Engine/Transmission (1994 - 1998) Where to put needle valve for fuel pressure gauge?

[SRath]

It is always recommended here that a needle valve be installed in the hose going to the fuel pressure sender to protect that expensive sender from pressure pulses. OK, that makes sense.



My question is: Where should it go?



I am planning on drilling and tapping my banjo bolt unless there is a better option. I will use a 1/8" npt tap, which is the same thread the Autometer fuel pressure sending unit uses. I am planning to mount the sender away from the engine using either a grease gun hose or braided stainless hose.



Just finding a 1/8" needle valve has proven challenging locally. All I can find are 1/8" npt (good) to 1/8" compression (bad). But I have located the right types (1/8" npt on both ends) online and need to figure out which to order, female-to-female or female-to-male), which in turn is dependent upon where I place the needle valve:



If I mount the needle valve directly to the tapped hole in the banjo bolt, I need a 1/8" male to 1/8" female needle valve. The grease gun/braided SS hose would screw directly into it and would need a female/female coupler at the other end where the sender would screw on.



If I mount the hose, which has 1/8" npt threads already, directly to the tapped hole in the banjo bolt, I could use a 1/8" female to 1/8" female needle valve right at the sender and no other coupler would be needed if I use grease gun hose which already has 1/8" male fittings at both ends. If I use braided SS hose, which I can get with 1/8" male on one end and AN-3 or AN-4 at the other end, it would require an adapter back to 1/8" npt.



Is there any advantage to mounting the needle valve either before or after the hose?

 

[hsmith]

I put mine in the banjo bolt. Mine is mechanical, so I went with the 1/8 pipe to 1/8 compression.

 

[SRath]

That would certainly make sense for a mechanical gauge and explains why no one has mentioned the difficulty of finding a 1/8 npt to 1/8 npt fitting. The 1/8 npt to compression fittings are everywhere and much cheaper. Are most guys here using mechanical gauges?

I am inclined to screw the hose into the banjo and then put the needle valve at the end of the hose and screw the sender into it.

That might cut down on the gauge response time since the needle won't slow the filling of the hose. I was also wondering if the constant diesel vibration and weight of the soft brass valve might eventually lead to the valve cracking where it screwed into the banjo if I mounted it there.

 

[BarryG]

I did mine as you suggested, needle valve by the sender. I didnt have any issue with the valve cracking but after a while it did start weeping, ok more than a weep but less than a leak, lets call it a heavy weep (where the valve handle comes out of the fitting). I have since switched to a snubber. Autometer sells one that is 1/8 npt male x 1/8 npt female. Genos sells it

AUTO METER FUEL PRESSURE SNUBBER-Dodge Cummins Diesel Truck Accessories – Geno’s Garage.



Just another option.

 

[DPashko]

You can use swagelok stainless fittings and stainless steel tubing, they are not cheap but will never break and they have all kinds of fittings and valves. parker is a bit cheaper and there are several other knock off brands bi-lok, hylok, etc.

Swagelok Products including Fittings, Valves, Tubing, Gauges, Modular Systems, Alternative Fuels, Sanitary, Plastic Products

 

[PToombs]

I'd recommend buying the tapped bolt from Geno's. For $7 it's not worth the hassel of tapping it yourself. The head is about 1/2" thick, double the stocker. The other thing is the stocker is hard as heck. I did mine, there's not much meat there, I think I have 4-5 threads, and it was a bear to thread because of the hardness.

I got my needle valve from Graingers, the # is 6MN31. This is a 1/8th male to female needle valve. It was about $25.

 

[SRath]

I don't see a tapped banjo bolt offered for 12v motors at Geno's. So I don't think I have much choice but to drill and tap the factory banjo bolt. Am I on the wrong track or missing something?

The snubber appears to be a good option.

 

[PToombs]

SR, this is the one; BANJO BOLT - TAPPED ('98. 5-'09, 5. 9L & 6. 7L) DODGE-Dodge Cummins Diesel Truck Accessories – Geno’s Garage



I think I'm going to send them an e-mail. They should correct that, lots of people get confused, and that fits from '89 to whenever.

 

[SRath]

That's the only one I saw, Pete, and it seems to clearly say it is not for 12 valves with that description. You are saying it WILL fit? I wonder what the deal is. . ?

 

[PToombs]

Scott, I had one in my '97 for troubleshooting, and have 1 in my '92 right now. It fits. I don't have a clue why they list it like that, it's been that way for years. If you did a search, you'd see a lot of posts where guys ask the same question you did, "is this it? ". It's a lot better piece than the stocker, even the cross holes are bigger. I drilled the rest of my banjos to the size on the Geno's one. I even picked up a couple spares, 1 for the house and 1 for work for test purposes.

 

[SRath]

Thanks, Pete. I ordered one today. It does look much beefier, not to mention easier, than drilling and tapping the stocker.

I was hoping to order towing mirror door reinforcements at the same time, but it appears Geno's doesn't carry those.

 

[PToombs]

No problem Scott, always glad to help a fellow TDR member!







PS, sorry, I can't help on the mirror brackets.

 

[SRath]

I checked a bunch of online dealers and settled on one that had them for $10 apiece plus about $10 shipping. They were the cheapest overall that I found. I also found a source for a boost gauge bolt for my 12 valve that will save me drilling and tapping a hole. I thought those, too, were only available for 24 valve motors.

Looks like the only drilling and tapping I'll need to do for this gauge install is a hole in the exhaust manifold for a pyrometer. That also looks the hardest to do and most risky since it is hard and brittle cast iron and no metal drillings can escape to the turbo.

 

[Hammer]

Scott...

Why would you have to drill and tap for a boost gauge on a 12v?.



There are ports with blind plugs right on the side of the intake manifold or you could tap into the back of the line at the AFC housing and get the same result.

 

[SRath]

Didn't know about the plugs, Andy. And I bought the intake bolt so I wouldn't have to drill and tap. There is a lot of how-to info out there for installing gauges on 24 valve motors, like this;



Gauge Installations at DieselManor- 1994-2002 5. 9L Cummins



but I can't find much on 12 valves. (Probably 'cause its so easy a caveman could do it... )



Now, please tell me there's an easier way to install the pyro probe!



Just who in the world owns an 'R' bit anyway... . ? I can't even find one in the stores around here.

 

[PToombs]

What's an "R" bit? I just used a regular ol' drill bit on mine. What ever size is recomended for a 1/8th NPT tap (i did drill a pilot hole 1st). I cheated though, I had the turbo off. The pyro is easy, drill, grease the bit, small magnet to suck out the small stuff. Grease the tap, tap the hole. Magnet again, then start engine to blow out the few filings left.

 

[kenny61]

My father was a machinist and the drill bit conversion chart hung on the garage wall for as long as i can remember. Heres a more internet friendly version.



Drill bit sizes - Wikipedia, the free encyclopedia

 

[SRath]

Did you read what that article I linked to says about greasing the bit and/or tap? Food for thought...

I did buy a nifty little tool magnetizer recently to use just for this purpose.

When I drilled my hubs to install grease zerks, ala Cumminspower98, I simply put a real strong pickup magnet, for reaching tools and such that you drop into the abyss, up against the drill bit while I drilled the holes. I then used a tiny o-ring pick with the magnet up against it to probe the holes real well. Very darned little got down in the holes for the magnetized pick to get out, so I was confident the bearings won't eat any metal...

The thought of missing even one little flake and trashing my turbo bugs me, though. And I'm waaaay too lazy, uh, I mean "busy right now", to take the turbo off and buy gaskets.

 

[kenny61]

I did mine with the engine running and the bit greased going real slow the exhaust pressure will keep out any pieces that dont get caught in the grease (at least in my calculations )

 

[kenny61]

Locations

Here's my set up. The red arrow is pointing to where a factory plug was located in the intake. The autometer kit I used included the proper fitting. Also on my truck for the gauge pillar I removed the factory pillar and drilled one whole for a screw at the top to hold it to the body the bottom is wedged against the dash. This gave me more room for wires and I still have the original undamaged piece. So my great great grandkids can put the truck back to original condition and sell it for millions... If they dont bury me in it:-laf

PS the trans temp sensor simply goes into the predrilled fitting on the coolers I got from Genos