# Fuel pump issues



## 1classicguy (Jul 16, 2015)

Hi all.
Could use a little help here. 67 GTO complete rebuild to stock spec's. Fired it. Started a few times, but had some issues. Fixed the issues. Went to re-start and the new mechanical fuel pump stopped working. Had maybe 10 starts on it. Put in another new one. Got less than 10 starts and this one is not working.
Any idea what is causing this? 

Thanks.


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## PontiacJim (Dec 29, 2012)

1classicguy said:


> Hi all.
> Could use a little help here. 67 GTO complete rebuild to stock spec's. Fired it. Started a few times, but had some issues. Fixed the issues. Went to re-start and the new mechanical fuel pump stopped working. Had maybe 10 starts on it. Put in another new one. Got less than 10 starts and this one is not working.
> Any idea what is causing this?
> 
> Thanks.


First simple thought is a problem with the fuel line/gas tank.

Just for fun, remove the gas cap to make sure the correct gas cap is installed. Might be a non-vented cap/tank and you are creating a vacuum within the tank and the fuel cannot draw from the tank.

Next, collapsed/pinched rubber line or cracked split line sucking air.

Debris floating around in the tank plugging the pick-up tube OR the sock on the end of the pick-up tube is collapsing. The sock can get plugged up as it is a fine mesh.

Carb issue, not fuel pump.

Fuel pump eccentric on the cam gear is bad or slipping.


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## BLK69JUDGE (Jun 10, 2010)

Jim nailed it
x2


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## 1classicguy (Jul 16, 2015)

PontiacJim said:


> First simple thought is a problem with the fuel line/gas tank.
> 
> Just for fun, remove the gas cap to make sure the correct gas cap is installed. Might be a non-vented cap/tank and you are creating a vacuum within the tank and the fuel cannot draw from the tank.
> 
> ...


Thanks for the reply's.
I already tried the following. Disconnected the fuel line to the tank and dropped a tube from the fuel pump into a gallon of gas. Also disconnected the fuel line going into the carburetor. I figure that isolates the fuel pump. Nothing.
I'm leaning toward the eccentric too. Needed some opinions before I tear it down and find out it could have been a simpler issue.

Thanks. really appreciate it!


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## PontiacJim (Dec 29, 2012)

1classicguy said:


> Thanks for the reply's.
> I already tried the following. Disconnected the fuel line to the tank and dropped a tube from the fuel pump into a gallon of gas. Also disconnected the fuel line going into the carburetor. I figure that isolates the fuel pump. Nothing.
> I'm leaning toward the eccentric too. Needed some opinions before I tear it down and find out it could have been a simpler issue.
> 
> Thanks. really appreciate it!


Yep, trying to avoid that for you as well. What you might want to also try is disconnecting the fuel line at the pump and back at the tank, and if at all possible, blow air back through the line. If you can hear/feel air, then the line is good. Next reattach it to the tank and remove the gas cap, and blow air though it again. You should also hear air/bubbling. In the past we had a member whose line got plugged up with some crap in it. It would not draw, but then when he blew the line out from the fuel pump side, he heard something "pop" (dislodged something) and the problem was solved. Same goes with the line to the carb. Disconnect it to isolate it as not a problem by blowing air through it. 

Now I assume you have gas in the tank and you are not relying on the gas gauge. True story - a neighbor brought his 1985ish Grand Prix over as it would not start. It cranked, but no start. Gas gauge read full and he said he filled it the night before. So I pulled a plug wire to make sure it was getting spark. It was. Then I put some gas down the carb - it ran momentarily. So I told him looks like the fuel pump went bad. I replaced the fuel pump. Same problem - no start. I don't know why, but it hit me to put a couple gallons of gas in it thinking the gauge was wrong after all. Bam, it fired right up and ran perfect. Someone had siphoned all the gas out of his tank that night. Then he told me that sometimes the gauge worked and sometimes it did not. So it cost him a fuel pump and my labor, neither of which he really needed because we both went on the assumption he had filled the tank up the previous day.


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## Lemans guy (Oct 14, 2014)

Spot on assessments guys, on a no start but cranking issue it is always good to start by adding a couple of gallons of gas to the tank.......also check the one or two rubber feed and return lines at the tank to steel fuel line connection under the tank. The feed line and or return may be collapsing due to a strong pull from these new pumps.

those hoses must be the correct fuel line hoses and not anything else like vac hoses,....just make sure. Anyone can make a mistake even th best rebuilder. It does sound like the pump pulls 10 times and then fails. That sounds more like a vacumn causing a collapse in the rubber line.

it could be anything PJ mentioned, and blkjudge agreed, it just does not seem like the eccentric is not working, ....as it works 10 times on two different pumps

so check the rubber suction feed lines front and rear real good they may be collapsing or kinking at a bend. Basically that is what vapor lock does. It is a combination of vacumn on the suction (feed) line and heat which lowers the boiling point and the gas vaporizes and vapor won’t pump.

let us know how you do!


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## 1classicguy (Jul 16, 2015)

Thanks guys. I'll try all of that on Sunday and let you know what happens. 
I have a full tank of gas and also the engine fires right up when I pour a little gas in the carb. Just not getting from the tank to the carb. 
Aren't cars fun?


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## BLK69JUDGE (Jun 10, 2010)

https://www.walmart.com/ip/Waterproof-HD-2M-7mm-Endoscope-Lens-Mini-USB-Inspection-Camera-with-6-LED-Lights-Borescope-for-Android-Smartphone-PC-Lapt-op/924102324?wmlspartner=wlpa&selectedSellerId=9869&adid=22222222227000000000&wl0=&wl1=g&wl2=c&wl3=42423897272&wl4=aud-430887228898:pla-51320962143&wl5=9033507&wl6=&wl7=&wl8=&wl9=pla&wl10=115780161&wl11=online&wl12=924102324&veh=sem&gclid=Cj0KCQjwka_1BRCPARIsAMlUmErQeOfjhzP4Y_MFzRPYgjQo0nCw1_nWqDfXKqfmMoiIWx4KheopFUMaAk4LEALw_wcB




what brand of pumps ? seems way odd 2 failed... but....
Im at 50 50 pump or eccentric issue .... 
being the pump needs to be pulled either way a borescope
is always handy and fun to have around ... bees nests .... rodent holes
looking in cylinders ,,,, gas tanks,,,, endless fun ,,,,

my money is on the tab on the rear of the eccentric that locks into the cam ..... any wear marks on the tip of the lever on the other new pump you just replaced ?? where the eccentric would ride ?

Scott


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## GTO44 (Apr 11, 2016)

Remove mechanical fuel pump. Install block off plate. Install holley sniper. Install high pressure electric fuel pump. Done.


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## 1classicguy (Jul 16, 2015)

I've order a scope. I took out the pump. Lever doesn't want to move much. Still have the old one and it seems fine. I'll vacuum test both this weekend. I'm afraid it's going to be the eccentric. No worries, I've gotten pretty fast at the tear down over the years. Have an electric fuel pump for a last resort.
I'll keep you posted.
Thanks again.


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## maw2078826 (May 1, 2020)

1classicguy said:


> Hi all.
> Could use a little help here. 67 GTO complete rebuild to stock spec's. Fired it. Started a few times, but had some issues. Fixed the issues. Went to re-start and the new mechanical fuel pump stopped working. Had maybe 10 starts on it. Put in another new one. Got less than 10 starts and this one is not working.
> Any idea what is causing this?
> 
> Thanks.


Check all your fuel lines & hoses to ensure you're not drawing air in the line somewhere, if you are using OE spring clamps make certain they are new ones. Finally, and I know this will sound weird, I have seen situations where the fuel pump eccentric was not torqued properly and came loose.


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## lust4speed (Jul 5, 2019)

1classicguy said:


> I already tried the following. Disconnected the fuel line to the tank and dropped a tube from the fuel pump into a gallon of gas. Also disconnected the fuel line going into the carburetor. I figure that isolates the fuel pump. Nothing.


Think some of you missed his test. That does bring it down to either eccentric or pump. At first thought I was wondering whether the pump was pushed into place with the lever in the proper position. A snake camera would be great at this point to check on the eccentric, but I've got by with a mirror and a flashlight. Basically just looking that the eccentric is in place, and if it is maybe it is just bad luck on the pumps?


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## 1classicguy (Jul 16, 2015)

Thanks.

If I have time, I'll work on it this weekend.


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## maw2078826 (May 1, 2020)

1classicguy said:


> Thanks.
> 
> If I have time, I'll work on it this weekend.


Yes...Good old fuel pumps. They used to be made by Delco, today they come out of China or Mexico, I've had bad ones right out of the box...Today I go to ebay and buy OE ones, a lot more money but worth it....same goes with AC Spark Plugs..none made in the U.S. anymore.


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## 1classicguy (Jul 16, 2015)

Vacuum tested my fuel pump. It's good. I got my scope and with a long screw driver I could see the Eccentric is loose. 
Let the tear down begin.


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## maw2078826 (May 1, 2020)

1classicguy said:


> Vacuum tested my fuel pump. It's good. I got my scope and with a long screw driver I could see the Eccentric is loose.
> Let the tear down begin.


At least with a Pontiac motor a timing chain cover job is simple.


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## lust4speed (Jul 5, 2019)

The eccentric is a two piece affair with the outer ring contained, but floating around the inner ring. There should be a small amount of lateral movement of the outer ring (you could call it slop) so that it spins freely on the inner -- so a slight up and down vertical movement is fine. You just don't want to see any movement in the shape of an arc.


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## 1classicguy (Jul 16, 2015)

Thanks for the input. It does move sideways. I won't be able to tell until I open it up.
I'll let you know what I find. The fuel pump appears to be good. There is nothing else.


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## maw2078826 (May 1, 2020)

Also, when positioning the eccentric, note that the inner portion has a small tang...this tang must fit within the cam key slot before torquing...check your torque specs (Ft. Pounds) and put some blue thread lock on the bolt. Finally, before installation put a coating of assembly grease between the two eccentric pieces.


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## 1classicguy (Jul 16, 2015)

Great guidance! Thanks!


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