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720 Weber z24 WOT dies out


Cory74700

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Close. After the Y there is a restriction in the return line or else pressure would not build and push into the carb and the fuel would simply take the open path back to the tank. In this way cool fuel is constantly fed past the carburetor and hot gas returned to the tank. These engines run hot and on hot days the fuel will boil in the lines making restart difficult. The return line prevents this. In addition the fuel in the tank is constantly being passed through the filter and the tank  stays cleaner.

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Is the return line restriction that little pot looking thing that sits on top of the fuel tank? I took a picture of it the other day when I was changing my fuel filter because I didn't know what it was

It's a one way valve to prevent gas expolsion if you roll over i think its actually connected to the evap line.. see my thread i replaced my whole gas tank and plenty of pictures. the y should be a big metal line which goes down through the intake on stock carbs and you may or may not have moved it to loop your fuel line behind the carb and in. 

 

I heard somewhere that weber 32/36 is too much cfm for the engine and when WoT the secondary just opens for air so try running richer to compensate for the mass air the secondary pushes. I havnt modified my jets on mine but i run 3.2psi and little rich to cruise at 70mph and have to slowly open secondary to prevent bog. but if you try to open it under 3k its just gonna hate it. 

 

on phone I open post image and the comment section that im trying to write in on another tab.

put image into postimage and take the "hotlink for forum" link and I paste it right into the comment and it pops up just fine after you post it.

 

EDIT: sorry i just looked on my topic and i guess my pictures expired... 

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My whole issue is when I'm at about 4,000 RPMs going uphill I still haven't been able to run it up the hill yet to see if the fuel filter fix the issue but after work today I'll be able to because I have to go up to the bigger town

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Im not a 720 expert but

 

on stock carbs one can rev the motor up and put your hand over the main barrel and the 2nds should open up.

 

You rebuit this motor?maybe cam sprocket off or dist off a tooth? and you have the distributor cranks to one side to the the 3 degs you need.Dist should be in the middle of the adjustment slotwith soem room to adjust

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If you stomp a stock DGEV Weber to the floor it will have a hesitation (flat spot).  If you steadily throttle down the Weber DGev it will pull just fine.  You can experiment with different venturies and dial this out.  If this was your intension to stomp on the pedal you would have been better off going to the side draft DCOE carbs.

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You can also drill the acc. pump discharge hole(s) larger, if you have a number drill set that goes from #60 (largest), all the way down to #80.

But the real problem is lack of pump volume.

I don't know if Weber makes a larger volume pump the way Holley does (30cc vs. 50cc).

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And I forgot about the acc. pump cam, and the pad it rubs on, getting worn out.

It sits at the front of the carb, and constantly getting showered with road grit.

 

I've had to braze up the pad on the arm that actually depresses the diaphragm before, because it had a grove worn into it from the cam on the throttle shaft, which means the cam was probably worn also.

The pump arm is easier to get at, but the throttle shaft would take a complete carb tear down.

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it doesn't happen from takeoff, it's when I'm driving normal highway speeds occasionally when I have to pull a long grade, I'll downshift from 5th to 4th and I'll get the RPM's up to about 4,500 and floor it to maintain Hill speed, about a quarter of a mile up the hill which is about a 6 to 7% grade it starts to bog out and then it gets worse about 4,000 RPMs to where I have to downshift to 3rd and maintain a 3000 RPM pull the rest of the way, I don't know what my speeds are as my speedometer cable broke when I was putting the new transmission in it slipped off the shaft that was going into the engine and the tranny drop down onto the speedometer cable and kinked it so I have no clue how fast I'm going I'm running stock gearing on 31 inch tall tires 3000 RPM I estimate 2 be about 55 miles per hour. The carburetor is newer than the rebuilt engine, the engine has 500 miles on it roughly and the carburetor has about 400 to 450, so I don't believe anything is worn out since then plus I only run 91 octane pump gas

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Here's all the pictures I tried posting before, the last one is for you Mike, you mentioned these engines run hot, this is my normal operating temperature, is this normal? It seems pretty cool.

 

20180604_185345.jpg

 

20180604_192611.jpg

 

20180604_192616.jpg

 

20180604_193933.jpg

 

20180604_202046.jpg

 

20180606_071554.jpg

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I never pinched off any fuel lines just to change the regular fuel filter, and no fuel leaked out of it. I also completely took the fuel pump off of the side of the frame to refit the new lines

If you raise the line going into the pump higher than the fuel level in the tank none leaks out because of gravity and stuff.

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It sounds like fuel cut because your on a hill and gunning it so your using whats in the fuel bowl and the stock pump isnt pushing enough gph to supply going up hill. I will suggest the carter 4070 pump because it is a high gph 75gph low psi pump perfect for webers as its output is about 5psi and get a good fuel pressure regulator i suggest holley 12-803 with any low psi 1-10 fuel rated pressure gauge hooked right on the front side of the fpr so you can pop the hood and easily see whats happening. it might be pricy compared to stock stuff but ive been dailying this setup for 4 months now and ZERO issues at all.

 

The temp gauge is a VERY common issue with 720s there are many forums on it.. your thermo is most likely sticking open. put a higher temp thermo on it and it will raise it up a bit. many gauges read about that on street and when on highway mine goes under the 2nd squiggly thing i believe i put a 185 in it.

 

you can also place the pump lower than the tank to gravity feed it better.

 

 

20180128_100831.jpg

 

20180128_104826.jpg

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Weber DG series 32/36 carbs run best at 3.5 PSI.  You do not need a high flow pump.  On the 720 that uses a stock electric pump there is a "Y" pipe that feeds fuel to the carburetor and also returns unused fuel to the tank.  For some reason many people that install Weber DG series carbs on the 720 do away with the return line to the tank.  You need the return line to the tank.  The stock 720 electric fuel pump is perfect for the Weber and is not noisy like all the aftermarket electric fuel pump.  I also run the Facet pump as an alternative to the stock electric pump.

 

1986720_Z24_Fuel_Piping_Modded_zps766c43

 

Factory fuel pump

Electric_Fuel_Pump.jpg

 

Facet redtop

FACET_PRO_60_FEP_60_SV_FUEL_PUMP.jpg

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I left the factory y-pipe to the carburetor for the fuel I just replace the rubber line that comes up from the intake manifold, as far as the posting about the temperature goes I have a 185 thermostat in there and it's brand new, I have never seen the temp gauge go above what my picture was except for one time when I had a radiator hose pop off but I did pull the thermostat housing and make sure that it didn't get stuck open, as far as lowering the fuel pump goes, that's not really an option in my situation. I do a lot of heavy 4-wheeling and if I hit a rock on it it's going to rip it off and then the engine will die. As far as the noise from the fuel pump is that normal? Also somebody mentioned replacing the filter inside the pump, I found one online with a part number 1640428530 from Parts. Nissan usa.com if anybody wants to look into that for me I would appreciate it to get some input as to whether or not it's the right part, also if somebody has an alternate part number for NAPA Auto Parts that would be even more appreciated because that would save me the shipping time

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Holy cow, I would never mount a pump this low, even for street driving, you are just asking for trouble.

 

20180128_100831.jpg

 

Anything could rip those wires right out of the pump.

It isn't that critical to gravity feed pump.

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