So last weekend I decided to replace my doddgy old S1 PTU that had been playing up, for obvious reasons (see photo) All seemed pretty straight forward and the result looked good Unfortunately when I started the car it would only run on 5 cylinders. No 1 cyl not firing. So started running through checks. 1. Crossed wiring - no, all checked and correct. 2. Dead plug/ coil pack - no 3. Continuity on either side of the PTU and back to the ECU - no all checks good. 4. PTU - no, all checks out and have tried another PTU but still the same problem, same cyl. 5. Checked the voltage from the wires comming out of the ECU with the car running and here is the problem, the wire corresponding to cylinder 1 has a negative figure, around -20v. The rest all read around 40v. So what does this mean and what is the problem and how do I fix it? ECU or right back to the CAS? Electrical problems certainly aren't my thing and this is the first time opperating a multi meter. Would really appreciate some input on this as I'm pretty much stumped at right now.
PTU installation likely to be the problem based on what you stated Hey there Whilst your ECU may have a faulty signal, I do not necessarily believe it is at fault given it was working fine prior to the PTU refit. Quite simply the signal could be induced by another connector into the ECU wiring. On this basis its doubtful your Spark Plug and Ground are also the problem given you were replacing the PTU and its relationship to the problem and circuits. Looking at the ECU to PTU diagram section of Spark no1 that I copied below and coming back from the PTU (having just being installed) There are only three wires to track back from the Spark no1 Cyl and two of them head to the PTU. The PTU has two wires relating to spark cyl no 1 and a common ground which is also a black wire. If you mix both black wires up (one is + and one is -), you will get the problem your having so check there first. This is still pure guessing without further testing but there are only three wires to track back from to the PTU in the immediate, so it cannot be too hard to work out. You can get the ECU and electrical diagrams from here http://www.aus300zx.com/forum/showthread.php?t=332982 So check the two black wires again to make sure you haven't mixed them up then if they are connected correctly just look at the diagrams and follow the problem back through the wiring one step at a time starting from the PTU and if you do this, I am confident you will succeed. Cheers Jamie
Recheck connected solder joints. When I changed my PTI it ran with a miss checked the pig tails wires and the cut of wires on the main input wires and found there was four wire crossed because the colors were almost the same, resoldered and fixed the problem :zlove:
Eureka!! At last she's running on 6 again. Thanks Super Z for showing me the light. As you said it had to be something I had done during the PTU re-wiring. I originally thought the same but could not figure it out. I re-checked all the wiring colour codes for the 4th time ane everything matched the wiring diagram so the only possibility was the 2 black wires which are identical, one on each side of the PTU. So a quick snip, snip twisted wires and and there you go 6 cylinders running. I confidently soldered the wires threw it all back together ready for a quick run and guess what................................ back on 5 cylinders, needless to say the language was pretty colourful at that stage and there may still be some tools imbeded around various parts of the garage. OK count to 10 a few deep breaths and back into it, soon found the coil pack was arcing out somewhere and the spark now dead. So all that is now resolved but by then it was pissing down outside so will save the run for tomorrow.
Hey pmac Glad your your resolving it Just be aware that you were running both - and + through the actual coil and this could cause damage to it, which now may be a by-product of the initial wiring mishap There is a possibility the coil might need replacing if you have further problems but they are cheap to obtain Hopefully it will be ok still - double check the wiring around the coil to make sure its ok as well JC
Awesome forumness !!! Yes that was the case, coil pack and plug have both been replaced. Here is the article I was following that was a big help. http://www.twinturbo.net/nissan/300...RITE-UP-tech-article-worthy-IMG-help-plz.html But it also sent me on a wild goose chase as I had the same problem as he had, No 1 cylinder not firing, that's why I started chasing problems with the ECU. Thanks JC for putting me back on the right track. BTW, what the hell would we do without this AWESOME FORUM, for sure we would all be a lot poorer from forking out mucho dinero for others to fix our cars. Also because of all the free help available here this keeps many more Z's on the road that in the past may have been given up on as too expensive to repair. So many thanks all that run this sight.
Started the car and found it missing and stopped it then fixed the problem strait away.[about 2 min.]
????????? How is this relevant to the problem that was being discussed. If you can't add any useful information into the discussion why bother posting? You haven't even told us what the problem was or how you fixed it.
My early question "How long have you had the car running for on 5-cylinders? Does the PTU get hot?" was in relation to mistaking the black PTU coilpack cylinder #1 and earth wires. Running the car with this error will cause both the PTU and Coilpack to get hot, potentially damaging both. How long you ran the car will give some indication as to whether or not components can be expected to be damaged. Guessing Bob had the same issue, and was answering such. Another thing to consider, although not directly related to your issue is to ensure that the earths at the rear of the plenum and properly tightened- Sometimes overlooked with plenum pulls and engine replacements, which can also cause irreversible damage to the PTU
