Fuel Delivery Issues - Fuel Pump Related - Draining to Tank

[engineerlutz]

I have recently been experiencing what I believe to be fuel delivery related issues. I've had an issue with fuel draining out of my fuel filter back towards the tank.

Initially believing it was the accelerator diaphragms, I tore apart the carb and rebuilt it. It has recently been worked on by the previous owner with fresh and supple diaphragms. I put it all back together. The issues persisted.

Having replaced the fuel lines when I first got the car my attention turned to the fuel pump. I drove it for months knowing I had to crank it excessively each time.

Finally a week ago it gained another symptom. After driving the car for a reasonable amount of time, I will park it. If I leave it for 20-40 minutes to sit and go back to start it, it will start up and then starve when it runs out of fuel in the float bowl. Curious I opened the hood and noticed bubbles coming up in spurts from the fuel pump line into the fuel filter. Nothing was spilling under the car. I would have to let the car completely cool and sit for an hour or more to drive it again.

After being stranded 3 times, I finally decided to go after the fuel pump. When i got it off i noticed three things. It wasn't the correct stock fuel pump. It is a sealed unit that isn't serviceable and appears to be a fuel pump from a Fiat 850 based on the brand name. It was put on with no gaskets, just sealant goop, and I was able to gently blow air backwards through the pump.

Based on this, I'm convinced a new fuel pump will solve my problems. Am I barking up the right tree? Anything else i should check or be aware of?

Thanks.

[bradartigue]

Yep - sounds like a bad pump. Get a new Spider mechanical pump and drive way.

[archiethe3rd]

I recently solved a fuel delivery issue with a new mechanical pump (and a lot of help from the forum). It turned out my new pump had the inlet and outlet ports reversed from my original pump. But to my point, in dealing with the fuel delivery problem I replaced fuel lines and filters. My 78 has an inline one-way check valve about 6-7 inches before the fuel pump. It is there to prevent fuel from flowing back to the tank. I had to post a picture to find out what it was. I don't know if this helps any, but I thought it could be pertinent.

[engineerlutz]

Thursday I had time to install the new pump. It seems to have solved most of my problems. It doesn't allow the fuel to flow back out of the fuel filter line now.

The check valve you're speaking of archiethe3rd I think is what's called the "UFO" check valve. I took mine out first thing when i got the car to see if it was working. Honestly I thought It had a slight leak, but it wasn't keeping me from driving the car. Odds are I need a new one. The fuel pump issues were a larger symptom, but it seems to have fixed the back flow of fuel to the tank.

[engineerlutz]

One last note, I had to rotate the in-flow nipple because it was interfering with the air hose going from the engine to the air box. Just loosing up the top bolt was enough to rotate it around.