>>> new pump not working no suction <<< please read

[1BAD65]

1972 C10 350CI V8 - QUADRAJET CARB - MECH. FUEL PUMP - FULLY STOCK

I need to clarify a few things.

I just searched several "New Fuel Pump No suction" threads here and I am having the same issue.

Question #1

First let me ask this question as I stumbled upon a thread that stated:

"THE SENDING UNIT LOCATED IN THE FUEL TANK SENDS FUEL TO THE FUEL PUMP WHEN THE IGNITION SWITCH IS TURNED ON"

wtf????

I never heard of this? I understand its call a "Sending Unit" but that is because it tells the fuel gauge on the dash how much gas is in the fuel tank and that is all. Right???

I know there is pickup tube along with it as well.

Question #2

Does a NEW mechanical fuel pump require PRIMING after being installed?

*********
Here are the things I have tried:

Replaced fuel pump twice

Made sure push rod was free and also used white grease to hold push rod in place so it would not slide down behind lever while installing new fuel pump.

Used a short piece of fuel line attached to "IN" port and placed the other end in a bottle filled with gasoline- cranked the engine - no suction - the fuel pump would not suck any gas from the bottle which was inches away from the new fuel pump.

********

all rubber lines replaced in the fuel line system.

dropped the fuel tank and cleaned out all debris and sediment

blew compressed air through the fuel line that connects to the fuel pump and when I did that allot of gasoline poured out from top of the tank.

*******

New Plan to Solve this Problem

prime carb with gasoline and crank the engine

reverse both fuel lines on top of fuel tank- maybe they are connected incorrectly

prime carb again - crank engine

if it still does not start then :

I will install a new mechanical fuel pump again for the 3rd time and repeat the priming process


GUYS, LET ME KNOW IF I AM MISSING ANYTHING

THIS A FUEL PROBLEM - I HAVE SPARK AND COMPRESSION

TRUCK LAST RAN FINE ON FRIDAY TODAY IS NOW WEDNESDAY

THANKS FOR ALL OF YOUR HELP

[snipescastle2]

Did you by chance replace the "Sock" or pre filter on the sending unt? the only other thing that might be a possibility here, is the rubber hose that the sending unit attaches to the metal line that passes through the floor.if it's dry rotted, it might be sucking air.....
HTH
Ben

[snipescastle2]

Did you by chance replace the "Sock" or pre filter on the sending unt? the only other thing that might be a possibility here, is the rubber hose that the sending unit attaches to the metal line that passes through the floor.if it's dry rotted, it might be sucking air.....
HTH
Ben

[1BAD65]

I replaced all lines with fuel line not the cheap vacuum line


but i need to know why the pump is not sucking fuel out of a water bottle with 10 inches of hose?

[1BAD65]

@davepl

truck runs as long as i keep spraying starting fluid into the carb

it will run until i stop spraying.

[1BAD65]

@snipescastle2

I DO NOT HAVE THE SOCK ON THE PICK UP TUBE.

I WAS TOLD THE SAME THING BY OREILY'S, AUTOZONE AND PEPBOYS THAT THERE WERE NOT PARTS AVAILABLE FOR THE SENDING UNIT.

DAMN BASTARDS LIED!!?

WHAT I DID DO WAS PUT A FUEL FILTER IN-LINE IMMEDIATELY AFTER THE TANK ABOUT A FOOT AFTER THE TANK

SORRY ABOUT THE CAPS

[everettelane]

Are you sure the push rod is contacting the fuel pump arm the lobe could be worn on the cam shaft and not pushing the fuel pump arm. Simple check remove the plate and have someone bump it over while you hold the rod against the cam.

[davepl]

Originally Posted by 1BAD65

@davepl

truck runs as long as i keep spraying starting fluid into the carb

it will run until i stop spraying.

I'll buy that!

Lines backwards? Fuel pump pushrod missing, or not installed correctly? Big block vs small block pump mismatch? I'm grasping, but you should be able to lift 10" I'd think.

[davepl]

Before you install a 3rd pump, how do you know you have spark and, in particular, compression?

A lot of times we see people who have a fuel problem say they have spark and compression because, after all, they know it's a fuel problem :-) It happens.

[Leonard60]

Is it possible that the push rod that operates the pump wore down now it to short or the cam lobe finally worn down now not pushing the pump lever. Also in my experience you may be putting the wrong pump on the pump lever could be wrong. There are several different gm pumps out there but I don't remember which applications they all were for.

[1BAD65]

@Leonard60

Yes I did think about that. I guess I better change that out too. Hopefully the parts store around the corner has one in stock.

Thanks for that tip

[Leonard60]

I would manually operate the pump and see if it will pump just take it back off the truck and run a hose into a jug of gas and pump the rod by hand. If you have a vice put the pump ear in to the vice and start pumping.

[1BAD65]

i will try that too

[dflarsen77]

I dunno if you can get it to pull fuel if you pump it by hand, the things are stiff as hell. To answer a couple questions:
- the sending unit in the tank just tells the gauge how full the tank is, it's not a pump. A 72 should have 2 lines coming out of the sending unit. The bigger one is fuel, the smaller one is a return line. You shouldn't be able to mix them up, they're different sizes. Fuel to the pump should be 3/8", the return line 1/4". From your explanation though, it doesn't sound like the sending unit is the issue.
- the pump doesn't need priming. It may take like a 2 seconds to charge the carb maybe?

I don't think you said why you are replacing the pump. Was it not working before? You said it ran on Friday, so I assume the old one worked. Did you try putting the old one in to see if it sucks gas out of the jar? I know swapping pumps is a pain. Also, look at the old & new next to each other. Are they the same looking? Angle and length of the arm, etc. The rod only pushes the arm like 1/2" or so, so if the arm is even a little different angle, could mean a lot. But sticking anything down there while you crank it sounds like an awesome youtube fail video waiting to happen. I'd just compare the old & new pumps arms.

If you had it set up like you said and it wasn't sucking from the jar, it should mean one of a couple possibilities:
- a bad pump, you said you replaced it twice, so it's not likely they're both bad, but not impossible.
- the wrong pump. Again, compare it with your old pump, but check with the place you got it from that it's the right pump. They can be kinda dense depending on the shop or employee, but it seems unlikely they'd give you the wrong one. The fuel pump should have 2 lines, the "in" from tank (3/8) and the return (1/4). I assume you're using it right if you used the "in" line.
- a bad pushrod. Possible but you said it ran.
- the wrong pushrod. Again, I assume you're using the same pushrod that was on it before. Just measure it. They're supposed to be 5 3/4" long, 1/2" thick.
- or the cam lobe is worn down low enough to be useless. I can't imagine the lobe would be worn that far. But again, you said it ran.

Even writing this up, I realize that if it isn't sucking gas now, but it ran before and it didn't break down, and you didn't change anything else, you either got 2 bad pumps or it's the wrong pump. And if you changed all those rubber lines, just double check that they're all going the right way. Visually check them from the tank all the way to the pump.

[KY_GMC]

I recently installed a replacement fuel pump and here are some things that I remember:

No priming was necessary. I pulled the old leaking one off and put the new one on and it started right up and didn't miss a beat.

With the rod in the engine, you have to hold it up while you are mounting the fuel pump on the block. A small wire or putty knife is good for this.

When I put my pump on, with the rod engaged to the crank lobe and the pump lever, the pump did not seat all the way to the block (because of the position of the lobe when the engine stopped). I had to use wrench on the bolts to get it seated all the way. Did the pump seat completely with the rod in place?

One thing to check would be to have someone crank the engine (with no fuel pump and no spark!) and place the rod in the hole and see if it pumps back and forth while cranking. That will tell you if the lobe is wiped out, but I doubt it.

Why did you replace the fuel pump to begin with?

[1BAD65]

@dflarsen77

DAMN !! GOOD WRITE UP!!

Thank you for addressing all of my concerns, I appreciate that.

Yes it was running on Friday night. We drove it and it ran normally as usual no shuddering or stalling as if it was not getting enough fuel.

So what happened between Friday and Tuesday I have no idea.

We put in the replacement pump#2 in on Friday and it ran, I even put the fuel hose to the carb in a water bottle and the pump was pumping allot of fuel not just a trickle.

So it sat 4 days and now we can't get it suck gas.

I put the old one back on today and it does not want to suck gas out of a bottle either.

I placed my thumb on the port opening while my brother cranked her over and there was no suction at all.

SO it must be the pushrod not engaging or a bad pump??

"But sticking anything down there while you crank it sounds like an awesome youtube fail video waiting to happen."

Yes I was thinking the same thing. I need all of my fingers.

Had both pumps (new&old) side by side they look identical. I picked up another new pump today for tomorrow morning

My fuel pump only has 2 lines - IN and OUT (to carb). There are two lines coming out of the fuel sending unit like you said one bigger than other. I traced the line from the pump to the frame rail and connected that to the larger line on the tank.

Going to drop the tank again and double check which line is which just to make sure I have it right. Suck because the tank is half full if not more.

Thanks again!

David Franco
Madera CA

[1BAD65]

@KY_GMC

Thanks for joining in brother. I had my brother replace it because he had broken down off the 99 highway in KIngsburg, CA. I was guiding him over text messages on what it could be. In the end we swapped out the filter first, then pump , then HEI coil. The coil was the answer.

Anyways that was Friday and it ran fine after that. He made it home and parked it now it won't run on its own without using starting fluid. Stop the fluid and it dies.

I used white grease to hold the push rod back out of the way while I installed the pump. Even with the rod held back it was not easy to put on.

I have a new pump to install tomorrow, I will check out the pushrod some how some way.

Thanks again

[1BAD65]

I am thinking the fuel pump sucked up a bunch of crap off the bottom of the tank.

the balloon filter was torn or ripped open so the pump may have been plugged now.

??

[dflarsen77]

The pushrod is only held in by the mounting plate under the pump. Remove the top 2 screws for the pump, the bottom 2 hold the mounting plate. Just have a new gasket for the mounting plate ready, if you bother with it, and get ready to clean crap off the mounting surface. You could then take out the pushrod and measure it.

But I really don't think that's the problem. From what you said earlier, if your sending unit doesn't have the strainer/sock, and there was a decent amount of sediment when you cleaned the tank, it really could have sucked up enough crap to clog somewhere. I would pull the line off the carb inlet, put that into a glass jar. If the lines are all clog-free, you should be able to pull gas from the glass jar like you did earlier, and it should pump it into the glass jar I mention there.

If that works, and then you plug it back into the carb and it doesn't work, you're carb is clogged somewhere.

[1BAD65]

@dflarsen77

Yes sir after everyone's input I am betting the fuel pump sucked up some debris.
it was pretty bad. There was some paper, looked like a piece of brown grocery bag and a 7 inch piece of fuel line and a small section of break off razors in there.

Since the balloon sock is now removed I went ahead and placed an in line filter outside of the tank. This way I can replace at 6 month intervals.

Going to get out there by 8am and install the new pump and hope it starts.

I will post an update tomorrow either way if its good or bad.

Thanks again for all of your input, much appreciated!

[midniteblues]

I have in the past done this.

Disconnect the in line at the pump put a bucket under it.
Pull gas cap off and cover the filler neck with your hand and blow air into the tank carefully here ya don't need 90#' of pressure here.

Be ready cause gas will come out the disconnected line. Leave gas cap off, Reconnect the line too the pump.
Prime carb and fire off.

You can blow air into the infeed disconnected line at the pump up into the tank. And gas will gush back out of the line once you let off the air so be ready.

That is of course your line are clear and not block up.

[1BAD65]

@midniteblues

THANK YOU !!

GREAT WAY TO FIND OUT IF I HAVE MY LINES CONNECTED CORRECTLY OR CROSSED!
ALLOT EASIER THAN DROPPING A HALF FULL GAS TANK BY MYSELF TOO!!

[midniteblues]

No problem, a lot of us have replaced fuel pumps and can't get gas up too the carb.
Me included, till I figured this out. most times the pump will prime it's self. But when it won't this will work every time.



This question is asked so many times it Should be a sticky.

[1BAD65]

>>>>>>> UPDATE - PROBLEM SOLVED <<<<<<<<<<

WELL I FOLLOWED midniteblues TIP OF BLOWING AIR INTO THE FUEL TANK THROUGH THE FILLER NECK AND FORCING FUEL OUT AND DOWN THE FUEL LINE TOWARDS THE CARB

MADE SURE THE FUEL LINE AT THE PUMP WAS DISCONNECTED AND A BUCKET READY TO CATCH SAID FUEL

NOW THE FUEL LINE IS FLUSHED OUT AND FULL OF GASOLINE!!

REATTACHED THE FUEL LINE TO THE PUMP AND PRIMED; YES "PRIMED" THE CARB WITH A LITTLE GASOLINE OUT OF A WATER BOTTLE.

CRANKED IT, SPUTTTERED, ADD A LIL' GAS AND CRANKED IT AGAIN

SHE LIVES!! TRUCK IS RUNNING AGAIN !!


LESSON LEARNED DO NOT BLOW AIR FROM THE FUEL PUMP LINE BACK INTO THE TANK - ALWAYS BLOW FROM THE FILLER NECK TO THE PUMP !!!

DID NOT NEED TO CHANGE OUT THE PUMP - PUMP#2 WAS STILL GOOD

JUST COULD NOT SUCK ANY GAS FROM A DRY LINE UNTIL I BLEW 120psi OF AIR INTO THE TANK .

120psi WAS OVERKILL BUT I WANTED TO MAKE SURE I GOT ALL THE CRUD OUT

THANKS AGAIN TO EVERYONE WHO CHIMED IN - I APPRECIATE YOUR HELP

[snipescastle2]

120 psi??? Holy crap! You're lucky that tank didn't blow apart at the seams!!!
5 to 15 psi should have been more than adequate.that could have been disasterous!!! Glad you came out of that ok.
Ben