Fuel Pump Diagnostics Options

[solex]

Hi All,
Need a little help to diagnose a fuel pump problem in a 75, I do not hear the pump when I turn the key to the run position.

The car was running, I had a few occasions where it would not start, let it sit for a few days and it was start right up.

The grounds: under the relay board, battery and transmission have all been cleaned.

All fuses are good.

The relay is working as I can hear it click into position.

When the key is in the run position relay terminals 30 and 85 shows 12 volts. Terminal 86 show 0.03 volts and terminal 87 show zero volts.

There is no voltage at either of the fuel pump terminals.

The readings at the relay is counter to to what Haynes states (86 should read 12 and 85 should be ground).

I not sure where to check next, really do not want to pull the tank. Any assistance would be appreciated.

Thanks,
Dan

[avidfanjpl]

It is not at all unusual to have 3 problems all at once. And I will throw in a 4th.

I know this is lengthy, but you do mention some symptoms that I have recently suffered, so I will throw it all out there.

1. Relays do fail, and mine by PO were Chinese made and were junk. Replaced them with good working German ones. I later opened up the Chinese relays and they are not even close to the German quality. Worlds apart, really. They were prone to metal deformation from heat.

To test my new board and the pump, I took the opened relays, and would push down to see if the heater fan worked on the rearmost relay with the heater lever pushed forward at the shifter, and if the pump worked with the ignition on and pushing down on the second relay from the rear.

The manual method worked in both cases, so I knew I had a new working board. (The other board did NOT work even with the manual method, so I knew I found an open, but the original board was so thrashed, I just replaced it and threw the thrashed one out.)

2. My similar problem was that the relay board (repaired by PO) would heat up and flex in warm weather with a warm engine (tar was removed and replaced by one hell of a lot of permatex), and stopped the relays from working. I could wait and let the car cool, but once, 10 miles from home, I took the relays out, put them in paper in a cooler I had with me. put another cooler block right on the relay board, and it all started working for a little while, enough to get me home. I was so pissed, the car sat in the garage for 4 months, which caused item #4.

3. The fuel pump can fail, mine started to go (reason shown below), and I got a replacement used one here. But, mine is a 3 port, and it sounds like you have a 2 port, which is MUCH cheaper to get even a new model. People here regularly bypass the 3 way return mess on the front mounted pump and go for a 2 port, but I am not sure which one is best.

4. I had a rusty tank and only by looking at the fuel filter, which was full of rust, did I realize that I had a much bigger problem. You might want to check your fuel filter just to be sure that you aren't suffering my fate.

So, you see, you may not have that much wrong, but those worn out relays can cause the symptoms you mention.

I am almost done with all the knuckle busting, and this week, I think I will actually pour clean gas back in and see what I have.

Hopefully no leaks!

Good luck!

J
avidfanjpl