How do you tell if Fuel Pump is bad?

[GetX'd]

At the risk of sounding totally naive I'm wondering if anyone knows how you can tell if you have a bad fuel pump. My carbs aren't getting fuel and I pulled the line from the tank off the pump and fuel - came out - I wouldn't say it poured out but there was certainly enough to start the car. So I'm thinking the tank and the line are okay. I can take the pump off - but it's a brand new holly with about 100 miles on it. I hate to just buy a new one without some kind of way to tell if this one is bad. At $150, they're not exactly throw a ways. The unit is mechanical. I thought one of you wizards might have a way I can if the pump is bad with it on or off the car.

Any suggestions or help would be greatly appreciated.

 

[MarPar]

 

[747mopar]

When I suspected mine was going out I ran a fuel line from under the hood and taped a fuel pressure gauge to my windshield then made several long hard passes. In my case it only acted up during long hard pulls, watching the gauge the pressure dropped like a rock at the same time. Kinda hard to do if yours isn't even running though. Have you confirmed that the fuel pump cam is still there? Some of the pumps can be opened up, if so you can check for a damaged diaphragm.

 

[69roadr]

pull the line(s) off at the carb, get a container to catch fuel, and have someone crank engine over. quick and simple way.

 

[69SportSatellite]

Maybe I'm missing something here...I'm in the same boat -- no fuel to the carb, pulled the intake line to the (stock) pump and fuel aplenty, so I'm replacing the fuel pump...but $25 for a stock replacement from the local NAPA, not $150?

 

[GetX'd]

Maybe I'm missing something here...I'm in the same boat -- no fuel to the carb, pulled the intake line to the (stock) pump and fuel aplenty, so I'm replacing the fuel pump...but $25 for a stock replacement from the local NAPA, not $150?

The $150 was what I paid for a Summit Racing site Holley Performer. It's a bigger pump and its chrome to go with the other cool looking stuff on my stroker. That's what I paid - so I don't want to lightly toss it. I was going to - if I have to - replace it with the same pump.

 

[69SportSatellite]

Got it - I'm not one to toss anything lightly - especially if I've paid that much for it! Good luck and let us know what the outcome is...

 

[GetX'd]

Would it make sense to run a line from a gallon gas can to the fuel pump and crank it up to see if the pump draws gas from the can? I can disconnect the lines at the carbs and do as you suggest to see if I get some action.

 

[Mr Gorsky]

Would it make sense to run a line from a gallon gas can to the fuel pump and crank it up to see if the pump draws gas from the can? I can disconnect the lines at the carbs and do as you suggest to see if I get some action.

Yep, that would eliminate any line, sender unit or tank issues.

 

[GetX'd]

Yep, that would eliminate any line, sender unit or tank issues.

So then that would isolate the fuel pump as the culprit? If it pumps gas out of the can and through the lines - then the problem still mAy be the tank, sending unit, or line leading up to the pump right?

I had gas that came down the line from the tank but it wasn't plenty - it was a slow dribble. But there's no gas beyond that.

 

[Mr Gorsky]

So then that would isolate the fuel pump as the culprit? If it pumps gas out of the can and through the lines - then the problem still may be the tank, sending unit, or line leading up to the pump right...

Yup.

That said, since your car had been laid up for a long while and it now has a new pump, my guess is that the issue lies inside the tank...clogged sender, rusty tank, etc.

 

[GetX'd]

Yup.

That said, since you car had been laid up for a long while and it now has a new pump, my guess is that the issue lies inside the tank...clogged sender, rusty tank, etc.

That's what I'm most concerned with. I don't have the facility where I live to fix that. I'm really hoping it's the pump. But maybe the pump is able to draw some fuel only so far and then it gives up. That's why I want to try and isolate the two and get a definitive. It ran fine for the first 100 miles. I thought I was past that concern - then it just died. I appreciate the thoughts.....

 

[Mr Gorsky]

If it ran fine for the first 100 miles, I'd very much suggest the problem is in the tank.

Many years ago I had a similar issue. I was able to confirm the problem was in the tank by disconnecting the fuel line and physically blowing down the line into the tank. This cleared the blockage and the car would run fine for 10 miles, until the sender unit filter clogged again.....

 

[miller]

You might consider looking over all of your rubber hoses on your fuel lines. Been told today's gas eats at rubber parts, including hoses...unless your using the right type. Gates makes a hose that holds up, but don't remember the part #. Maybe someone else does...
Kinda the same deal on the sending unit filter, gas eats at them, too. I finally took a suggestion, and left it off! Have two inline filters, before the carbs anyway.
If your not getting good flow 'to' the pump...that's a problem.

 

[GetX'd]

Thx for the suggestions Miller. All my lines are new
Including new braided lines above the fuel pump. Everything seems to continue to point to either the tank ( which I was getting some fuel thru) or the pump itself - that's why I'm trying to find out how you know for sure its the pump - if it is.

 

[eric383]

Is this a big block? If it is measure the fuel pump rod length. I believe it should be 3.22". A worn push rod will affect fuel pressure. You could also install a fuel pressure gauge to measure your pressure. Good luck.

 

['73bird]

Maybe its your carb not letting in gas to it like the needle is stuck (especially if its been sitting). So pull both fuel lines. The one from the carb and the one coming from the tank. put the one from the tank in a gas can and put the one to the carb in a bottle. Crank the car over and see how much gas you are getting into the bottle. If all seems right then put the one back to the gas tank and then crank it over again. If all seems right then its probably your carb or fuel filters.

 

[Shorthorse]

When I suspected mine was going out I ran a fuel line from under the hood and taped a fuel pressure gauge to my windshield then made several long hard passes. In my case it only acted up during long hard pulls, watching the gauge the pressure dropped like a rock at the same time. Kinda hard to do if yours isn't even running though. Have you confirmed that the fuel pump cam is still there? Some of the pumps can be opened up, if so you can check for a damaged diaphragm.

2X on what 747mopar said. It never hurts to have a fuel pressure gauge. $14 at Summit. Stay away from a liquid filled one if possible.

 

[Yatzee]

At the risk of sounding totally naive I'm wondering if anyone knows how you can tell if you have a bad fuel pump. My carbs aren't getting fuel and I pulled the line from the tank off the pump and fuel - came out - I wouldn't say it poured out but there was certainly enough to start the car. So I'm thinking the tank and the line are okay. I can take the pump off - but it's a brand new holly with about 100 miles on it. I hate to just buy a new one without some kind of way to tell if this one is bad. At $150, they're not exactly throw a ways. The unit is mechanical. I thought one of you wizards might have a way I can if the pump is bad with it on or off the car.

Any suggestions or help would be greatly appreciated.

May not be the pump at all, may be the rod that pushes on the pump lever that is worn. You can remove the pump, attach lines to it temporarily and actuate the lever by hand if you carefully "vice" the pump. While it's off, pull, measure and inspect the push rod. You can (if they are the same body) switch the internals from a new pump to the chrome one as you may find a torn diaphragm or faulty valve.

 

[Ranger16]

I'm with 69roadr (post#4). Simplest way is to just pull the supply line to the carb and crank it. If it pumps a solid stream of fuel, the pump is good. It's just that easy.