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WOT Fuel Starvation


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Is it possible for an electric fuel pump to stop pumping enough fuel? I have a 1985 ST Kingcab that runs out of fuel after about 5 seconds of wot. It runs great as long as you don’t give it full throttle. It has the factory fuel pump and this pump has right at 400,000 miles on it, as does the engine. Here’s what I have done:

(1) Replaced the fuel filters, the one between the tank and pump, as well as the one in the pump. Didn’t know it had one in the pump, till I read about      

(2) Used an air compressor to blow the fuel line from the carb to the tank. Blew gas out of the tank, about 3/4 full.

(3) Ran it with the gas cap off.

(4) Cleaned the float bowl, there wasn’t anything in it. Blew carb cleaner through all of the jets and passages.

(5) Then used datzenmike’s suggestion of checking the float bowl for fuel by shutting it down when it’s acting up. Not easy on a Weber. There was

      barely any fuel in it.

I’ve been running this carb over 100,000 miles, never a problem. A new fuel pump looks like the answer, but I figured I would ask here first. Thanks in advance for your help.

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Float may be set too low.


Does the Weber have a small filter at the inlet to the float chamber? It may be plugged if it does.




If you pull the hose off to the carb and direct into a suitable container. The pump should deliver about a liter and a half per minute.

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The Weber does have a filter at the inlet and cleaned that also. I don’t understand how the float would be set to low, I’ve run this carb for over a 100,000 miles and this is the first time I’ve ever opened it up, but I’ll check it the next chance I get. I’ll check how much fuel I get in a minute. Thanks for the quick response. 

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If you’ve never checked the float bowl before you might be surprised how little fuel there is in there . When you say there is hardly any fuel - well there isn’t much really . It maybe 1/4 if the bowl has fuel in it under normal conditions . I’d go with the pump before I start changing float specs - especially with that kind of mileage . 

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Check to see if the needle and seat are sticking.  The fuel additives in todays fuel are hard on carburetor parts.   I run a can of Seafoam through my gas about every six months to clean some of the residual fuel crap out of the fuel system.  Been doing this for the last 10 years.

Edited by Charlie69
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11 hours ago, datzenmike said:

I wasn't suggesting changing the float height only checking and if needed returning it to the correct height.

I wasn’t suggesting to adjust float either , but some have no idea how much fuel they should see in the bowl when they take the cover off. 

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So in replacing my fuel pump filter, I didn’t get the cover gasket (I thought it would come with the filter, I guess that’s what I get for thinking) and it’s leaking. I’m waiting for it to come in at Nissan. Madkaw you’re right about how much fuel is in the float bowl normally, it’s not much compared to the stock carb. Before I preformed my test, I let it idle for a couple of minutes to check and see what was “normal”, then preformed the test and it was nearly dry. I still want to check the float level, not to necessarily change it but to make sure it’s still in spec. The suggestion to run sea foam through it is not a bad idea. Thanks for everyone’s input.

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