2.5 petrol with twin choke webber - fuel pump problems

Got the 80 MOT'd yesterday morning, ran round in it all day enjoying the sunshine Only hicup was pulling up a steep hill in 4th overdrive - as it got steeper the 80 started to cough a bit like its running out of fuel or the igntion is cutting out. Ease off the throttle and change down to 4th and it pulls up the hill. Try and use full throttle it starts coughing. Once on the flat I can put my foot down and it goes like a train. Just not in a high gear under a heavy load like on a hill.


Went out in it today and along a flat bit of road it started to cough like it was running out of fuel. Sure enough it cut out and I coasted to a halt. Looked in the tank and it was low. Rang my wife and she brought be a jerry can of fuel which I put in. It won't start and the fuel pump isn't ticking. Pull the fuel lines off and suck fuel through to the carb but the pump won't go. Resigned to being towed home when the pump bursts into life. Still won't start, so I wonder if there's rubbish in the carb. Eventualy I nearly give up when one last press of the starter button and it fires up!


Drive home no problem. Park on the drive turn it off. Then try and start it and ... nothing, no pump. Decide to watch the gand prix and have a look later. Turn the ignition on and tada! Pump work and it starts. I'm wondering if the pump is getting hot and breaking down?


For those who don't know its a 2.5 petrol with a Weber 32 34 dmtl and the pump is a normal SU


This is a long way of saying that I guess the pump is on its way out Could this explain the coughing under load (not getting enough fuel?) Would an SU deliver enough fuel for a Weber 32 34? If not does anyone recommend one? and, I've not serviced the carb (prefered to run it and see first), can you service them and is it worth it?

I'm thinking of getting a facet pump. Should the carb have a return feed to the tank? At the moment there's only what looks like a overflow pipe.


At least I got home under my own steam and didn't turn up being towed in front of the neighbours

That's a pain in the hole

We had a LWB safari V8 years ago, did the same thing now and again, Dad kept a truncheon behind the drivers seat, and used to give the pump a smack with it......................worked every time

I got a 87 90 2.5 petrol with exactly the same juddering problem, dont think it is fuel pump tho as i can hear it when i turn the ignition... however, now she wont start at all, fuel is coming out the jets in the carb but not firing at all... did you get any useful answers?

retro80 - yours sounds like pump. I got a crappy solid-state one off ebay that let me down in the worst of all possible places a couple of months ago. Since then I bought a genuine facet fitted that with a pressure regulator. It has been a lot better.

I've still got the mech pump and pipe work on the engine though in case of trouble, ten minutes with a 9/16 spanner and I'm back in business rather than being stuck with a load of lay abouts moaning that I'm blocking their pavement!

teagle, check you've not flooded it.

Also, check the routing of your fuel lines. It was common to have them routed straight over the engine leading to all sorts of problems with vapour lock on modern fuels especially the 10% ethanol stuff some 97 octane brands are using.

I tried BP's 97 octane when I still using mech pump and it was terrible for playing up the problem there is the mech pump is on the block and gets hot enough to boil out the alcohol as gas which stops it pumping properly and it cuts out under load.

dominicbeesley said:

retro80 - yours sounds like pump. I got a crappy solid-state one off ebay that let me down in the worst of all possible places a couple of months ago. Since then I bought a genuine facet fitted that with a pressure regulator. It has been a lot better.

I've still got the mech pump and pipe work on the engine though in case of trouble, ten minutes with a 9/16 spanner and I'm back in business rather than being stuck with a load of lay abouts moaning that I'm blocking their pavement!

teagle, check you've not flooded it.

Also, check the routing of your fuel lines. It was common to have them routed straight over the engine leading to all sorts of problems with vapour lock on modern fuels especially the 10% ethanol stuff some 97 octane brands are using.

I tried BP's 97 octane when I still using mech pump and it was terrible for playing up the problem there is the mech pump is on the block and gets hot enough to boil out the alcohol as gas which stops it pumping properly and it cuts out under load.

Click to expand...

eh? you saying that some of the stuff you get at the pumps has ethanol in it?cheeky feckers

I've got a 2.5 Defender petrol with the weber in my 88, running off the standard series mechanical fuel pump on the side of the block. It's really fussy on hot starts - sometimes it'll go on the turn of the key, others it'll need 10-15 secs of cranking with the foot flat to the floor before it'll fire... I've still not figured out why

pump gets hot, vapour forms in the top of the catch bowl and the valves and then its pumping vapour is one theory.

Also get vapour in pipes and filters, and float bowl of carb - though a 2.5 should be better as there is a vent solenoid.

rerouting the pipe work forward of engine round top of rad cowl helped on mine but was still a right c***t on a hot day and would often die just after setting off..usually when pulling on to a dual carriageway or motorway.

With an electric pump and DMTL carb it behaves impecabbly...

I've tried re-routing the pipework round the bulkhead at the back instead of across the front, it doesn't seem to have helped, but it's it's a problem fuel pump side it wouldn't do.

Touch wood it's been OK when it's started, it's just the starting itself that's a problem...

Before the two and a quarter died a horrible death it would start instantly every time though, with near enough the same setup...

I think I've still got the defender fuel lines and swirl pot thing, will have to look for an electric pump to go with it.

While we are talking about 2.5 petrols - does anyone have a timing figure for UK petrol at idle? The manual quotes TDC static, or 20 I think at 2000 RPM dynamic - which is hard to guess at as a series doesn't have a rev counter (and nor does my timing light!). It's also for 90 RON fuel (2 star?)

Facet pump ordered. Is the fuel pressure reg obligatory if I don't refit the gravity feed flow and return system that the defender uses?

I fitted one, not tried it without. Facet pumps put out around 4-7 psi and I think Weber needle valves are for 3.5PSI. I just got one of those cheapo inline diaphram/button ones. you may get away without one but might waste more petrol than it costs...

OK - I'll try and find the gravity flow/return system in my box of bits if I can, that'd be closest to what the defender setup is. If not I'll be scouting for a pressure reg!

or you could fit manual lift pump