Capping A Fuel Rail
 

To cap a fuel rail on a CR you need a 19mm wrench, a tap, and a set screw. (not sure on the size of the tap or set screw)

Here is the pressure relief valve and banjo bolt on a 06 in the truck

Attachment 57005

Here is the pressure relief valve on a 05 out of the truck

Attachment 57006

Here is the banjo bolt

Attachment 57007

Remove out the banjo bolt

Attachment 57008

Tap the banjo bolt

Attachment 57009

Put set screw in the banjo bolt

Attachment 57010

Reinstall banjo bolt

Attachment 57011

Now your relief valve can blow off but no pressure can get out. **CAUTION** Doing this can cause harm to the fuel system. This relief was installed by Chrysler for a reason, keep that in mind.

Awesome! Thanks for the write up, I'm proably gonna wait on this mod till I get a rail pressure gauge installed so I know exactly what is going on! Whats the highest "safe pressure to run at? 27,500ish? :pca1:

it might be hard to hold that kind of pressure with some aggressive tuning

But 27kpsi what i run:U:

Alright, I got the Rail pressure gauge in my truck to day and at WOT I can get about 24,000ish +/- Is that normal sounding with the mods I have? Plus when I floor it, it'll get around 15,000 and it will drop 1 to 2k then scream up to 24k ish, it does it every time. Normal? I'll try to get a vid of it when I get some free time.... Side note though Di-Pricol gauges are some awesome lookin and the quality is second to none! Nice stuff..... :U:

thats a good pressure, what kind of tune are u running

90 hp tune on both the Smarty and on the Banks Six Gun. Thats all the clutch is willing to take at the moment :lol:

I honestly have not really looked at mine lately, but I am fairly sure I have seen in excess of 26K a few times.

well thats good enough, if only there were a way to see commanded RP.

too bad u dont have efi. But if it goes any lower u can mod ur FCA to maintain higher RP. A bigger tune should demmand the same ammount of RP if not more, if u notce that it is not as high with a bigger tune time for some fuel upgrades to get more psi :U:

Went out and played alil to day and I was in fifth matted and got'er wound up to 3350 and the rail pressure was pegged to 28K :choochoo:

very helpful thread! :argh:

1/8" NPT tap and plug. But I recomend just getting a real cap. You've now got 25000psi of diesel trying to cut between the banjo bolt threads and the relief valve housing, and that top sealing washer having to hold it back. Neither were designed to do so. I always had a little weep around my banjo bolt untill I just got the real cap.

where do I get the "real cap" ? Complicated or easy to do like this?

Or you could just get the dual fuel line kit..... :humm:

Floor It sells the cap that takes the place of the relief valve fitting. very nice piece. the dual feed line kit doesn't really do much for performance, but it will act to cap the rail.

Got her plugged. Just so everyone knows, need a 3/8 FT(24 tpi) tap and 3/8 24tpi set screw.

Appreciate the re-loc!!!:U:

Right, need a fine thread tap. But which size plug? 1/8" or 3/8"? I forgot when I did mine.

What is this mod for? Im:humm:

Wow, you're alive after all. :tttt:

It keeps fuel from returning over relief--the valve will open but no fuel can get out so it'll continue to keep the rail pressurized.

Ok, stupid question. I can see the possible damage that might happen if you cap the rail and it keeps hitting the roof. Something has to give somewhere.

I can understand that if it is capped and it keeps the rail pressurized, you will keep the fuel in the rail compared to draining back through the relief valve when you are in a WOT situation.

But, my truck is basically still stock (2005) except with RokkTech Sensor to advance timing, slightly better airflow (not aftermarket), RokkTech muffler and a somewhat heavy right foot now and then. Would this benefit me since I really don't have a guage to see what my current fuel pressure is when going down the road or even WOT? Would I feel it with my SOPG (seat of pants gauge)?

102,000 miles on truck so I don't really want to blow the thing up but always looking for a better performance mod if possible. Yes, some day I would like to purchase Smarty and all the guages that I currently don't have, but in the mean time. As long as it wouldn't blow it up upon first WOT, should I be fine?

How would I tell if something was starting to go bad due to this mod? Popping noise, damage to injectors, anything like that?

Worse case is take it back out.

Just asking. Thanks. Scott

I'm no 3rd Gen guy but I think this mod only benefits those who have upgraded their fuel delivery system to the point where the engine demands exceed the system's factory limits.

Maybe...just guessing here.

Basically this is only needed if you have your rail pressure turned up and have the oppertunity to blow the relief valve. You will see no change if you have not blown the relief valve. It is not capped on my truck, I do not need it capped yet since I have not blown the valve. You can spend the few dollars on this cap, or buy a new relief from Dodge that is around $400 iirc, or get a solid bolt made for around $25 iirc. My choice is to do this, just a personal perference. If you are constantly experiencing high rail pressure and you cap the relief valve it very well could cause something down the way to give up. Note the disclamer at the end of the origional post.