The Rail Plug and the fuel pump Overflow valve
 

Technical: The Rail Plug and the fuel pump Overflow valve

Hi

Have found your website giving very good info on diesel engines.

I am from Ford Ranger Club (TDCi 2.5) of Thailand who normally distribute knowledge and info for the members as well.

However, lately, our club have an ongoing issue about the Rail Plug because one guy who sell performance chip to our members choose to replace the Rail Pressure relief valve with a rail plug because it gives more easy power.

A lot of people follow him because of the huge power gain. The chip owner guy claims that BOSCH commonrail system is durable enough to withstand the over pressure situation.

I am trying to search for more knowledge on this issue and most of the info says do not plug the rail. And I am telling them not to do. But guess what? they think I am trying to discredit him for doing business.

Well, the guy and the followers say their cars have been just fine, and nothing has been broken. Well, two or three trucks have had problem with commonrail pump but they still think it is not relevant to the Rail Plug they are using.

Also they claim that the Fuel Overflow valve at the fuel pump will handle over pressure good enough that using rail relief pressure valve is nonsense. Well, if it regulates the pressure that well, why do we still need the rail pressure relief valve then?

So, anyone has anything to say to let us clearing up the issues, once and for all.

Thank you very very much for your time.

Regards,
Meta

Rail plug info
 

I don't have your answer but, H & S Performance sells one that is for both the Duramax and the Cummins. Their website may give some more pro's and/or con's.

Thanks Joefish

I just have the answer for myself from examining the signal that controls the overflow valve at the pump during engine run.

I have found that the Rail pressure relief valve is there to drain any pressure that surges over a specific pressure level, say 170 MPa, a static operation. It is mostly mechanical spring loaded valve. And 99% of its time is in close position.

The high pressure overflow valve at the pump will drain any excess pressure at specific time that is determined by the ECU, a dynamics operation that is. It is a solenoid valve. It will open to drain any excess pressure that is read out from the MAP sensor against the pressure requirement in the ECU mapping during any dynamics operation. So, it almost always works whenever there is a sudden drop of rail pressure requirement.

Therefore, if anyone use rail plug, the rail pressure can reach the maximum of pump ability (anything over 200MPa!) without a proper control from the ECU if the rail sensor output is alternated by any performance chip that the ECU is enable to see the real excess pressure. The overflow valve stays close!


Now...I am clear. :jump: