Cylinder 1 dead

[lvdisturbed1]

Had a loss of power last week so I did a power balance check. Cylinder 1 wasn't firing. Tested the injectors and sure enough, #1 was out of spec at 58 ohms. Ordered a replacement, and installed it via Ye Olde dremel method. Fired her up, took a quick test drive and she still wasn't right.

Redid power balance check and cylinder one still wasn't firing. Tested injectors from ECU harness, all were reading fine. Tripped new injector on 1 manually with a 9v battery, it's clicking fine. Checked coil pack, working fine. Decided it was time to do compression check.

Cylinder 1-150psi, 2-150, 3-145, 4-145, 5-145, 6-150.

Looks good to me, yet cylinder 1 still doesn't want to work. What else could it be?

[Ace2cool]

Numbers are all a tad low, but low together, so nothing to worry about. So are you saying the injector isn't firing, or have you checked spark? CAS hand crank method would be a great way to tell if the injector is the issue or not at this juncture.

[lvdisturbed1]

It reads just fine from the ECU harness, so I know it has connection. Coil pack is working and I replaced the spark plugs a month ago (PFR6B-11B). I'll try the CAS hand crank test tomorrow. For now I need some sleep since I work graveyard tonight.

[lvdisturbed1]

Did the CAS test. It didn't want to work at first. I pulled the fuel pump fuse to stop fuel from flooding the cylinders while testing the injectors. Unfortunately this caused the injectors to not fire when turning the CAS. Had to reconnect it to get it to work right.

Anyway, all 6 injectors clicked when I turned the CAS (I actually heard 7 clicks, one was by the battery) so they have connection, and are clicking. I went ahead and tested spark as well. All good. No ECU codes either.

I noticed this thread, and wonder if it could be applicable to me.
dead-cylinder-can-t-figure-out-why-fuel ... 95189.html

I used the dremel method to replace the injector. Perhaps the fuel rail seal underneath deteriorated enough to kill the cylinder?

[lvdisturbed1]

Tested the PTU today. I have the newer style one, and it checked out ok. Started the car, and listened to each injector using a screwdriver. Injector one sounded a little off. Other ones were nice and clicky, but the one on 1 was hard to tell. Tried wiggling the connector around, and no change. I had tested the connection to the injector from the plug to the ECU and got 12.8 ohm, so the connection should be fine.

I decided to yank the injector out and test to see if it was still working. I used a 9v battery and some wires to test the injector. It clicked, and spit out a few droplets of residual fuel left in it. I did this a few more times, and concluded the injector works.

I plan on doing the CAS test again with the injector out. I cant right now because I had let the engine get hot, and need to let it cool off.

Any more suggestions?

[NolimitZ32]

I'm sorry if you wrote this and I just didn't catch it but have you tested the actual injector signal form the ECU, its not unheard of for one injector driver in the ECU to die and very possibly having the old injector at such high impedance could've brought the driver along to its death.

[lvdisturbed1]

I checked from the plug that goes into the ECU. Pin 58 and 101 or something like that. If that's not what you mean, could you tell me what I need to do?

[NolimitZ32]

What I am talking about requires an injector test light, you find the wire that closes the circuit and probe it with the test light, if the ECU is sending the signal you get a blink, if the ECU is not than no blink and bad injector driver. I believe the full procedure is in the FSM, if not it can be found on many how to websites or even on youtube.

[lvdisturbed1]

I don't have an injector test light, and couldn't pick one up today, but I think you just set me on the right path. The connector is getting power, but not the ground signal from the ECU to trip the injector. I tested by plugging a working connector into the injectors and rotating the CAS. It worked fine. Tested for power in the non-working connector and it has power, just won't pulse. I'll pick up a test light (noid?) to confirm tomorrow.

Is there a chance it could be the CAS? The CAS sends the signal to the ECU to fire the injectors right? Is it possible for the CAS to not send a signal for 1 injector? If so, how would I test for it?

[Ace2cool]

The CAS is just a switch. Basically a newer, more reliable form of a distributor that uses LED's and photosensors with a rotating disc.

http://twinturbo.net/nissan/300zx/forum ... -info.html

Not likely that a CAS would only cause a single cylinder not to pulse.

[NolimitZ32]

CAS could theoretically have something wrong but it is a fair bit more reliable historically than other possible culprits. That, and injector drivers have been known to go out, good thing is getting a hold of a good condition ECU isn't very expensive and changing it out isn't too much of a pain.

[lvdisturbed1]

It's definitely the ECU. I don't know how to go about replacing it. Mines a JWT tuned one with a socketed EPROM.

Anyway here's some pics.

https://www.dropbox.com/s/6oz8othxj1h0k ... 0.jpg?dl=0
https://www.dropbox.com/s/wepyql1rng0qy ... 7.jpg?dl=0
https://www.dropbox.com/s/51pzo2ehmxnq8 ... 7.jpg?dl=0
https://www.dropbox.com/s/2lo4zj3h0l0i3 ... 4.jpg?dl=0

[lvdisturbed1]

My car is a 90 5-speed TT. The JWT ECU in it has a part #A18-B04 MF0, which points to a 93 ECU.

Can I use any 8-bit (90-94) M/T F (federal) ECU? If so, could I solder the EPROM socket from the JWT ECU onto it to keep my tune?

I think my only other option would be to get a Z1 ECU upgrade and eat the $300 core charge for a final cost of $500 plus shipping. Another JWT would cost me $575 provided I have another ECU.

Anyway, thank you guys for helping me hunt down my issue.

[NolimitZ32]

Wow yeah your ECU is definitely a culprit if not THE culprit. If your car is manual, you can use any 8-bit ECU because all the important stuff is on the EPROM. I ran a chipped (custom manual tune) 8-bit Auto TT ECU in my swapped NA 5-speed and it never complained. If you can get your EPROM out without damaging it then you could by all means run it in the new ECU you would just have to solder a bed into the new one. I recommend you get an electronics repair shop to be the work unless you are awesome as soldering because if you overheat the EPROM while trying to desolder it you can burn it up.

[lvdisturbed1]

Update: I got an ECU for $150 that was already socketed by CZP. It's an auto TT ECU, and I swapped over my JWT EPROM. My dead cylinder issue is gone!

Unfortunately, now I'm only pulling stock boost. I should be getting 14-15 psi. Something is amiss.

[NolimitZ32]

1. Have you checked all your vacuum lines on the boost control loop?
2. Are you using the factory boost gauge or an aftermarket one?

[lvdisturbed1]

Yes I am using the factory boost gauge. I know it's not the most accurate, but it seemed to work fine before. Climbed up to 14 when in full boost, limited to 7 when det sensor failed, and now ~9 after changing the ECU. I looked for codes, but got 55. I feel something must be causing the wastegates to open early.

I'll do a vacuum/boost leak test soon to rule it out. It's not the det sensor, I disconnected it and got 34. Plus when it was disconnected, boost dropped to 7 as it should. Reconnected and cleared the code; back to 9ish psi.

It is a CA ECU, and my JWT one was a FED. Could that have something to do with it? I didn't think it would matter, since all the maps would be on the EPROM that I swapped into it, but maybe there is more to it?

[NolimitZ32]

AFAIR the "Cali" ECU becomes a not- Cali ECU once you swap the EPROM, the only difference should be the tune. How is your boost controlled, still on factory WG solenoids?

[lvdisturbed1]

That's what I thought. Furthermore, the fact that the ECU hasn't thrown a code for the EGT sensor supports this.

Yes, still factory solenoids. Only difference is the boost jets installed to the air inlet hoses on the throttle valves.

[evildky]

Have you tried moving parts to other cylinders to see if the problem moves? Swap COP's and spark plugs with another cylinder and see if the problem moves, then try swapping the injector. Also there is enough slack int he harness to move the swap the connectors from #1 to #3 and see if the problem moves.

[lvdisturbed1]

Evildky I solved my dead cylinder problem. It ended up being the ECU like NolimitZ32 suggested.

New "problem" is lower than expected boost. I should be getting 14-15 psi with boost jets installed, but now I am getting 9-10. Just ruled out vacuum leaks. Not det sensor, because when I unplug it I get the code and 7 psi.

[Ace2cool]

Any update? Hoow did you rule out vac leak? ave you done a boost leak test?

[lvdisturbed1]

No update yet. I had a friend helping me with the tests, but he hasn't had time to continue. We hunted around with some carb cleaner, but no change in idle so ruled out vaccum. I might just buy an air compressor and boost leak tester and do that myself. I'll update when I have more info, or reply to more suggestions.

[evildky]

Boost jets are very unreliable, they are consistent but assuming you got them in the right hose you might try a smaller orifice or tightening up the wg actuators.

[lvdisturbed1]

Sorry it's been awhile for an update. I was able to get the boost leak test done, had one very small leak from a small hose where a boost jet was installed but it was just a clamp I forgot to secure when I checked it earlier. Wastegate actuators seemed to be in working order, they opened and closed fine and nothing was loose.

I suspect the ECU I got is bad as well. On a hunch, I reinstalled the old one and even though the injector driver is fried on it, it will still build to 15 psi with 5 injectors. Something on the new ECU is limiting boost, but I don't know what! There are no codes, and there are no signs of fried circuitry like my old one. I'm at a total loss!

[lvdisturbed1]

I figured it out!! Bad news is I need another ECU.

It turns out the ECU is not for a TT auto, but a NA auto. There is a blue sticker by the LED window that has 6 digit serial. Those 6 digits should match with the last 6 digit's of the part number on the front plate. They did not match. The blue sticker had A75 MB9 whIle the front plate reads A18-AA18-A79 MC3. ECU scamming is not cool...

[NolimitZ32]

Damn, that's messed up man.

[haddox19]

If an ECU is bad, will it always be burnt like that?

With the ECU all burnt up I am curious how you were getting a reading out on the injector pins, mind blown! And yes, you were correct in your statement about the CAS sending a signal to the ECU to fire the injector.