Alfetta DHLA40 trouble

[simmi1983]

Hi all,

Just seeing if anyone could give me a bit of guidance with me carbs.

I've had to replace a carb body as one of the idle air mixture threads is flogged and wouldn't retain the screw.
I swapped over all the jets , throttle plates, bearings, seats etc using new o rings and gaskets.  It only just had a kit through it.

Since doing this it's being a really bugger to start and if you can get it to go it runs like crap, wont idle and seems to miss. Ignition all OK, it seems it's dumping too much fuel in as it back fires almost instantly when cranking it and even hinders the cranking speed and plugs gets wet with fuel especially #1.

Pulled off float covers,  checked the needle and seat( can't blow through when seated) and checked the float levels 15mm to floats and 27mm to fuel level from top of carb body.

Balance is as close as I can get it without it running.

Where else could I be getting excess fuel from?

Does anyone have any idea what I could've missed?

I dont know think this matters but the replacement carb has taller idle mixture towers but is also a " G".are they internally different in any way?

Any help will be appreciated and considered as im really over it haha.

Thanks,

Luke

[NSharpley]

If starting is one of your key issues then it'll be accelerator pump jets.

Have you removed the ball and weight from the pump circuit?

The ball gets stuck and doesnt allow the flow.

Makes it almost impossible to start the engine.   If you do manage to get it started, it wont rev properly from low down.

Once the RPM gets up to around 2500, the main circuit will kick in and it should run fine but then after each gear change it will bog down briefly.

Pull the jet out, then turn the carb upside down to get the ball and weight out.

Turn it back over, put some fuel in the bowl and turn the throttle open.

Ensure fuel is flowing into the chamber where the pump jet was.

[simmi1983]

No,I haven't removed the ball and weight. But I did spend 2 hours looking for it when it fell out obto the floor. I will remove it tomorrow.

 So ball, weight and spring all get removed for good?

That could be an issue coz this car has always been a bastard to start, but I definitely feel there's too much fuel getting in as it backfires pretty much instantly from just cranking over?  Sounds like the timing is out and sparking at the wrong time, but I've checked that.

My other observation was that the butterflies doesn't quite close as much as my other carb does. I'm talking maybe .5mm. It just covers the first progression holes tho.

Thanks for the help, I'll keep at this as I REALLY want to drive it again.

Luke

[simmi1983]

Update.

I pulled the tops off the carbs today and removed the accell pump metering balls, weights and springs. I also pulled out all the jets to have a double check and found a blocked idle jet on cylinder 1. I also noticed one of the needles on the float wasn't bouncing back as well asthe other, so i found some brand new 1.5 needle and seats in my spares and decided to put them in.

It started ! No backfiring and carrying on!

After some tuning and mucking around with idle and balancing it runs fairly well. I think I've got a dud fuel pump coz my fuel pressure gauge reads .5psi.. but still drives.. it does feel a put doughy at times but that's a future problem. 

My question for today is this.. I have a gunson colortune and no matter what I do on all cylinders I can only get a orange/ rich flame.  Even when I screw the mixture in till it misses I still get orange.  Anyone know what this means? Low compression?

Also it's impossible to start hot! I will If I leave it for 10mins and hold my foot flagt. It's been a bugger to start hot before but not this hard. Any ideas?

[giulia_veloce]

Backfiring is a LEAN mixture,,Not a rich mixture.

3-4 PSI is perfect for Alfa Carbys

[Colin Edwards]

+1 for backfiring "usually" = lean mixture, but not always.

I used the Gunson colortunes to confirm each cylinder was seeing similar mixtures. Problem is the Gunson colortune is a poor substitute for a spark plug.  I found when I installed the clourtune to a well carbureted engine, it idled poorly - probably due to misfiring.  The non ignited mixture usually gives a rich (orange) flame colour - similar to a candle.  Unburnt / glowing carbon!