Maz

your "what" sucks mate ..fuel pump , pressure in the tank ?

swap it with my manual adjust passenger seat ???

OK New petrol cap ordered, new OEM pump ordered and I´ll check the whole carbon canister and release valve stuff and if need be remove the whole thing :) Thanks for all your help guys, really appreciate it

Z centers "low level spoiler" ? http://www.zcentre.co.uk/shop/product_info.php?cPath=21_22_27&products_id=82

well, over here in Germany we already have 5% and the goverment was on about the new one with 10% only effecting older cars and therefore only a small percentage of cars over here. However, figure from the manufacturers were seriously drastic ..something like Mercs before 2006 wouldn´t run..porsche before 2005 wouldn´t run VW´s built before 2005 wouldn´t run and it got more and more ( official manufactureres figures) to the point that over 3 million cars wouldn´t run on it would be forced to use V power or the equivelent...so the idea was scrapped..they are sticking to 5% and have told the manufacturers they must come up with a soloution on their new cars. Will be interesting to see if they force it through in the UK.

James Here you go mate http://www.twinturbo.net/ttnettech/illrp/illrp.html hope that helps :)

Dave, ,to disconnect the carbon canister on the tank side what do i have to do...removing the plastic cover beneath the drivers side wing reveals the carbon canister, but the only hose i can see from there going into it is at the bottom of the cannister ..do I have to take more apart ? or can I bypass it by removing and capping the vac hose on the throttle body and the one on the balance bar ? John are you refering to the fuel vapor vent line check valve on the drivers side behind the tank ?

Thanks for all the replies, I really appreciate it :) Topless: getting a new fuel cap isn´t that easy either mate, according to courtesy Nissan the 300zx from 89 to 06/90 is different to the later models.perhaps that´s where the double valve system with pressure release is. the cap is cheap enough, but $75 just for mailing it. I´ll have to get hold of a fuel pressure guage to test the pressure and unfortunately Z´s are rare around here and I don´t know anyone else with a Z other than Jonce who´s in the UK now for a few months. I will remove the fuel pump and take a look at it, possibly buy a new OEM one too plus I´ll see if I can´t get a new cap from Nissan here. Dave That theory sounds good to me. Can I bypass the carbon canister without removing it (and the front facia to get to it) I don´t think it has to do with the fuel vapour or gases though as the pressure is quite high after only 3 mins of running the car, it doesn´t go that quickly, surely ?

do you mean the rear centre panel´s 300ZX illuminated in red ?

Topless The fuel cap does have a pressure release vavle in it..if you take the cap apart you will see that if you stick a pin in to one of the holes around the centre hole you can lift a small plate which is kept down by a spring..this is to release preassure...in the centre of that plate is a small plastic pin which you can see when the top part of the cap is off...you can push the pin in...that is the valve that allows air into the tank ..it´s like a double valve. I´d need to get the equipment to test the fuel pressure first :( and as for a used OEM one being pennies...i wish I could find a TT pump for "pennies" I´d have snapped it up long ago mate.

Andy Looking at the diagram it states that when blowing through the check valve in the direction of the carbon canister there should be resistance with only little going through. blowing in the direction of the fuel tank from the carbon canister it is free flowing.so in theory, if air is coming from the direction of the carbon canister it would find it more difficut to return the same way, or at least I would have thought so. so are you saying you think the problem could be either the check valve or the pressure release valve in the filler cap ? Topless I was thinking the same thing about getting a new OEM pump, the only thing stopping me is the fact that the car ran fine for about 6 months with the Walbro..the car still runs fine...just the pressure in the tank now. And no, i haven´t checked fuel pressure , but like i said, engine runs well..no issues with fuel pressure to the injectors etc.

i´m not sure topless...the OEM fuel pump worked fine for 4 years and then it died....baring in mind the car has done over 250 000 km i think it was time the OEM pump died. had no issues with the petrol tank in that time , wiring and fuel system worked fine and did for about 6 months on the Walbro mate.

because my OEM pump failed and I needed a replacement quick as I was driving to France the next weekend. quickest option was the Walbro.The pump has been in about 6 months though and this problem is only since last weekend. The walbro pump never felt as good as the OEM one though ..plus i kept wondering what the purpose of the round metal diaphram on the OEM pump is: http://www.mkiv.com/techarticles/fuel_pumps_test_2/nismopump3.jpg the army green coloured round thing pointing to 1 oclock

but after about 100 -150 km the pressure is so much that the pump starts to fail. open the cap, let the pressure out and she runs fine again...that can´t be normal. it didn´t do that for the past 4 years..so something must be wrong.

petrol cap off = a 12 inch wide cascade of petrol down the rear wing after about 10 km valve open on cap = little puddle of petrol beneath the cap when you open the little door thing and the cap is soaked. yep..pplumped the walbro in exactly the same way and place the OEM one was mounted.

topless it does the same . i.e spit the petrol out even on half a tank mate

Andy the carbon canister and EVAP system is stock, nothing changed or tampered with. I looked at the same diagram and concluded there are only 2 ways pressure could possibly enter the tank and that is: A: via the vapour vent line as the fuel check valve runs freely in direction of the petrol tank but i can´t see how it could pressurize the tank..i.e force air into it. and B: through the fuel return pipe these are the only fwo in going pipes, I changed the OEM pump for a Walbro when it died...wondering if that could be causing it.

Topless I thought the pressurized system as such doesn´t start until after the petrol has passed through the pump on it´s way to the fuel pressure regulator ...the vaccum in the tank is caused by the petrol being pumped out and the empty space requiring air to fill it. The air is sucked in through the two way valve system on the petrol cap....how is pressure then obtained within the tank ..enough to force the petrol up the filler neck ?

anybody ?? could it have anything to do with the Walbro pump not having that funny disc shaped membrane thing on it that the OEM pump has ? ( still haven´t figured out what it´s for i.e what it´s function is ) could it be the fuel flowing back to the tank from the fuel pressure regulators ? I´m at a total loss here as I can´t even get my head around the basic physics of it on how you can pump out liquid from a container and get outward pressure as opposed to a vacuum. Maz

could it be a problem with the carbon canister not absorbing evaporative gases which are produced in the petrol tank and thusbuilding up until released by opening the patrol cap ?

in Germany mate..they were supposedly "leading up" this enviroment campaign thing and had been talking about introducing more ethenol since early last year based on figure that showed only a small amount of cars would be effected. more recent figures showed a hell of alot more cars would be effected and they scrapped the idea stating " they didn´t want the campaign to save the enviroment be the cause of forcing people to user super plus or their cars failing" just thought they might have followed suit in the UK.

are you sure ?..i.e is that still going ahead in the UK ? They had planned to up the ethanol contents from 5% to 10% over here next year January. They scrapped the idea last weekend after figures showed that over 3 million cars wouln´t be able to run on it. so plan was scrapped this weekend gone.

hi I´m still trying to sort out the problem I’m having with the petrol tank. I know all about the petrol tank causing a slight vacuum through pumping the fuel and the air not being replaced entirely until the vacuum pressure opens the valve on the petrol cap to allow air in but mine is doing the opposite, when I open the fuel cap air isn´t being sucked in it’s actually being blown out, so much so that if I jam the small valve on the petrol cap open it starts to spit petrol out. How can the petrol tank be under pressure like that? :confused: I have to open the petrol cap every 20-30 km to release the pressure otherwise the pump starts to fail. Any ideas would be greatly appreciated. Maz

yep! I think you guys are right ..as usual :) ..found a larger pic where you can see it better ..and i have to say i like that with the vents cut out and mesh inserted :) http://media.motortopia.com/files/8806/vehicle/471d01216c1d1/01.jpg cheers :)

you think so stellaZ ? ...i know he´s just selling the lights..but that front bumper looks different