| Author | Message | ||
     John Rowney Experienced User Username: johnrowney Post Number: 150 Registered: 02-2015 |
In another thread I have outlined some problems I have had with my Solex 4A1 carburettor on my Corniche DRH32489. Recently it was running rich and blowing black smoke at idle after a while, and it was suggested that the float might have been too high. I took the Solex apart and adjusted the float level, but to no avail. I took it to a Mike Bushnell at Caloundra on the Sunshine Coast today, and one of the first things he noticed was that the float weighed 14 gm. We can't find any information regarding the weight of the float, but 14 gm looks very high for a float. Similar sized floats look like they weigh around 6 to 7 gm. Has anyone any idea of the weight of a new float, and where it would be possible to buy a new one. | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 830 Registered: 11-2017 |
Does the float have a flat or "hip roof"? The hip roof is the later one. This Solex was also used on Mercedes 280S in the early 70's.Also used on BMW's. https://e21.tricord.be/forum/view.php?view=788 | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 505 Registered: 07-2018 |
If the float was sticking because it's too heavy, thus not shutting the fuel off, there would be gasoline leaking out all over _ would it not ? There would be so much fuel flowing into the engine, I don't think it would run at all. Black exhaust (and fouled plugs) are a sign that the choke is stuck on, and/or the carbs are set too rich. If the float had a hole in it and it filled with gas, maybe then. | ||
| John Rowney Experienced User Username: johnrowney Post Number: 151 Registered: 02-2015 |
Hi Robert and Jeff. Many thanks for your responses. The float has a hip roof. I will have a look at the site. At idle, the car would run smoothly for a while then suddenly run rough and black smoke would pour out. Keeping the revs up would prevent the problem. The carburettor is slightly warped despite using the torques specified in the manual. I use a bicycle torque wrench to tighten the 8 screws down to 10 in-lb, and the 4 holding bolts down to 10 ft-lb. The carburettor repair shop is making some thicker gaskets to try to overcome the warps and we are trying to find a source of a new float before the Solex is reassembled. | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 831 Registered: 11-2017 |
The Solex 4A1 is a very finicky carb especially with float issues and idle. Have you checked the accelerator diaphragm? | ||
| John Rowney Experienced User Username: johnrowney Post Number: 152 Registered: 02-2015 |
Robert: Yes, I checked the diaphragm some time ago - it was OK. For an update - I have ordered a used float from the UK, and I think that it would be coming from Germany (Mercedes or BMW origin?) since the vendor has to wait 3 days before he receives it and sends it to me. The "new" float weighs 8.5 g, which is well below the 14g that the old float weighed. A rough calculation of the volume of the float comes out at around 20 cc, so with a petrol density of .75 g/cc the float fully submersed would displace about 15 g of fuel. ie the net buoyancy of the float would be about 1 g. With the new float this buoyancy would change to about 6.5 g. Therefore, with the new float, it is much more likely that the needle valve will shut effectively as the petrol level raises to a reasonable level. I reckon the float has most likely been the source of my troubles for over 18 months or so. I wait with interest for the float which may take a couple of weeks to arrive. I have also bought a second hand Solex 4A1 carburettor (ex Mercedes) from the UK. This should give me more than enough options to sort the problem out. However, I have had such a history of not getting things right on this car, I am prepared for the worst and something else might be causing the problem. Watch this space! | ||
| John Rowney Experienced User Username: johnrowney Post Number: 156 Registered: 02-2015 |
I have been on holidays and engaged with fixing my 1938 Wraith WXA68, so I have neglected my Corniche DRH32489. I am now back on deck and I can report the following. I measured the displacement of the float on the Solex and it was actually around 15 ml. So with a weight of 14 g it would certainly sink with a fuel density of about 0.7 to 0.75. Mike Bushnell made a thicker gasket for the Solex and I put everything together. It was surprising that after torquing the 8 screws and the 4 hold-down bolts the carby leaked. I checked the torque on all 12 screws and bolts for a second time and they were all loose. I retorqued everything and guess what? No leaks. I have had a couple of quick runs and the carby is a lot better. I purchased a multimeter with a rev counter, and have adjusted the idle to match the manuals revs at idle (650rpm). Everything seems good. I tried to use the CO meter to check the idle mixture, but was unhappy with the results. I left the idle mixture at four turns out on each idle screw, and will look at getting a tuning company to do a proper tuning with decent instruments. The timing done using a strobe and the rev counter was perfectly aligned with the values in the manual. I am going to the RROCA (Qld) AGM tomorrow which is about a 300 mile round trip - this might be a good test. If something adverse happens, do not expect a report - my wife will have probably taken punitive action against me. | ||
| John Rowney Experienced User Username: johnrowney Post Number: 157 Registered: 02-2015 |
I did 276 miles on the weekend. The car is a little rough on starting from dead cold, but is ok after about 30 seconds. It ran faultlessly with a variety of speeds on suburban streets and 100-110 km/h on the freeways. The Sunshine Coast Highway was its usual stop-start on Sunday afternoon, and the car ran beautifully. Looks like I have fixed the major problem - the float was too heavy. Whew! what a mission to find the problem - I am much relieved. | ||
| John Rowney Experienced User Username: johnrowney Post Number: 158 Registered: 02-2015 |
I forgot to mention in my post of 9 September that I replaced the bad float with the new one. Just went for a short spin today with a mate - he was impressed with how the car went, particularly since the last time he was in it, the Corniche stalled going down a gentle incline, and took about 5 minutes to get started and blew heaps of black smoke in the starting process. Hopefully this will be a thing of the past. |
