IP outlet check valve

[rgafitanu@gmail.com]

Anybody has the part number for the IP fuel outlet check valve?
I have 15 PSI with the return blocked but only 9 PSI in normal operation. I believe the check valve got weaker over time.

[Pawel66]

Just had EPC open at hand, but do not want to give you a wrong number...

[Shvegel]

There are 2 versions of the valve that I know about.  The early 280 version is a traditional spring and disc valve with brown plastic internals and the later one is simply an orifice with white plastic internals.  Not much can go wrong with the first and virtually nothing can go wrong with the second. 

I am wondering if you have measured the volume of fuel at the outlet as well as the pressure? 

[rgafitanu@gmail.com]

I did check the volume and I have about 17 sec/ltr. I actually have 2 tall pumps that I swap every time the tank sheds more rust. It gets collected in the intake screen to the point of obstructing it and the engine stalls. I do it every 5-6 fill ups when the pressure gauge drops below 7 PSI but the intervals are increasing.
I know that they are very simple but I was thinking that if the spring got weaker the valve would open before 11 PSI. Having a lower pressure in the IP would allow for vapor lock.
What is interesting is that EPC shows the valve being used only on M130. I have the M127.981 engine and it is there. It wasn't used on the other engines or EPC didn't show it as a part? If it wasn't used then how was 11 PSI maintained?

[Pawel66]

This is the only valve that is on IP parts list in 127.981. Maybe it is this one you are looking at. I do not remember if there is a valve for oil line in this pump...

[Shvegel]

I don't know the answer to the question I am going to ask but thought it might be relevant.  Are you sure the specification is 11PSI without the return line blocked or perhaps the spec is for a later 280 with the return orifice?  The spring in the valves is a very weak one and I doubt it would hold 11PSI.   You might want to try the later 280 fitting with just an orifice in it as it was designed as an improvement over the previous design.  It was first used on the pump with the last digits of 24Y  I am sure if you looked at the pump for a 1971 280SL it would be the right one.

[ja17]

I believe the "t" fitting and by pass at the electric fuel pump is used in conjunction with the later check valve. Normally temporarily closing off the fuel line will produce around 20psi or higher in the system.