weber 32/36 carb installation

[nissan720]

when installing the weber 32/36. Do you use the stock gas line.The weber installation guide states to eliminate the return line.Will i need a regulator to drop the fuel pressure? I am using the stock factory fuel pump.

[datzenmike]

I would keep the return line. Mainly because it's the easiest thing to do. It's there to circulate cool fuel through the lines and past the carburetor making hot restarts easier.

 

Stock electric pumps are rated at 2.7 to 3.4 PSI. Run it like it is, a new Weber should handle this. If there is a flooding problem worry about a regulator then.

[nissan720]

thank you once again Datzenmike!!

[nissan720]

i was out wrenching on my 720 today.I have that weber 32/36 dgev carb.I had the air cleaner off looking down the carb. When i gave it the gas.Only was squirting out of on side of the pump jet.I noticed it was very lean when i drove it home today and it cut back a few times.Could not get over 35 mph .Trying to accelerate it buckecd and would not pick up speed? As always thanks for any help in advance.Hadn't been posting to much on this forum lately due to tha fact that my father passed and this was one of our projects.Really just got myself involved in finishing what we started.

[datzenmike]

32/36 should only squirt one side because only the primary is open.

 

It's a progressive carburetor and the secondary begins opening when the primary is 60% open.

 

 

 

Check that the mounting bolts and the adapter are on tight.

 

Engine off, have someone floor the gas while you look to see that the primary and the secondary are fully open.

[yenpit]

I don't think the Weber 32/36's offer a fuel return, so I don't think you can hook it up.  Put a piece of rubber fuel hose on the return line, coil it up a couple rounds & zip tie.  Having that return line "vent" won't hurt a thing.  Plugging it might............??

[datzenmike]

The 720 fuel line has a return built into it. Fuel is pumped to and past the carburetor. On the return line near the carburetor is a restriction, a pin hole so that the pump can build pressure against this. Without the restriction the fuel would take the easy path back to the tank.

 

This is the restriction on an L20B return...

[yenpit]

17 hours ago, datzenmike said:

The 720 fuel line has a return built into it. Fuel is pumped to and past the carburetor. On the return line near the carburetor is a restriction, a pin hole so that the pump can build pressure against this. Without the restriction the fuel would take the easy path back to the tank.

 

This is the restriction on an L20B return...

 

Ahhhhh, so UN-like the 68-73 510!  The 510 Hitachi carb has a fuel inlet & a fuel outlet, to the return line on the left strut tower.  This 720 is built in to the fuel rail?

[banzai510(hainz)]

can not go over 35mph???????

get this fixed? was the distributor swapped or changed? even if the 2nd barrel didnt work it should go over 35mph

 

Did you hookk up the elelctric choke so the choke plate is open.

Or is this a water line choke?

[nissan720]

yes the distributor was changed.Do you think it could be off a tooth? Electric choke is working fine.

Edited April 29, 2022 by nissan720
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[datzenmike]

 

Check this first. Most likely, and the easiest.

 

Next check the ignition timing. Should be 3 degrees before TDC

[nissan720]

willl check it tommorrow

 

[nissan720]

guy has truck at shop. told me the fuel pump was only pushing about 2psi. andit dropped when accelerating. would this have any bearing? he did say that the timing was set at TDC.

[banzai510(hainz)]

7 hours ago, nissan720 said:

guy has truck at shop. told me the fuel pump was only pushing about 2psi.

Never heard this one before but could be possible

 

but I would think when the float bowl is full at idle you could get above 35mph for a few seconds.

 

key is look at the distributor if you have removed it. Why you didnt say this in the first place ?  if dist is off a tooth it will cut out. Before the carb change what was the proplem Maybe the fuel pump was the whole proplem all along and you swapped the carb out for nothing?

 

But Im not a 720 Napz expert. Mike knows more on these as alot of emmisions stuff on these

Edited May 2, 2022 by banzai510(hainz)

[datzenmike]

8 hours ago, nissan720 said:

guy has truck at shop. told me the fuel pump was only pushing about 2psi. andit dropped when accelerating. would this have any bearing? he did say that the timing was set at TDC.

 

Timing at TDC is close enough but it should be 3 before TDC.

 

2 PSI is perfect for a Weber but dropping as revved up is strange. Do you have the stock fuel lines to the carburetor? This includes the return. In the picture below there is a double fuel line up past the intake to a single line to the carburetor.  Do you have this?

 

 http://i.imgur.com/i5Bnh.jpg

[nissan720]

no i do not have the return line set up,i think the instruction told me that it was not needed.I will hook up the return line while its at the shop. will put timing  at 3 before TDC

[Thomas Perkins]

All you do is connect the gas line from the oem fuel line to the Weber,Don't loop it Check mine out.I have the oem fuel pump.

[Stoffregen Motorsports]

Fuel pressure can fluctuate and be hard to read. Especially when it it such a low PSI. There's a thing called a fuel pressure snubber which was designed to give an accurate reading on the gauge. I've never had to use one, but they are cheap and maybe worth a try.

 

Ok, I'd be curious to see how one works, but I doubt this is your fix.

[datzenmike]

On 4/24/2022 at 3:43 PM, nissan720 said:

i was out wrenching on my 720 today.I have that weber 32/36 dgev carb.I had the air cleaner off looking down the carb. When i gave it the gas.Only was squirting out of on side of the pump jet.I noticed it was very lean when i drove it home today and it cut back a few times.Could not get over 35 mph .Trying to accelerate it buckecd and would not pick up speed? As always thanks for any help in advance.Hadn't been posting to much on this forum lately due to tha fact that my father passed and this was one of our projects.Really just got myself involved in finishing what we started.

 

This mimics it not getting enough gas. I've had a blocked and partially blocked jet and as the speed increases you get to a point where it won't go any faster. If you step down on the gas it stumbles and actually slows down.

[nissan720]

datzenmike thats exactly what it is doing!! the more you try to accelerate the more it slows down and buck!! I also noticed when looking down the carb the squirter has a drip its not spraying out. a slow drip when pressing the accelerator

Edited May 3, 2022 by nissan720
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[datzenmike]

1/ Seems to have a fuel delivery problem so replace the fuel filter between tank and electric pump. The pump is on the frame just forward of the right rear tire. They are cheap, easy enough to change and if this doesn't help it was likely time to change anyway.

 

 

2/ Before we tear into the carburetor one test. Doesn't cost a cent. Drive as fast as you can at the 35 MPH, and when you can do so safely, turn the ignition off and clutch in and out of gear. Pull over safely. The intent is to preserve the condition of the float chamber while this is happening so the fuel pump has to be stopped ASAP. So don't let it idle at all. 

 

Now take the air filter off and look at the little window on the front of the carburetor. Is the fuel level showing at the dot on the glass?? Now let it idle for a few seconds. Where is the gas level? Is it in the middle of the glass or barely showing? or not showing? If low or not showing the float may be set too low.

 

If full of gas not the float or the fuel pump...

 

 

3/ Take for a drive of at least 20 min. Run as close to your top speed of 35? as you can and hold there. Take a wrench with you and pull over and remove the spark plugs. The sign of an over lean engine are the porcelain tips of the plugs are very white. Like new. This is because a lean mixture runs very hot and no or almost no carbon produced. The heat burns off all deposits.

 

 

Assuming this is the case, then the carburetor is at fault. Likely a jet is partly blocked and not enough fuel is getting by.

 

 

[nissan720]

will do this tomorrow raining right now

[datzenmike]

Try to do in that order. Poor fuel delivery is most likely a badly plugged up filter. It's what they do. The best $5 you'll spend.

 

Fuel level in the float chamber is next after you are sure the filter is new.

 

If float chamber is always full, pretty sure the plugs will show very lean, white and this confirms a dirty jet.

[Thomas Perkins]

Get a new oem fuel pump,new fuel filter and replace all the  rubber gas lines,also the one's by the starter.I replaced all of mine.Start with the one coming out of the fuel tank,also use new clamps.Nissan still has fuel pumps for sale.I have a brand new one.Still in the box.Also a new filter that goes in it.You have a drain plug on your gas tank.Empty it and pour some fresh gas in it,park on a hill.Check it out and see if it has trash in it.Do this first.If it is full of trash,then it will clog your new fuel filter.I have never had trash in my Weber's little plastic filter.You may just have a leak in one of your gas lines.I think the gas lines are 5/16.Autozone here didn't have that size here,but Advance did.

Edited May 4, 2022 by Thomas Perkins

[datzenmike]

Right now this could be anything. If the filter is being plugged by debris that would be worth looking into. For now need more info.