International Lancia Forums

I'm reassembling the 35PHH carbs for my Fulvia, after installing new accelerator pump membranes and also bottom gaskets. This appears to have fixed the leaks I mentioned in a previous thread. But, I can't find any specifications for adjusting the accelerator pump levers.

It would be nice to get this right before I put the carbs back on the car, since the locknut adjustment looks virtually impossible to reach once they are in place.

Thanks,

Peter

The pump delivery is specified. For most Solexes it is 6 - 10 cc. I suppose this is for 20 strokes. See the specification for Dellorto's.

I have never done it, but I would start trying by making a test set up. Put the carbs in a horizontal position or perhaps better with the entrances 4 degrees up as on the car. Or try both positions.

Connect a fuel container through a hose and put the container above the carbs. The specifications say the height should be 3 to 3,5 meters, but I think less will do as the accelerator pump is at the bottom and its operation is not really influenced by float level. Best is to be exact and go for the 3 meters.

Flip the throttle 20 times and collect the fuel squirted from the pump injectors in a measuring glass.

It is not clear if the 6 to 10 cc is for one barrel or both. Since it says "pump delivery" in the spec I would I assume it is for both like for the Dellorto's. The difference is large enough to get a feel if it is for one or both barrels.

Be exact and suspicious. Put your test results on the forum for discussion before you put the carbs back on the car. I would appreciate photo's and a report for putting on the Q & A.

I think there is a very old thread on this forum related also to the adjustment of the pump levers. I remember measuring the distance from the nuts to the end of the lever for someone. This might be a secondary check.

On the Dutch forum there is (again) a thread about the time needed to prime the cars when the car has been standing for some weeks and possibly solving that by inserting an electric pump in series with the mechanical pump to prime the carbs with a push button.

It would be nice however to do some measurements to see why it takes such a long time. Is it because the fuel has to go through the 1,3 mm float needles? Or is it delivery from the fuel pump? Or something else?

When you have the test set up with the fuel container at 3 meters, please, measure how long and how many cc's it takes to fill an empty carb. Also see if you can measure the deliver of the fuel pump when the engine is operated by the starter. And measure the pressure of the fuel pump. If you do not have a pressure gauge put a transparant hose of 4 meters straight up and measure the height of the fuel column. I would be very happy if you can do the measurements with the fuel return line connected but closed and same measurements with the return line open. It may be asking too much but it would also be interesting to know if the level in the tank plays a role.

Huib, I would be happy to measure the accelerator pump output, but I'm not sure how I could accurately collect fuel from the outlet nozzles. As you know, they are deep inside the carb, just before the butterflies.

What I was hoping to find was a specification for pump lever travel, like this for the 40PHH Mikunis:

http://www.petercripps.com/Lancia/40PHH ... stment.jpg

I did check where the levers were set before I took the carbs apart -- dimension A in the above link was approximately 6mm. And the car did run well, with no hesitation when I floored the accelerator pedal, so it can't have been too far wrong.

Regarding the fuel pump output, I will measure how long it takes to fill a carb, and report back. But, based on how long it took for the engine to fire when the bowls started out empty, I would guess in the 10-20 seconds range.

Incidentally, I believe the rear carb fills first, followed by the front carb. This is because the hose outlet for the front carb is above the level of the intake for the rear carb. The return line is above both, so should not come into play until both carbs are full and their needle valves have closed. This ties in with what happens when I try to start the car with empty bowls: first, I crank and crank, then it fires, but runs roughly, as if only 2 cylinders were working. A short time after that, the engine smooths out and runs on all 4 cylinders.

I had a very similar problem with the Weber 40IDFs on my Fiat 124 coupe, although in that case I never did find the leak. My work-around was an electric pump; on the Fiat there was a pair of contacts on the ignition switch that closed just before the starter operated -- this was actually a Fiat design feature! I also had a relay that switched the fuel pump off if the oil pressure light came on. This all worked very well, but I hated wasting that fuel in the bowl -- even with cheap US gasoline prices!

Peter

A way of converting the 6 - 10 cc per 20 strokes to pump lever travel would be to measure the surface area of the membrane. Calculate the delivery per stroke en divide that by the surface area of the membrane.

I would prefer to measure the delivery itself though as specified. As I said I have never done it myself, but I have seen the test set up in carb shops from a distance although I have never seen the test being done.

I would expect the fuel coming from the nozzles would drip out the carbs at the end. You could try what is more convenient to collect. Have it drip out at the rear or at the front.

Alternatively if the supply of fuel is coming from a measuring glass you could measure it there. I like this idea. You could first measure how many cc's are needed to fill the bowl (and how long it takes (with the supply 3m higher than the carbs!!!)). Then count the number of strokes needed to use another 6 - 10 cc. If you need better accuracy you can double the figures.

I would appreciate that you split the measurements if you are measuring how long the mechanical fuel pump takes to fil the carb as I outlined in the earlier posting. I strongly suspect that the small float needle valves and the return line do play a role.

One of the reasons I like the Fulvia is that it never let's me down because there is almost nothing which can go bad. I have been in a business for many years where customers always wanted MTBF (Mean Time Between Failure) calculations for the products my company designed and manufactured, I have done numerous of those calcuations and know how quickly MTBF goes down if parts count increases.

Rather than adding an electric pump with wires switch, fuses etc I prefer to see if there is a solution which does not affect MTBF. But we have to know first exactly what the cause(s) of the problem are.

Huib,

Here are my results:

First, I measured delivery rate of the fuel pump with free discharge. After 10 seconds of cranking the starter, I measured just about 100cc of fuel in my collection vessel. This is with a fully charged, fairly new battery.

Then I checked float bowl capacity. This appears to be approx 75 cc, depending on what the intended level should be. Therefore, if the pump delivered its full capacity into both carbs, they would fill in about 15 seconds.

However, as you point out, there is possible flow restriction in the needle valve, and it’s also possible that some fuel goes back down the return line. So, I mounted the rear carb in position, connected the fuel line, and blocked off the feed to the front carb. I connected the return feed to a pressure gauge. Then I ran the starter for 10 seconds, removed the carb cover and checked the level. It was not quite full, although close. This seems to indicate that the needle valve restricts the flow somewhat, since if the full output of the pump was available, a single carb would fill up in about 7.5 seconds.

The pressure gauge peaked at approx 3 psi. The reading was not steady since the engine doesn’t crank at constant speed on the starter motor.

Then I emptied the carb, connected the return line, and ran for another 10 seconds, again with the feed to the front carb blocked off. The resulting level was about the same, *maybe* a little lower.

BUT, by this time the engine was not cranking as fast as at the start of my tests. So, any reduction in level could simply be due to the pump not running at full speed. In view of this, I don't think the return line makes much difference.

My overall conclusion is that if the float bowls are empty, we have to live with 10 to 20 seconds of cranking. But hopefully, I’ve fixed the leaks, so the bowls should remain full, at least if I drive the car every few days.

Oh, and I agree with your comments on parts count MTBF, and electric fuel pumps!

Peter

Many thanks, Peter

I agree with your conclusion that we have to live with 10 to 20 seconds of cranking, probably closer to 20 if the car has been standing for 2 weeks.

If it takes longer than 20 seconds I alway assume something is going wrong such as filters or fuel lines getting clogged or the valves in the pump are no longer fully closing. A good tool to diagnose early if a mixture might go lean and burn holes in pistons.

If it is less than a week it usually fires immediately. I never use the choke though but fast short pumps on the throttle pedal and start cranking near the end of the first pump stroke most of the time or near the end of the second pump stroke if the weather is cold. Since the accelerator pumps hold the fuel longest and fills first it reducs cranking time. Ignition and plugs have to be perfectly in order to be able to ignite a "wrong" mixture.

"I never use the choke though but fast short pumps on the throttle pedal..."

Excellent advice for all; Harry Manning used to say exactly the same thing. (For those who don't know, Harry was THE Lancia man in England until his death in 1989.

No one has mentioned 1600s in this thread; I have never measured the output of the pumps etc., but experience has taught me that there is only one setting for the pumps on a 1600: maximum!

It's strange, but despite their bronze spindle bushes, the aluminium 42mm Solexes seem to wear out much more than the Mazak 35s. Therefore many 1600s suffer from flat spots. If you can get good petrol or use octane booster, sometimes advancing the ignition a couple of degrees can help things along a bit.

Paul

20 Seconds of crancking will also get oil back into the engine, and lubricate the lot before the engine fires up. A good thing!
Bart

PS. Paul, I'm driving around now with lengthened lower wishbones (8mm), a 2000 berline stabilizer bar and a specially made 15mm one in the back. What a difference!

"PS. Paul, I'm driving around now with lengthened lower wishbones (8mm), a 2000 berline stabilizer bar and a specially made 15mm one in the back. What a difference!"

Well, Bart, I told you so.

What tyres are you using?

Paul