[RogerD]

Gradually working on getting my 1972 Euro market Berlina on the road. It has solex C40 DDHs and a mechanical fuel pump. The PO had it for many years off the road and only did minor work on it. I had the carbs serviced enough so it could be driven onto the transport 1 1/2 years ago. After some work I got it to start and run OK last week. Now it won't start. It will fire briefly on a good shot of ether starting flluid, so I assume I'm still getting decent enough spark and that timing didn't mysteriously change. I checked down the throats and there is no "squirt" in either carb when actuating the throttles, so I assume a fuel problem (plugs are also dry). There is fuel (with pressure) at the inlet hose from the filter and fuel in both float bowls. The needle valves work and the little filter screens are clear. I changed the fuel filter in the glass bowl and the fuel level is an inch or so up from the bottom in the glass bowl after cranking.

So, I have fuel into the carbs and in the float bowls, but it's not making it out into the engine, either through the acc pump or by engine suction. It fires on ether and it ran last week. What gives here? Any ideas? A solution that did not require two separate simultaneous failures of both carbs is more sensible, but the common elements (fuel pump, filter and lines up to the front carb) check fine, and there is fuel in both carb float bowls. It's acting as if there is no atmospheric pressure on top of the fuel in the carbs. The bowls must be vented, right? Any chance those could both be blocked? I'm tired of staring at this and could use another brain on it.
Thanks!

 

[ciscotex]

Roger,

Given the long time it has sat, and the quality of "fuel" we have masquerading as gasoline, I'd guess that the internal passages and/or jets are clogged. Best answer is rebuild the carbs. But as a quick check remove the jets and check for blockages and clean. I don't know Solexes so don't know if the jets are easily accessible, but that would be my next step.

You have fuel all the way to the float bowls, thus the problem is downstream from there. Gordon Raymond has posted in the past on filling the bowls with carb cleaner and letting them sit overnight to partially clean the carbs in situ. Please don't take these comments as instructions for the procedure, but search for his post.

Good luck and HTH,

Paul

 

[RogerD]

Thanks for the suggestion. I forgot to mention that there is fresh gas in the tank. And it did run last week.
I also figured out how the float bowls are vented to the atmosphere: through the air box... no obstructions there.

Just to check my troubleshooting: I should get a squirt of gas into the barrels when working the accelerator, right? Neither side does.

 

[ciscotex]

Yes, that's why I suggested clogged jets.

 

[RogerD]

Does anyone have a shop manual for these specific carbs? I have an exploded diagram in one shop manual, but nothing else. Nothing turns up on the web, either. Nice to have some guidance before I go mucking around in the guts.
NEVER MIND, Brooklands is coming out with a Solex book, available MAY 1. I've pre-ordered mine!

 

[DPeterson3]

If the fuel line is very old, and was stored dry, there is a good chance they've collapsed and/or are feeding crap down into the carb. I suggest you consider replacing the rubber hoses asap, and before going much farther, either remove the carbs for a good cleaning, or walk through the in-situ carb cleaner process.

Also, although I have a set of 40ADDH carbs out in my shop, I've never really studied them. I suspect they use a diaphragm accelerator pump. It is quite likely that they have perished after being stored dry for so long, then asked to perform regular duty with gasoline. If they are similar to other Solex accelerator pump diaphragms, they should be easily accessed on the bottom of the carbs after removing same from the car. I'd say those were highly suspect on the DOA list.

 

[RogerD]

The PO (who imported it from Italy, worked on it some, but never made it roadworthy) evidently replaced all the rubber fuel lines. They look fresh and the hose clamps are your basic 'merican parts store versions, not original, so those seem fine. I've got fresh gas in it now, a new filter in the glass bowl (old one was nasty and there was fine sediment in the bowl. The little cylindrical screens in the carb intakes are clear. The guy who got it running enough to drive onto the transporter replaced the acc pump diaphragms and other gaskets. And it fired up and ran 3 weeks ago. But not now.
Only thing I can do is check the float levels (although hard to imagine they changed on their own in the past 3 weeks) and clean the jets (although with the filter screens clean, it's hard to believe that the jets are fouled.) But there is nothing else to do.
I'd just like to be sure that I have eliminated "the one stupid thing I missed" before I go tearing into the carbs.

 

[Andrew]

It's in the interest of just what you say at the end there that I'd go through and verify the "objective" easy stuff like spark, compression, cam timing before digging into the carbs. It seems unlikely, but I've been caught out any number of times by such things, including having knocked a wire or fitting loose, etc.
Good luck, very interested in what you find.
Andrew

 

[RogerD]

Update

Wanting a second set of eyes on this before I started surgery, I enlisted a good Alfa buddy. We repeated what I'd done, finding the same thing: fires on ether so spark, compression and timing are OK. Fuel to the carbs and filling float bowls, but no gas squirting when throttle linkage actuated. As pointed out above, this looks like problems in the carb guts being blocked.

We were able to get the engine running, but just on the "enrichment" circuit. Depressing the accelerator leaned things out and it would start to die. Shutting off the enrichment would kill it too. So gas is at least getting out to the enrichment circuit, but not to the acc pumps or main circuit. If I can get decent diagrams of the circuits, I could figure out where the blockage likely is, I guess.

So although I logically preferred a common cause of the problem, rather than two independent failures, it does seem to be two gunked up carbs, the common cause being the same fuel. I guess I managed to get the last gasp out of it a few weeks ago when I got it to start, but not again. The gas although "fresh" looked like dark yellow urine, not gas. I had removed all but a gallon or so before I put in fresh gas, but now it looks like I need to empty the tank and start from there. And it's carb renewal time. As I noted in a post above, I had the carbs rebuilt when I bought it 1 1/2 years ago, but, my bad, I then let it sit, regunking things. So I'll be on the phone in the morning to Centerline for a rebuild kit. A lesson, not expensive in parts, but in time. But, hey, now I get to learn about my carbs!

 

[DPeterson3]

It may be something simple like a ball one-way valve that is stuck on its seat in both carbs. I haven't worked on ADDH carbs, but Solex likes little rising/falling ball one-way valves, and if they get stuck in place they don't rise and let fuel through. You might just try rapping on the carburetors with a little hammer (calibrated blows, of course) and see if one or both pop loose.

Don

 

[RogerD]

Just remembered that Centerline does not stock Solex kits, just weber and dellorto. I think my choice is probably Highwood, unless someone has a reference to a US supplier?

Yes, I see in my cross section diagrams some ball checks. Now I just need to find that calibrated hammer... hmm all my hammers are standard, do you know the metric conversion factor from ft-lbs to newton meters?

Maybe I'll give the Gordon Raymond insitu carb soak a try, first.

 

[DPeterson3]

Roger,

All kidding aside, just take a small hammer and tap anywhere that you don't think will do any harm. tap-tap-tap-tap. You might be surprised. I've had this work on other Solexes, and if you've confirmed ball check valves, I'm ready to double down on the bet.

If it works, you may not really need an in-situ soak. The fresh gas will tend to dissolve whatever is there. Maybe some carb cleaner in the gas tank wouldn't hurt, once you get them running.