Won't pick up fuel

1985 35 mercury, Sat for about 4 years but carb was clean. It does not seem to be picking up fuel to run. Can put mix in the inlet and it will run till it is out. Had the carb apart atleast 3 times, can not find and problems. Can take the cap off the fuel bowl and it is full of fuel. The bulb will harden up, I will try to start and it will soften up. It obviusly has fire cause it will start on spray. I did get it running once tonight after backing the fuel screw out about 4 1/2 turns.


All help is appreciated. This this is driving me crazy.

Fuel pump is bad

lovedr79 said:

Fuel pump is bad

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Was wondering about that. Is there a way to test it to make sure that is the problem?

Sure does sound like the fuel pump. If the motor will run if you keep pumping the ball on the tank then it is usually a sure sign the pump is bad. Also you can elevate the tank so gravity feeds the motor, this is also another test. But the real professional way to test it is to get a fuel pressure tester.

one way is to unhook the tank side of the pump and fill a cup with gas and try to start, if the cup empties pump is good. another way is to unhook the carb side and see if fuel shoots out of it when you crank it over. or get a fuel pressure guage.

lovedr79 said:

one way is to unhook the tank side of the pump and fill a cup with gas and try to start, if the cup empties pump is good. another way is to unhook the carb side and see if fuel shoots out of it when you crank it over. or get a fuel pressure guage.

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How much should be squirting out when you turn it over?

How much fuel pressure should it have?

How much fuel should be in the fuel bowl when you open it up?

I know I have alot of questions, But I am having to convince someone else and these are questions that keep coming up. The pump is pushing fuel just not much, but then I don't know what it should do. Not exactly feeding a big block ford here.

Again thanks for the help.

Not sure in pressure, that will vary from motor to motor, maybe 12-16psi I am really not sure. how much fuel in the carb?

lovedr79 said:

Not sure in pressure, that will vary from motor to motor, maybe 12-16psi I am really not sure. how much fuel in the carb?

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Float is about as high as it is allowed to go in the bolw when you pull the top off.

JKM4874FORD said:

lovedr79 said:

Not sure in pressure, that will vary from motor to motor, maybe 12-16psi I am really not sure. how much fuel in the carb?

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Float is about as high as it is allowed to go in the bolw when you pull the top off.

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Float has one setting, and that is parallel to the carburetor body. Unless mercs are different? This could be your entire problem.....

If the float us that high it doesn't matter how much pressure. As said above float should be level. Try adjusting the float level.

A shot in the dark, but I have had both of the following happen to me.

Defective vent cap on a brand new fuel tank. :shock:

Bad primer bulb. I read that primer bulbs have a check valve in them and if defective due to being damaged, such as stepping on it, it will not allow gas to flow well. Another article I read stated that having the primer bulb sit as close to the engine as possible and also in the vertical position while running helps.

I have not checked the fuel pump yet. My father-in-law is insistant it is in the carb and he makes a good point. If there is fuel in the bowl it should pull that fuel and either start or flood. It is not even pulling the fuel out of the bowl. We have clean the carb mutiple time and yet to find a problem. I am going to check the butterfy to make sure it is closing correctly so the motor will pull vacuum as it should. I never have easy to fix problems. We continue to plug away at it we will find it.

My next steps would be to verify compression and fuel pressure.

You only need 3 to 5 #'s of fuel presure.

Mercs are level to carb bodies for floats.Try giving more throttle when starting,maybe your low speed jet is clogged.
If your primer ball pumps hard, motor should start providing you don't still have carb issues.Even if your fuel pump is bad & your primer ball is giving you problems it will start,just may not run for very long.

crazymanme2 said:

You only need 3 to 5 #'s of fuel presure.

Mercs are level to carb bodies for floats.Try giving more throttle when starting,maybe your low speed jet is clogged.
If your primer ball pumps hard, motor should start providing you don't still have carb issues.Even if your fuel pump is bad & your primer ball is giving you problems it will start,just may not run for very long.

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This is what we were thinking. If the bowl is full of fuel it should run. We spray fuel in the carb and it will try to run. This leads us to believe it is not sucking fuel into the motor. Stopped up passage maybe. We have been thru this stupid thing several times. all passages look to be clear, carb cleaner blows thru all passages as far as we can see. We may have to resort to taking it to someone. I really did not want to do that. It would be admitting defeat and that would would be bad.

:x

Well checked compression this afternoon, bottom cylinder is at 125# and the top is at 60#. Could be the problem. Thought it would at least try.