Carb problems

[!aj!]

Hi,
I thought i had a pump problem. Car idling with choke out, then cut out and no clicking from pump. Cleaned Earth connections and car running again.
The symptoms now are the car idles fine with choke out. If i drop the choke in it cuts out. If i drop the choke in and keep foot on throttle it idles. However, throttle pedal to floor does not increase engine revs noticably (something wrong here) and the engine seems to run faster with the choke out than with the pedal to floor.
The throttle cable and linkage is working as it should (i believe) so it looks like the carb. I don't understand why the engine would run faster on the choke than the throttle - i thought they worked off of the same linkage.

Any thoughts?

[Alec]

Hello Taj,

a couple of things, there are two idle screws, one on the choke and the other on the throttle spindle, it sounds as if the latter needs increasing. However don't adjust the throttle setting until the engine is good and warm, ideally after a few miles drive. If it runs better with the choke out, it sounds as if it's too weak, but again, this needs checking when hot. It is normal for a cold engine to run better with at least partial choke when cold.

Alec

[!aj!]

Hi, yeah problem is when i say running i mean stationary running. If i start it with choke and don't touch anything else then it is relatively 'normal'. If i try and drive, it dies on me. Just tried reversing it up the drive and it just keeps dying - ended up pushing it.

I'm thinking somethings sticking or blocked in the carb, but i realise (as per usual with cars) it could be any number of things.

[kittyfell]

If you have a servo, check for a leak in the vacuum pipe. Otherwise start by checking if the carb piston rises and falls as it should. Has this problem 'suddenly happened, ie it was fine yesterday and today it's like this?

[!aj!]

Just gone out to check piston. (Labour intensive as air filter is attached by a number of bolts to a number of brackets and i've just got to work out the simplest route.) Havn't done that yet as i was looking over the engine and the dizzy cap was loose. Re-attached it and tried engine. Idling as expected. However, i then noticed a leak from the outlet manifold gasket dripping rather nicely onto the exhaust. This is an 803 engine and it appears the inlet/outlet manifold share the same body. Looks like new gaskets are the order of the day - would this cause the running problems.
The car hasn't been driven since i bought it for my darling, who after driving it home, went off the idea. I was meant to sell it today but i've had to shelve that now. Are there any trusted garages in Manchester i could use if i decide not to do it myself? Worse scenario, which i can easily see occurring, is that i do this and the running problems persist. Either that or sell it as a non-runner i suppose. The chap i sold it to is expecting me to fix it though.

[kittyfell]

The leak sounds ominous, but may be due to your constant use of the choke. Piston check is the way forward I think and surely can't take more than a few minutes.

[!aj!]

Hi, i've taken the filter off and tested the piston - it falls with an audible clunk. Although there is oil in it i don't know how far up to fill it - should the level of oil be visible? Ran it like that with no choke and no throttle and seemed improved (that is to say it ran) - maybe clean the filter?
I've also had the pump cap off to 'clean' the points and observe. With car running - no throttle, no choke - the points are closing roughly once every 2 seconds. Is that normal?
There is still a leak from the manifold - the central port only. I was thinking of ordering a replacement gasket from BM for a £1.00 or could i get away with some sort of sealant for a quick fix? Thoughts please?

Ps All help is really appreciated. Thanks to all concerned.

[mike.perry]

Any drips of petrol onto the exhaust are definately not good news, have you got a fire extinguisher to hand! The petrol is probably leaking from the carb and running down the body and onto the manifold so it may be that the manifold gasket is not the problem. Do you still get dripping with the engine off and the ignition on? If so then it could indicate that the fuel in the float chamber is too high and it is flooding the carb, especially if the pump continues to tick.
It is always easier for an experienced owner to stand looking at an engine to identify problems than to try to spot faults from the other end of a computer, so it is a case of eliminating points a bit at a time or waiting for a flash of inspiration!

[!aj!]

The odd thing is i don't think the leaking fluid is petrol. It could be the water from the combustion process or something worse. (The coolant level is fine). The thing is the engine revs faster off the choke than the throttle. Now it was driven 90 miles back home when purchased so the carb settings should not need tweaking. I'm now thinking the problem may be the electrical side although that said there is a very strong smell of fuel and judging by the black mark on the house wall it's running rich (or just parked too close)

I'm also thinking the throttle linkage may be loose although again, with the filter/silencer off it seemed to perform better. I'm at a loss.

There is a metal lead between the carb and the distributor - what is this for?

UPDATE

Remembered i bought and fitted a rotor arm off BM and i have tried the old one and it starts and idles ok off of the choke, revs increase too with throttle, so could this be it?

[aupickup]

keep the old one in if it works ok,
could be the answer

[!aj!]

Definitely running better now although risking a test drive is giving me sweaty palms! It's idling ok but the ignition light is staying on. Is that normal or should it be idling fast enough to put the light out?

[aupickup]

light will stay on a t idle thats normal, and will go out when the revs are picked up

[bmcecosse]

Sounds like you had wrong type (or faulty) rotor arm! Well done finding the fault - you should always retrace steps/reverse any changes made when a fault like that appears. Maybe the drip you see is just condensation from the atmosphere on the cold inlet ? Catch it on your finger to find out if it is petrol.

[!aj!]

Yep, just glad i kept the old one. The reason for selling is it is not too practical for daily use which is what it was bought for. I just didn't research it enough. However, i am certainly going to get another later model version and actually one has taken my fancy already. I need the funds off this first though. Great cars and i love the space in the engine bay!

[kittyfell]

Don't dismiss it too easily - that 803 engine may give the best fuel economy if set up correctly and with a different rear axle ratio.

[aupickup]

yes but an 803 is hardly an engine for everyday use in todays roads
a later moggy will cope much better

[!aj!]

Hi gang, the rotor arm definitley improved starting and idling but the car still has running issues. I went to drive it down drive and as soon as i depressed clutch it stalled or nearly stalled. The same happened reversing back up. I took the plugs out and they are very sooty. I also believe cb points can have a bearing on matters but too dark now to have a look.
Is there anywhere i can pick up plugs and points i.e Halfords or will i have to mailorder? Another question is that i have tried adjusting the throttle screw on the carb ( increase the revs). There is a throttle stop screw below it but i don't know what i should be doing with that?

[Alec]

Hello !aj!,

plugs are sooty due to an over rich mixture. Certainly check and re set the points if required. (if re set then the timing will need checking also)

Make sure the choke is free and the jet tube is returning back up when you push the choke knob in. At the base of the carburettor are two hexagons, the upper secures the jet tube holder and the lower adjusts the mixture. The jet tube should be hard up to the base of that assembly when the choke is in. Check the air filter is not badly clogged.

The basic mixture setting for an S.U. is for the mixture nut (the lower one) to be two full turns down from the top. Although this is a simple operation, there are a couple of things to do. Remove the piston damper assembly, and check the needle shoulder is flush with the bottom of the piston. Look down to the jet in the base of the carburettor then screw the nut up until the jet is flush with the bridge (you'll see what I mean if you look inside) Screw the nut back down two full turns or twelve flats. Reassemble and try.

Alec

[mike.perry]

There is a metal lead between the carb and the distributor - what is this for?

That is the vacuum pipe. There are extensive topics on the site explaining its functions.

[!aj!]

Hi and cheers for that Alec, I've bought and fitted some new spark plugs but before starting it thought i'd have a look at float chamber. To be honest i didn't know what to look for! lol. Anyway, saw your post and as i'd checked damper etc thought i'd look at the mixture nut - it must have been around 5-6 'turns' off the top! I tightened it up, marked it, undid 2 full turns and started engine. What a difference! Roared into life - much happier!

Problem i have now is the two adjusting screws on the throttle linkage - one above the other. Is there a starting point to set these or just play around with them?