Just fitted one of these and it seems to be causing major fuel starvation. My 2.0l can now barely manage 50mph. There is a pressure pulse every 3-4 seconds which has deformed the fuel filter and I can hear it whilst driving! The valve is in the manual position so that eliminates any electrical problems and I checked that the valve was fully open before fitting. Anyone else had problems with cut off valves?
This sounds like blockage somewhere. Like bits of rubber from pipe cutting while fitting the new valve . These go down the pipes blocking the carburettor needle valves. If your fuel filter is swelling it must be downstream of the fuel pump with a lot of pressure. Scary ! On my setup with a similar cutoff valve I ended up with the feed going: Tank - filter- shutoff valve- fuel pump- carb as the dirt from the tank jammed the shutoff closed.
I suggest you may have misunderstood the instructions and it's actually switched off, but the pump is managing to draw petrol past it and struggling at speed.
Actually, looking at the OMB spec (I'd never heard of one), the inside diameter is 3.2mm. Doesn't seem very big to me.
Think I've sorted the problem. I'd had the tank out to sort rust and when I put it back in I replaced all the hoses with R9 and all the fuel filler rubber. My fuel vents are plumbed into the air filters to get rid of the petrol fumes and I think I was creating a vacuum in the tank. So the pump was working against a vacuum and crushing the paper filter. I've tested this by removing the petrol cap and it now appears to run OK. The pressure pulse has gone and now all I have to do is work out how to vent the tank and still get rid of the fumes. The reason I'd not noticed this before was the old filler rubber had a split in it which allowed in air behind the petrol. Thanks for all your replies and I'd be interested in any ideas on how to re-plumb the venting system.
That's how the vents should be have you tried blowing down the vent pipes to make sure they are not blocked
My vent pipes are as in the diagram. The only change is that I've removed the charcoal canister and connected to the air filters. I'll check the vents to see if they are blocked.
If you're connected to the air filters, then I'm at a loss as to how they would be creating a vacuum so great that it would cause a negative pressure in the fuel tank
I went to fill up the tank after it was reinstalled and the petrol cap was hard to remove. I now think that the OMB valve maybe too small to allow the required flow for my pump/carbs?
