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DCJ 306 Carb Questions


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36 replies to this topic

#1 Dan-AZ

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Posted 27 April 2013 - 01:50 PM

OK. On top of fuel pump issues, I have questions concerning the carb on my 1979 GL Wagon. It seems I am leaking fuel to some degree down the inlet valve on the bottom of the bowl. I checked my fuel float level after 3 days and it dropped quite a ways down. It then takes 5 to 10 seconds of engine cranking to get enough fuel into the bowl to start and run the engine. Here are some questions I have in anyone can answer them:

1. This shouldn't cause a bad fuel pump should it? The fuel pump works and it fills the bowl as needed once I have the engine running.

2. What would cause the inlet valve to leak? Can I fix it without tearing the whole carb apart?

3. Where does the gas go while it leaks through this valve? I don't smell gas at all when she sits.

 

I don't want to tear apart the carb anymore if I don't have too.

 

Any ideas here?



#2 vwBrat

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Posted 27 April 2013 - 08:03 PM

I have an 80 Brat.  I think I have more junk on my carburetor but other than that they should be similar (Again I think).

 

The float valve is on the top, so no way anything could leak down from that.  The main jets are on the bottom, and have access plugs on the bottom of the carburetor.  The access plugs could leak as they are on the bottom, but I don't think it's likely they would just start to leak on their own without having been messed with.  I think the ports from the main jets went up in the carburetor, so would not leak fuel out of the bowl.  The accelerator pump has a fill port at the bottom, but again goes to the top so should not leak without something drawing fuel to the top of the carburetor.  Some carburetors have a power valve that goes into the bottom of the bowl.  Mine doesn't so I can't say where that goes.

 

The top of the carburetor can be removed without removing the carburetor from the car.  It gives access to much of the inside of the carburetor.

 

The sight glass on the side of the float bowl is a very possible source for a leak.  I am not sure how to fix, or if it really can be fixed at home.

 

If filling the float bowl could ruin a fuel pump, then driving the car would ruin it.  I don't think that is a source of fuel pump trouble.  If it's an electric pump a few seconds with the key on before you try to start the car should fill the bowl even if it's empty.



#3 Dan-AZ

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Posted 27 April 2013 - 08:14 PM

The leak is a mystery. I am not sure where but it definitely drops. I had a bad groud on the fuel pump so I hope that solves the issue. This one is a tough one to solve; other than the leak she runs great. Gonna do a tune up in a week so I am not sure what's up.



#4 mikaleda

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Posted 27 April 2013 - 09:10 PM

In the other thread about your fuel pump you said your milage hasn't gone down, like vw brat said unlikely the carb will be the problem with your pump

#5 Dan-AZ

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Posted 27 April 2013 - 09:16 PM

The car is running just fine, but the loss of another fuel pump has me worried about being stuck out somewhere.

#6 talldude

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Posted 28 April 2013 - 11:58 AM

This situation will not harm your pump.  Make sure all your fuel hose clamps are tight not allowing air into the system.  I have had a very slow leak at the sight glass gasket, no fuel smell because it is a small seep.  This will empty the float chamber over time requiring the fuel pump to fill the line/chamber before any fuel gets out into the intake when you go to start it after even overnight.  You could also put a wrench on your main jet plugs (bottom of the float bowl)  in case they are seeping, but the sight glass gasket doesn't come with any overhaul kit I've ever seen, so you might have to send it out for repair.  National carburetor factory has these shipped for around $240, make sure they jet it for your altitude; mine came too rich for 4000 feet I live at.  Honestly,  it was worth the $ knowing I had a rebuilt tested carb,  but I also have to pass smog checks here...



#7 moosens

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Posted 28 April 2013 - 04:09 PM

Thanks ! I might send one out to National now. I'll search when the time comes but if you can post a link that might make a few people happy.

The glass sight needs to be glued in , doesn't it? I don't recall a gasket there or easy way to remove it - can't picture any retainer.

Btw I just re-kitted mine last year and the boot on the accelerator pump is shot already. The rubber looked and felt great but you know it's a 30'year old kit , or close to that. Ticked me off but that life with an old car.

#8 Dan-AZ

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Posted 28 April 2013 - 05:27 PM

I checked all the hoses from the tank to the carb. They are fine and I put new clamps on them all. When I tune her up in a week, I am replacing all the hose from the firewall to the carb. I guess the bad ground was more of a headache than I thought. I have a good solid one this time. Rock Auto has rebuild kits for the carb if there are any souls out there that want to rebuild their carb. My boot on my accell pump is also shot.

 

I will continue to monitor the fuel pump. If the new ground hiolds and the pump doesn't quit, I am good.

 

Thanks all.



#9 mikaleda

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Posted 28 April 2013 - 05:27 PM

There are two kinds of sight glasses on these hitachies, my 80 has the soild eyeglass, but some other years had a removable sight glass with two screws and a gasket.

#10 Dan-AZ

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Posted 28 April 2013 - 05:33 PM

I looked it over... Mine is not removable -- solid.



#11 mikaleda

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Posted 28 April 2013 - 05:37 PM

Ya I think the newer ones had the removable sight glass, it makes it easier to rebuild them because you can soak the bowl without hurting the glue for the sight glass

Edited by mikaleda, 28 April 2013 - 05:37 PM.


#12 talldude

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Posted 28 April 2013 - 08:11 PM

http://www.nationalcarburetors.com  

 

Or you could ditch it all for a megasquirt ecu, throttlebody fuel injection, and distributorless ignition.  Now THAT would be a fun project!  I'm thinking 100hp and 35 MPG highway...Any takers?



#13 Dan-AZ

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Posted 28 April 2013 - 08:20 PM

I'd love to, but my car is pretty much factory original. Wanna keep it that way...



#14 moosens

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Posted 29 April 2013 - 06:55 AM

Quick search shows plenty of rebuilders and carbs out there.

Doing your carb kit isn't so hard. But doing it so it performs close to 100% means soaking , cleaning , using compressed air , following directions , etc.
You can do it right if you're set up with a small tub and parts cleaner.

I'm hoping to find those jets new too.

#15 mikaleda

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Posted 29 April 2013 - 10:50 AM

http://www.nationalcarburetors.com  
 
Or you could ditch it all for a megasquirt ecu, throttlebody fuel injection, and distributorless ignition.  Now THAT would be a fun project!  I'm thinking 100hp and 35 MPG highway...Any takers?

Man that would ruin it, these old subies are great cause of how simple they are :grin: save that for the later 80s ea engines ;) just my $0.02

#16 talldude

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Posted 29 April 2013 - 11:15 PM

I admit,  I am ruined after too many years of modern computer controlled engines. The BRAT does great around town and in the snow just the way it is, the way they always have...

 

Almost forgot to mention, when I called national carburetors about mine running too rich they said to ship the carb back and they will re-jet to my needs, as a warranty job; they do this frequently for people living at higher altitudes.  A pain, but I don't have the correct jets either.



#17 Dan-AZ

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Posted 01 May 2013 - 09:45 PM

New information for my problem with my car. I had some gasket material so I created a new top gasket for my carb. It seems to be better now. However I have picked up a new issue and was wondering if anyone had any ideas.

 

The car runs. However it doesn't run great until I restrict airflow into the top of the carb. Then it runs smoother and idles at a rather high rpm [ 1500 rpm]. If I don't restrict airflow, it's very hard to start and won't run well. When I attempt to reduce the idle speed below 1200 rpm with the adjustment screw, it begins to sputter some and then quits. Also, when I bring the engine speed up to 3000 rpm, the engine then acts like it's starved of fuel, looses rpm, and then wants to quit. I take my foot off the gas and then it returns to the high idle without losing a beat.

 

I have literally burned up 4 fuel pumps in 6 months. I opened up the gas tank when I had run it for a bit and when I took the cap off, air rushed into the tank. I am thinking a a blocked vent. Although the car has been doing this for years, the engine at highway speeds would very slightly pulse like a momentary lack of fuel and then resume. It's been doing this for years so I never took notice or thought twice about it. I was told it was a vacuum leak and this was common but this was only at speed of  60 mph at about 3700 rpm or greater.

 

Could the lack of airflow into the tank cause that much difficulty and cause my fuel pumps to burn up? I am sure the fuel pump that's in it right now is probably shot. I was able to limp it home when she quit last time. A bad fuel pump could cause the engine to get enough fuel to get the rpm up and then fail when it wasn't delivering as much fuel as it needed to keep the engine running at the rpm.

 

Any ideas?



#18 talldude

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Posted 01 May 2013 - 11:35 PM

If the engine only runs well choked it isn't getting enough fuel.  Sounds like you are on the right track as far as a vent restriction.  Might be worth disconnecting everything at the tank and clearing hoses/lines and also check the charcoal canister plumbing.  Also, check fuel filter and fuel supply hose/lines for restrictions.  Almost sounds like you have carburetor issues, too.  When was the last good overhaul?   Any vacuum leaks anywhere?  The multiple fuel pumps could be due to the pump working too hard to draw fuel through a restriction in your line, generating extra heat/friction, incorrect voltage,  or just really bad luck.  I think I would concentrate on finding your plumbing/vent restriction first and then see about the carburetor.

Sounds like you are weary of these issues, as I saw you put her up for sale.  I hope you have other reasons for selling, because I believe you could figure this out without great expense.  Look at it as an experiment and then tell us all what fixes it so we're all smarter!



#19 vwBrat

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Posted 02 May 2013 - 08:49 AM

It's very very difficult to make a carburetor gasket that actually seals.  It's well worth buying a kit if you need the gaskets.

 

There are venting issues with my Brat too.  It's not stopped it from starting, running, or damaged the fuel pump.  After a long drive I get gurgling noises out of the tank and if I take the fuel cap off I get a pretty significant whoosh of air.  If everything is sealed well enough to make more vacuum than the 3 psi of the pump can pull then I could see it becoming an issue with running but it still shouldn't damage the pump.



#20 Dan-AZ

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Posted 02 May 2013 - 09:01 AM

I think the reason she’s not getting enough fuel is the fuel pump is half shot. She was able to limp me home after I got stuck in town again for the 4th time. I am not a mechanic, but I figure things out pretty quick. I know very little about carb overhauls. I know how they work and stuff.

 

The problem with the fuel pumps has been getting progressively worse. I am thinking a vent is still my problem unless someone who didn’t like my bumper stickers on my car put something in my tank. I don't have the room or desire to take the fuel tank off.

 

The fuel lines from the tank to the firewall all look good. I can’t see the metal ones from mid-body to the firewall, but I’d have to rip apart the body to get at those. I have replaced all of the lines from the firewall to the carb. No stains around the only 2 pieces that aren’t metal under the car – one at the tank and 1 just aft of the front- passenger door. Both look old but are solid. No dirt in the fuel filter so that’s also good. No charcoal filter that I can find, just the fuel filter.

 

Weary is not the word for me now. I have been able to fully restore this car and after 12 years, she’s no longer dependable. As a family we’ve out grown the car and she’s nickel and diming me to death now. I have a small garage, but at this point no time to work on her. Parts are tough to get if not impossible to find, I can’t stick all my kids in this car anymore, and I need something bigger and dependable. If I was retired or I had more time to keep this hobby going I’d keep her and work on her, but my wife and kids would rather see me and not see me under this car.

 

Since I am not a carb guy, I am unable to diagnose and really don’t want to put any more serious money into the car.


I am going to put the new fuel pump in her this Saturday and see what that does and how she runs. If she runs OK and the rpms stay up, then OK. I will look for vacuum leaks as well.

 

I do have a potential buyer who is a mechanic, so the future could be possibly better. I’ll post on what happens Saturday.



#21 Dan-AZ

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Posted 02 May 2013 - 09:14 AM

I was able to take my gasket off the top of the carb and do an exact copy. It's not cork material like the one I took off, but was an exact copy. Got the material from NAPA many years ago when I was working on my 71 Chevelle. No change in the running. The leak around the accellerator plunger remained the same.

 

Per an old time Subaru mecanic, these carbs have a tendency to warp from the heat and need to be milled flat when they are overhauled. Again, more money to spend I don't have. I think my vent on my tank is gone plugged or non-existent so I am gonna go with a loose gas cap to see if that makes a difference.

 

The pumps overheat to the point they no longer run. I watched one run for about 5 minutes and then quit when it heats up. Gets pretty hot. Much hotter than it should. :(  After they cool, they run but never run right again. The voltage to the pump is good at 12.6 to 12.8 volts.



#22 mikaleda

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Posted 02 May 2013 - 10:18 AM

The vent problem could be causing the fuel pump failure and the carb problems both, try loosing the cap and running it and see what's happening. These hitachies have a tendancy to warp over time and creat vaccume leaked even with new gaskets. I know you probably don't want to here this, but a webber would probably fix all your problems, get a vented tank cap and delete the charcoal canister and run a webber you would probably find your problems fixed. Just my $0.02

#23 Dan-AZ

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Posted 02 May 2013 - 10:29 AM

Thanks. That will be my next step on Saturday. I was gonna do a quick vacuum check, put on the new fuel pump, loosen the fule cap, and do a test. Yes, I am familiar with Webber and I have installed new ones on a few engines. I just don't rebuild them.

 

What is this charcoal canister everyone talks about? Where is it?



#24 vwBrat

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Posted 02 May 2013 - 02:31 PM

I looked up quick and don't see any mention of it, but you do have a fuel filter before the pump, on the tank side, right?  If not then junk can make the pump not work. If you have an oem style pump you should just take it apart instead of replacing it .  It's one piece to unscrew and then pay attention to the little bits that come out.  Clean everything and put it back.  It should work fine.  If you can get the top off and back on the carburetor you can clean the insides on the fuel pump with no problem.

 

If you do think you have a vent problem, you can check by driving with the gas cap off or loose next time you have about a half tank or less.  If the problem goes away and reappears when you put the cap on properly then you know to look for venting issues.



#25 Dan-AZ

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Posted 02 May 2013 - 04:24 PM

Yes, OMG I change them regularly. I just bought a new one and have it in hand. I change fuel filters every 6 months.

 

I will disassemble the fuel pump on Saturday. I plan on checking this Saturday. I also plan on checking the run with cap on and off.






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