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Discussion Starter · #1 ·
I've been helping the neighbor kid rebuild the engine in his SS. New pistons, rings, gaskets, seals but it won't idle and leans out. I rebuilt the fuel pump but I can still only get a trickle out of one fuel line. I double checked the pump, seems good. How much vacuum should I feel on thepulse line with my finger on it?
 

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I've been helping the neighbor kid rebuild the engine in his SS. New pistons, rings, gaskets, seals but it won't idle and leans out. I rebuilt the fuel pump but I can still only get a trickle out of one fuel line. I double checked the pump, seems good. How much vacuum should I feel on thepulse line with my finger on it?
You will not feel a vacuum, you will feel a pulse which operates the diaphragm in the fuel pump.
 

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It will run on the primer so I assume it would run on gravity feed. It runs poorly on the primer but I assume it's just tight with the new rings. I even tried a known good fuel pump.

New crank seals, o-rings and I used flange sealant on the crank halves. I'm starting to think we must have missed something in that step but I can't find any fuel leaking anywhere. I don't feel anything on the line, no pressure or vacuum.

I am totally stumped on this one.
 

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Did you pull the lines off the carbs and look to see if the pump is pumping fuel?
 

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Discussion Starter · #11 ·
Seals fit about as I expected. With the lines off the carb, I was only getting a trickle out of one line. I did get a bit more out of another pump I know is good but only on one line. I tried replacing the lines, there just wasn't enough to push the fuel up to the level of the carbs.

I'm thinking if this engine can't generate enough pulse to run the pump, it's not going to run very well even if I can get more fuel in it. There must be a leak somewhere, I will have to tear it down to find it.
 

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Stick a probe in the pulse fitting in the case. maybe some of your case sealer ran down the case and covered the pulse line fitting in the case?

Do a leak down test on the motor. You may but more so will not find a leak by tearing it down and looking.
 

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Seals fit about as I expected. With the lines off the carb, I was only getting a trickle out of one line. I did get a bit more out of another pump I know is good but only on one line. I tried replacing the lines, there just wasn't enough to push the fuel up to the level of the carbs.

I'm thinking if this engine can't generate enough pulse to run the pump, it's not going to run very well even if I can get more fuel in it. There must be a leak somewhere, I will have to tear it down to find it.
Fuel will only dribble out but should do so even with the spark plugs removed when you can pull over faster.

A dozen pulls should give you a half a cup at least.

It should come out of both lines.

It doesn't take much pulse to run the pump.
 

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Discussion Starter · #14 ·
We tried pulling it over with the plugs in and the intakes blocked as well, no major difference. I put a line down the impulse port and was able to feel the crank lock as I turned it by hand. With the plugs in and the intake blocked, it may have been slightly better but still only got 1/4 cup or less after a dozen pulls and only out of one line.

I did not see the case halves go together on this project, I only got him started with the flange sealant and saw that the seals were in the right place once it was done. Is there any other way that the impulse would be so weak? Do the o-rings on the bearings play a part here? They were replaced during the rebuild but maybe got damaged in the final assembly

It's possible that the crankcase is full of fuel, I noticed it started firing when I was pulling it over with no carbs. I couldn't explain how that could happen but I did see some fuel vapor shoot out the impulse port when pulling it over. Would that affect the pulse? I had it running on the primer before and after the fuel pump rebuild.
 

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If you had a bad seal you should still get a pulse.If a seal fell out maybe your pulse would be week.

Are you sure your hooking the pulse line to the pulse fitting on the Pump?

Is the pulse line the correct diameter. If it is to big it will leak at the fitting and give a week pulse even with a clamp on it.

Did you have the pump hooked up while cranking then remove it and crank some more, then see the fuel vapor come out the pulse fitting.

Please post an image of your fuel pump hooked up.
 

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Discussion Starter · #16 ·
Thanks skidoo118. I won't be near the sled again until Saturday. I did have the pump hooked up while pulling it over and then unhooked when I roped it over and saw the vapor out of the pulse port. Pulse line is a pretty snug fit, I'm sure it's the right size.I tried the pulse line that came with the sled as well as a new pulse line that I had just used on a '92 Safari 377.
 

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We tried pulling it over with the plugs in and the intakes blocked as well, no major difference. I put a line down the impulse port and was able to feel the crank lock as I turned it by hand. With the plugs in and the intake blocked, it may have been slightly better but still only got 1/4 cup or less after a dozen pulls and only out of one line.

I did not see the case halves go together on this project, I only got him started with the flange sealant and saw that the seals were in the right place once it was done. Is there any other way that the impulse would be so weak? Do the o-rings on the bearings play a part here? They were replaced during the rebuild but maybe got damaged in the final assembly
You say only out of one outlet?

Block that one off and fuel then must come out of the other outlet, if not you have a pump issue. It should pump fine with the plugs out.

The "O" rings on the crank bearings are just to keep the outer race from spinning in the case.
 

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Discussion Starter · #18 ·
Yes, only got fuel out of one outlet line. it was trying to push fuel up into the line but it just couldn't push it up to the top. Same thing happened with the second pump I tried that I know was working fine on the original sled. I tried changing the lines as well, didn't seem to be an issue with the hose. Both outlets pump from the same chamber so it seemed to be an issue of which outlet hose was longer.

When I pulled the carbs off to tear them down again and look for problems, I noticed that one float bowl was empty, that's how I started to narrow it down to the pump. Needle/seats function normally on each carb.
 

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Are you positive that the fuel supply to the pump flows freely?

I know you checked the pick-up but I have seen junks of crud in the Elbow or the footvalve not working right causing a restriction.
 

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Discussion Starter · #20 ·
Great thought, OSN. I tested the function of the check valve but I did not check the flow at the elbow. The primer seems to pump fine but I didn't put a lot of volume through the primer. I will definitely check the input to the fuel pump a lot closer this weekend.
 
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