1996 940 DTIC air in fuel lines
 

In my 12 months of ownership my Volvo 940 dtic has always had an issue where if the fuel level is low, eventually it will lose power at motorway speeds and need the fuel filter bleeding and the fuel topping up. Once bled the problem would not come back for days/weeks. However, this problem now happens all the time on the motorway, regardless of how much fuel is in the tank and how often I bleed it. I've no idea where the air is getting in.

I've replaced the fuel filter to no avail. There does not appear to be any diesel leaking anywhere and all the obvious connections under the bonnet have been checked.

It has what looks like an aftermarket fuel pump (very noisy) wired in just before the fuel filter. Should it have another pump near the tank? When the feed from the tank to the inline filter was disconnected and the engine run, there was no fuel being pumped to the disconnected pipe, so it seems that the pump under the bonnet is the only one.

Cheers

there is no lift pump on American models so not sure if what you have is factory or not, also air can get into the system much easier than fuel can leak out so I would replace all rubber hoses coming from the tank to the pump and injector crossover hoses

Thanks for your reply. The pump doesn't look like a factory fit and it is very noisy. As soon as the ignition key is turned on (prior to starting the engine) there is a very loud clicking noise from the pump which doesn't sound right to me.

I think I will replace all the rubber connections and cross over pipes under the bonnet as you suggest and replace the pump at the same time.

How do I find a replacement pump that is suitable? Clearly I want one that can pump enough diesel to the engine so that it isn't starved of fuel at high speed.
But what happens if I fit a pump that sends too much diesel through? How is it regulated and what happens to excess fuel?