1988 560 SEC Inconsistent Fuel Pump Power Issue

[angust]

I've got a 1988 560 SEC that I am restoring that sat for 5 years under leaves. It only has 65,000 miles on it. We got it running beautifully, but all of a sudden, it will only start inconsistently. It seems to be a problem with getting power to the fuel pump. We had replaced both the fuel pump and relay last summer. Now, it is anybody's idea when it will or will not start. We thought it was a problem with the power connection at the fuel pump, but we seem to have ruled that out. What do you ladies and gentlemen think? One last thought. I just recently got new keys for the car. Did the 1988 560 SEC have a security thing in connection with the key where if the wrong key(blank) is used, then the operation of the car is affected? Sounds stupid, but with chips and things in keys these days, you never can tell.

 

[OZ420SE]

Are you sure it is a power problem to the pump? Does it stop pumping or can you hear it when giving the car ignition?

How are the fuses? Are they all copper fuses or horrible alloy? Change to copper and clean the connectors - surprising how many problems that fixes.

I'll take it as given that you replaced the fuel filter when you did the pump, but did you clean out the fuel lines and tank? 5 years sitting will allow a lot of varnish build up which can clog up lines.

Are you getting fuel to the fuel distributor? Have you cracked open the lines to see if fuel is coming out?

Nothing to do with the key, they are the good ol' fashioned non-chip type.

 

[wscheffer]

This may sound dumb but I have to ask. When you changed your fuel pumps did you clean your tank and install new fuel filters?

Did you check your pumps to see if they're not receiving current when the key is switched on?

As far as the chips. I'm sure if I'm wrong someone will correct me but, W126 models did not have chips on the keys (at least they don't on mine).