PTU Testing

[nissanfreak12]

I need help, can someone that has access to a DMM and PTU test some terminals for me. I think mine is bad with the write up that either Mark or Anton Posted on the new style PTU, I just want to compare mine to a known working one.

The positive needs to be on the G terminal and the negative needs to be on any of the E1-E6 terminals. Have the DMM set to the 2000 mark. Let me know the results please, hopefully tonight. Thanks guys.

[NolimitZ32]

When cold it should show either infinity, 1 (not 1 ohm but 1 as in open loop), or drop off to 0, when hot it will show in the MegaOhms, my good one doesn't go to infinity when its hot but still works just fine.

[nissanfreak12]

When cold it should show either infinity, 1 (not 1 ohm but 1 as in open loop), or drop off to 0, when hot it will show in the MegaOhms, my good one doesn't go to infinity when its hot but still works just fine.

Hmm, When I test mine off the car and cold, obviously, it shows it has resistance. I know you did a write up or had a the testing procedures,and with what the test said, it said the PTU was good. But, I ended up finding out from another FSM that it shows mine bad. Im just really confused. That is why I was hoping someone would give me actual hard numbers if anything comes up.

Here is my issue, I am dead in cylinder 4. Here is what I tested;

Compression- 150psi, shows 5psi higher than cylinder 2

Coil pack- test fine, even switched with a known working pack to double check and all is good.

Spark- It has it, just seems weak, even on cylinder 2, but not as weak as cylinder 4

Injectors- Good, shows 12ohm at the actual injector, 10ohm at the terminal from ECU. Even checked them at CAS, it clicks and sprays. I alos replaced them with the newer style about a month ago.

Wiring-Good order, has connections no breaks.

PTU- See above

My only concern is the ECU, just don't have an extra one or know someone around here, just moved to Denver. I even drove the car from Phoenix to Denver with zero issues. It just decided to go bad out of the blue. Easy driving, cruising, just went dead. Only that cylinder, all the other ones are working just fine. Any insight?

[NolimitZ32]

have you checked continuity in the PTU subharness (if you've got one)

[nissanfreak12]

Yes, continuity is good with the sub harness. I did have the ECU tuned through Coz at Conceptz, he said it may be an Ignition driver, it could have gone bad. But, if it went bad, why would it have spark.

Is it possible the PTU could be weak?

[300ZXttZMAN]

When cold it should show either infinity, 1 (not 1 ohm but 1 as in open loop), or drop off to 0, when hot it will show in the MegaOhms, my good one doesn't go to infinity when its hot but still works just fine.

Exactly I had did this for Anton when he was trying to figure out his issue.

I have a new oem PTU in the box that I had tested and it came out with those results.^

[nissanfreak12]

Yeah, I also found someone to test theirs, they also got the same results. PTU is definitely not the issue, I am getting the same voltage from all six terminals. Injector is working properly. Ecu wouldn't be giving the same results if part was bad.

I started thinking, on my boost/vac gauge, after I installed the new injectors, i noticed my vac psi was down 2-3, it sits roughly about 15-16 psi when warm at idle. I pulled the plugs one more time and the cylinder 4 plugs looks to be running leaner than the others, I pulled a third plug just to make sure. Even though I put new fuel rail insulator and a new plenum gasket, I wonder if the gasket or insulator is not sealing properly causing more air to go directly in that cylinder. It could cause a misfire if that is the case. Its either that or the cam lobe broke off, but that would not give me the proper compression.

I am in the process of taking apart the plenum to check all those out. The only thing that got me wondering is when I got the new Insulators from Coz, they looked different than the original ones. Like he gave me the newer style ones vs the older style. They fit around the fuel rail, not entirely snug, but they fit. They were very loose in the plenum. Hmm, maybe could be my problem. I guess I will find out.

How different are the old style vs new style insulators? I have never seen the newer style insulators.

[nissanfreak12]

Well, in case someone starts to run onto the same issue, I have found my answer.

I went back and checked everything, even did a boost leak test. I did find a leak, fixed that. Started the car, ran great for about a min, no missing or anything. Thought i figured it out, but alas, I drove it around the block, went back to missing on cylinder 4.

So I decided to check the compression again, found my issue. Cylinder 1, 2, 3, 4 are all at 100psi, not sure why it read close to 150psi before, maybe I read it wrong. I didn't even want to check the last two. Yes this was on a full battery and engine at operating temp. I guess I am just really lost why it only affected cylinder 4?