ok, i need some expert help here guys.. please.....

 

cylinder no.3 [back left as you look at engine] is dead. ive tried a new coil/changin coils around , ive also tried a new spark plug and tried changin them around. so it appears to not be one of these faults. the car has no other problems except this no.3 cylider is dead - and also it cuts out some times and stalls ?

 

someone has suggested that it may be the PTU that is not operating properly - does anyone think this may be the case? does anyone have one that I could borrow/buy to test if it is the PTU? or does anyone have any other ideas what may be the problem?

 

im goin to get my garage to do a compression test this week aswell - but apart from this - i lost - i dont know what the crack is!

 

help............Ben.Leicester.down and nearly out.

What state is the loom plug in mate???

 

Clean it up if it's green and corroded

 

Funny that, exactly the same cyl that was down on mine.

 

PTU swap can't do any harm, process of elimination as with most things.

er, here comes the dunce question.......

 

loom plug? what would that be.

PTU is a definite pissabolity. It is quite possible that one of the internal transistors or physical connections has packed up. See if you can get someone to do a swap with a known good'un and if that works then I can have a stab at fixing yours before you stump up £-hundreds for a new one.

sounds good andy.

 

i just need people to take note of this post and enlighten me to the wearabouts of a PTU i can try.

 

anyone..........?

 

 

Hi Ben

 

From the discription you have given it sounds like the actual coil is not the fault and it could be a cable or connector fault. A quick way to check is to connect a timing light to that coil pack to see if it flashes in rytham with the engine revs, or at all.

Slow proccess but back tracking from the coil pack may reveal a fault in the loom.

I personally would not think the ptu can cause a repeat fault on the same cylinder and as they are dear enough 2nd hand let alone new, I would concentrate the search on the coil loom and connector.

If you can get to my place could check it out for you. Jeff TT

 

 

[This message has been edited by Jeff TT (edited 04-12-2001).]

it costs nothing to do compression test.

Then just run through the elimination process.

At least that will be piece of mind.

 

cheers, everyone, cheers jeff.

 

i will do compression test and take it from there.

 

i may take you up on that offer jeff!.

 

thaks, ben

If I was putting money on what the problem is I'd go for a bad connection on the ptu connectors or the coilpack connector. Remove the little wire clips that hold the connectors to the ptu and remove them. Give the contacts a good spraying with electrical contact cleaner (even if they look ok) and reconnect them. When you take them off have a look at the metal contacts inside for and green crap.... Also do the same with the coilpack connector. There is one other possibility though and that is the injector for that cyclinder.

 

Does you CAT overheat warning light come on??? If not then it could well be the injector or its connector or possible even the CAS/Cas connector - repeat the cleaning on these too

 

This should give you a few things to try.....

 

CheerZ,

 

Andy

I had new PTU fitted on mine but my wiring loom was Phuket! Clips were knackered on the coil pack connectors which was not good.

 

New PTU and problem didn't go away, new wiring loom and problem DID go away.

 

 

Back left cylinder is number 5 if I remember correctly. This is the same one that went on mine and it was the PTU.

 

I took my PTU off (5 minute job) and followed the continuity test detailed in the service manual. Basically it just involves using a multimeter across some of the pins. This test confirmed that pin 5 had an intermittent problem

http://300zx.co.uk/cgi-bin/manual.cgi is where the service manual lives online

 

 

 

------------------

Yep, I seem to remember it being No. 5 aswell

ok, i know that all the coils work, and the spark plugs work. i have just done a compression test and they were all the same compression [about 95-100].

 

so i am thinking either that the fuel injector is being a tit on that cylinder. or that there is a problem in the connection to the coil on that cylinder.

 

andy - that sounds like a good idea [giving ptu area connectors a clean] but im not sure where to find this - CAN ANYONE tell me where exaclty this ptu and the clips are???

 

also,i think it is cylinder 3 that is out - it is the one closest to the driver/sterring wheel/whatever and also it says '3' on the coil.

 

cheers.

 

Should help...

 

CheerZ,

 

Andy

Ben mate,

 

As you stand in front of the engine bay looking at the cam belt cover there is a smallish square box with fins on it bolted to the cover. It's on the left hand side as you're looking at it. Black plugs going in and coming off it I think?

 

'tis yer PTU mate

 

AndyP posted a diagram of the Z engine bay up before to somebody else, maybe in the tech section. Check that out geeZer, is marked on there.

 

Check the plug/connector that plugs onto that particular coil though, still think that could be the main culprit! Look at the contacts inside the plug and see what state they are in.

 

You should be able to hear the injector ticking, get a screw driver with a long shaft...ohhhh errrr Mrs...and put the blade on top of the coil pack and stick yer lug on the handle. As I say, you should hear the injector pulsing which is a loudish ticking noise

 

Good luck mate, hope you get it sorted soon.

 

 

Yep that's the one!

Definitely check your PTU before anything else. If you know anyone who has a multimeter then its a very simple test, or get someone who has a Z to swap their PTU with yours and try both cars. Someone here must live near you (cylinder nearest driver is number 5, they are numbered from front to back).

 

Dylan

 

 

ok i pulled the coil and turned the engine over - the spark in question did its simple job and sparked!

 

so now i am thinking that there is no fuel gettin to that cylinder.

 

anyone any ideas on hoe to test this?

Oh I love being right

 

First thing would be to check the connector on the injector in question. Next job is to remove the CAS to manually turn the thing to simulate the engine turning over. Before you remove the CAS, mark it's rotational position either with a light scratch or some paint... Remove the bolts holding the CAS to the head and remove it. Now turn the ignition on but don't try to start the car. Rotate the CAS and you should hear each injector firing in turn - don't over do it though cos you'll fill the cylinders with fuel.... You need to have somebody listening for the injector you think is not firing though otherwise the job can get quite difficult....

 

Let us know how you get on or if you want more info I'll post my mobile number

 

CheerZ,

 

Andy

cheers andy, ill just watch the end of seinfeld and then ill give it a go.

 

only not sure if i got an allum key to fit the engine cover. amyway. ill let you know.

 

ps. does anyone know what kind of level of compression u should get in a turbo z's cylinders . i did a test and got 100psi in each cylinder. ? dont know if thats good or what. at least they were all the same anyway.

 

 

cheers for the mo.

from memory the specs are between 120 and 170psi, but all cylinders must be within 15psi of each other...

Ben,

 

The standard compression is 186 PSI with the minimum allowed being 142 PSI and the difference between cylinders not exceeding 14 PSI.

 

However, the compression test must be done with a warm engine - had it been running??? Also, at the moment, compression is not your problem so don't worry about it

 

CheerZ,

 

Andy

well mine were certainly within 15psi of each other. but the figures were more like 95 - 110. is that too low? or is that ok because the car is 11 years old?

 

i assume that over time a bit of compression would be lost ? is that right? i dunno.

crap question alert and sorry for slightly off topic but how do ya do a compression test plz?

But was the engine up to temperature??? This is CRITICAL to do a proper test - if it aint the pressures will be considerably lower....

 

CheerZ,

 

Andy

Get a compression tester and follow the instructions Martin

 

Seriously though, all you do is unscrew the relevant spark plug, screw in the compression tester and turn the engine over with your foot on the throttle (basically speaking). Make sure you disable the PTU first though

 

CheerZ,

 

Andy