HI guyts

 

a bit of advice needed if possible, as you are aware i have only just bought my 300 so still learning the ropes so to say..today i went to the local petrol station to check my tyres pressures etc, i left the car runnign with no issue whilst i did it but uopn starting to drive home i got a big backfire which scred the crap out of the granny walking her dog and the car just wouldnt go, i managed to splutter my way home luckily and get it on the drive.

however after getting it there it now wont start, it is turning over but doesnt seem to want to fire, ebvery so often the engine management light comes on but goes off too sporadically.

i think i may have a fueling issue but have no idea wher to start..

 

any help will be gratefully appreciated..

obviously im gutted as ive done less than 30 miles since buying it and my trouble has already started...

 

cheers cutty

Mark Derby at Automodz is the closest specialist to you mate give him a shout.

Probably a spark issue, check your coil pack connectors for corrosion on the pins, also the temp sensor on the water pipe in front of the cambelt cover and check the PTU connectors to the left of the temp sensor on the cam belt cover.

 

If you are getting a management light on, it is likely a sensor or connector to a major component like the CAS as a duff coil pack or injector connector will not throw up a management light, it will run rough.

If the engine management light came on at all whilst it was running, it's an ECU or chip issue.

 

When you put the ignition on, do the fans run automatically?

 

If not, then I'm going for a faulty CAS or associated loom given the backfire and subsequent trouble with starting.

 

If you can't get it somewhere, or get someone to come to you, all you need is a cheap Consult (Nissan's name for their diagnsotic system) cable and some free software such as Conzult Free or ECUTalk. Alternatively, you can pull the codes immediately by searching for the diagnostic procedure on the forum :)

When you say fans do you mean the heater etc blowing on the windscreen or engine fans ?

Sorry for sounding stupid but the 300zx is totally new to me..

 

Cheers cutty

When you say fans do you mean the heater etc blowing on the windscreen or engine fans ?

Sorry for sounding stupid but the 300zx is totally new to me..

 

Cheers cutty

 

Engine fans :)

i'll go check..

 

cheers mark.

right a bit of info now.. having looked down into the engine bay i noticed what could be a missing belt, as you look from the top down to the right of the engine there are two pulleys and they dont have a belt on them, when i spun the top most and right most pulley i heard a click ? it spun very freely so i spun it again and tried the engine !! guess what it started !!! i can only presume i have lost a belt but have no idea what the belt would do, im not going to run the car until i can find out which belt is missing, it appears to go over the 2 said pullys and the main engine pully,,,

 

any ideas guys ????

 

cutty

Aircon pulley I'm guessing.

 

Did you knock the connection to the CAS when you heard the click?

 

Edit: CAS = Cam Angle Sensor. Silver/grey sensor on the front end of the nearside exhaust camshaft.

Edited December 4, 201411 yr by Noz

Edited December 4, 201411 yr by Noz

i think your right with the aircon pully from the diagrams i can see, i suppose there is a chance i had knocked the cas or disturbed a loose wire, but honestly dont think i did, im pretty sure the engine fans wernt running until i spun the pully either - would this support your theory of the cas being the culprit ??

The car is running fine for the moment, i presume not having the air con compressor belt on will only mean the air con wont work, im just baffled as it all seems to be working from the fact id spun what appears to be the air con compressor i can only hope that i did inadvertantly knocked a cable to the cas and this was my problem all along, is it a big job to put the air con pully back on ? and where can i get one.

 

cheers cutty

Edited December 4, 201411 yr by cutty

Aircon pulley is on there if you spun it :)

If the fans run with the ignition on idle, it's an ECU or chip issue, thought I would check that first with you. The car will run with no chip installed, it just runs the fans constantly and pegs the AFR (Air Fuel Ratio) to an incredibly rich 9.5 to 10:1, causing the car to run like a nail and belch black smoke out of the exhausts.

 

The CAS being disconnected whilst attempting to start it will have left a DTC (Diagnostic Trouble Code) stored in the ECU. It can be checked at a later date, either reading the EML flashes off the dash once in diagnostic mode, or by using a suitable diagnostic tool & software.

Could this not just be a simple case of a failing PTU, the fact the car has now been stood for a while, cooled down & now restarts makes it a possibility?

When my PTU was failing, it would start from cold, run perfectly for a good few miles, then misfire and cut out, refusing to start until it had cooled off.

I borrowed a good PTU, waited until it broke down again, swapped it at the roadside and immediately it restarted. Swapped it straight back and it wouldn't start - conclusive result.

Spinning the air con pulley and the restart is purely a coincidence, the belt has probably been removed because the air con compressor may have gone bad, or for a tiny performance gain.

I'm sure a failing PTU sometimes throws a EML, so worth looking in to.

 

ETA:

It does, code 21.

 

As for injectors, coil packs and other sensors other than the CAS, the engine will start and run with a duff injector, coil pack etc all be it rough and down on power.

Edited December 4, 201411 yr by lonezedder

i suppose it could be the ptu has cooled down, it does appear that my ptu has been upgraded to a later type as its black plastic not metal tin looking and from what ive found on the web that looks like the swop has been done, to be fair though the petrol station is only 1/4 mile from my house so i cant think the engine will have been too warm by then, but its a fair point if the problem i have had can be caused by an over heating ptu, i will start it on the drive tomorrow and let it heat up and see what happens from there..

 

out of interest does anyone know wher is best to get a replacement ptu from as it looks like a handy thing to have on the shelf anyway..

 

cheers cutty

can anyone post a link to how i can use the dash to diagnose any codes ??

 

cheers cutty

Here you go....

 

http://z32.wikispaces.com/ECU+Diagnostics

 

If the PTU has been upgraded to the later series 2 version, then its less likely to be that, but I have heard that they can and have still failed.

Could this not just be a simple case of a failing PTU, the fact the car has now been stood for a while, cooled down & now restarts makes it a possibility?

When my PTU was failing, it would start from cold, run perfectly for a good few miles, then misfire and cut out, refusing to start until it had cooled off.

I borrowed a good PTU, waited until it broke down again, swapped it at the roadside and immediately it restarted. Swapped it straight back and it wouldn't start - conclusive result.

Spinning the air con pulley and the restart is purely a coincidence, the belt has probably been removed because the air con compressor may have gone bad, or for a tiny performance gain.

I'm sure a failing PTU sometimes throws a EML, so worth looking in to.

 

ETA:

It does, code 21.

 

As for injectors, coil packs and other sensors other than the CAS, the engine will start and run with a duff injector, coil pack etc all be it rough and down on power.

 

You don't get an EML, you get a DTC. The only thing that would cause the EML to be illuminated whilst driving his G-reg car would be a faulty ECU or EPROM. On vary rare occasions (twice I think out of all the Zeds I've worked on or supplied chips for) has the EML been due to firmware issues on the chip itself. Mark Derby's car was one of them.

 

If the car backfired and then didn't start it would have been due to the CAS connection and the subsequent mis-timing of the spark, causing the mixture to explode whilst the intake/exhaust valves were open. Dead PTU, no spark, no backfire, just flooding. If he was playing around with the aircon pulley from the top and heard a click whilst the ignition was on, somehow bringing the car back to life and allowing it to fire up, it'll be the CAS. The CAS makes clicky noises. It's the CAS.

 

But yeah, worth looking into the Series 2 PTU that rarely fails and is definitely not the problem here :wack:

 

Just kidding! I'll look like a right idiot if it's not the CAS, won't I? :laugh:

 

 

 

 

 

 

 

Good job it's the CAS.

:surrender: I'm sure you're right, was just trying to provide another possibility to help a fellow Zedder.:hammer:

:surrender: I'm sure you're right, was just trying to provide another possibility to help a fellow Zedder.:hammer:

 

It's going to be really funny if I'm wrong :laugh:

 

Luckily no one has quoted me so I can delete delete delete :D

 

What if there's a historical DTC 21? We could both be right. Then I would have to kill you.

Startin to think I should have kept the porsche 924 I dropped in px for the zed !!! Lol.

at least the porsche was simple.

 

I will keep you all updated

 

Many thanks for all your help

 

Cutty

^^^ Wash your mouth out fella! Can't you see I've put my life at risk trying to help you!:biggrin:

TBH, they're not as bad or complicated as they first seem. The engine bay does look daunting, but its basic 90's electronics at the end of the day.

Generally very reliable, sophisticated enough, but not too much.:)

Lol ^^^ I'm kidding I've done 30 miles in the zed and fell in love already.. had our first tiff today but hopefully we've made up...

lol

 

 

Cutty

Cutty, unfortunately the most common mistake when diagnosing running issues is with an over technical approach, keep it simple at first and then step up as required.

 

The engine was running ok and then it changed very quickly, chances are it is something simple, mentioned earlier in this thread but overlooked is the temp sensor, a bad connection here Cutty will cause all sorts of running issues including flooding, poor tick over, black smoke etc. and will also cause the ac electric fan to run. Leaving the car for a while will often allow the engine to un-flood and restart, chances are when you was checking around the area at the front of the engine the loom was slightly moved and that is why it restarted. So clean up the connector and sensor and start from there.

 

Jeff TT

Big backfire....

 

Timing, not overfuelling. Disconnect the ECU temp sensor from a running car and it doesn't produce a "big backfire". Had it happen on my Pulsar at TOTB around hard left corners. Just ran really crap, but it was sort of drivable. Did nothing for my times though, with the AFRs in the low 10s :laugh:

 

So that's another DTC, this time lucky number 13.

 

Who knows, exciting times!!

Big backfire....

 

Timing, not overfuelling. Disconnect the ECU temp sensor from a running car and it doesn't produce a "big backfire".

 

 

Mmm...... well it would if a plug fouled stopped sparking filled the chamber with fuel and then managed spark especially if the op was trying to rev the issue away, with any engine running issue diagnosing it with it not in front of you is just a series of suggested checks and overloading the op with tech speak however low level is not always helpful, the most likely culprit is a bad connection spark or fuel related ( temp sensor) or as it often the case a combination of more than one low level fault.

 

Jeff TT