Capping the rail pressure relief valve. Who's doing it?

[JDiepstra]

Well after having my truck for about 2. 5 years and having an MP-8 installed for 6 months I am just now reading about the pressure relief valve on the rail. For those who don't know, when rail pressure exceeds a certain limit, the relief valve blows, releading pressure into a return line. From what I hear this part is a one time use and then it's a gonner, so you are constantly losing some pressure out of it. It's about $500 to replace from the dealer. Now for about $65 I got a nice rail cap to cap it off, and I got a rail pressure gauge to monitor it for about $205. Much better deal.



Who's doing it?



Good or bad?

 

[rholcom2]

No

I am not doing this. I do have a RP gauge and after ~10-12 weeks of having it installed and watching the pressure react to acceleration/load I feel it would be very hard to regulate pressure with your foot alone. Especially given the chance to dust a Duramax or Powerstroke. After lengthy conversations (with injector vendors) and reading many posts on the matter, I decided to not do this. Reason being is the pressure valve is meant to protect our VERY expensive injectors from damaging pressures. I don't doubt that many members have capped the rail and have yet to experience adverse effects of doing so. I would rather not this savings be the cause of me dropping $2K on a new set of injectors. Just my $. 02.

 

[JJPage]

I have had my rail capped since about 2005, I pulled the banjo bolt, took it to the local "Fasteners", for a solid bolt replacement and a neoprene washer.



My rail relief valve was kaput, blew fuel all over the underside of my hood when I pulled the banjo to check it. Like JDiepstra says, the Dealer wanted a fortune and as I remember, Cummins was not a whole lot better.



I was apprehensive at first, but I have not given it another thought for quite some time. All the duel feed kits remove the valve and use that entry on the rail for the 2nd feed. I understand that pressure spikes, like the ones that occur when you go wot, and then suddenly let off can crack injector bodies and tips, but until someone actually builds a "reasonable priced non-throw away" relief valve, the solid bolt stays put.

 

[JDiepstra]

One for and one against. Keep it coming guys. I just received and installed my cap today but the gauge has not come in yet. Needless to say the MP-8 is staying turned down for now.

 

[MMeier]

Capped mine about 6 months ago. Relief valve was bad and after looking at it for a few minutes, I could not see what is worth all the $$$, so I threw it aside and capped it. Seems to have given back some bottom end that was missing.

 

[Briman]

I capped mine about two years ago. Like JJPage, I went out and sourced a bolt locally. I can't tell you what it cost but I'm pretty sure it was less then two bucks. I think I had to cut it down to a shorter length because I couldn't find one short enough. I have had a rail pressure gauge the whole time the bolt has been installed. I don't push the truck as hard now as when it was newer. I almost never get above 20K psi, let alone 27K.
I think I compromised my relief valve when the truck was young on a WOT run and like MMeir, my butt-o-meter tells me I got back a little performance. The old valve ticked while the truck was running as well.

 

[JDiepstra]

Good info guys thanks.

 

[SRadke]

I've seen one blow up after letting off under hard acceleration with dual pumps. Just wasn't big enough to handle the extra flow of the big pumps when the injectors shut down and the pressure spiked. It's there for good reason, I'm not capping mine.

-Scott