EmTee Posted July 7, 2022 Share Posted July 7, 2022 @Machine Gun, what is your float made from? Is it Nitrophyl? Link to comment Share on other sites More sharing options...
Machine Gun Posted July 7, 2022 Author Share Posted July 7, 2022 It's made from a black plastic-like material. It's very light and does not appear to be saturated with fuel. Two issues with the possibility of a bad float: first, the same problem existed with a brass float that was empty of fuel. Second, if the float was saturated, then the bowl would always and consistently overflow, not only after things dry out. Considering that I have a different float and the carb came back with a proper tag on it I believe that I got an exchange carburetor instead of mine having been rebuilt. Mysteries abound. 1 Link to comment Share on other sites More sharing options...
EmTee Posted July 7, 2022 Share Posted July 7, 2022 28 minutes ago, Machine Gun said: the same problem existed with a brass float that was empty of fuel. Interesting... Link to comment Share on other sites More sharing options...
Rusty Heaps Posted July 8, 2022 Share Posted July 8, 2022 If you’re resigned to live with it, be sure to have good insurance and don’t let your insurance agent see this thread! 2 Link to comment Share on other sites More sharing options...
60FlatTop Posted July 9, 2022 Share Posted July 9, 2022 Didn't try putting that spare fuel pump on, eh? Link to comment Share on other sites More sharing options...
Machine Gun Posted July 10, 2022 Author Share Posted July 10, 2022 I did not. I had forgotten about that, thanx for the reminder. It's on my to-do list for this week. Link to comment Share on other sites More sharing options...
Machine Gun Posted July 11, 2022 Author Share Posted July 11, 2022 @60FlatTop I installed the new fuel pump this morning. The carb puked fuel right on startup. I cleaned off the top of the engine, and less than five minutes later I restarted the car and all was back to normal. Same as always. NOW I'm resigned to live with the problem, unless I decide to use the A/C budget on a fuel injection system instead. Link to comment Share on other sites More sharing options...
carbking Posted July 11, 2022 Share Posted July 11, 2022 There is a reason, it just hasn't been found. I still think something is causing the float to stick when the bowl is empty. Suggestion, rather than clean the engine each time after a prolonged no-start: Try cranking the engine for maybe 3 seconds, wait a minute, 3 more seconds, wait a minute, then start the engine. Jon. 2 Link to comment Share on other sites More sharing options...
JohnD1956 Posted July 11, 2022 Share Posted July 11, 2022 54 minutes ago, Machine Gun said: NOW I'm resigned to live with the problem, Well, that is not a recommended plan of action. 99.9% of these don't do that. I left the .01 for your carb. Could the hinge pin for the float be bent? Or the holes it rides in enlongated such that the float gets tilted and stuck? Link to comment Share on other sites More sharing options...
JohnD1956 Posted July 11, 2022 Share Posted July 11, 2022 How about the airhorn gasket impinging on free float travel? Since it would seem that the float has to be non functional for this to occur what about any debris underneath the seat of the needle valve? Link to comment Share on other sites More sharing options...
Machine Gun Posted July 11, 2022 Author Share Posted July 11, 2022 20 minutes ago, carbking said: There is a reason, it just hasn't been found. I still think something is causing the float to stick when the bowl is empty. Suggestion, rather than clean the engine each time after a prolonged no-start: Try cranking the engine for maybe 3 seconds, wait a minute, 3 more seconds, wait a minute, then start the engine. Jon. I agree, there's a reason for everything. Today's episode makes me question the empty-bowl theory. I had the car running for several days in a row, with yesterday being the only day I didn't start it. The bowl would not have been empty from evaporation, yet the problem recurred with a bowl that would have had at least some fuel in it. What's different about today? I changed the fuel pump, and during that process the fuel in the line between the pump and the carburetor drained, but I don't see how that would have drained the bowl. As to the crank-wait-crank idea, I mentioned that a few posts ago. That seems to be my best recourse at the moment. Link to comment Share on other sites More sharing options...
Machine Gun Posted July 11, 2022 Author Share Posted July 11, 2022 12 minutes ago, JohnD1956 said: Well, that is not a recommended plan of action. 99.9% of these don't do that. I left the .01 for your carb. Could the hinge pin for the float be bent? Or the holes it rides in enlongated such that the float gets tilted and stuck? I agree that it's not a recommended plan of action, but that's all I have at the moment. BTW, this is the second carb that has done this, so maybe we're down to 99.8% and my situation represents 0.02% 😄 I made as close an examination of the needle, seat, float assembly, and gasket as I could and found nothing obviously amiss. Note that I used the term "obviously." 1 Link to comment Share on other sites More sharing options...
JohnD1956 Posted July 11, 2022 Share Posted July 11, 2022 Yeah,I figured you had done so. These are just WAGs (wild ass guesses). I have only experienced this once, on thec56, a d it was due to a non floatable float (solder seam broke). 1 Link to comment Share on other sites More sharing options...
carbking Posted July 11, 2022 Share Posted July 11, 2022 One other possibility: SOME of the fuel valves for Rochesters come with a spring clip that clips the valve to the float. The float has a small hole that looks like it was meant for the clip. IT IS NOT! If the clip is used, it should hang from the back of the float, not from the hole. Using the hole will sometimes cause the valve to hang midway when filling an empty bowl. Many mechanics and carburetor folks omit the clip. Jon. 3 2 Link to comment Share on other sites More sharing options...
EmTee Posted July 11, 2022 Share Posted July 11, 2022 Another WAG - your needle has a rubber tip, so the seat should just be brass, right? I have seen some that are the opposite; metal needle and rubber seat. Could the seat be the wrong type for the needle? Link to comment Share on other sites More sharing options...
Machine Gun Posted July 11, 2022 Author Share Posted July 11, 2022 @carbking I'm familiar with the clip you referred to. Neither of my 2GCs with the problem had a clip. @EmTee The tip is rubber, and the seat is brass. @JohnD1956 Any and all WAGs are welcome. I'm fresh out of likely causes, logical ideas, and I may have used up all of the available WAGs. I appreciate all of you who continued to scratch your heads over this. It might have been less of a mystery to me had the problem been with only one carburetor, but the one in there now that worked fine for two years was a rebuilt exchange. The only common thread that connected both carbs was the fuel pump, which is why I changed I changed it out at @60FlatTop/Bernie's suggestion. I didn't think that was the problem, but as I'm fond of saying, "If you don't know what the problem is, you don't know what it isn't." I'm actually glad that Bernie made the suggestion. I have a bit more room in the trunk without the spare fuel pump, and it was better for me to swap out the crusty old one in my garage instead of in some parking lot somewhere. 1 2 Link to comment Share on other sites More sharing options...
EmTee Posted July 11, 2022 Share Posted July 11, 2022 Hmmmm, still thinking... 1 Link to comment Share on other sites More sharing options...
60FlatTop Posted July 12, 2022 Share Posted July 12, 2022 Well, you eliminated one easy variable. Interesting about wiping off the engine. Have you ever had someone crank it or used a remote starter button and watched it puke? Is there a shrouded vent on the float bowl or does it spew from the vent tube in the air horn? Does the spilling appear to be under pressure in a stream or more like a bubbler? Is the carb front feed or side feed, were both the same, were both carbs correct for the engine? In my garage you might find I moneyed around and swapped an air horn for some reason. Is the air horn and bowl cover the correct one for the body? Is there a brass screen or porcelain filter missing from the inlet? If you blow into the inlet and manipulate the float with your fingers does it seem alright. Your breath won't give you 2-3 PSI but one step deeper could be a loose electric pump to make a dangerous mess with. Remember when I mentioned TEE-ing off with a fuel pressure gauge. It may be time. You are at the fun part now. My experience tells me you need to deeply evaluate all the work you can think of that others (and yourself) have done on this fuel system. Someone did something that is defeating logic. Someone like me who tends to oversimplify carburetors and just calls them "a pot of fuel on top of the engine". You know the type. Had all the parts lying there, shrugged, and confidently "made it work". My departed friend, Mike, got a couple of cars from me and had to have them serviced in shops. They'd call me and ask things like "Why does that '94 Roadmaster have a '68 Chevy starter in it and wadoo you mean the resistor in the key doesn't matter". That type will drive you nuts. 3 Link to comment Share on other sites More sharing options...
Machine Gun Posted July 12, 2022 Author Share Posted July 12, 2022 (edited) @60FlatTop It pukes from the shrouded vent on the bowl cover. I've seen it puke. It's a bubbler. Both carbs were visually identical. The one that came with the car was an AutoZone rebuilt that had no ID tag on it. The replacement is a 7024046, the correct one for a '64 Skylark V8 with auto trans. The carb is front feed with no inlet filter. Too late for the blow thing...the carb is back on the car. I agree that a pump pressure test would be a worthwhile effort, but I'm not sure what the result would tell me. For example, if the pressure is higher than spec, then what can I do about it? It'll be the second "correct" pump for the car. Remember, this problem is intermittent, and only occurs under very specific circumstances. I would think that an overzealous pump would give me fits consistently. Regardless of what I think, I'll do a pressure test to see if that reveals anything. I'll let you know what I find. Edited July 12, 2022 by Machine Gun Unintended implication. (see edit history) 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted July 12, 2022 Share Posted July 12, 2022 Not after you clean the old "known working" pump and put it back in the trunk for a spare. 1 Link to comment Share on other sites More sharing options...
carbking Posted July 12, 2022 Share Posted July 12, 2022 Somehow, I missed the fact that you have had TWO carburetors with the same issue. This points to a fuel pressure problem; and the pressure test is very important. Item: we have tested "new" pumps in a U.S. company box which were made in China with fuel pressures north of 10 PSI. No way will a fuel valve and float hold this pressure. Item: there was (maybe still is) a vendor who rebuilt fuel pumps and sold kits whose philosophy was that if the part fits then the part is correct. The wrong diaphragm spring will effect the output pressure of the pump. So this thread is not deleted, will not mention the name; but telephone calls don't get threads deleted. Since I do nothing with fuel pumps, I see no conflict of interest in sharing this information. Jon 2 Link to comment Share on other sites More sharing options...
old-tank Posted July 12, 2022 Share Posted July 12, 2022 3 minutes ago, Frank DuVal said: Not after you clean the old "known working" pump and put it back in the trunk for a spare. Any pump that has been in service and removed and allowed to dry out is junk. The diaphragm will be hard, crack and leak. Hopefully it leaks externally instead of dumping 2 gallons of gas in the crankcase. (personal experience) 1 Link to comment Share on other sites More sharing options...
Machine Gun Posted July 12, 2022 Author Share Posted July 12, 2022 I just completed a pressure test through a tee fitting. At high idle the pressure reads 6 psi. That's 14% higher than the maximum spec of 5-1/4 psi, and 50% higher than the minimum spec in the manual that calls for between 4 and 5-1/4 psi at the carburetor inlet. Fourteen percent doesn't sound like much, but perhaps it's enough to cause me grief. What say you all? Link to comment Share on other sites More sharing options...
Bloo Posted July 12, 2022 Share Posted July 12, 2022 It sounds like too much to me. 1 Link to comment Share on other sites More sharing options...
EmTee Posted July 12, 2022 Share Posted July 12, 2022 2 hours ago, Machine Gun said: I just completed a pressure test through a tee fitting. At high idle the pressure reads 6 psi. This is for the 'new' pump. correct? It would sure be interesting to see what the old one was doing... Maybe the issue is with the fuel pump sitting idle for a few days - not the carburetor! Is it the spring in the fuel pump that sets the pressure? If so, I wonder whether there are any removable shims involved... Link to comment Share on other sites More sharing options...
Bloo Posted July 12, 2022 Share Posted July 12, 2022 (edited) Yes it is the spring that sets the pressure. To be clear, this is the coil spring behind the diaphragm, not any other spring like one you might see pushing on the arm. The laws of nature make the pressure what it is. "Pounds per Square Inch" in this case boils down to the area of the diaphragm in square inches, and the force the spring provides in pounds at it's installed height. Edited July 12, 2022 by Bloo (see edit history) 1 Link to comment Share on other sites More sharing options...
carbking Posted July 12, 2022 Share Posted July 12, 2022 I think you just found the problem. The fact that is close probably is why your issue is intermittent. Jon 3 Link to comment Share on other sites More sharing options...
EmTee Posted July 13, 2022 Share Posted July 13, 2022 So, can the pump be modified to lower the pressure, or is the only practical solution to add a pressure regulator ahead of the carburetor? Link to comment Share on other sites More sharing options...
Machine Gun Posted July 13, 2022 Author Share Posted July 13, 2022 @Bloo Yes, I guess it's high enough to be problematic, but not all the time. @carbking seems to think so, too. @EmTee The fuel pump is a new Korean-made Carter. It's crimp-sealed, and so the innards are not accessible without destroying the pump. Not modifiable, unfortunately. It does indeed seem like the fuel pump pressure is indeed the problem. I'm glad that @60FlatTop suggested changing out the fuel pump. I would not have thought to try that. Unless someone has another idea, I guess the most practical solution would be to install an external pressure regulator. Trying another fuel pump would probably be a crap shoot, hoping to find one with a lower pressure. 1 Link to comment Share on other sites More sharing options...
Bloo Posted July 13, 2022 Share Posted July 13, 2022 Beware cheapo pressure regulators. There are some out there that do not do what they claim. Link to comment Share on other sites More sharing options...
Bloo Posted July 13, 2022 Share Posted July 13, 2022 (edited) 55 minutes ago, Machine Gun said: Unless someone has another idea, Back when the 2GC was in vogue, most cars had pumps that were about 4-5 PSI. Really old cars maybe had 2-3 PSI. 6-7 PSI pumps were available, mostly for hot rodders, probably looking for more pressure to combat boiling in the lines or the pump. Maybe those were higher volume pumps too. Probably they were. If I remember correctly there wasn't usually a regulator, but sometimes there was. On a Holley double pumper (and similar carbs) there are little plugs to check the float level, and you can adjust to account for the higher pressure (and SEE where the level is). At least you can if the difference is not too much. I vaguely recall setting up a Carter AFB or two to deal with that. Not as easy, but not impossible. If we make the grand assumption that the float valve is even capable of shutting off reliably at the higher pressure (maybe, maybe not), and we know the fuel pressure is too high, then we also know that the float level is too high. The leverage of the float on the float valve and the spring in the fuel pump fight each other. It is a balance. If we make a bunch of other assumptions like: 1) The float valve is a rubber tipped one. 2) The float valve is not damaged, scored, cracked, and is preferably new. 3) The float is good, tested, and completely beyond reproach. Preferably it is brass. Plastic ones must be weighed to verify. They don't "look" bad. Brass needs to be sunk in hot water. Look for bubbles. 4) The float level and float drop are set properly. 5) The clip is present and installed properly. 6) The pivot holes on the float pin are not too tight, not gummy, and do not bind in any way. 7) You can turn the float and valve right side up and upside down a bunch of times and it never sticks, binds, gets out of sorts in any way.... Then I would try lowering the float level 1/8" and see what happens. Edited July 13, 2022 by Bloo (see edit history) 2 Link to comment Share on other sites More sharing options...
EmTee Posted July 13, 2022 Share Posted July 13, 2022 21 minutes ago, Bloo said: ...and we know the fuel pressure is too high, then we also know that the float level is too high This is because the higher pressure allows more fuel into the bowl before the float can react and shut the valve? 1 Link to comment Share on other sites More sharing options...
Bloo Posted July 13, 2022 Share Posted July 13, 2022 Yes. 1 Link to comment Share on other sites More sharing options...
Machine Gun Posted July 13, 2022 Author Share Posted July 13, 2022 @Bloo Thank you for the list of assumptions. I've covered all of them in recent days with the following exceptions: #3 - The float is not brass. I did not weigh it. #5 - There is no clip installed on the float arm. At this point the consensus seems to be that the fuel pressure is too high for the 2GC. It makes sense to me to get the fuel pressure within spec before I continue to blame the carburetor and start messing with it. I'm looking at Holley fuel pressure regulators right now. 1 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted July 13, 2022 Share Posted July 13, 2022 (edited) 17 hours ago, EmTee said: So, can the pump be modified to lower the pressure, Yes, cut the spring. Corvair owners do this to correct the new pumps. One enterprising individual will sell a spacer block to space the spring "closed" length longer. But crimped pumps are more difficult than the screw together pumps.... Ha! Need much tooling, so not practical. Those numbers on typical pressure regulators do NOT correspond to PSI, just a scale the manufacturer cast into the housing. Adjust to make the car perform, not to a set number. Edited July 13, 2022 by Frank DuVal (see edit history) 1 Link to comment Share on other sites More sharing options...
Machine Gun Posted July 17, 2022 Author Share Posted July 17, 2022 I installed a Quick Fuel (Holley subsidiary) dead-head fuel pressure regulator this afternoon and reduced the pressure down from the 6 psi that my fuel pump was delivering to 5 psi, which is near the maximum recommended spec of 5-1/4 psi as noted in the service manual. The hardest parts of the install were deciding on a mounting location and sourcing the brass fittings. Because it's a dead-head unit I wanted to keep the regulator as far away as practical from the hot parts of the engine. I fabricated a bracket and hijacked two mounting studs on the power steering pump. Here's hoping that I solved the problem once and for all. I only ran the engine once so far with no problem, but due to the intermittent nature of the problem I'm not ready to celebrate with my best Scotch and cigar. It'll be a glass of Jack and a second-string cigar this evening. My thanks to all who took the time to offer suggestions. 2 Link to comment Share on other sites More sharing options...
EmTee Posted July 18, 2022 Share Posted July 18, 2022 Anxious to see whether this solves the problem. Jim, will the regulator go below 5 psi if need be...? It looks like Part # 30-803QFT will go as low as 4.5... Link to comment Share on other sites More sharing options...
Machine Gun Posted July 18, 2022 Author Share Posted July 18, 2022 9 hours ago, EmTee said: Anxious to see whether this solves the problem. Jim, will the regulator go below 5 psi if need be...? It looks like Part # 30-803QFT will go as low as 4.5... Yes, it's the 30-803QFT so I can supposedly go 1/2 PSI lower if need be, although I didn't adjust it down below 5 to see if it would indeed go that low. The literature states that it comes from the factory set to 6.5 psi, but the gauge read only 6 on initial startup because that's all my fuel pump puts out. I took it for a test drive around town yesterday to ensure that the regulator worked properly and didn't leak. It worked just fine under varying load conditions. Today is radiator day. The replacement three-row arrived yesterday. The tanks are a bit wider than the stock radiator, so I will likely have to play with the mounts. 1 Link to comment Share on other sites More sharing options...
60FlatTop Posted July 18, 2022 Share Posted July 18, 2022 Benny Hill did a skit a long time ago and he was reading a music album, and one of the songs was read by the buxom blonde, "Whats this thing called, love." (The song title has no comma.) It's odd, the things that bring back old memories. 1 Link to comment Share on other sites More sharing options...
Machine Gun Posted July 18, 2022 Author Share Posted July 18, 2022 I remember that sketch well. Benny Hill was a master of sight comedy and innuendo. I have a DVD set of his shows. Link to comment Share on other sites More sharing options...
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