, California
Posts: 2,296
Keep in mind, that if you did all of this work with the battery connected, you could have cycled quite a bit of fuel into some of the cylinders. There is a good chance that some of the plugs are fouled out. You might try pulling them out and drying them off first.
When your dad checked the ecu, he made sure that the injector pins on the ecu had battery voltage per this fsm page ---> HERE?
If so, the next thing to check for is battery voltage at each injector connector. Having voltage at each connector will tell you if you did the wiring correctly. Then you need to ohm check the injectors themselves.
Obviously, you know that you should have disconnected the battery before working on your car.
When your dad checked the ecu, he made sure that the injector pins on the ecu had battery voltage per this fsm page ---> HERE?
If so, the next thing to check for is battery voltage at each injector connector. Having voltage at each connector will tell you if you did the wiring correctly. Then you need to ohm check the injectors themselves.
Obviously, you know that you should have disconnected the battery before working on your car.
03-28-2006, 06:29 AM
#3
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Thread Starter
Join Date: Dec 2005
Posts: 33
reply
i went ahead and checked the ecu again using the diagrams you gave me a link to, most things checked out i will look into those that did not. I removed 2 of the spark plugs and found one had fouling (dry carbon deposits) and cleaned the ones with fouling, it did not do anything though.
I then started the car and nothing has changed, i proceeded to get really, really naked and then cry myself to sleep in the drivers seat.
I then started the car and nothing has changed, i proceeded to get really, really naked and then cry myself to sleep in the drivers seat.
Last edited by Z'sOwnTheRoad; 03-28-2006 at 04:30 PM.
03-31-2006, 03:27 AM
#6
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Join Date: Jan 2006
Posts: 191
Originally Posted by Z'sOwnTheRoad
...i proceeded to get really, really naked and then cry myself to sleep in the drivers seat.
There is a thing as too much information. You about accomplished that. As for your car...the ohm loads for the injectors are good? NO codes? Nothing? Everything pretty much checked out? What does that mean? I am not sure we can help you if you don't post your specific findings? What all did you touch? Just the fuel injector harnesses? You are certain you made no mistake in replacement? Only that you may have crossed a wire? This is something you would remember. Did you reset the ECU?
03-31-2006, 02:13 PM
#7
Registered User
Thread Starter
Join Date: Dec 2005
Posts: 33
When i say that everything pretty much checked out i mean, i have ran the ecu diagnostics 3 times, i have checked all the connections going to and from the ecu, the injector harnesses and all the fuel injectors are around 12 ohms. all sic of my spark plugs are getting great sparks. Cylinders 1 2 and 6 are not firing at all, i unplug the coil pack plug and these cylinders make no difference in the way the engine runs, i have no idead what i touched otherwise i would not be so baffled at the fact that changing six electrical connectors could cause me such a big headache. I am never positive if i made a mistake, but i am willing to bet my Z that i replaced them all correctly. I have reset the ECU, twice. I also went so far as to buy a new eprom chip and replaced it thiking that would help, it didn't. All of the things i have checked have been in working order. THe only thing i can think of now is that the ECU has something fried in it that i am unable to see. I will probable end up taking it in to some moron in town (Omaha, Nebraska) who has no idea what he is doing.
One thing i ask is if anyone knows the schematics for the 300zx 90-96 ecu that would be amazingly helpful,
PS the difference in being really naked and just naked is that, i have mastered the art of being naked, i spend most of my time naked, i even brush all fibers off of my skin to reach optimum nakedness. Your welcome for the odd visual.
One thing i ask is if anyone knows the schematics for the 300zx 90-96 ecu that would be amazingly helpful,
PS the difference in being really naked and just naked is that, i have mastered the art of being naked, i spend most of my time naked, i even brush all fibers off of my skin to reach optimum nakedness. Your welcome for the odd visual.
03-31-2006, 03:44 PM
#8
Jack Of All Trades
Join Date: Jun 2004
Location: Acton, California
Posts: 2,296
1, 2 & 6 are not firing....... as in igniting fuel.
You have verfified that the injectors have 12 ohms of resistance.
When you pull the coil packs and put a spark plug in the coil pack and crank the engine, all of the coil packs fire.
Do you have battery voltage at the injector connectors?
You have verfified that the injectors have 12 ohms of resistance.
When you pull the coil packs and put a spark plug in the coil pack and crank the engine, all of the coil packs fire.
Do you have battery voltage at the injector connectors?
03-31-2006, 05:59 PM
#9
Registered User
Join Date: Jan 2006
Posts: 191
If yourself or anyone has a spare ECU then try to plug one in.
Cylinder miss...well, benefit of a friend
STEPS FOR
DIAGNOSING CYLINDER MISS
FOR THE NISSAN Z32
Necessary Tools:
Volt / Ohm meter (preferably digital)
Fingernail polish or paint
3/8-drive socket set
Turkey Baster Bottle(optional)
Small Paper Clip or Wire bent in U shape with thin flattened ends, or two small “jeweler” or precision screwdrivers (spade type not Phillips).
Long shafted screwdriver
Compression gage (preferably the screw in type)
Noid Lamp for injector harness (optional)
ASE Nissan Certified Master Tech trained spider monkey with very small hands. (Optional)
The following steps can be used in order to isolate and diagnose a cylinder(s) that are not firing properly.
1. Start with the simple things. Run the ECU codes and see if anything pops up. Check the PTU, Coil Packs, CAS, MAFS, and ECU temp sensor harnesses. Look for any corrosion, clean if necessary and make sure the harnesses are tight and have a solid connection. If all this checks its time to move on to step 2.
2. Start the car and warm to normal operating temp and check the timing. It should be set at 15 degrees BTDC +- 2 degrees. Leave the engine running and make a note of the RPM at idle. Now, starting with the #1 cylinder, disconnect the coil pack harness and see if there is a momentary drop in the idle. If there is, reconnect the coil pack and move on to the next cylinder. Continue this process until you find a cylinder(s) that has no effect on the RPM at idle when the coil pack is disconnected. This is the cylinder(s) that needs to be examined closely.
3. Once you have isolated the dead cylinder(s), shut the engine off. Let the engine cool, and then pull the spark plug for the dead cylinder(s). DO NOT pull a spark plug from a hot engine!!! Doing so can cause damage by allowing cool air to enter the combustion chamber. Examine the plug closely. The center electrode should be light tan in the center and the plug “well” (the area surrounding the center electrode) should have only slight carbon buildup. If the center electrode is dark, wet, or has a dark shine, the plug is fouled and needs to be replaced. Replace the plug and determine if the miss is cured. If the spark plug checks out move on to step 4.
4. Determine if the cylinder has spark. My advice here is to disconnect the fuel pump relay or unplug the fuel pump and then start the car. Let it die and then turn the car over for at least 3 – 4 seconds. That relieves any fuel pressure in the system. Now to check for spark you need to remove the coil pack and plug from the bad cylinder. Next connect the coil harness and place the spark plug into the coil pack. Ground the plug threads to the plenum and have someone turn the engine over. The plug should have a visible spark to it. If not swap a coil pack from a good cylinder, connect it to the dead cylinders coil harness and try again. If the plug sparks, the original coil pack is dead and needs to be replaced. (If this is the cause of the miss go out and buy a lottery ticket, as you are one lucky person. Coil packs RARLY are the problem). If the plug has spark its time to move on to step 5.
5. Ok so far you have eliminated an ignition / timing problem. Now you need to determine if the fuel is getting to the cylinder. First connect a fuel pressure gauge to the line that runs from the fuel filter to the fuel delivery tube that is connected to the balance tube using a 5/16” T fitting. (RELIEVE THE FUEL PRESSURE!! AS DESCRIBED IN STEP 4). Once the gauge is connected to the fuel line turn the engine ignition on but do not start the car. The fuel pressure should spike to 40psi +- 3psi and hold there for at least 45 seconds. Now if this checks you need to start the car and make sure the fuel pressure is at least 36psi at idle. If that is good its time to inspect the injector circuit. There are a couple of ways to determine if the injector is working or not. One way is to remove the crank angle sensor (CAS), leaving the harness connected. Once the CAS is removed, turn the ignition switch to on but DO NOT crank the engine. Now SLOWLY rotate the CAS and you will hear each injector click in sequence. If the injector on the dead cylinder does not click move on to step 6. If the injector clicks move on to step 7. NOTE: Before removing the CAS use paint or fingernail polish and paint the CAS bolts around the washer on the bolt before loosening. That way you can re-install the CAS at the original settings and not disturb the timing. Another way to see if the injector is clicking is to start the car, and using a long shafted screwdriver place the tip of the screwdriver on the injector cap. Now place your ear on the screwdriver handle and see if you can hear the injector clicking. If it makes a loud audible click through the screwdriver handle it is working but it may not be pulsing correctly so move to step 6.
6. Now you are getting close. This is where you may need to enlist someone with small hands. The next step is to remove the harness from the injector. To do this you need to remove the wire-retaining clip from the injector harness (IF your Z32 has the retaining clips) and pull the harness off. I use a thin paperclip (flattened a little on the ends) bent in a U shape and place the flattened ends of the paperclip under the wire retaining-clip where the wire retaining-clip slides under the sides of the injector harness forcing the retaining-clip outwards. That done, you can gently lift the harness off the injector. You can also use two small flat bladed “jewelers” or precision screwdrivers that most parts stores handle to do the same. If you have the tab type locking injector harnesses simply depress the locking tab and remove the harness from the injector. Once the harness is removed inspect the harness and injector terminals for corrosion. If there is corrosion clean the harness and injector terminals using “Lime A Way” which is available at most grocery stores. Let the Lime A Way foam up then use a toothbrush to clean the terminals. Dry the terminals completely using compressed air. I use a computer keyboard duster that is nothing more than a can of compressed air that has a thin tube on the can that will direct the air into the harness. Once the terminals are cleaned you also need to test the injector’s resistance with the volt/ohm meter, set to ohms. Do this by placing the probes of the ohmmeter on the injector’s terminals. The factory calls for a resistance range of 10-14 ohms. Any reading greater than 14ohms means the injector is bad and needs to be replaced. From my experience I would recommend replacing any injector that has resistance greater than 13.5 ohms when the engine is cold as resistance in the injector windings increases with heat. You can also check to see if the injector harness is providing power to the injector by plugging in an injector Noid lamp (available at automotive parts stores) in the injectors harness and turn the engine over (or rotate the CAS if you removed it) The Noid light will pulse if the harness is good.
7. If the injector checks out and the injector harness is good, you now have to run a compression test to see if the cylinder has enough compression to fire. To do this you need warm the engine only to the point where the temp gauge is touching the C mark on the temp gauge. Kill the engine by pulling the fuel pump/ IGN fuseable link that is located in front of the battery in the fuseable link box. After that is done pull ALL the plugs (#5 & #6 cylinder require the removal of the engines balance tube). NOTE: If you have never replaced the balance tube “O” rings (there are 3) do so now as the old ones are most likely hard and flattened. They will not re-seal correctly. Be sure to reinstall the balance tube correctly with any brackets or braces set on top of the balance tube flange. Screw in the compression gage and turn the car over for at least 5-7 seconds, at wide-open throttle. Write down the reading and move on to the next cylinder. Normal compression for a N/A is 181psi; a TT is 171psi, with a minimum reading of 140psi (100psi is required to fire a cylinder). There can be no more than 14psi variance per cylinder. If you have a low cylinder you can do a “wet” compression test by placing 2 tablespoons of oil into the cylinder and re-test (I use a turkey basting bottle to do this). If the reading has a significant improvement in compression you have a ring / piston problem. If the reading changes only slightly the low compression is probably due to a stuck or burnt valve. Or there can be carbon deposits on the valve as well. If the compression is low in adjoining cylinders the head gasket is probably leaking. Low compression will cause a rough idle.
Cylinder miss...well, benefit of a friend
STEPS FOR
DIAGNOSING CYLINDER MISS
FOR THE NISSAN Z32
Necessary Tools:
Volt / Ohm meter (preferably digital)
Fingernail polish or paint
3/8-drive socket set
Turkey Baster Bottle(optional)
Small Paper Clip or Wire bent in U shape with thin flattened ends, or two small “jeweler” or precision screwdrivers (spade type not Phillips).
Long shafted screwdriver
Compression gage (preferably the screw in type)
Noid Lamp for injector harness (optional)
ASE Nissan Certified Master Tech trained spider monkey with very small hands. (Optional)
The following steps can be used in order to isolate and diagnose a cylinder(s) that are not firing properly.
1. Start with the simple things. Run the ECU codes and see if anything pops up. Check the PTU, Coil Packs, CAS, MAFS, and ECU temp sensor harnesses. Look for any corrosion, clean if necessary and make sure the harnesses are tight and have a solid connection. If all this checks its time to move on to step 2.
2. Start the car and warm to normal operating temp and check the timing. It should be set at 15 degrees BTDC +- 2 degrees. Leave the engine running and make a note of the RPM at idle. Now, starting with the #1 cylinder, disconnect the coil pack harness and see if there is a momentary drop in the idle. If there is, reconnect the coil pack and move on to the next cylinder. Continue this process until you find a cylinder(s) that has no effect on the RPM at idle when the coil pack is disconnected. This is the cylinder(s) that needs to be examined closely.
3. Once you have isolated the dead cylinder(s), shut the engine off. Let the engine cool, and then pull the spark plug for the dead cylinder(s). DO NOT pull a spark plug from a hot engine!!! Doing so can cause damage by allowing cool air to enter the combustion chamber. Examine the plug closely. The center electrode should be light tan in the center and the plug “well” (the area surrounding the center electrode) should have only slight carbon buildup. If the center electrode is dark, wet, or has a dark shine, the plug is fouled and needs to be replaced. Replace the plug and determine if the miss is cured. If the spark plug checks out move on to step 4.
4. Determine if the cylinder has spark. My advice here is to disconnect the fuel pump relay or unplug the fuel pump and then start the car. Let it die and then turn the car over for at least 3 – 4 seconds. That relieves any fuel pressure in the system. Now to check for spark you need to remove the coil pack and plug from the bad cylinder. Next connect the coil harness and place the spark plug into the coil pack. Ground the plug threads to the plenum and have someone turn the engine over. The plug should have a visible spark to it. If not swap a coil pack from a good cylinder, connect it to the dead cylinders coil harness and try again. If the plug sparks, the original coil pack is dead and needs to be replaced. (If this is the cause of the miss go out and buy a lottery ticket, as you are one lucky person. Coil packs RARLY are the problem). If the plug has spark its time to move on to step 5.
5. Ok so far you have eliminated an ignition / timing problem. Now you need to determine if the fuel is getting to the cylinder. First connect a fuel pressure gauge to the line that runs from the fuel filter to the fuel delivery tube that is connected to the balance tube using a 5/16” T fitting. (RELIEVE THE FUEL PRESSURE!! AS DESCRIBED IN STEP 4). Once the gauge is connected to the fuel line turn the engine ignition on but do not start the car. The fuel pressure should spike to 40psi +- 3psi and hold there for at least 45 seconds. Now if this checks you need to start the car and make sure the fuel pressure is at least 36psi at idle. If that is good its time to inspect the injector circuit. There are a couple of ways to determine if the injector is working or not. One way is to remove the crank angle sensor (CAS), leaving the harness connected. Once the CAS is removed, turn the ignition switch to on but DO NOT crank the engine. Now SLOWLY rotate the CAS and you will hear each injector click in sequence. If the injector on the dead cylinder does not click move on to step 6. If the injector clicks move on to step 7. NOTE: Before removing the CAS use paint or fingernail polish and paint the CAS bolts around the washer on the bolt before loosening. That way you can re-install the CAS at the original settings and not disturb the timing. Another way to see if the injector is clicking is to start the car, and using a long shafted screwdriver place the tip of the screwdriver on the injector cap. Now place your ear on the screwdriver handle and see if you can hear the injector clicking. If it makes a loud audible click through the screwdriver handle it is working but it may not be pulsing correctly so move to step 6.
6. Now you are getting close. This is where you may need to enlist someone with small hands. The next step is to remove the harness from the injector. To do this you need to remove the wire-retaining clip from the injector harness (IF your Z32 has the retaining clips) and pull the harness off. I use a thin paperclip (flattened a little on the ends) bent in a U shape and place the flattened ends of the paperclip under the wire retaining-clip where the wire retaining-clip slides under the sides of the injector harness forcing the retaining-clip outwards. That done, you can gently lift the harness off the injector. You can also use two small flat bladed “jewelers” or precision screwdrivers that most parts stores handle to do the same. If you have the tab type locking injector harnesses simply depress the locking tab and remove the harness from the injector. Once the harness is removed inspect the harness and injector terminals for corrosion. If there is corrosion clean the harness and injector terminals using “Lime A Way” which is available at most grocery stores. Let the Lime A Way foam up then use a toothbrush to clean the terminals. Dry the terminals completely using compressed air. I use a computer keyboard duster that is nothing more than a can of compressed air that has a thin tube on the can that will direct the air into the harness. Once the terminals are cleaned you also need to test the injector’s resistance with the volt/ohm meter, set to ohms. Do this by placing the probes of the ohmmeter on the injector’s terminals. The factory calls for a resistance range of 10-14 ohms. Any reading greater than 14ohms means the injector is bad and needs to be replaced. From my experience I would recommend replacing any injector that has resistance greater than 13.5 ohms when the engine is cold as resistance in the injector windings increases with heat. You can also check to see if the injector harness is providing power to the injector by plugging in an injector Noid lamp (available at automotive parts stores) in the injectors harness and turn the engine over (or rotate the CAS if you removed it) The Noid light will pulse if the harness is good.
7. If the injector checks out and the injector harness is good, you now have to run a compression test to see if the cylinder has enough compression to fire. To do this you need warm the engine only to the point where the temp gauge is touching the C mark on the temp gauge. Kill the engine by pulling the fuel pump/ IGN fuseable link that is located in front of the battery in the fuseable link box. After that is done pull ALL the plugs (#5 & #6 cylinder require the removal of the engines balance tube). NOTE: If you have never replaced the balance tube “O” rings (there are 3) do so now as the old ones are most likely hard and flattened. They will not re-seal correctly. Be sure to reinstall the balance tube correctly with any brackets or braces set on top of the balance tube flange. Screw in the compression gage and turn the car over for at least 5-7 seconds, at wide-open throttle. Write down the reading and move on to the next cylinder. Normal compression for a N/A is 181psi; a TT is 171psi, with a minimum reading of 140psi (100psi is required to fire a cylinder). There can be no more than 14psi variance per cylinder. If you have a low cylinder you can do a “wet” compression test by placing 2 tablespoons of oil into the cylinder and re-test (I use a turkey basting bottle to do this). If the reading has a significant improvement in compression you have a ring / piston problem. If the reading changes only slightly the low compression is probably due to a stuck or burnt valve. Or there can be carbon deposits on the valve as well. If the compression is low in adjoining cylinders the head gasket is probably leaking. Low compression will cause a rough idle.
04-18-2006, 03:55 PM
#12
NisTuner
Join Date: Sep 2005
Location: Cleveland, Ohio
Posts: 2,800
I'd say you'd best run yourself a compression test. Sorta sounds like my Z31. It was at somepoint overheated. It ran fine for a while, it was running better than ever. One day we had it running for most of the day and it was running fine. We turned it off and fired it back up later, it was missing, blowing smoke, wouldn't hold an idle, was about to die unless revved, etc. For some reason the car decided to all at once crap out after it had been fine.
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