450rman Posted August 6, 2015 Report Share Posted August 6, 2015 85 720 weber carb new fuel pump and fresh rebuild on engine. Was running good until recently. All of a sudden its not getting enough gas. I can let the fuel pump run for about 15 seconds then the truck will start but quickly runs out of fuel and dies. I did put an inline fuel filter under the hood and still has filter by fuel pump. I am stumped. Quote Link to comment
datzenmike Posted August 6, 2015 Report Share Posted August 6, 2015 Your replacement pump is maybe too small for the job. There is a fuel filter before the pump. If dirty, the pump won't work. Take the hose off the carb and direct into a bucket. Try the pump. If working properly it should deliver 1.4 liters or about 48 US fluid ounces in a minute or less. If it passes then the carb float is set too high or there is a blockage in the carb. Do webers have a screen on their inlet? 1 Quote Link to comment
banzai510(hainz) Posted August 6, 2015 Report Share Posted August 6, 2015 I had a sticky needle valve in carb when this happened. I just wacked the banjo fitting where the gas went into carb and then could see gas go in(stock 521 carb with the window glass) Quote Link to comment
Stoffregen Motorsports Posted August 6, 2015 Report Share Posted August 6, 2015 Yes, DGV's are supposed to have a screen at the inlet. Agree with banzai. Try whacking the carb near the inlet. Use a screwdriver handle. If the float is stuck, this may help free it up. Question for OP: How long did the truck sit while the work was being done? Quote Link to comment
banzai510(hainz) Posted August 6, 2015 Report Share Posted August 6, 2015 fuel pump should be more than enough at idle Quote Link to comment
450rman Posted August 14, 2015 Author Report Share Posted August 14, 2015 Hi guys, thanks for the input. So i pulled the fuel line off at the carb and it definately seems like its not enough fuel. It will idle all day but as soon as i drive it, it runs out of fuel. Either filter, faulty pump that isnt pumping enough fuel, or old fuel line collapsing? Quote Link to comment
450rman Posted August 14, 2015 Author Report Share Posted August 14, 2015 Not a sticky float. I just took the carb apart. Quote Link to comment
datzenmike Posted August 14, 2015 Report Share Posted August 14, 2015 Pull the fuel line off at the electric pump. If normal flow, then the fuel line to the carb is part blocked. 1 Quote Link to comment
450rman Posted August 15, 2015 Author Report Share Posted August 15, 2015 How do i check if its normal flow? Quote Link to comment
Doctor510 Posted August 15, 2015 Report Share Posted August 15, 2015 How do i check if its normal flow? Should fill a coffee cup in about 30 seconds, check your filters too. Quote Link to comment
datzenmike Posted August 15, 2015 Report Share Posted August 15, 2015 On the 720 the manual says 1,400ml or 1.4 liters or about 50 fl oz in one minute or less. Pressure should 2.7-3.4 PSI Quote Link to comment
450rman Posted August 15, 2015 Author Report Share Posted August 15, 2015 Thanks guys i will check that today. Quote Link to comment
datzenmike Posted August 15, 2015 Report Share Posted August 15, 2015 Don't be complacent... that's gasoline! Quote Link to comment
450rman Posted August 15, 2015 Author Report Share Posted August 15, 2015 I got about 30 fl oz in a minute. That was right out of the pump. Quote Link to comment
450rman Posted August 15, 2015 Author Report Share Posted August 15, 2015 The fuel coming out of the pump is pretty sputtery. Its not a solid stream. Is that normal? Quote Link to comment
datzenmike Posted August 15, 2015 Report Share Posted August 15, 2015 30 is probably enough. Sputtering is normal. How much comes out of the line at the carb? There is a fuel filter before the pump. If dirty, the pump won't work. Quote Link to comment
450rman Posted August 15, 2015 Author Report Share Posted August 15, 2015 Seems to be about the same flow at the carb. Quote Link to comment
datzenmike Posted August 15, 2015 Report Share Posted August 15, 2015 Well if there is fuel to the carb maybe the carb is not letting it in. Usually there is a brass screen at the carb inlet. This could have collected some debris and id part plugged. The needle valve on the float may be stuck or the float set too high. Quote Link to comment
450rman Posted August 15, 2015 Author Report Share Posted August 15, 2015 I pulled the screen out and it is clean. I did put a visible fuel filter inline by carb and it seems to be running out of gas so it has to be somewhere before the carb. Quote Link to comment
450rman Posted August 16, 2015 Author Report Share Posted August 16, 2015 I installed new factory fuel filter and new soft fuel lines and i removed the fuel pressure regulator. It is better but it still starts to cut out. It used to die though and now its not. Quote Link to comment
datzenmike Posted August 16, 2015 Report Share Posted August 16, 2015 Your replacement pump is maybe too small for the job. There is a fuel filter before the pump. If dirty, the pump won't work. Well it was replaced, maybe too small?. Then there is still the carb float set too high. Quote Link to comment
Stoffregen Motorsports Posted August 17, 2015 Report Share Posted August 17, 2015 Have you checked the float level? Do you know how? Quote Link to comment
808nissan720 Posted August 21, 2015 Report Share Posted August 21, 2015 I'm having the same problem right now. Only thing is that I have a stock carb and not getting fuel to it. Was running fine last week now it doesn't even idle. I have a brand new fuel pump and filter. But not getting nothing at the carb. Idk how to check the actual line since its a metal line between the fuel pump and carb. Any suggestions would be awesome! Quote Link to comment
banzai510(hainz) Posted August 21, 2015 Report Share Posted August 21, 2015 how about cycle the carb and if you see gas shoot in the main barrel then you got gas in the carb.. Not idle doesnt mean it dont run. Iff you keep pumping the gas does it still run.Then you got a plugged idel jet or mixture is off is best 2 guesses i got Quote Link to comment
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