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| 1920 accelerator pump question https://slantsix.org/forum/viewtopic.php?t=52886 |
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| Author: | dpstark2 [ Mon Jul 29, 2013 3:52 pm ] |
| Post subject: | 1920 accelerator pump question |
Guys, I don't know much about these 1bbls, but it seems like I should be able to figure this out. I'm having issues with the accelerator pump on my '71 Demon. I got this car recently. The carb needed work, among many other things. I rebuilt the carb, set the timing, and it worked great. It was like a completely different car. Then the accelerator pump stopped working. I could visibly see the diaphragm lever moving in super slowly, no gas coming out the squirter, and obviously it stumbled any time you moved the throttle. So I took it apart again, cleaned everything again, blew out all the passages... they seemed clear. Same problem... So I put on another metering block from another carb. Same problem. I tried another diaphragm and gasket and WOOHOO it worked. For a drive. Then it stopped again. Pumped it a few times by hand, and it finally let go and sprayed gas in my face. But I doubt it will work for long (again). There's no debris in the bowl, the filter is new, the carb is in great shape, the metering block seems clear, and the carb body is clear. Is there something I'm missing? For what it's worth, the car sat in a guy's garage for several years before I recently picked it up. One thing at a time, but it's running well aside from this issue. |
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| Author: | 64ragtop [ Mon Jul 29, 2013 8:05 pm ] |
| Post subject: | |
Sounds like there's still a piece of trash in a passage related to the accelerator pump. I've read of folks running monofilament fishing line thru the passages to push stuff out that blasts of carb cleaner and shop air have failed to dislodge. BC |
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| Author: | dpstark2 [ Tue Jul 30, 2013 9:24 am ] |
| Post subject: | |
I agree- I didn't have anything handy that would fish through those tiny passages. The next step is to put it in the ultrasonic cleaner over at a friend's place. Curious that it would clear/plug/clear/plug, repeat though. Compared to other carbs I've seen from these years, it seems to be in good shape, but you can't see inside the metering block. |
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| Author: | kxracer728 [ Tue Jul 30, 2013 11:41 am ] |
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Quote: but you can't see inside the metering block.
At the top of the metering block there are aluminum clean out plugs i believe that you might have to carefully drill into to remove. You might be able to get replacement plugs from this guy http://www.carburetor-parts.com Here are the links to two videos he has on youtube about rebuilding the holley 1920 Holley 1920 Carburetor Rebuild Part 1 http://www.youtube.com/watch?v=d-htTHAkBvc Holley 1920 Carburetor Rebuild - Part 2 http://www.youtube.com/watch?v=c1_BgrLEgrM On my holley 1920 the clean out plug on the metering block for the weighted check valve (that allows fuel from the accelerator pump into the barrel of the carburetor) had been removed so the fuel from the accelerator pump wasn't making it's way to the barrel and was probably going back into the float bowl... What i did was make my own clean out plug out of a bolt head that was slightly bigger than the hole and used my dremel to shape it and then tapped it in...other people on the forum may know of a good way to make clean out plugs You might have to remove some of the clean out plugs to see if theres any debri causing the problem...i would start with the clean out plug for the weighted check valve. I believe in one of the videos he shows you how and explains it I boiled my carb in a crock pot with anti-freeze for about 2 days before i put it back together with the rebuild kit...Also you might need to look at the accelerator pump springs and see if they are allowing the pump to move back and forth correctly |
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| Author: | crater [ Tue Jul 30, 2013 12:20 pm ] |
| Post subject: | |
I'm glad mine did not look that bad when I opened it up. |
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| Author: | dpstark2 [ Mon Aug 05, 2013 9:12 am ] |
| Post subject: | |
I re-checked everything very carefully yesterday after boiling the carb in an ultrasonic cleaner for half an hour. The cleaner definitely shook loose some dirt I couldn't get by hand. I haven't had a chance to run it yet. My much more experienced carb friend (and ultrasonic cleaner owner) seemed convinced the check ball in the accelerator pump discharge was sticking. I guess it's function is to keep fuel from being sucked out the pump nozzle under vacuum. It makes sense it could get stuck in gunk and keep the pump from working. Regardless, the carb is a lot cleaner now and I'll try it before I go pulling plugs out that are hard to replace. |
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| Author: | kxracer728 [ Mon Aug 05, 2013 9:24 am ] |
| Post subject: | |
Let us know how it turns out... |
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| Author: | Aggressive Ted [ Mon Aug 05, 2013 12:30 pm ] |
| Post subject: | |
If the economizer body is clean and the pump shot gasket hole has been enlarged, balls not sticking, both diaphragm pump springs in place, etc..... I have also had to clear the squirter entrance in the throat....sometimes that can oxidize and partially plug the opening for an inconsistent pump shot. I used fishing line about 10 pond test hard Mason leader material. Worked fine for awhile but eventually corroded over again at the exit (throat side), so I drilled it out. That was about 5 years ago. I think the hole was so small that the salt air may have corroded it shut. The pump shot is super healthy and has never corroded shut since. |
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| Author: | dpstark2 [ Wed Aug 07, 2013 11:23 am ] |
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One thing I was able to do up at the shop that I couldn't do at home was use these carburetor probes my friend has. We found the pump nozzle passage to be about .025". It's possible we dislodged stuff using these to probe the body too (this was pre-ultrasonic cleaning). Maybe that's too small and the corrosion is really bad in there? So far, the carburetor works great. However, it worked great for a day twice before! We'll see what happens when I drive it this weekend. I am interested in trying the Carter I have. Now the caveat- the body of it where the seat goes stripped. Threads came right out... And I didn't even gorilla it. This is sad because it looks to be in really good shape overall. So if anybody listening has a good body or parts carb for a '71 Carter BBS... feel free to let me know. It's been fun bringing this motor back from its neglected state. The car is currently very driveable (carb issues aside for now). The only remaining task is rear wheel bearings. Well, that and moving the fan closer to the radiator (there's a 2" gap now- no spacer). And a few more oil changes to flush it out. |
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| Author: | Aggressive Ted [ Wed Aug 07, 2013 12:07 pm ] |
| Post subject: | |
dpstark2, To keep the economizer body clean you may have to invest in a better fuel filter. Since your car sat for awhile, you can bet that the tank may have some pretty nasty varnish in the bottom. I know when I bought mine it had sat for several years with bad gas and trunk full of water collapsing the springs.... Something to consider........standard over the counter fuel filters still bypass a lot of debris..... I eventually installed a marine fuel water separator (filters out water and debris down to 2 microns) after the fuel pump, which was contaminated too... I just got tired of taking off the float bowl every few weeks to clean it out and respray out the economizer body. If it wasn't varnish, it was old black fuel line slivers and pebbles..... Since installing it, I have had no more fuel related carb problems. That was about 10 years ago...The Holley 1920 is an great carb, easy to work on, provides awesome power when dialed in and get's super good gas mileage. Click on the red link below to view photos of the fuel water separator. |
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| Author: | dpstark2 [ Thu Aug 08, 2013 1:48 pm ] |
| Post subject: | |
Ted- thanks for the pointers. You make a good case for changing the fuel tank in the future. I'm not sure where I'm going with this car, so I'm trying to not put a lot of money into it and just have a back-up-back-up car. Regardless, after I run this tank empty, I'll definitely change the filter again. I've only been through about a tank of gas at this point, and I'm sure it's pretty bad gas. Your pictures were very helpful! I love the chin spoiler/splitter and I may have to copy that for my Dart that is going to be my commuter.[/img] |
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| Author: | Aggressive Ted [ Fri Aug 09, 2013 6:24 pm ] |
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Quote: I love the chin spoiler/splitter and I may have to copy that for my Dart that is going to be my commuter.
Thanks, sometimes experiments do work out......I put that on to direct more air up into the radiator. However, on deeply rutted freeways it really calms the front end down. With new tires and new alignment my car would hook in the deep asphalt ruts. Now I can take it easy and not have the steering wheel wrenched out of my hands. So it provides a dual benefit. The fans run less and the car doesn't hook anymore. By the way I built one about about 18" wider just for fun....it goes from the inside of both tires......and really stabilized the front end. |
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