1971 911T fuel pump test and replacement

[cvillegas71]

My T is not pumping fuel to the Weber carbs so I am trying to find a test procedure that will help me track down what the issue is. The first suspect is always the fuel pump but I want to make sure that I go through a set procedure and just make sure.

Can someone help with this and as for a replacement what do you think about our hosts
Brand: Hardi

Or

Brand: Pierburg

The second one says some modification needed any one done the project and can show pic’s?

Any assistance is appreciated

[pors1968]

Make sure the line is not plug or try to blow some air in the line(10psi ) take gas cap off .On the output line you have small filter Inside the tankthis might be plug.

[wayner]

On my 73 I installed a new pierburg up front.

It wasn't pumping at first but I could hear it running.
1) We removed the gas line fitting at the back and nothing.

2) To make sure that is was getting fuel, we removed the line from the input side of the pump until fuel came out. Hooked it up and tested the other side. Fuel came out. Maybe priming the pump helped.

Still nothing at the carbs.

3) Back to our first test. Very quickly fuel made its way to the back and onto the floor.

Connected everything up, still nothing.

4) Disconnected the line at the carbs, as well as at the old pump location (#1)
Blew air through that section. Nothing, then a loud pop and a small pellet hit the bottom of the drain can we were using. One of the guys claimed that it was spider spit.

Hooked it all back up and no problems since.

[cvillegas71]

Ok, I will look at the fuel tank and see where this screen filter is located, I did see a nut, perhaps a 17mm nut, and I assume the filter is behind that nut.

So:

1: Find screen filter and make sure it is clear
2: I don't have a compressor at home and the gas station is a bit far, would flowing air through a hose by lung power help?
3: Prim the pump

As for a replacement pump, I guess it is always better to stay as close to OEM as possible and I am leaning toward the Hardi which is $180.00 compared to the Pierburg at $110.00. My concern is Bar pressure as well as the Pierburg seems to only have one inlet and one outlet where the Hardi has 3 hoses coming to it.

I know one hose goes to the carbs and the other one is fuel, the 3rd must be for fumes.

[bobolsn]

Be careful. The screen that is referenced is inside the gas tank, but accessed from outside the tank. When you take the 17mm nut off gas will pour out of the tank. The filter is essentially on the upstream side of the outlet hose. So just loosening the outlet hose will provide some indication of the integrity of the screen.

I would first check fuses, make sure the pump is getting power, does it make noise, remove a line at the carbs to ascertain if fuel is getting there, blow the lines (lung power first), then look inside the tank. Easy things first, then the harder/messier/dangerous.

Good luck

Bob

[cvillegas71]

Thanks for the heads up Bobolsn I will do the easy firs, check the hoses. I did disconnect the hose to the carbs and turned on the key so the pump makes the hissing noise it normally does. I did find a bad hose and will replace it first to test.

I will not remove the nut on the tank until I change that Hose and retest as indicated.

[cvillegas71]

I went through the procedure recommended and found that I had a leaking rubber hose. Not easily visible nor was it leaking gas but enough to not pull fuel from the tank and push into the carbs. I started from the front and worked my way back.

Started and is running again. I will test drive the car later today. I wondering what the correct fuel pressure should be, my pump works but it looks like the original perhaps a future project but only if my pressure is not up to spec.

[jjeffries]

Be sure to follow basic safety rules, such as keeping a decent size, up to date fire extinguisher close at hand while working on fuel system, and if you do replace the pump, disconnect the battery first. Replace any perished rubber fuel line/hose. Sounds obvious, but just in case.....

[jass]

If you had one cracked fuel line, you probably have more. I would suggest you replace all of your rubber fuel lines while at this. There have been many an engine bay fire due to cracked/split fuel lines. Cheap insurance.

[cvillegas71]

I will change all the lines including the return line to the tank. I also replaced the one in the engine bay and will work on the ones at the tank and canister in the hood.

Still would like the pressure specs to look for when I am testing the system. I do feel some hesitation during acceleration that I had attributed to a recent change of point to my Marelli dizzy. I was still working on the dwell setting and timing when the starting issue turned up.

[70basket]

Don't forget the line connecting the tunnel and engine bay hard lines. It is near the front of the transmission and easy to forget about (been there).