Tim Murphy

Randy,
If you don’t mind saying, where did you get the gauge and fuel rail adaptor from? (Hopefully it wasn't one that I make)
I have never seen a gauge fail where the media is allowed to leak through the gauge but then again there might be some different designs out there other than a bourdon tube style that I am most familiar with. I suppose after it has been cooking for a while that might happen but this one doesn't look like it was cooking for very long.
How was/is the adaptor sealed on the fuel rail? I'm just curious what might have happened.
Thanks,
Tim

blown 87

I have seen MANY of them fail on Chevy motors, most seem to fail at the threads where there are all those nice stress risers called threads.

That is why I always mount them to the structure coupled to a isolator and hose.

only a couple have leaked from the Bourdon Tube type, and those have such a small leak due to the restrictor orffice built into them (the ones designed for fuel have them)

That being said, I have never seen a reason for a gauge on a FI motor, on a carbed motor, yea, possibly due to having a little to much pressure is very bad, and having just a little less is even worse.

User 41221

+100. I have seen numerous fuel gauges fail, especially back in my drag racing days. It seems like the aftermarket fuel gauges have only gotten cheaper since then, I do not trust them. Use them for tuning then pull them off and cap it, or else spend the money for an electronic sender and gauge.

Glad it looks like you will ultimately wind up good as new when done, Randy.

Tim Murphy

The failures you guys have seen might be the quality difference between the industrial world and the aftermarket automotive world.

I have a Nordskog fuel gauge here somewhere that is really low end quality. It is not dampened to the point where you can accurately read fuel pressure while the engine is running because the needle is bouncing back and forth so much. It's a perfect gauge to check pressure when jumping the fuel relay but there is no way I would ever leave it hooked up. I made a mistake once and bought a batch of "really good deal" gauges only to throw them away once I received them. Never had a problem with them but you could just tell the quality was not there.

To be more specific, the reason I asked Randy where he got the gauge from was to know what method of sealing was used with the fitting on the fuel rail. You can't just wrap a bunch of teflon tape on the threads and expect it to seal, at least for long term. Without the proper sealing surface you will have a leak and ultimately a fire, which is what I suspect happened here.

I have used literally thousands of gauges, mostly all industrial quality, and I have never had one fail on its own, where it leaked out the monitored media (at least not that I can remember). I have had them fail to function properly but that's about it.

I do not see the need to keep a gauge mounted permanently on the fuel rail. It is a nice diagnostic tool if you suspect something might be up with the fuel pump, but that's about it. In recent years it was more important to have one there with some of the supercharger setups, but that is no longer the case since I run stock fuel pressure and stock fuel system components. There is no need to ever change the fuel pressure.

I do like to have them on cars when we dyno to make sure we are not running out of fuel due to an inadequate or failing pump. We have found both cases over the years.

ROG100

Randy sorry to see this.
Thanks for drawing my attention to the thread.

Looks like one of our gauges and adapters though we do not have a record of selling one to Randy.

The gauge is an industrial good quality gauge and the type depends on when Randy purchased it.

The adapter allows sealing to the ball face on the rail - in other words the correct seal as designed by Rennlist committee back when.

I have no other details regarding the failure whether it was the gauge, thread, adapter or rail.

Randy V

Correct - I bought the gauge from you, Rog.

I have the email invoice you sent me when I purchased it - I have sent it to you for your review.

Tim Murphy

I totally back Roger on the design of the gauge adaptor he uses/sells. It is most definitley the right way to do it from what I have seen. I don't know anything about the gauge though but a good quality industrial gauge is what I have always used with no problems.

This did not look like yours, at least I didn't think so.

ROG100

Randy,
Sorry but I did not check as far back as 2008.
I have the invoice copy - thanks.
Roger

ROG100

Talking with the gauge supplier - very rarely do they have failures where the Bourden Tube fractures.
It would be interesting to better understand where the failure occured - rail, nut or gauge.

Tim Murphy

https://rennlist.com/forums/928-foru...e-gauge-7.html

Based on when Randy chimed in on the old thread it looks like he received the right parts.

It would definitely be nice to know the root of the cause. If it was due to a structural failure of the gauge I would be very surprised, but stranger things have happend.

Please let us know what you find.

FredR

Fully support Tim's "nice to know" about root cause of failure. I hope Randy can enlighten the list on this one- quite a lot of potential learning here!

Bourdon gauges do fail- end of discussion on that point- 32 years oil industry experience backing me up on that statement! The thing that matters is "how often?". The pressure gauge heads we use are built like a brick sh*thouse- yet they fail. We always mount a manfold valve between the gauge head and the pipe carrying the pressurised fluid to provide back up isolation such is the known risk. Our gauge heads are roughly 4 inches or 6 inches in diameter so the Bourdon coil inside can be built in such a way to make it easier to control build quality. Good operating practice is to close the isolation valve and only open it when a reading is required [a practice rarely followed]. For those that do not understand, if the head unit snaps off, the operating pressure of 3 barg is sufficient to propel the gasoline [SG=0.77] 40m into the air [that will not happen in practice because of the air resistance but you get the point].

Such measures on our cars are somewhat unpractical but with small gauge heads the risk of failure is that much greater because of the low intrinsic value of the component [and the presumed limitations of quality control commensurate with the pricing]. Does anyone actually know where the gauge heads are made and the quality standards that are applied before the factory releases them?

Whereas I can see the need for a gauge occasionally I cannot see the need for a gauge to be fitted permanently-if this is required by the owner fit a sender unit and read the pressure from an electrical receiver gauge in the cabin or on a data logging system. Just ensure it is well engineered and mounted safely [as I said in an earlier post- I would try to mount it in the fuel pump discharge area.

If you look in the w/s manual Porsche designed test gauges do not mount directly to the fuel rail- rather they have a flexible hose connection, they are chunky and of course they are only temporary units- you cannot see the gague once the hood is down and you cannot drive the car with the hood open.

That the units supplied have been engineered as well as can be reasonbly expected is, I dare say, a fair statement but they have not been engineered by Porsche. Furthermore I doubt Porsche would ever hard mount a Bourdon gauge on their design of fuel rail.

Another consideration is that by mounting a gauge this way, you are effictvely putting a larger mass further out from the rail mounted on a joint that is [by my judgement] relatively flimsy and not fit for [the newly intended] purpose. Notwithstanding the heat in there, that thing is likely subject to vibration causing an overturning moment on a joint that was not designed with this in mind- increased risk of fatigue and/or working itself loose.

Whereas it is difficult to say with any certainty what the risk levels are, the one thing that is unquestionable is that by installing such kit you are taking on more long term risk for?- no added benefit- if you need sucxh a gauge remove it when finished!

Any time I work on the fuel system before firing the car up I have a live hose pipe in hand- I have someone else start the car knowing that if I yell they immediately switch off. I am watching for the slightest signs of leakage. Once a fire starts in there you have literally only seconds to avert serious damage. I learnt this lesson the hard way years ago- after doing a fuel pressure test I removed the temporary kit I fitted- forgot to fit the end cap and ball! I tried to start the car, wondered why it was not firing up and then saw fuel mist everywhere in seconds! It was pure luck that the petrol did not flash off- the engine bay and half the car port was covered in fuel.- lesson learnt!

Regards

Fred

ROG100

Fred,
Likewise I am interested in the failure result. Randy is going to take some pictures. However his comment that fuel was leaking from the breather hole in the gauge seems to point to the failure of the bourden tube.
I talked with McMaster Carr the gauge supplier and they have no records of failure relative to the manufactures.
Roger

928mac

Can the tech prime up the fuel system in the shop and watch for the wet spot, or have the lines been burned to bad.
It would be nice to have the correct leakage point verified for everyone that has a gauge

Was it a liquid filled gauge?

I installed my own gauge and pressured it up to notice the weeping at the treads.
I then used teflon sealing tape and rechecked.
I check it now and again to be sure that it dose not start to leak.
Bottom line is I installed it so I am responsible.
If the gauge I bought fails then I guess I should have checked into it further,
eventhough sometimes you just cant tell.

Randy I hope your damage is min.
Dont let something like this get you down.
Some would say, why wasn't the leak found during the last service.
Maybe it just happened.

shadowknight

I had one that I removed after it started to weep around the glass and housing.
not sure of the manufacture.

928mac

I don't know the quality of the McMaster Carr but I know Roger dose a lot of leg work and will not sell junk.

Mine below is just a Russle but the thing is it needs to be liquid filled to handle the viberation.