New Dead Cylinder Question... Im stuck

[bgbadaz]

Ok guys, first off, I searched thru everything on here and didnt find anything that answered this, so if I overlooked it somewhere... my bad. Heres the deal... I have a 90 300 non turbo car... I dug it out of a neighbors garage after her husband died. It hasnt been driven since 03, and apparently he had pulled some stuff apart before he died, so i got a little bit of a puzzle. I think im almost back on the road though. I charged the battery, changed the oil, drained the fuel and put some fresh stuff in, tossed in a new set of plugs, and tried to reassemple all his stuff. It turned over but wouldnt fire. Well, I shot some ether in the throttle bodies and it fired off, but ran ROUGH. Like on 4 cyl kind of rough. I figured the injectors may be clogged, but before pulling the intake, I tried some simple stuff. I checked the compression, its ok. I checked the timing belt... everything is timed right. I checked to make sure it was getting good fuel presure... it does. Then i pulled off the crank angle sensor to listen for the injectors firing.... it soulds like they do... at least 5 of them, couldnt tell on 6. Then I pulled the coil packs and plugs. I rotated the CAS to check for fire. 1, 3,4,5,6 all fired, but not cyl 2. I swapped the coil pack and plug on that one. Tried it again... same thing. I made sure it was gorunded, but that didnt matter too much on the other 5, they would jump a 1/2 inch spark to a ground. So im not getting a signal to the number 2 coil pack. I checked the wires and everything looked ok... what now???? Since I know that one is dead, I want to worry about it before I worry about injectors... I may not have a problem there anyway. Oh, and im not sure if this matters, but on a couple plugs, they fired but I wasnt very impressed with the spark... it seemed weak, but like I said... some could jump 1/2 inch to a ground. Since the battery was dead for so long and the Service light was off I didnt bother to try to pull any codes. Now, its time for me to be humble and ask for advice... and please, be detailed... this is my first time in one of these, im still learning my way around. Thanks, Bobby

[t.mcginley.jr]

Coil packs themselves can go bad, but normally it is something else. If you aren't getting any voltage to a coil pack, you need to check the PTU. It's located on the front passenger side of the engine bolted to the front of the timing cover. It's possible it still has an old style one, which would probably be the issue. Even if it has a newer style one, that also could be bad. It's easiest to swap in a known good one. Here's a pic of the old style vs new style PTU:



You should also ohm check each of the injectors, they should be between 10-14 ohms. If its out of that range, it's shot.

[nissanfreak12]

Still pull codes. Sometimes the ecu will store codes but not trip the light on the dash, especially since you have started it since then. Check the connectors at the PTU. If your not getting any signal at the coil the next place would be the PTU. Do you know which style it has? The old style have like a silver fin look on the front, the newer style is just all black and has a sub-harness attached to it.

If the car has been sitting since 03, you really need to change the timing belt. It could snap on you at any time, then you will definitely have a non running car. How did you check the timing anyway? Probably not your issue, for how long the car has been sitting, my guess its injectors, corroded connectors, ptu. Make sure you also put the correct plugs in, not the stuff you get at any auto parts store, those are not the right ones.

[t.mcginley.jr]

Still pull codes. Sometimes the ecu will store codes but not trip the light on the dash, especially since you have started it since then. Check the connectors at the PTU. If your not getting any signal at the coil the next place would be the PTU. Do you know which style it has? The old style have like a silver fin look on the front, the newer style is just all black and has a sub-harness attached to it.

I think you were typing your response as I was posting mine haha nice

[bgbadaz]

It definately has the new style ptu and subharness in it. Is there anyway to check it without swapping it??? I can tell it has been replaced with a used unit at some time (yellow paint marker on it). Also, can i check the injectors without puling them? Thanks... bobby

[t.mcginley.jr]

You can check the pins on the PTU, but you'll have to check the FSM for the procedure and voltages. They are interchangeable with a number of other Nissans that's why yours probably came from a junk yard, not uncommon at all. Used ones are like $25 on ebay. And yes you can ohm check the injectors without pulling them out. Check the sticky called "Everything you need to know about Z32"

[bgbadaz]

next update... i just replaced the PTU and the small harness that goes with it and i have the Exact same problem. This also came off a running car. I also tried to pull the codes but have nothing to report there. Im now thinking that i have a harness problem. I cut the harness wrap(carefully) away from the #2 coil pack plug, and it has 3 wires to it. Where can I trace these to? Im also assuming that power comes thru the Crank Sensor, thru the PTU and then to the coil packs/injectors. Is this right? I can hear the #2 injector firing. Am i way off base here or am i on the right track? thanks again...

[bgbadaz]

after finding the factory wiring schematic, i think i have a better understanding of the routing here. CAS output goes to the ECCS, which then transmits power to the injectors and PTU, which then goes to the coilpacks. Does anyone know what color wires go from the PTU to each coil pack? As i see it, the other 2 coil pack wires are a ground and a common resistance wire, right? Shouldnt I be able to check those by continuity to another coil pack plug with the Ign off? thanks, bobby

[bgbadaz]

and theres more... im on to checking injectors, only 2 are firing, i cant tell why yet, but numbers 1,3,4,6 are dead right now. as far as the ignition... i pulled the coil plugs off... all the resistance wires (center pin in the plug)on the good cylinders had power with the ign on(checked with a circuit tester), but the dead cyl was just the opposite. no power to it, but the outer pins were hot with the ign on. is this right???

[t.mcginley.jr]

And you're sure your CAS is working correctly? If you aren't getting power to the coil packs or the injectors, then both the CAS and PTU are suspect. If neither of them is confirmed bad, then it's possible its the ECU itself. It could also just be corrosion on the connectors thats your issue. When you pull any of the connectors for the coil packs or injectors do you see any buildup on the metal terminals?

[bgbadaz]

All the injector terminals are badly corroded and I just pulled the plenum to clean and replace some injectors that tested bad. The coil terminals are all spotless though. The strange thing is when I tested the coil pack leads and the number 2 wires seem to test opposite the others. I can't find an issue with the harness but with the ign on the center wire is not hot but the other 2 are and the other coil pack leads are just the opposite. I would assume the CAS is ok since all the injectors get fire when I turn it. I checked the injector leads with a noid lite and they all fire. Also, is there a chemical that I can use on the terminals to remove the green corrosion or do I have to scrape when all?

[Oh Em Zee]

It's also a possibility for o2 sensors and other connectors to be plugged into the coilpacks, so just double check.
DeoxIT has been recommended before. I've seen sand paper, files, tooth brushes with simple green and other simple methods. pack the connections with dielectric grease when you get everything clean.

[davidp94]

It's also a possibility for o2 sensors and other connectors to be plugged into the coilpacks, so just double check.
DeoxIT has been recommended before. I've seen sand paper, files, tooth brushes with simple green and other simple methods. pack the connections with dielectric grease when you get everything clean.

What do you mean by O2 sensors and other connectors plugged into the coilpacks?