StratfordShark

I got my pressure gauge today from 928Motorsports - will be great to track down suspected fuel pressure problem (cold starts fine, needs blip of throttle to start warm).

Since we're talking gas here I just want to make absolutely sure I install it correctly.

I pulled the pump fuse and waited for engine to die, so when I unscrewed test cap from rail (and caught the ball bearing!) there were only a few drops of fuel.

The gauge comes with o-ring and adaptor. Does the o-ring slip over the fuel rail thread, then do you tighten adaptor down onto o-ring, then screw on the gauge? Or does the o-ring go over the fitting on the gauge (doubt it)?

Have asked Carl but hope he won't mind if I also ask here as I thought if I got quick reply I could finish the install tonight and at least measure the pressure drop.

TIA,

Adrian

Mrmerlin

pictures please? I drilled and tapped my fuel rail end cap with a NPT pipe tap its tapered so the gauge threads and cap threads seal better, I used some teflon tape on the gauge threads and also on the fuel rail threads ..........careful that you dont get any tape inside the fuel rail, tighten the assembly on the car so you can read the gauge

Mike Frye

+1 for mine, but I think the ones from 928 Motorsport are 'plug and play' no drilling necessary. I'm not sure about the o-rings though.

wg928

the teflon tape and gasoline not a durable / reliable sealant AFAIK. advice needed please?

underdog928

Teflon works very well with gasoline.

http://www.efunda.com/designstandard...%20Virgin#chem

Mike Simard

Teflon itself is impervious to just about anything but being in tape form is bad, pieces can get into the system. I use Loctite 545 for fluid fittings.

dr bob

Two things--

Teflon tape is intended to fill in gaps behind the loaded threads on tapered pipe fittings. So long as you tape job is done correctly, and doesn't lap the first thread on the end of the male pipe thread, there's almost zero risk of getting shreds of tape loose in the fuel manifold tubing there. I like the sealant-in-a-tube stuff because it works effortlessly, requires no special care on the end of the threads, and looks a lot better (read: "can't see it at all") when applied correctly. It just takes a little smear of sealant to do the trick, really.

The threads for the cap on the end of the fuel manifold rail are not tapered pipe threads, so teflon tape is definitely not the weapon of choice for sealing them. Yes, if you pack the threads and wrap the end of the rail with tape there's a chance it will hold, but it's far from ideal. That's why there are o-rings, copper sealing washers, and in this case a ball-bearing doing the sealing from the factory. When installing the gauge in a drilled-and-tapped factory fitting though, you need a ball bearing with a hole in it. Consider a brass edelman-style compression sleeve normally used for a tube fitting. The brass is soft enough to form the seal needed between the nut and the end of the rail, and therefore needs no sealant on the threads at all. A stub of copper tubing, with the ends tapered by the tubing cutter, might be an acceptable short-cut on this too. I've looked at the parts and the way they assemble, but not actually installed a gauge this way, so take this suggestion with a grain of salt.

the flyin' scotsman

IIRC I fitted the o ring into the brass fitting toward the guage side with no tape required...........its easy to figure out, the fitting has 2 different threads; metric for the fuel rail and imperial for the guage.

This is the guage, fitting and o ring from Carls kit:

StratfordShark

Thanks for all the tips and advice. Carl gives great service and got back to me to confirm that the o-ring goes on the fuel rail thread to seal against the adapter.

I've now installed the gauge. I got in-spec readings for the pressurized situations (3.4 Bar engine running, 3.85 Bar with engine off and fuel pump running with jumper).

The pressure looked like it was holding fine after about 10 minutes with pump off, but after the 30 minute test interval in the WSM I was only on 2.1 bar and falling!

Car is outside and too dark now to do any more work here in the UK, but tomorrow I will establish whether problem is with check valve (unlikely - I changed it recently), FPR or injectors (very likely - I smell fuel on several plugs and I believe the injectors have never been cleaned and are original).

Quick question - if it is leaky injectors, is that fixed by cleaning or only by buying new injectors? If so is there any issue with matching new injectors to old?

Thanks,

Adrian

StratfordShark

Hi Malcolm,

Not sure I get your meaning when you say "towards the gauge side". Carl has confirmed with me that the o-ring goes over fuel rail thread, the adapter screws down onto the fuel rail (seats hard against the rail with o-ring invisible in recess), and gauge then screws into open end of adapter.

I've just installed mine that way and tested that I have no fuel leaks, but I will probably replace the stock end cap and ball after checking where fuel pressure is being lost.

the flyin' scotsman

I re-checked last night...........I have the guage, adapter and O ring as Carl describes. There is only one way because of the difference in threads. I also reshaped the fuel rail cover end with a dremel to accomodate the extended adapter.

BTW........I leave mine in place all the time

StratfordShark

Hi Malcolm,

Yes I've put a couple of marks on the rail cover (off the car right now) as I also want to cut a piece out to accommodate the adaptor and leave the gauge on

bfellows

Just trim away, you have to cut deeper than you think - nearly to the radius. Looks fine when done.