Z28NEL Hard to Start

[lee632]

Hi, My car is very hard to start after i fill it up at the pump, runs fine rest of the time??? Any ideas

[Rebellion]

Failed fuel filter is letting through all the dirt that gets disturbed in the tank as you refuel....?

[lee632]

changed fuel filter....

[Rebellion]

What fuel do you use?

[byebyeitsagsi]

This a common thing usually on ex police vehicles though. Its the EVAP valve sticking and will need replaced.

Is it low on fuel by any chance and does it do it after filling up? I reckon its the EVAP valve as its quite common on the Z28's.

[lee632]

Funny you should say that because it is ex-plod. I use Tesco Momentum 99. And it only does it when i fill up and i dont usually let the tank fall below 1/4. What is the EVAP Valve and where is it as i will replace it.

[Grimy]

I'll repost the reply I gave to the same question on vxr online last year, it explains what might be going on.

I wonder if theres a problem with the EVAP system. To meet emissions regulations the fuel tank cant be allowed to breath directly to atmosphere, it has a charcoal canister which it breaths through. The charcoal captures any vapours from the tank and stores them. There is also a pipe from the charcoal canister to the intake manifold that is opened or closed by the evap purge valve. When the engine runs, the ecu cycles the purge valve to suck through the vapours and burn them off, thus purging the canistor. The ECU knows when it is perfoming this purge cycle and expects a richer A/F ratio and compensates automatically. Its not uncommon for the purge valve to stick, which can royaly screw your fuel trims. The charcoal canister can be found in the front right wing of yout vectra, if you lie on your back and put your arm up under the bumper you can feel it just behind your fog light. The purge valve is under the bonnet, just behind the air box, fixed to the same bracket as the bonet alarm switch.

I'd start looking at these two components if I was you. Perhaps start with the purge valve. Id remove it and try sucking through it whislt applying and removing 12v across the terminals to check its switching, but I fear the pipes are going to be F'in tight to get off. If they are cheap, perhaps just replace it anyway? If it is stuck open, then it may be sucking through all the freshly stired up vapours after filling your tank, enriching the A/F ratio too much for the car to start properly when its already warm and not expecting that level of choke? When the cars cold, the ecu would be running rich on choke anyway and so it wouldnt really effect it. The theory sounds plausable anyway given your symptoms.

If thats ok, then your going to have to move your attention to the canister. I think your going to have to whip the bumper off to check it properly with good access to the two pipes. One goes to the evap purge valve, the other is the fuel tank breather pipe. Blow through each to check for a blockage and do the same with the canister itself.

Or of course if its still in warentee, ask your dealer to check it all properly. That is if you can find one that knows his **** from his elbow. Frankly if they doubt a fuel tank even has a breather, they're not going to be too clued up on the evap system either.

I hope this gives you something to at least start with. I doubt there is anything wrong with the actuall pump as youd have running issues all the time, and accusing the swirl pot is rediculas.

Let us know how you get on.

Adam

[lee632]

Thanks for the info, i will whip the bumper off tomorrow and have a look and take it from there. I can remember finding a small hose on the garage floor one morning i wonder if this is from that area ???

[bowler]

I also have this problem on my 2.8T Elite Auto, only after filling up the car needs to be cranked for a considerable time before it starts, it always starts 1st turn of the key at other times. i have also had an unexplained EML light, the stored codes were Fuel trim errors.

Will have a look at the evap system, at least I now know where it is, Thanks All

[lee632]

Right, i finally got time to have a look today and im confused to say the least. i took the bumper off and traced the breather pipe from the tank which runs up into the engine compartment on the drivers side and connects to an array of other pipes all of which go to various parts of the intake manifold and one to the brake servo.

The valve (part no.171005) at the back of the air filter box which i think is the EVAP Purge valve is connected in this circuit of pipes and the pipe which comes out of the back of it and dissapears down the back of the air box and under the wing connects to a Vacuum pump, no carbon canister, the electrical box on the side of it (part no.12762936) was totally burnt out.