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Threading fuel rail for 1/8 pressure gauge

T

ThaSnyGuy

Member
Joined
Jul 14, 2023
Hey guys I'm wondering if anyone has ever drilled into the end of the fuel rail to tap it for a gauge before. How thick is the material there? Is there enough meat to stay out of the way of the regulator port?
 
I doubt there's enough material.

Why do you need a gauge?

If it's just for diagnosing, later redblock cars got a fuel rail with an integrated schrader valve for testing fuel pressure.
 
it is very thin. i once tried to remove the weird return pipe that connects between the FPR and return rubber hose and it tore out the side of the main rail body. I been thinking about trying to braze it though.

it is possible the end caps are thicker but I would not trust doing that with high pressure fuel.
 
I thought about putting a sensor on the fuel rail and looked at some adapters 14x1.5 to -6AN, -6AN--6AN with 1/8 NPT port, and -6AN back to 14x1.5. Decided to put the sensor in the banjo bolt on the fuel filter.
 
threewagons said:
I doubt there's enough material.

Why do you need a gauge?

If it's just for diagnosing, later redblock cars got a fuel rail with an integrated schrader valve for testing fuel pressure.
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I had some problems a while back with fueling and now I would just love the peace of mind of having a gauge there. This car is a '88 240. My '93 940 does have the Schrader though.
 
Is the Schraeder valve fuel rail a straightforward swap? You might be able to just convert... FPR style is different though.
 
They both seem to be identical other than that valve. I'd really like a permanent gauge mounted though. I had to get rid of the hard plastic fuel supply line as it was very kinked at the filter. I went back with a rubber line so I guess I could use a barbed t with a gauge to monitor fuel pump output.
 
A gauge at the rail doesn't tell you anything when you're driving. For any real diagnostic info you need to be able to see fuel pressure as you drive.
 
Khrrck said:
Is the Schraeder valve fuel rail a straightforward swap? You might be able to just convert... FPR style is different though.
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It would be a straight swap pretty much. You’d go to the newer style FPR. The return line would likely need to be shortened a bit but that’s not a big deal. Might as well delete the cold start injector and replace it with the block off plate found in the earlier LH cars.
 
Or you can get a Nuke Performance fuel rail with a port for an NPT gauge or even better use the port for a fuel pressure sensor so you can have a gauge inside the car to watch while driving.
 
dl242gt said:
Or you can get a Nuke Performance fuel rail with a port for an NPT gauge or even better use the port for a fuel pressure sensor so you can have a gauge inside the car to watch while driving.
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I have the cheaper ebay fuel rail, probably the same thing as the nuke rail, I use a Radium Engineering direct mount FPR which threads into the end of the rail, has a return port and two extra ports for gauges or sensors.
 
Radtap said:
I have the cheaper ebay fuel rail, probably the same thing as the nuke rail, I use a Radium Engineering direct mount FPR which threads into the end of the rail, has a return port and two extra ports for gauges or sensors.
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This sounds like a solution I might want to explore more. Does this el cheapo fuel rail mount in the factory location?
 
Radtap said:
I have the cheaper ebay fuel rail, probably the same thing as the nuke rail, I use a Radium Engineering direct mount FPR which threads into the end of the rail, has a return port and two extra ports for gauges or sensors.
Click to expand...
Also the direct mount fpr doesn't utilize vacuum from the intake manifold does it?
 
The original connection used is ermeto. However maybe difficult to source in the USA.
2nd I would not mount a (cheap) pressure gauge on an engine. If it leaks/rips all hell will break loose.
For diagnostic purposes with a long hose so you can place a gauge near the windshield wipers, good idea.
 
the answer is yes- (B230 with LH 2.2 or 2.4) 1/8 NPT works fine -there is plenty of material to install one on the end of the factory rail. We have 3 cars done with many happy miles. great to troubleshoot fuel pump and FP regulator issues. the rail is a hard brass type material you should drill a very small pilot in the center point of the fuel rail end- then drill and tap it squared up properly. i dont have any pics handy but can send if needed.
 
Fastguns45 said:
the answer is yes- (B230 with LH 2.2 or 2.4) 1/8 NPT works fine -there is plenty of material to install one on the end of the factory rail. We have 3 cars done with many happy miles. great to troubleshoot fuel pump and FP regulator issues. the rail is a hard brass type material you should drill a very small pilot in the center point of the fuel rail end- then drill and tap it squared up properly. i dont have any pics handy but can send if needed.
Click to expand...
I ended up going with a AliExpress rail and a el cheapo 2 port regulator. It looks great and works well too. It actually sounds like my fuel pump is working a lot easier too. I had to file down the radius on the mounting hole extrusions so it would line up correctly and play around with fittings that had tighter bends to keep it off the firewall but the car seems happy and the setup looks fantastic.
 
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