Leaking carburetors on a 1974 1.3s

[ThomasW]

Hi everyone,

Last weekend I went to take the car out of the storage for a spring run, but I didn't drive more than 10 metres. The car fired up after its usual 20 second turnover but fuel smell was noticeable immediately and a nice trace of fuel was on the floor behind me.

I pushed the car back in its place and a quick look learned that it was coming directly form the carburetors and the leaking pan underneath was filled to the rim and dripping down the side of the engine. It looks like the gaskets around the accelerator pumps are leaking may be due to the fact that the hadn't run all fall/winter and the gaskets dried out, but it was just a first guess.

The Q&A section tells something about leaking carbs, also saying right away it can have several possible causes. I checked the barrels and fuel is squirted in nicely in all four barrels. So no blocked nozzles?

I am a bit confused about the possible cause, anyone has an idea where to start looking?

[bmarler]

i'd pop the tops of the carbs off to make sure your floats aren't stuck. the fuel could be coming out of the vents and running down to the pan while hidden from view. if that's not it, it still could be an accelerator pump failing, just not bad enough to stop the pump from squirting in the barrels.obviously, leaking carbs are dangerous, so i'd find the source before starting the motor again.

[ThomasW]

Thanks for the tip! I'll have a look at the floats first.

My plan was to pull of the carbs anyway to do some checking/cleaning and may be do a revision. But first things first and find the problem before starting so I can drive it again.

Anyone else experienced this? Is it likely that the floats get stuck after a period of non running?

[ThomasW]

I have checked the floats and chambers, they are moving freely and the chambers are nice and clean. When taking a closer look at the barrels it seems that the near side carb in squirting slighty less stronger than the front carb. Can this indicate something?

As for now my next job will be to take of the carbs and do an inspecting on the bench with proper light.

You said fuel can leak trough the vents, where exactly are these?

[bmarler]

certainly if one carb is squirting less than the other there may be either restriction of the output or damage to the pump diaphragm. if it is a damaged diaphragm it is likely to be the cause of your trouble. you may be lucky and just clean and put a kit in the carbs and be fine, but i'm here to tell you, rebuilding these to be perfect can take some doing.with the good advice of another lancia owner i've just done a lengthy revision of a set of 35phh2 that i haven't mounted on the car yet. this took a considerable amount of time and some precision equipment. if there is play in the throttle shafts you may have to deal with that to really get them right. i bored the carb bodies to accept small roller bearings and added vacuum ports for syncing each barrel after the butterflies. the small check ball seats in the body may need a little polishing as well to get them to seal well and ensure that both barrels are receiving the same amount of fuel from the accelerator pump. i actually had to make a small tool to re cut the seats in one carb as i couldn't get the output i wanted. you should get a small graduated tube to measure the pump output to be sure you have it set right. i know this may sound like a lot, but i believe it's worth it to achieve the best performance.
when i was new to lancia, i just put a rebuild kit in the carbs and thought i was ok, but after some time, i realized that things should be better, so i went down that road. but again, if your carbs don't have much wear, you might just clean and put new gaskets in and be just fine.
good luck!
brian

[ThomasW]

It's been a while since I had a change to work on the carburetors, but I have opened them up in the meanwhile and gave them a clean where necessary and blew trough all the nozzles. They where actually very clean throughout however the pump diaphragms did not look that well and I have the suspicion that one is indeed leaking.

Since the carburetors are of the car I decided to fit a new gasket set while I am at it. In the kit there are two small black O-rings per side and I don't know where they should go. It surprises me that they are in the kit because I did not find any of these O-rings in the carburetors while doing the taking apart and cleaning... Does it make a difference when they are not fitted?

Does someone know where they should go??:)

[bmarler]

i wouldn't worry about the extra o rings. many times there are extra parts for different variations of carburetors. i don't know exactly how many variants of the c35 exist, but there are many.

[ThomasW]

Ok, I wont worry about it then

[ThomasW]

Well, the leak is still there, on both sides?tt?. After a close inspection I found out its still coming from the gaskets around the pumps. Its most likely that the the surfaces aren't flat. So next job to do...smoothing these.. Otherwise I cannot imagine why its leaking after fitting new gaskets..

What amount of force should be used for tightening the screw of the pump bodies? I closely followed the advice from the Q&A not to over tighten any of the screw on the carbs in order not to bend or warp anything. But may be they can be set a bit more tightly in order to prevent leaking?

[bmarler]

those are very small screws and don't require much torque to set. they're pretty strong though, i don't think i've ever stripped one out. usually i have more trouble taking them out than putting them in. whenever i have worked on these pump castings, i put a piece of fine sandpaper around a flat file to dress the mating surfaces.
on the latest set i worked on there were two different gaskets in the kit for the pump mounting. the thin red one didn't provide an adequate seal so i used the paper one. it was a very tiny amount of weeping, and i'm sure it wouldn't have been a problem but i'm a bit fussy. i don't know if that's an option for you, but it worked for me.