1bad91Z

iTrader: (1)

I need the specs of a TPI fuel rail's schrader valve thread.

I'm trying to figure out what I would need to convert the schrader valve's hole in the rail to adapt an Autometer electric fuel pressure guage's sending unit.

Any one with pics of the Autometer sending unit for the electric fuel pressure gauge mounted / adapted to work with stock TPI fuel rail?



Thanks!

RMK

Mike,

The Schrader valve is a -4AN thread. You can remove the centre of it and have it free flowing. From there I went with a 90* elbow. The sender unit uses a 1/8 NPT thread so you will need a -4AN to 1/8 NPT connector the sender.

The pic below shows, from left to right:

-4AN to 1/8NPT
-4AN to -4AN with 1/8NPT gauge port
The sender itself
90* -4AN fitting


Regards

Robert

1bad91Z

iTrader: (1)

Do you have pics of it on the car?

If you remove the schader valve, is that hole in the rail 1/8 NPT ??

1bad91Z

iTrader: (1)

ANyone?

92 zzz28

I installed an Auto meter electric fuel pressure guage on my HSR'd 385. If you want, I will take some pics in the morning to post. I know it is not the same as the stock fuel rail, but maybe it will give you an idea of what to get for the installation...

Kuejo

Mine does NOT tap into the actual fuel line/rail - at leat not the fuel carrying portion of it!!

Is it supposed to tap straight down (ie, do I need to tap it DEEPER) or off the side (ie, do I need to enlarge the port to one side?)

VERY frustrating diagnosing a fuel problem, untl I decided to PULL the schrader valve completely, realizing then that it was a completely blind tap. Called the service guys at my local GM dealer - they had never heard of or seen such a thing (just my luck). I'm WAY out of warranty, so I guess I'm on my own...

Jonathan

8Mike9

When you say "blind tapped", do you mean that it's not drilled all the way through into the rail?

That's wierd.

Could do one of a few things, try an icepick and knock it through, could be just needs a few thousands to clear into it.

If you're concerned about knocking something loose and clogging an injector, then just pull the rail and drill/blow/flush it out.

Another option might be to tee and flare into the Cold Start line. Or disable the CSI in the PROM by running the '89 MAF chip with VAT's deeted, then use he CSI hole at the end of the rail for your gauge and adapt accordingly.

Kuejo

"fuel carrying" portion of the rail.

What I don't know, is if it just needs to be tapped a few thousandths deeper, as you suggested, or if it's supposed to access the fuel rail "from the side."

That last part is hard to descibe - the valve clearly comes from above, and taps vertically down, but does it tap straight down into the hollow fuel carrying center of the rail, or does it catch it along one edge? (ie, is it off center?)

Has anyone looked down through the tapped hole for the valve and noted this?

It is odd isn't it? - lucky me, huh? There's no rush to get it fixed - but I would like to run a line to a gauge somewhere in the near future. I will take the rail off when I fix it, just to be sure I don't get any debris in the system, but I was curious if anyone culd clarify the "anatomy" for me.

Thanks!

Jonathan

Morley

I believe it just goes down as far as the opening in the rail, as in it sits flush with the passage the fuel flows in. If it protruded into the fuel passage it would obstruct fuel flow to the injectors on that side of the engine.

1bad91Z

iTrader: (1)

Still need to know what size the hole in rail is !!

Anyone?

Gambit69

Okay this thread is a little old but I am getting ready to put my fuel pressure gauge in and I need to know what parts go where. From looking at the pic, would you put the parts on in this order: put the 90* elbow on where the schrader valve was, then put in the -4AN to 1/8NPT on the other end of the 90* elbow, then put the sender on the 1/8NPT side, then just run the wires. Also, this is the schrader valve, right?

RMK

Yes, that's the schrader valve. Unscrew the cap, remove the core in the center of the valve, and screw on your fitting.

My set-up is slightly more complex as I'm running 2 gauges. If you are running only the 1 (like normal people) I would use the 90* bend, some -4AN hose, then a fitting that takes you from the -4AN hose to the 1/8 NPT fitting that the gauge would screw into.

You can get a gauge that fits right in at the valve itself, but I wanted mine positioned elsewhere hence why I put in some hose.

BTW, from what I have read you shouldn't use teflon tape with fuel and these fittings. I double checked that with a couple of people on here and thy confirmed that was correct.

Robert

Gambit69

Okay, I am starting to get this figured out. On the schrader valve, you take off the cap and there is something underneith it in the middle that needs to be taken out. So the threaded part that is showing stays there for the 90* bend to attach to, right? Is there anything special needed to remove the core and how long should let the car sit before taking the shrader valve apart so I know the pressure in the lines has gone down? Let me know if this is right at all or if I need anything else to do this.

As for the hose, I am running and electic fuel pressure gauge so I don't think I need any of the hose at all since after I get the sending unit on the schrader valve, all I need to do is run the wires into the car and hook them to the gauge. I got the autometer cobalt series fuel pressure gauge. Thanks for helping me out with this. I really do appreciate it.

Gambit69

Can anyone tell me if these would be the parts that I am needing to put in my fuel pressure gauge. I am going through summit

aer-fcm1031 90* elbow bent tube -4an
aer-fcm2001 -4an to 1/8 npt
ear-991001 1/8 female coupling. (Catalog says this but website says it is a -3an to -3an but at the holey website for the earl performace plumbing it has this number as well for the 1/8 female coupler.)

If anyone knows of any other parts or different parts I should use please let me know.

RMK

Take the cap of the schrader valve and have a look at it. It's just like the valve thats mounted to your wheels. A decoring tool from Walmart for $1.49 will remove the core.

twolfe

iTrader: (2)

I removed my shrader valve and i happened to notice that i have a "blind" hole. it looks like only a bit of the hole is opened in to the fuel rail. not a full 1/8 hole all the way down. should i knock it out? i am taping my n20 of of that spot.. or should i relocate the wet side?

also what exactly is the hole drilled on the fuel rail? I broke the shrader valave and will need to replace it with somethign from summit.. any one know exactly what the hole is that the shrader valve fitting screws in to?

-Tony

RMK... hey do you have a part number to that 4an-4an-1/8npt ? i cant seem to find them in a 4an size.. i see many 6an and 8an..

thanks

jgifford

Here's how I did mine 90* elbow to a 'T' Fitting, then custom made hose to the sender, and mechanical gauge for tuning.

Parts Needed:

-4AN 90* elbow
-4AN 'T'
2 -4AN to 1/8 NPT adapters
1.5 ft of hose

Accel Mech. Gauge and Electric Sender

twolfe

iTrader: (2)

any one have the exact thread of the shrader valve? i m pretty sure the top is a -4an. but what is the side that goes in the fuel rail? i reed some where that it was a 5/16 x 18 but when i tryed to thred it in to somethigng at auto zone it would not go in properly. any one know where to get tahat information or have it on hand???

onebinky

iTrader: (1)

Anyone ever find this out?

twolfe

iTrader: (2)

it is a 5/16 x 18 hole on the fuel rail. good luck finding a fitting that will fit in it . i used a allen head bolt to stick in there untill my shrader was in from the dealor. by the way they are 40 bucks. what a rip..

i talked to the local aeroquip supplyer and they couldnt find me a 5/16 - an at all.

onebinky

iTrader: (1)

Cool, thanks for the info.

Is the schrader O-ring the same size as the injector o rings?

twolfe

iTrader: (2)

I would have to say they are completely different.

The shrader fitting that threads in to the fuel rail uses a washer with a "O" ring molded in to the center. I dont think you would be able to use a normal "O" ring in place of the washer "O" ring.

i think it is molded in to the washer to prevent it from pressing out when you tighten the shrader. also it will make the ring stiffer and less prone to tear (IMO)

Hope you didnt loose or break it as i wasnt able to find a replacement for mine.

onebinky

iTrader: (1)

No, I still have it. I just don't like to reuse seals unless I have to, which it sounds like I might now.

twolfe

iTrader: (2)

if you buy one from the dealer. you will get a new cap, shrader, needle valve and new o ring/washer for a low price of 40 $

-t