OK, this may be a properly dumb question, but can I do this with just pressurised air from a footpump, instead of using petrol, if I block off the return line, and pump up from the feed at the firewall?

I want to check everything's sealed properly, but figure this way is a lot less messy than using fuel if I have a jumbo leak (plus there's no fuel in the tank )
Only thing I'm worried about is whether it's likely to damage the injectors?
Talking about up to roughly 60psi (38PSI base pressure + more boost than I'm likely to run )

Cheers all

 

Here's what you do. Put the key in the "ON" position with the engine off. Jumper the yellow two prong connector on the right hand side strut tower (or at least, that's where it is on the LHD harness). That's a diagnostic connector to pressurize the fuel system for you. Usually the system is under enough pressure from that to find any leaks. But if you really want to raise the pressure even higher, take the vacuum line off the fuel pressure regulator and apply pressurized air to that. That will raise your fuel pressure to base value + whatever pressure you pump the FPR up to.

 

Yeah, I've got that one under my belt. Not sure what the us cars are like, but in mine (JDM) there's just 2 terminals in the diagnostics box that can be jumped.

However, it's a fresh build, from a bare bay, with completely new home build fuel lines, and if I'm brutally honest, I don't want to run the risk of drenching fuel everywhere if my plumbing skills aren't up to scratch. A quick air pressure test would be simple and clean with it in it's current state, IYSWIM?
Oh, and the tank's empty at the moment

 

Fuel evaporates reallly quick... And it honestly won't damage anything if it leaks. I would fill the gas tank up and pressure the hoses with fuel.

 

I'm sorry, I said the connector on the passenger side strut tower. That's for a USDM 2nd gen car, I thought I was looking at the second gen forum.

On the 3rd gen it's the F/P terminal in the diagnostic box. Jumper that to the GND terminal. Apologies for any confusion.

 

Pressure testing the stuff with air should be a useful test. Rather that test to high pressure I'd just test at 10psi and watch the leakdown rate.

 

Most crazy big leaks can be avoided with a good eyeball once-over of the system and general due diligence - making sure you tightened everything and did it all properly.

Really, jumpering the connector is the only way to really know for sure.

Good thing is you can insert the jumper wire and quickly yank it out if necessary. For extra peace of mind, keep an extinguisher handy.

Dale

 

This thread makes me wonder if it's easier to smell a hard-to-find fuel leak or hear a hard-to-find air leak.

 

Cheers guys
The main thing is I've just re-piped it with braided lines and AN fittings, all cut and made up at home - I'm not 100% confident in my own talents so I'd quite like to try it in a less messy way before cranking open the fuel!
The main reason for this is I'm in the process of super idying my bay, and am worried about the consequences of fuel on the not yet fully cured paintwork :o
Yes, I'm that vain!

 

Anybody know how to test for leaks under boost? I'm smelling fuel while driving under low (wastegate pressure) boost but not under 60 psi through the fuel system and suspect that it might be my primary rail.

Any help would be appreciated.

 

See my response to your other thread. If it's not showing up when you use the diagnostic box, it is highly unlikely you have an actual fuel leak. You've got an exhaust leak or just a rich tune (most likely the latter).

 

Thank you for your replies. I moved my questions here because I suspect that it's a missing insulator on the primary rail which doesn't have anything to do with tuning.

I'm going to pull the rail and verify that the insulator is indeed installed. If it's not, that would explain why I get a fuel smell under boost. The pressure would be forcing air and fuel past the injector rail and since it would already be atomized, the smell would dissipate rather quickly and not pool on top of the engine (which it's not). Also would explain why I don't smell it under vacuum.

I will follow up when I've pulled the rail.

 

I was right, I was missing the insulators on the primary fuel rail.

I replaced them and no more fuel smell under boost.

 

Who built up the block and installed the fuel system? That's a pretty glaring omission.

 

Yeah that's gonna be me. Sometimes you get to the point at 2:00 am where you should just put down your tools and go to bed because you're going to do more harm than good. Apparently I didn't do that.

I started questioning whether or not I put them on there and went to check my engine parts tray, sure enough, they were sitting right there still in the original packaging.

Sometimes in life, your purpose is to serve as a warning to others.