72 510 Carburetor problem

[Enrique20]

Yesterday i was driving my 510 on the freeway, i floored the gas pedal it started speeding up bu then it was just slowing down, i pulled over and opened the hood and water or gas was boiling out of the jets, it will start but only after  flooring the gas and cranking the engine for like about a minute. the Datsun is basically my main means of transportation is there any reason why the carb is spewing water from it? all parts on the engine are original. not upgrades.

 

any help would be greatly appreciated. 

[racerx]

type of carb you have.  Be specific. 

[LenRobertson]

The first thing to check is your carb float level. On the front of the carb is either a glass window with a white etched line, or a small round glass porthole with an etched dot (assuming you have a stock Hitachi carb, not a Weber). With the engine off or at idle, the gas level should be at the etched mark. If the engine is off, you can rock the car up and down a little to  get the gas in the float bowl to slosh around. That make it easier to see the gas. If you can't see the top of the gas level, either there is no gas in the float bowl, or too much gas - it is above the top of the window. I'm guessing the too much gas may be your problem, but check the level and post what you see.

 

Len

 

 

[Enrique20]

All i saw on the carb was "ISO", and the there is no port hole or window on the carb that i would be able to see the level of fuel.

[LenRobertson]

Can you post a pic of your carb? That would take a lot of the guess work out of this. If you can't post a pic, look here:

http://community.ratsun.net/topic/33493-for-sale-datsun-620-l18-used-hitachi-carburetor-combo/

 

Does yours look like that one?

 

If it doesn't, do a Google Image search for "Weber 32/36". There are a bunch of pics, so it would be better for you to look at several of them to get different views, rather than me posting a link to just one pic.

 

Len

[Enrique20]

it loosk exactly like that! except without the little glass.

[LenRobertson]

The third pic in that link shows the big glass window version. In the pic, you can see the white etched line about 2/3 of the way up the window, and the black float behind the window. Are you sure you don't have the glass window, but it is so dirty either inside or outside that you can't see through it? Someone else posted awhile back about having a solid metal piece in place of the window, but I don't think it is very common to find that type. I'm hoping your glass window is there but needs a good clean. Spray carb cleaner, or WD40, or even dish soap in water and a little scrubbing should get it clean.

 

Len

[Enrique20]

len its a solid metal plate no dirty glass

[LenRobertson]

That is too bad you don't have a window. I'm starting with the guess that your gas level is too high in the float chamber, which is easy to check through the window. Without the window, you need to take the side cover off the float chamber and see what is going on in there. Which may be a bit of work that will lead you nowhere if something else is actually wrong. If you want to give it a try, remove the three screws through the frame holding the window (or metal plate in your case) onto the front side of the carb. Gas will pour out when you take the plate off, so have a rag or bunch of paper towels to soak it up. Pry it off carefully so hopefully you can reuse the gasket. The black float hangs from a horizontal shaft in the float chamber. Before sliding the float off the shaft, look for a little piece of tubing that slides onto the shaft after the float is installed. It is easy to lose this if you don't know it is there. Take it and the float off. There may be a tiny hairpin spring holding the float arm to the needle valve above the float. You should be able to wiggle it off so the float comes off the shaft, then the needle will drop down out of the top of the carb.

 

Two things might be wrong here: The float, if it is a hollow type, may have a pinhole and has let enough gas inside so it doesn't float anymore. The float's job is to push the needle up into it's seat and shut off the flow of gas from the fuel pump. If it isn't floating, the needle valve stays open and the gas level gets too high and floods over into the carb throat. You might try setting the float in a pan of gas and see if it starts to sink. Or shake the float next to your ear and try to hear if any gas may be inside.

 

A more likely problem would be a chunk of dirt or piece of rubber from the fuel hose stuck in the needle and seat assembly, keeping the needle valve from closing. Try spraying some carb cleaner up the hole where the needle came out of and see if you can dislodge anything.  It is possible something has gone bad in the seat itself. A new needle and seat come in a carb rebuild kit, so I guess they do wear out. 

 

You can also take out the bolt that holds the banjo fitting the rubber gas line hooks to, located on top front of the carb. There may be a fine mesh screen in there that should be cleaned anyway. With the banjo fitting and screen off, you can look and spray right down into the needle seat.

 

With the float out, try to spray carb cleaner around inside the float chamber if it looks dirty and wipe out as much crap and dirt as you can.

 

Does this still have a points distributor, or has it been upgraded to electronic ignition?

 

When you get it started, does it idle at a fairly low speed, like it did before the problem started? I'm trying to think of something other than the float level that may be wrong.

 

Len

[Enrique20]

well i tried it the float seems to be fine nothing in the needle, but how does this explain the water boiling out of the carb? when i opened the hood there was steam and water bubling out of the carb, =\

[LenRobertson]

Eeew, you mentioned water in your first post and I didn't really catch it. Some Datsun intake manifolds have water ports going from the side of the cylinder head to circulate water through the manifold. If the intake manifold gasket blew out, it could let water into the intake port and suck it into the cylinders. And maybe blow back out the carb throat (that part I'm just guessing at) when the engine stops. The radiator pressure would force water through a blown manifold gasket. Try looking all around the gasket where it bolts to the head, especially underneath, and see if any water is seeping out.

 

But a blown head gasket could let water into the cylinders too. Does you temp gauge work? Has it been running warmer than normal recently? Was it running hot after it quit on the freeway? Hopefully not the head gasket, but I'm just trying to come up with ideas. Have you pulled out the spark plugs and looked at them? If you are getting water in the cylinders, I'm not sure what the plugs will look like, but take a look. They should all be the same color anyway. With the plugs out, try cranking the engine and see if water comes out of the plug holes. I have a feeling you will end up needing to do a compression test to be sure the head gasket is okay.

 

I'll keep thinking.

 

Len

[Enrique20]

Ok so i took off the carb and the intake manifold and the seal was blown and worn out. thank for the help i guess i have to replace it. do yall know wwhere i can find the gaskets.

[LenRobertson]

Good to know you found something. Probably most any auto parts store can get you a manifold gasket. They may not have it in stock, but it shouldn't take long to get one. Autozone is an example:

http://www.autozone.com/autozone/parts/1972-Nissan-Datsun-510/Exhaust-Manifold-Gasket/_/N-ipm01Zalizo

Felpro is a brand with a good reputation. NAPA would be another good place to try.

 

I don't know if you have an air compressor, but it might be good to try to blow any water out of the cylinders, through the spark plug holes or manifold ports. Turn the engine over to get each piston to the top of it's cylinder and if it isn't on compression stroke, there should be an open valve to let compressed air through. Look in each plug hole with a flashlight. There may not be any water at all. A wet/dry shop vac may work somewhat, but compressed air would be better. I don't know if enough water got into the cylinders to have any leak down past the rings into the engine oil. An oil change might be a good idea. If you got any water in the oil, the oil will look light brown and "milky" after you run it. The running engine mixes the water and oil together. When the oil is cold, it floats on top of the water in the pan and you won't see any water on the dipstick, so you need to run it to detect water.

 

If you haven't changed your radiator and heater hoses in awhile, now would be a good time. Pretty cheap insurance against being dead on the freeway with an overheated engine. And possibly a warped head from getting too hot.

 

Len