Originally posted by SqueakyBrake
My new OVP relay that I ordered from the site came in today and my problem still exists. My fuel pumps cut off and the engine dies. I can't say that it has a pattern to it, %70 of the time it will start and run for about two minutes and then the fuel pumps cut off. For two months it would not start due to this, but the other day it started and ran fine enough for me to drive it around my neighborhood. They next day, no fuel pumps. I believe they are the original pumps and quite audible, believe they need replacing, but I don't think that that is the current problem. My old OVP rattled when I shook it so I replaced it. There was some corrosion on the old OVP so is it possible that my fuel pump relay needs replacing as well due to corrosion? They look in good condition.(002 545 16 05 & 002 545 18 05) Is there something that I am missing? '83 BMW 733i was totalled by a Cadillac last week and the rental car is a Pontiac!
Hi Roy & others
This problem occurs particularly after the engine has been running due to the pressure relief valve located at the back of the pump inside. It is activated by a small spring which in time weakens and do not allow pressure to be relieved.
As the pump is driven by a permanently excited electric motor (when the engine is running) the pressure is reduced. After stopping, the fuel reservoir maintains pressure in the system to facilitate starting and with this pressure if the valve is stuck it develops an inner leak.
When this happens, if you tap the pump firmly it releases the pressure valve and the engine starts again. When the tapping affair becomes more frequent, it is time to replace the pump.
However, Mercedes have realized this and they provide a Check Valve which can be installed by replacing the existing hollow screw to the pipe connection to the pump, effectively providing a secondary pressure relief valve and avoiding having to buy a new pump. ( $7.50 for the Check Valve).