Rover v8 won't idle with out choke.

V8classic · Post by **V8classic** » Wed Dec 30, 2015 11:03 pm

I have eventually got my rover 3.5 v8 which I on su carbs ticking over and running. The only problem is I leave the choke on to warm the engine and once I flick it off it struggles and stalls. Even when I take the choke off and hold the throttle open nothing seems to happen. Some people have said I could have an air leak. How do I check this? Do you guys have any other ideas what it could be? Cheers Will

unstable load · Post by **unstable load** » Thu Dec 31, 2015 4:53 am

To me it sounds like the settings are set up for it to run on choke and thus need to be "standardised"...
I'd start with he basic settings of the carbs, first. Is the needle fitted correctly, is the jet height set properly, is the float height correct, dash pot etc etc.
Return it all to basic and start again, you are on the right track, but just in the wrong range.

DaveEFI · Post by **DaveEFI** » Thu Dec 31, 2015 9:49 am

With SUs, there is a very easy way to check the mixture at idle. With the engine warmed up, raise each piston in turn about 1mm. Some versions of SUs have a lifting pin to do just this.

If the engine slows down, the mixture is too weak. If it speeds up, too rich.

Is the engine standard, and are the carbs correct for that version?

But as said, check they have the correct needles etc, and are in good condition. A sticking piston will give the wrong mixture, as will the wrong float level. And any leaks - like say round the throttle spindle with worn carbs.

But before fiddling with the carbs, the ignition timing must be set correctly.

V8classic · Post by **V8classic** » Sat Jan 02, 2016 11:53 pm

As far as I'm aware yes it's all standard. It's in a range rover classic 1984/85 I think it's the old sd1 engine. How do I check whether the needles will be standard? Can all these checks be done while the carbs are on the car? I've had a look inside them today and all seems good. I have set the mixture so the jet is flush with the top which I think I had read elsewhere. I will put them back on get it running on choke and double check the timing too. Thanks for the advice much appreciated!

unstable load · Post by **unstable load** » Sun Jan 03, 2016 6:30 am

Jets level with the top is a baseline if I recall correctly, so you would need to turn the jets out to achieve your idle. Somewhere in the recesses of my mind is the number 2.5 turns out.
The choke lowers the jets to enrich the mixture, so if it only idles on choke, then pull the choke out and see how fa the jets are down and set them to that level with the choke in and see what that does.

v8250 · Post by **v8250** » Sun Jan 03, 2016 8:40 am

More or less as said above but to add the following. With your current set up get the engine at full operating temperature, then disconnect the choke and set up SU idle setting...this will enable the engine to start even when cold. Follow this by setting up off idle, followed by mid-peak off idle advance.

The important thing with SU's is getting the carbs air/fuel ratio matched correctly. You'll need a good air flow meter to monitor at the air intake and to ensure the carb linkages are undone when setting up...if not the SU's will not balance and you'll be chasing your tail.

Once idle+off idle are set up individually reconnect and tighten the carb linkage, recheck air intake and fuel balance. If perfectly balanced refit air filters, if not rebalance until correct. This can take a few goes to obtain correct balance...though this is an enjoyable and satisfying process.

One last point...assuming the SU's are in tip top condition...the carb floats do need to be set up correctly. If not, they can play havoc with fueling and appear to cause a number of other set up errors.

For good reading, the Des Hamill book 'How to Build & Power Tune SU Carburettors' has all the data required for getting any SU carb set up on song; good luck...

v8250 · Post by **v8250** » Sun Jan 03, 2016 8:55 am

V8classic wrote:As far as I'm aware yes it's all standard. It's in a range rover classic 1984/85 I think it's the old sd1 engine. How do I check whether the needles will be standard? Can all these checks be done while the carbs are on the car? I've had a look inside them today and all seems good. I have set the mixture so the jet is flush with the top which I think I had read elsewhere. I will put them back on get it running on choke and double check the timing too. Thanks for the advice much appreciated!

I have the Burlen Fuels SU reference catalogue. Your carbs should be standard HIF44's FZX 2005's or 2006's and NZX8076BGC needles. There should be an alloy tag plate attached to one of the carbs on the dashpot screw with the FZX model marking. If different pm me and I'll check the factory setting data as there was a changeover in 1986/1987.

here's a link to Burlen Fuels tech data

http://sucarb.co.uk/carbspec/carburetto ... s/id/2291/

V8classic · Post by **V8classic** » Sun Jan 03, 2016 10:30 pm

V8250 your right! It does have fzx on and it does also have BGK on the needles as I checked that the other day. When I had the dash pot off and put the choke on the jets in the centre of the carb didn't seem to move but I will check that and alter it so it starts with no choke even from cold then set up from there. Is it right that both carbs should have an alloy tag on? I was chuffed it bits when I first got the engine fired up as it's not run for over 10 years now. I just need to get it running correctly now. Thanks once again.

v8250 · Post by **v8250** » Mon Jan 04, 2016 9:00 am

V8classic wrote: Is it right that both carbs should have an alloy tag on? I was chuffed it bits when I first got the engine fired up as it's not run for over 10 years now. I just need to get it running correctly now. Thanks once again.

It's a great feeling when we start up an engine that hasn't ran in years; ka-boom!

SU's normally have only one tag, even twin or triple sets. You can buy additional tags from Burlen Fuels. Only note re' tags is that we never know what jet, needle, float and spring types are in a used pair unless we check side-by-side as a previous owner may have tinkered with them. Again, Burlen come to the rescue as every component is available individually...it's worth changing the springs for a new matched pair and/or buy a new service kit from Burlen that includes all new gaskets and seals. One last note, if memory serves right, the HIF44 throttle disc should be a plain type...if this has been changed to a disc with an overrun valve, replace the discs to non-overrun discs as the overrun valves are a considerable restriction to air flow.

DaveEFI · Post by **DaveEFI** » Mon Jan 04, 2016 9:47 am

The SD1 HIF carbs don't move the jet for cold start enrichment. They have an additional cold start valve, if a manual choke, which would be from an early SD1. Most have auto chokes.

IIRC, this arrangement was to give more consistent emissions at idle.

With any unknown SU, it's best the strio it down carefully and give it all a good clean, and check for wear. Most BL manuals give instructions on how to do this and set up from scratch and I'm sure you'd find it online too. Most spares are available.