fuel starvation? hesitation once up to 45 ish

[paulandchez]

I've just recently changed my fuel pump to a posi flow low pressure one, and I'm getting hesitation once reaching about 45-50. The van won't go over this and unless I lift off slightly, it feels like it would lose power and cut out. I've got a small paper cone filter between the tank and pump, and them a large canister fuel filter as the line enters the engine bay. This filter is off a ford ka I think, and was recommended by a vw bus mechanic who I'd trust to know what he's on about.
So....any ideas what I should be looking for to stop this?

Carbs are twin brosal solex btw

Cheers

[AdrianC]

You've just changed the pump for a different type and - since doing so - you're having fuel starvation at high fuel demand.

Well, I know where my money lies...

You don't ever need two fuel filters. Ever. If the first one's working, the second one's redundant. If the first one's not working, why's it there?

[paulandchez]

Yeah I know what you mean about the pump, but I changed it as these carbs are supposed to run off 3-4 psi only. With regards to the filters, do you think putting the cannister one between the tank and pump is enough then? That way I've got the finer filter in the line. I suppose it could be restricting too much eh having the 2 in there

[AdrianC]

Yeah I know what you mean about the pump, but I changed it as these carbs are supposed to run off 3-4 psi only.

Yes, that's all carbs need - injection needs much higher pressure. But that's not the only variable. Peak flow volume is what's likely to be your problem. All you need is enough pressure to get the fuel to the float chamber. But if the carbs are passing fuel through to the engine faster than the pump's delivering it, then you've got a problem.

I presume these carbs have return pipes, so some of what's fed is going back to the tank all the time. Without a return, all the fuel going to the carb "stays there", but the needle valve has to hold back the pressure the pump delivers. With a return, once the needle closes, the excess is returned - but, of course, some will be taking that path of least resistance anyway. You could try blocking up the return pipe, but I'd definitely run it at idle first - WATCHING CAREFULLY - to make sure the pump wasn't overcoming all the joints and the needle and overflowing everywhere.

As for the filter - you need a filter. Just one. Doesn't need to be anything clever for a carb setup.
Just one of these or similar...
http://www.screwfix.com/p/in-line-petro ... arge/12466" onclick="window.open(this.href);return false;

Tank - pipe - filter - pipe - pump - pipe - carb(s)

[paulandchez]

Well.......after a very frustrating day, I'm home. Initially I couldn't get above 45 ish, but in the end I was struggling to get 30 and any hill at all was nearly a stopper. I took out the filter between the pump and carbs, still no improvement. I replaced the filter between tank and pump in case that was blocked, still no joy. Van runs fine at idle, apart from one spell when it wouldn't idle and just cut out, but that stopped after a bit of revving. So.....I'm now thinking crap in tank?
Any thoughts?

On the plus side.....passed MOT

[paulandchez]

Oh and no there isn't a return line on these carbs

[AdrianC]

So.....I'm now thinking crap in tank?

There is a strainer in the tank pickup. That could be blocked.

[paulandchez]

Am I right in thinking you can't remove the strainer on its own? Is it a tank off, drain and check job?

Thanks