Brosol H30/31 running rich at idle - wont adjust

[dave123]

Before I start, I'm sticking with the Brosol carb, so please dont suggest a rebuilt solex as my fix

Got a new Brosol H30/31 carb, v pleased with it, runs great... only problem is it starts very sluggishly from cold or hot. Everything else is set well - i have a feeling this is an idle mixture adjustment issue, it seems very rich on start-up.

But, when i turn the small volume screw all the way in when it idles, nothing happens (engine keeps running same).... whats the problem?

I'll go take it off now and clean it out, but would appreciate suggestions, Cheers

[Towel Rail]

Runs well, but rich at startup? Sounds normal, that's the choke doing its job. I generally don't futz with the volume screw -- just leaving it 2.5-3 turns out works.

Been here? http://www.vw-resource.com/34pict3.html
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[dave123]

No, i mean REALLY rich - seems like its almost dribbling fuel into the manifold - plumes of fumes when i start up, and smells very rich.

I took the carb apart and cleaned it all out, re-set the mixtures... now it seems that the volume control screw DOES have adjustment... but when i screw it IN the engine gets faster, which is the opposite of what i was expecting Am i going nuts?

Ive currently left it set at about 1.5 turns out

[dave123]

yup, just been out for another fiddle - engine runs fastest when volume control screw is all the way in!

[bciesq]

What idle jet are you running?

Is the accelerator pump leaking? With the car at idle and warmed up, stick your finger under the accelerator pump nozzle and see if it is dripping.

Normally these H30/31 carbs aren't that sensitive to fuel pressure, but you may check that as well as the float.

What distributor and timing are you using?
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[dave123]

Running a 55 idle jet, which is what was recommended to me.... the fuel pump is a new standard one (brosol though )

I'm running an aircooled network SVDA modified for the H30/31, timed at 7.5deg BTDC at idle with strobe and vac line off.

What would be the cause of fuel coming out of the accelerator nozzle when at idle? I will check when it gets light outside again

[bciesq]

[dave123]

Thanks for your suggestions - nice to hear from someone who has exactly the same set-up as me, actually!

Presumably the accelerator pump only works when the throttle is pressed, i.e. it only squirts when the throttle moves? In which case if its leaking at idle then i'll suspect excessive fuel pressure.

I guess i shold also suspect the needle valve in the float chamber (or a sticking float), though it all looked ok when i had it apart yesterday

[bciesq]

[dave123]

Cheers for the help

i've just been watching footage of that stretched, widened, 993 bi-turbo engine'd splitty and how they made that

... and i can't even tune my bloody carb!

[dave123]

OK, just been tinkering

1st - I re-set the choke... it was set to be fully on at start-up. Cold weather is not that common here in Aus so i slackened it off. I get this problem also on immediate re-start so I dont think this is the cause of my rich at idle running/poor starting.

2nd - Stuck my finger down the throat of the carb, under the accel nozzle... no leakage. Blip the throttle, wet finger. Ergo- accel pump working as expected.

BUT, screwing volume control screw in still makes it go FASTER What now? How do i diagnose high fuel pressure (i dont have a gauge) with the car running - will there be a leak somewhere? How many gaskets alter the pump pressure - are we talking like 1 or 2, or 5 or 6?

Cheers

[bciesq]

[Rowroy]

Just throwing this out there . . .

My '69 Beetle had a similar problem. It turned out to be a sunk float. It developed a crack and began to take on gas (causing it to sink) which prevented it from seating the float valve.
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[dave123]

bciesq - yes, thats exactly what i'm saying... screw the vol control screw in and engine speeds up... screw it all the way in and it runs fastest! WTF?

I'm not saying this is the cause of my problem - its just that i have a problem and this is an observation i made.

The float looked OK... i didnt immerse it in water or anything but it didnt have any fuel inside it when i took it off, and it is a brand new carb I checked the valve by blowing thorugh it then pressing the plunger, and it blocked off fine.

???

[[email protected]]

sounds like the idle jet is too big.

John
Aircooled.Net Inc.
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[dave123]

Idle jet is a 55 - was recommended to me for a 1600 sp - this sound too big?

Would it cause the volume control screw to play up? It came with a 50

[MetalKing00]

I used to have 30/31 on a 1600. It's been a little while since then, but I recall it having 2 screws for adjusting the mixture. One is the little tiny one for the fuel volume, and the other is the big one next to it for the air volume. Turning the big one in would make it run richer, turning the little one in would make it run leaner. Might that be your problem? It took me a while to figure out what the big one did, since I never had a real diagram for it until I bought a rebuild kit.

Hope you get it worked out

EDIT: I did a little lookin around and found this:

"The 30PICT/3, 31PICT, H30/31 and 34PICT/3 all have two adjusting screws in the left side (the smaller Volume and larger Bypass screws) and a fast-idle screw on the throttle arm. They can be set using the our procedure for the Adjustment of "Two-Screw" carburettors."

Taken from http://www.vw-resource.com/carb.html#brosol

I felt pretty sure there were 2 adjusting screws....

[dave123]

Yes, i have 2 adjusting screws.... the big one is doing its job fine, its the little one thats playing up.

I changed the 55 to a 50 and still have the same problem - the small one doesn't seem to stall the engine/slow it when screwed all the way in. I left it at 1.5 turens out and adjusted the speed on teh big one to suit.

It still takes some cranking and stamping on the acc pedal to get it started

[malley56]

Are the power jet and idle jet swapped? This carb comes with a 50 idle jet and a 65 power jet. They are both on the right side of the carb. The power jet(65) should be in the diagonal hole...The idle jet(50-55) should be in the hole that goes straight in to the side of the carb. If you have the 65 in the idle jet hole it would be pretty rich.

BTW I use a 55 in my 1600DP and it works great!

Hope this helps!
Mark

[hsosa1]

I have a similar setup 1600dp 009 dizzy h30/31 carb. with the lower temps. I have a problem with being in 4 then downshfting into nuetral. the engine cuts off. the car starts fine and idles. I figuare I need to run richer. what size jets can i adjust to? Im went over all the basics. Iam going to adjust the valves. this coming weekend.
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