Odd problem (carburettors)

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Landlover99

Landlover99

Active Member
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Location
Extreme North West
Hi all,
I've encountered a problem with my 1989 V8 3.5 petrol engined Landy. It's like totally dead. No signs of life even though it's spinning like a top on the starter. It *will* run fine on Easy Start, though, so the ignition system's fine. However, pumping the accelerator like mad and pulling the choke out, then spinning it over for 10 seconds and pulling a plug out confirm it's fuel starvation as the plug is dry as a bone. It *is* getting fuel pumped right up to the carbs, though, as it gushes out on the key II position if the feed's disconnected at that point. So there's something going wrong inside the carbs. Any suggestions and does anyone know what the designation of these carbs is? I know they're SU (HIF?) type but the model number would be helpful. Many thanks.
SU carbs.jpeg
 
If it runs on easzistart and you have fuel then I guess its time to get them off and take a look inside.

Has it been stood for a while? Cos this can gum things up.

They are pretty simple carbs TBH.

J
 
It's only been standing for two weeks. Whatever the problem is, it's affecting *both* carbs which is what made me initially suspect the fuel pump. But that's fine. So it's a real head-scratcher for sure.
When I did the Easy Start test, I placed a brick on the accelerator pedal so it was flat to the floor and no choke. The battery is A1. It fired-up and revved right up to its limit before the Easy Start squirt ran out. I suppose a sudden influx of dirt in the fuel could cut-off both carbs at once, but where would that come from? The tank is low, but certainly not empty as I'm getting a flood of juice coming out where the feed goes into the carbs. Do these carbs have an internal filter that might have got blocked?
 
If I remember they have a restriction (where the 2 carbs join with the black pipe). Which maybe why you get plenty out from your other disconnected black pipe.

Would need to look for filters as I can’t remember.

J
 
AI reckons they're type HIF6, so unless anyone knows better, I'll run with that for now. I need to look into the options, the two most likely being exchange recon units or DIY with a service kit.....
 
Your carbs are plumbed with a return line back to the tank. It needs a restriction in the line down stream so that the fuel feeds to the carbs otherwise they won't receive fuel. I'd suggest checking the two 6mm nylon lines from your carbs heading towards the passenger's side of your engine bay. They are the overflow lines from your float chambers. So IF you had a needle valve passing fuel it would piddle fuel out through one of them. Check that neither line flows fuel.
Try blocking half of each carb inlet with your hands while a trusty assistant cranks it over. It's a rare occurance that SU's give a no start problem.
 
Have you checked the two filters to the carbs normally grey from the rocker covers. They can gunk up occasionally. I used to clean them yearly. Su pots can jam with oil being low or none in.
 
I have no experience of these carbs on the V8s but I'd just whip them off and take them apart as much as possible to try and figure out whats going on.
They do look like pretty simple carbs to be fair, simpler than the Weber on my 17H... and even on that when I started digging into it, it wasn't that hard to figure out.
 
Could be stuck needle float valves.
As others have said, they are simple and loads of stuff ont tinternet to help you strip and rebuild them.
I doubt rebuild kits are too expensive, but replacement ones sure would be!!
They are very easy to rebuild as there is so little to them.
Just taking them apart, cleaning stuff, then putting them back together again will make em run again, usually. Do one at a time so you can see how they go back together again.
Just don't go trying to polish the dashpot inners or the piston edges!!! Clean yes, polish, no!!
And if they ran fine 2 weeks ago don't go trying to alter the tune, by playing with the jets or anything.
Don't polish the needle either! Don't even take it out of the piston, just clean it with carb cleaner.

Best of luck!!!
 
Thanks for the tips and suggestions, everyone. I've since checked out on the price of exchange units and they're obscenely expensive, so it's going to have to come down to a strip down and rebuild instead. Yes, their operation is certainly simple; getting them off might not be, though. There are four bolts that secure each carb to the intake manifold and one of them on each unit looks a bitch to get at. Sigh.......
On the plus side, I've got one of those ultrasonic cleaning baths, so chuck the carbs into that, in bits, one at a time of course and top it up with cellulose thinners. Switch on and let ultrasound do the hard work. Hopefully!
 
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