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Discussion Starter #1
This is driving me crazy, I need some help!!! I am running the same combination in my 67 for quite a few years now without any problems. It is a mildly built 350, 4 speed with a Holley 1850 600 cfm vac secondaries. The car sat for a couple of years with some treated fuel in it. I have recently started driving it and had a fuel starvation problem where I almost didn't make it back home. The old pump was all wet on the outside and I figured that it was going bad, so replaced it with a new Holley mechanical unit and installed a see through filter and pressure gauge between the pump and carb. Fired it up, filter is full of fuel and 5.5 psi, then it slowly starts loosing pressure until it wouldn't stay running. Figured it must be the sending unit, since it was the original one. Pulled it out and the filter/sock was all deteriorated so I thought that was the problem. New tank, new sending unit, new steel line from tank to pump and all new rubber fuel line sections. Fire her up and same problem. Has to be the pump right? Summit sends me a replacement. I install it and same problem. I fire it up, 5.5 psi and fuel filter is full of fuel, but it slowly starts loosing pressure and volume. What the heck is the problem. The carb is the only part of the fuel system that I have not changed. So does it just need to be disassembled, cleaned out and rebuilt or is the problem somewhere else?!?!?:confused:
 

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Is your gas cap vented? It could be that you are developing a vacuum in the fuel tank from the fuel pump which is causing fuel flow to come to a halt. A quick test is to just take the gas cap off and see if your problem persists. Taking the cap off will create a massive air bleed into the tank which will not allow a vacuum to form in the tank.

Imagine a quart of beer with a straw and the straw is hermetically sealed to the cap. You will only get so much beer before you just can't suck anymore thru the straw.

alan
 

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Discussion Starter #5
Is your gas cap vented? It could be that you are developing a vacuum in the fuel tank from the fuel pump which is causing fuel flow to come to a halt. A quick test is to just take the gas cap off and see if your problem persists. Taking the cap off will create a massive air bleed into the tank which will not allow a vacuum to form in the tank.

Imagine a quart of beer with a straw and the straw is hermetically sealed to the cap. You will only get so much beer before you just can't suck anymore thru the straw.

alan
Stock, vented gas cap. I have run it both with and without the cap, no difference.
 

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Discussion Starter #6
You have a sluggish running fuel pump push rod due to it being partially bent!....Purchase a new, straight push rod and you'll be all set!:yes::thumbsup:
I've had this same motor in the car for a decade or more and just replaced the fuel pump for the first time. How does a push rod get bent during normal operation? It seemed free, when I had the old pump out, the push rod just slid right out. I had to use the bolt hole in the front of the block to hold it while I installed the new one, making sure not to mar the surface by only snugging it by hand.
 

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Install a deadheaded vacuum gauge, gauge only at inlet, at the fuel pump inlet and with a full carb of fuel, see how much vacuum the pump creates. Should be a min of 15 inches of vacuum.

If it passes, then blow shop air into tank sealed with a rag at the filler neck and see volume of fuel coming out of inlet hose, should be quite a bit. No fuel, then a rubber line has been sliced when installed or kinked.
 

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Discussion Starter #9
Install a deadheaded vacuum gauge, gauge only at inlet, at the fuel pump inlet and with a full carb of fuel, see how much vacuum the pump creates. Should be a min of 15 inches of vacuum.

If it passes, then blow shop air into tank sealed with a rag at the filler neck and see volume of fuel coming out of inlet hose, should be quite a bit. No fuel, then a rubber line has been sliced when installed or kinked.
I'm not sure if I follow you. First part of test, install T-fitting before pump and install vacuum gauge and read while running? Second part of test, disconnect hose to carb inlet and see how much fuel comes out when blowing into filler neck?
 

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Yes, disconnect the inlet hose from the tank and install a vacuum gauge on the pump inlet, crank up the the engine with a carb full of fuel and see how much vacuum the pump creates.

You can 'T' the gauge with the inlet hose if you like after doing the above test and watch the gauge. There should be no vacuum created if pump is primed and no faults with the fuel supply.

Blowing air into the tank filler tube, no more than 10-15 PSI, short squirts with the air nozzle, pressurizes the tank alittle and forces fuel out the tank through the fuel line and to the pump inlet, if the inlet hose is disconnected at the pump. If there is a good flow, all is well from the inlet hose back to the tank.

Does the inlet hose at the tank have a kink in it?
 

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Discussion Starter #11
Ok, ran the test as described. Steady 15" Hg. Only let it run about 45 seconds, wasn't sure if the pump diaphram would get damaged if being run dry for too long. Forced air into the tank and had a steady stream of fuel coming out of the supply line. What next?!?!?!?
 

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Did you clean out the tank when you had it apart? Those socks plug pretty easy. Also, did you dump the old gas and start with fresh?
 

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Good vacuum and no restrictions in the line. Now hook up the inlet hose to the pump and outlet line/hose to a qt jar or gas can and pump should fill qt jar in approx 15 seconds. Try it with tank filler cap on & off.

What happens to the see-through filter if you pressurize the fuel tank while running?
Does the engine die or keep running?
 

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Discussion Starter #15
Good vacuum and no restrictions in the line. Now hook up the inlet hose to the pump and outlet line/hose to a qt jar or gas can and pump should fill qt jar in approx 15 seconds. Try it with tank filler cap on & off.

What happens to the see-through filter if you pressurize the fuel tank while running?
Does the engine die or keep running?
Thanks Everett, I'll run these tests today after I get done with my honeydos!
 

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Discussion Starter #16
Ran the volume test with the pump. Somewhere in the 15-20 second range (lost track of time) the quart bottle was full of fuel. But I think the problem is with the carb. I tried to run the second part of the test;pressurizing the tank while running and watching the volume in the filter, but it would not stay running on it's own, wouldn't even idle, I had to nurse the throttle by hand. I had to continually actuate the throttle to keep it going, if I steadily increased the throttle then it wanted to die, if I let the throttle return to the idle position it would die. So, is it a an accelerator pump problem and if so, would that affect the volume of fuel the carb would allow the pump to provide or am I dealing with two seperate problems?!?!?!
 

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If you had to constantly move the throttle to keep it running, then I would think the accel pump is working, you should see the squirter squiting every time the throttle opened.

If the engine cannot run on its own, whether at a fast rpm or idle, then I would think the carb needs alittle cleaning, it may be gummed up in its small passages.

Since the jar has gotten filled by the pump, it pretty much rules out the supply system all the way up to the carb fitting.
 

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Discussion Starter #18
That symptom just showed up today. In fact before I tried the 1 quart volume test, I first wanted to fire it up and make sure the carb was full of fuel. Actuated the throttle, squirters squirted and reached in to turn the key, it fired right up and ran on it's own like it had been. Then I put the fuel line back on the carb to try the second test when it started acting up. I will take it apart, clean it up and order a rebuild kit tomorrow. So, if the carb is not functioning properly it can cause the fuel pressure/volume problem that I have been experiencing?
 

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Fuel line disconnected, it runs good?
Fuel line connected, it acts up?
If the needle is stuck to the seat, as in being gummed/varnished into one piece, the pump will not fill the bowls. Are the floats set correctly? Top of the float should be parallel to the top of the bowl when the bowl assembly is turned upside down, maybe alittle more distance between the top of the bowl and the float, i.e., lower fuel level.
 

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Discussion Starter #20
Yes, Floats are set correctly. If I remove the plugs from the sides of the bowls and gently rock the car side to side the fuel just barely spills out of the holes. I went back and ran the car again with and without the fuel line hooked up. Believe it or not the thing ran fine either way both idling and accelerating. So I let her run for a few minutes and it's holding pressure at 5.0 psi and the filter is staying full and then.......she starts losing pressure. I shut her off at about 3.5 psi, the filter is still full, still idling and accelerating fine. I think I'm gonna name her Christine!!!
 
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