Why is it slow to start only after filling up?

[Joe H]

The car is running well, starts instantly whether cold or hot and after a short run or long.
Except when it has been refuelled.
Then it will crank on the starter for ages (likely 5-10secs but that seems ages) before reluctantly firing and slowly revs creep up then everything is normal.
It has happened each of the last 4 times, at different garages, not overfilling, without the fuel level being particularly low.
What is going on?
Cheers
Joe
1999 V70 2.4 non-turbo, manual

[Maccmike]

Not sure if these are pressurised but be interested to know what happens when you remove and refit fuel cap.
Think I would lean towards fuel pump.

[Joe H]

Originally Posted by Maccmike

Not sure if these are pressurised but be interested to know what happens when you remove and refit fuel cap.
Think I would lean towards fuel pump.

Yes, I've been thinking about it since posting. I had thought of the tank being de-pressurised when filling up, but was ruling that out as a problem as it is the same after sitting overnight? Same with fuel pump.

What I can do is drive the car, stop engine, remove and refit cap and then see how it restarts. I'll try that at the weekend.
Joe

[pff]

Check your evap valve, follow two hoses from the inlet manifold to the radiator fan shroud under the bonnet. One on the right should lead to a solenoid, rubber hose in and out with an electrical connection.
If you take it off you shouldn't be able to blow through it when disconnected.
This valve allows fuel vapours to escape from the fuel tank and burn them off when you are cruising, it's an emissions thing.
When you fill up the vapours all flood into the manifold and choke your engine.
Try putting the gas to the floor next time you start up, tells the ECU to wide open the throttle and airs it all out, should start a lot easier if it's too rich.

[Joe H]

Originally Posted by Joe H

What I can do is drive the car, stop engine, remove and refit cap and then see how it restarts. I'll try that at the weekend.
Joe

I didnt have the time to drive that I expected at the weekend, but started and let it run for a few minutes, turned off and removed filler cap (it hissssed so the tank was pressurised), replaced cap, and....it started straight up as normal. Hmm.
Joe

[Joe H]

Originally Posted by pff

Check your evap valve, follow two hoses from the inlet manifold to the radiator fan shroud under the bonnet. One on the right should lead to a solenoid, rubber hose in and out with an electrical connection.
If you take it off you shouldn't be able to blow through it when disconnected.
This valve allows fuel vapours to escape from the fuel tank and burn them off when you are cruising, it's an emissions thing.
When you fill up the vapours all flood into the manifold and choke your engine.
Try putting the gas to the floor next time you start up, tells the ECU to wide open the throttle and airs it all out, should start a lot easier if it's too rich.

Really helpful, pff. I may not get time to try this for a days but it sounds like a logical explanation.
Cheers
Joe

[Joe H]

Originally Posted by Joe H

Really helpful, pff. I may not get time to try this for a days but it sounds like a logical explanation.
Cheers
Joe

So to check I have got this right, pff, with ignition off I disconnected the pipe and elbow at the arrow and blew through the elbow towards the valve and manifold.
There was no resistance.
Does that point to the valve being faulty and a straight replacement needed? Google says it is called and evap or purge valve so every day is a learning day...
Cheers
Joe

[SteveSarre]

Hi Joe,

I think when a normal engine is operating normally, the purge valve purges every few seconds. You should be able to test that this operating correctly by disconnecting that tube that runs from the purge valve to the carbon canister under the left front wing. At idle, you should be able to hear switch in and out. The vacuum leak may cause a lean mixture which may have a noticeable effect. If you put your finger on the opened connection on the purge valve, you will probably be able to feel it open and close.

Another test: If you disconnect the tube between the purge valve and the carbon canister under the left wing, and plug the tube both ways (towards the carbon canister and also toward the valve and manifold), then I think a normal engine should operate normally.

By the way, I think the purge system sucks from the fuel tank, ie the hiss that you can hear is due to negative pressure in the tank in order to bring fumes into the engine, not a positive pressure.

I may be completely wrong, but maybe someone else has a better idea.

I don't think that "When you fill up the vapours all flood into the manifold and choke your engine" but maybe someone else has an opinion on that. There are always fumes in your petrol tank.

Or with the right diagnostic equipment I think you should be able to observe the cycle of the purge valve, and that might tell you if it is involved.

But I don't have any solutions on the slow starting. Just my two cents worth.
Steve

[PNuT]

I had this strange starting problem years ago, I blanked the evap of at the inlet and it never failed to start after that!

Every car I have had since I now do the same.....

[CarlW]

If the vacuum pipe to the Purge Valve is original(yellow stripe down it and very dirty to touch) then it will be porous now