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Old 07-11-2010, 10:11 AM
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fuel pump issues

SO I have a problem. My 350 will not fire. I have spark and compression no fuel though. I op checked the fuel pump on the car and it doesnt work. I removed the fuel pump and op checked it and it worked. Why is the fuel pump not working on the engine.
BTW it is a mech fuel pump.

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Old 07-11-2010, 10:25 AM
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Could be a bad diaphragm inside the pump and can't suck the gas from the tank which is a longer distance in the car.
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Old 07-11-2010, 10:54 AM
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I tried using just some hose and a gas tank right by the pump.
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Old 07-11-2010, 11:09 AM
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You need to make sure the fuel pump pushrod is moving when the engine turns over. Also, let's make sure that the inline filter on the carb isn't clogged.

I find the easiest way to check the pump is to remove the metal fuel line from the carb and slip a good length of 3/8" fuel line over the end of it and put the tag end into an empty gas can. Then you can use the key to crank the engine over a few times. If you get gas in the can then you know the problem lies in the filter or carb.
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Old 07-11-2010, 11:21 AM
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I did that already. tube into gas can and another tube to a bucket nothing happens
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Old 07-11-2010, 11:30 AM
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Disconnect your coil and have someone turn the engine by hand while you hold your finger against the end of the pushrod. There's an eccentric on the camshaft that bumps the rod as the engine turns over.

If you're using a known good pump it leaves a few possibilities- an obstruction between the tank and pump, an improperly installed pump or pushrod, a bent pushrod, or a damaged camshaft.

Is the pushrod all the way up in its bore or is it dropped down and resting against the plate? If you try to put the pump on with the pushrod dropped down it will be a bear to put on, and will damage the pump and rod.
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Old 07-11-2010, 11:32 AM
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Quote:
Originally Posted by southernculture
I did that already. tube into gas can and another tube to a bucket nothing happens
you need to test it on the car to see if there is a blockage between the pump and carb.

If everything else checks out and you get gas to the test line then replace the inline filter. If you don't get gas and you know that the pushrod is functioning and everything is installed correctly, then it goes back to what 1bad80 said- the diaphragm is too weak to pull gas all the way from the tank and the pump needs replaced.
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Old 07-11-2010, 11:38 AM
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I made the mistake of leaving the longer bolt in the front of the block to hold the push-rod once. That will stop it from pumping real quick.
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Old 07-11-2010, 11:42 AM
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Quote:
Originally Posted by sqzbox
I made the mistake of leaving the longer bolt in the front of the block to hold the push-rod once. That will stop it from pumping real quick.
I've seen that done once, and that was enough to convince me to not use that method. Instead I just load the pushrod up with moly to hold it in place.
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Old 07-11-2010, 11:46 AM
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Ok, just a shot in the dark. Could also be fuel pick-up in the gas tank issue.
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Old 07-11-2010, 02:04 PM
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Sounds like you need to replace the pump it's that simple. JMO 1bad80 is right on this.


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Quote:
Originally Posted by 1BAD80
Could be a bad diaphragm inside the pump and can't suck the gas from the tank which is a longer distance in the car.
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Old 07-11-2010, 02:25 PM
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I took the pump off of the car and cranked it by hand and it worked. I hooked a tube to a gas can and a hose off the other side. I granked it and no gas pumped. I have isolated it down to either the shaft or the pump. The pump came from a friend and it is a known good fuel pump. My cam is brand new. I was starting to think that the cam was the issue. I have no problem getting a new pump but I was just gonna get an electric pump and call it a day.
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Old 07-12-2010, 01:35 AM
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Brand new carter mechanical pump $18
Brand new Carter pushrod $15
For a total of $33

El Cheapo Mr Gasket electric fuel pump 4-7psi $25
Good enough pressure regulator to keep you from overcoming the float and flooding your carbs: $30
Block off plate: $5
For a total of $60

Takes about 15 minutes to replace the mechanical pump and rod, assuming that the pushrod even needs to be replaced.

You can figure on a good hour or two to drain your tank, cut up your existing fuel lines, patch in the electric pump, mount it to the frame, ground it, wire it to ignition power (personally I would run it off power from the oil pressure sensor so that in the case of an accident it doesn't keep dumping gas into a fire) and then install and dial in the right pressure from the regulator.


If you don't mind the extra cost and work the electric pumps are nice for cars that don't get driven very often, as they will fill the carb bowl by just turning on the key so you don't have to crank forever.
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Old 07-12-2010, 01:55 AM
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Wish I could get a cheap electric pump for 25 dollars lol. I tend to switch everything over the electric pumps tho when the mechanical ones fail. Ive had so many new mechanical pumps that wont pump that i just get the point of not messing with it anymore.
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Old 07-12-2010, 02:14 AM
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Quote:
Originally Posted by Torque454
Wish I could get a cheap electric pump for 25 dollars lol. I tend to switch everything over the electric pumps tho when the mechanical ones fail. Ive had so many new mechanical pumps that wont pump that i just get the point of not messing with it anymore.

They're $24 at my local auto parts store for the Mr Gasket universal 8cyl pump. In fact I've got a brand new one sitting in my garage, complete with everything but the 2 mounting screws it came with. I just went through the same issue as the post starter, and ended up finding a bent pushrod. Because I needed the truck to be up and running by the next morning I grabbed both the mechanical and electrical pump. I lost one of the 1/4" screws that holds the mounting plate on so I used the 2 screws from the electric pump kit.
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