Dellorto problem. disaster averted, garage reeks of fuel Options

[rhodyguy]

all set, ready for fire up, energize the pump (didn't spin the engine) and the pump doesn't quiet down (cb carb pump) as the bowls fill as it did with the webers. i look over and there's a thin fountain the coming up and fuel welling thru the square in between the main stacks on the dr side carb. puddles on top of both of the throttle plates.

the pass side has the duel banjo fitting. fuel supply line connects to one fitting and the other fitting is supposed to supply the dr side eliminating the need for a 'T". does it make any dif which fitting gets the pump supply and which one connects to the dr side carb? top fitting as opposed to bottom. the dellorto book mentions the dual banjo but doesn't specify if it makes a dif where the lines are/how hooked up.

i had just changed out the oil so i know the 3 1/2 quarts of BP will get dumped. any ideas?

k

[FourBlades]

This happened to me twice when my float valves would get stuck open.

Usually when assembling the carb they get hung up somehow and can't close.

I was lucky because I noticed it to before firing the ignition.

Always check for this when you have had the float plate off the carb.

John

[rhodyguy]

i was lucky not to have tried to start it. this was just the prestart pressure check for fuel leaks. i found one. just switched the lines over, same show that's eliminated. carbs were supposed to have been freshly rebuilt @ ACE, hardly any miles on them and came with the green car. can i get away with using the same gasket under the top plate? so remove the 5 screws and the plate lifts off? any need to pull the main stacks? what was the solution during the 3 fix? the float hangs up or the valve itself is stuck wide open? i really don't want to go back to the webers at this point.

k

[DBCooper]

does it make any dif which fitting gets the pump supply and which one connects to the dr side carb? top fitting as opposed to bottom. the dellorto book mentions the dual banjo but doesn't specify if it makes a dif where the lines are/how hooked up

No, it makes no difference. Once you get pressure the whole system is pressurized, and then fuel flows to where it's needed, in other words where the float has opened a needle valve. If your bowls overflowed it's almost certainly a stuck needle valve, as John mentioned. Can be any number of things, usually a bit of lint or grit in the valve seat that doesn't let it fully close and stop the fuel flow.

[nathansnathan]

I had this same thing happening after about a year running carbs that had been rebuilt by Gabriel off ebay on my drla 40s. It ended up being a "heavy float". You could see the outside of the float had been compromised and it was absorbing fuel.

I also noted some stiction in the springs in the plungers of the needle valves. Though Gabriel's worn out bits were worlds better than what you may find in a cb performance rebuild kit, you can get the real deal, a viton-tipped dellorto oem INC needle valve from Dellorto uk along with a new float or 2.

Don't listen to the people who want to talk about their 'Dellorto drip'. That is in every thread about Dellorto problems, someone saying, "yep, the Dellorto drip...".
(IMG:style_emoticons/default/rolleyes.gif) (IMG:style_emoticons/default/smile.gif)

[rhodyguy]

took the top off. big goober of debris was lying on the shelve in the float bowl. put the top back on, turned key to the first position to energ the pump and no puddles. but, now it won't spin (coil lead off). stater engages but the rotation doesn't happen. over 12 v on the bat. i'm going to pull the plugs on the offending side a see if it might be hydro-locked. back in a few.

[rhodyguy]

while i'm under there...turn the key to the first position-turn off and i hear a click from the rear. it's been so long...does the small red with go on the same stud? it's one off those aftermarket hi torque jobs. small red on the stud on the back of solenoid? back in a minute after i pull the plugs...

edit-floats are plastic and have dellorto on them. no sign of fuel coming out of them when the top was off. back in a minute....

[rhodyguy]

plugs out and it turns over nicely. briefly, all i wanted to see. i'll give it some time to evap the fuel and drain the fresh today oil. maybe call it good for a few hours. still enough time to avoid the subaru syndrome on thurs.

[rhodyguy]

a portion of the crap that was in the bowl. was about twice as big kind of a chalky substance. hard but not like a rock.

[sixnotfour]

Carb Stone, It wont pass though..

[rhodyguy]

seriously? if the coil had been hooked up and the engine fired up it could have been a nightmare. note to self...contact Fire Safety Supply and get an extinguisher.

[ThePaintedMan]

If it was completely hydrolocked, it wouldn't have started anyway (at least I don't think). Back in high school I had an 84 Thunderbird which came with TBI that I converted to a Holley carb. Of course this is before I knew that carbs had to have a LOW pressure pump... and that the car would automatically try to keep pressurizing the system even when it was off. I ended up with an engine completely full of gas and after once crank, it wouldn't budge an inch further. (IMG:style_emoticons/default/headbang.gif)

Drained the gas, and oil and after it did it AGAIN, I figured out the problem. (IMG:style_emoticons/default/smile.gif) Long story short, it never ignited (whew).

I have had the same problem as you and John though Kevin. Glad you found the debris, but sometimes they just get stuck. Everytime I reinstall carbs I give momentary 12v power to fuel pump while rapping on the side my Webers, on the steel block-off plate to get the floats to unstick. It's worked so far and IMHO, just worth doing anyways to avoid a big fuel spill.

[nathansnathan]

Hydrolock will definitely happen, cylinder is filled with fuel. You can turn it over with difficulty by hand and then the starter will be able from there. -Did this a few times when I had to get to work - would be worse when I parked nose-down. Depends on which carb it is, though, with regard to that. (IMG:style_emoticons/default/smile.gif)

[rhodyguy]

nathan, thanks for the tip about dellorto uk. other than the one piece of junk the bowl was clean.

[DBCooper]

You didn't mention the needle valves. You say except that one piece of crud the bowls were clean, the needle valves too? When the tops of the carburetors are off you can hold the tops up level, let the floats dangle. and raise the floats up until the needle valves close, watch the action. Then you can action the needle valves manually, feel them to see if they're sticky, if they hang up for any reason. No problem there? And with the floats off, needles out, looking down into the seats, nothing?

Those valves are what control gas coming into the carbs, managing the fuel level in the bowls. If there was overflow they pretty much have to be involved, for some reason didn't close and shut off the fuel flow. You may have already dislodged anything that was keeping them from closing, but you need to be sure. Probably need to look at your fuel filter too, since that crud in the bowl means something isn't working as intended.

[rick 918-S]

Kev,

You may know this already but when viewing the float and needle valve assembly be careful not to change the float contact to the needle. The float height shuts off the fuel flow. This height is important. You can take some carb cleaner and shoot it through the needle and seat assembly with the float dangling. When carbs sit they will often dry up. the fuel will leave a chalky residue. With the float bowls dry this causes crud to form on the open needle and seat. You have to be sure these are clean or the float won't be able to close the needle as the fuel rises.

[rhodyguy]

thanks rick. i checked the float/valve action when i took the top off yest. the valve operates freely as does the float swing. no sign of the floats full of fuel. whether the float height is correct, is uncertain. when i reinstalled the float plate and powered the pump up the crisis was gone. thomlinson' del book is not as comprehensive as the weber one. at least to me. i'll be buttoning up yesterday's take apart in awhile, bolting the triad up, and we'll see how things go. i haven't been this excited about the 73' in a loooong time.

[FourBlades]

The thing which caused my floats to hang up was the 90 degree arm that goes down and controls the float range of motion. If the float arm got cocked up it was this lower arm that would get stuck and not let the float move up and close the needle valve.

I am sure this makes no sense unless you have taken a weber or dellorto apart.

I caused this problem when bending this lower arm to reset the open versus closed height of the float. Make sure your float can still move correctly after adjusting it.

BTW, these heights were wrong on 2 sets of carbs I got in the mail. The floats bounce a lot in shipping with no fuel to cushion them leading to them being out os spec. (I think McMark id-ed the cause of this problem). If the float levels are off then you run leaner or richer than you should and it makes tuning harder.

John