Big carb problem!!

Post by **FrankM83** » Tue Apr 07, 2009 9:20 am

Ever since I rebuilt the engine I have not stopped having problems with the carb, the first carb was thoroughly cleaned and isntalled with a rebuild kit!! but the engine kept misfiring and smoking black and burning lots of petrol, 2nd carb was just cleaned inside out and still the engine burned black but less than the first one! the thrid carb was just cleaned from the outside! and the engine started working a lot better but still there is a hint of black smoke!!! unfortunly this was too late as the engine started doing a knocking noise and drainage of the oil revealed lots of petrol has gone down with the oil and probably damaged the brand new conrod bearings!!

What can I do???

y r all the carbs giving this problem?

Post by **tortron** » Tue Apr 07, 2009 10:23 am

are they all running extremely rich? chokes stuck on? fuel float sunk causing over fueling?

Post by **d_harris** » Tue Apr 07, 2009 10:56 am

If you've had similar symptons from 3 carbs I would suggest its not the carbs causing the problem!

Is the engine itself in good health otherwise?

Post by **Stig** » Tue Apr 07, 2009 11:25 am

It's not got a mechanical fuel pump has it? I think Marina engines had them. I've heard of them failing and leaking petrol into the sump.

Post by **FrankM83** » Tue Apr 07, 2009 1:42 pm

well the engine is very healthy! to be honest before this happened it was the smoothest A series engine I've ever heard! I could even put a mug of the on the top cover and not fall off!

it has an electric pump it's a 1098cc engine

choke not stuck float is OK :S

Post by **bmcecosse** » Tue Apr 07, 2009 9:07 pm

Well -huge amounts of petrol must have been flooding into the engine - the black smoke and now petrol in oil certainly confirm that! By any chance - have you been connecting the fuel feed to the overflow pipe on the carbs - rather than the correct fuel entry pipe ?

Post by **FrankM83** » Wed Apr 08, 2009 7:03 pm

the fuel feed is where it alwas was the correct entry pipe

could it be the unleaded fuel that's causing the black smoke?

Post by **bmcecosse** » Wed Apr 08, 2009 11:05 pm

No! Certainly nothing to do with unleaded. It's just getting far too much fuel somehow! What type of carb is it - old type with seperate float chamber - or later HIF (Horizontal Integral Float) carb ? The type with seperate float chamber MUST be mounted with the chamber absolutely vertical - or they will flood mercilessly. The HIF is much better - it doesn't really mind what angle it's mounted!

Post by **FrankM83** » Wed Apr 08, 2009 11:13 pm

what's an HIF? on what cars can I find it?

Post by **bmcecosse** » Wed Apr 08, 2009 11:20 pm

Later 'improved' SU carb - has no separate float chamber. Many Rover/MG cars - all Metros I think ! Can you post a pic of the carb you are using ?

Post by **FrankM83** » Wed Apr 08, 2009 11:23 pm

will do tomorrow if it's a metro carb I need is it from a 998cc or 1275cc?

Post by **bmcecosse** » Wed Apr 08, 2009 11:33 pm

Best with the 998 carb for a 948/1098 engine - if 1275 engine then obviously get a 1275 Metro carb!

Post by **FrankM83** » Thu Apr 09, 2009 11:00 pm

here's my carb what is it?

the last pic is of the carb I had before this was fully rebuilt but ended up burning petrol worse then the one I have put now on the engine!! the only difference is the outake where the black pipe is on the last pic!

Post by **toginthemog** » Thu Apr 09, 2009 11:20 pm

Frank what did you connect the black pipe on the last picture to as I think it was connected to rocker top as a breather

Post by **bmcecosse** » Thu Apr 09, 2009 11:21 pm

Bog standard 1.25" SU carb ! I thoought when you said 'Big Carb Problem' - that you had a problem with a 'big carb'. I now see it's a big problem, with a small carb !
Most likely is that the float valve is tsicking or leaking - and the fuel is overflowing the jet into the engine. To test - take the bell off complete with piston (is the piston nice and free inside the bell ??) - switch on the ignition - does the fuel pump tick constantly ? Can you see fuel flowing over the jet ?

Post by **FrankM83** » Thu Apr 09, 2009 11:28 pm

yes the pipe was connected as a breather

Roy, what im sure is that the piston is free, when I turn ignition on the pump ticks till I see the filter full of petrol and then stops

what concerns me is that all 3 carbs I tried, same problem :S

Post by **bmcecosse** » Thu Apr 09, 2009 11:32 pm

Hmm - well I have to say - I'm stumped !! You can try dropping the fuel level - but if the pump stops ticking then the float valve would seem to be ok.

Post by **FrankM83** » Thu Apr 09, 2009 11:38 pm

is there a way to see if the float is stuck or sinking?

Post by **FrankM83** » Sun Apr 12, 2009 11:52 am

could it be from the HT leads?? :S

Post by **crossword** » Sun Apr 12, 2009 3:19 pm

Frank I would strongly recommend that you remove the in-line fuel filter that we can see in your picture of the carb & replace it with a piece of fuel pipe . I have just gone through several weeks of heartache , having last year fitted an in-line filter , to allow me to check for fuel being pumped to the carb & if any dirt was in the fuel . This was because i was trying to find the cause of a misfire .Since then the car has become increasingly unreliable .

I think that the filter was adding additional resistance to the fuel flow & not allowing enough into the carb , particularly at road speed , it seemed ok on tickover . ( Roy , you may remember a few messages on another thread regarding cutting out when warm .) What made me realise this was that yesterday the fuel pump was not ticking , the filter had fuel in it but the pipe into the carb was empty .

In any case the fuel pump should have a filter inside it , you could remove the lower plug of the pump & clean it , but not with cloth I think the various books suggest paraffin .

Hope this helps . Regards Andy