vim LT4

I received my fuel pressure gauge today (with a long red hose) and after reading all the warning signs, I'm scared to even bring the thing close to the car

I need to measure the fuel pressure at WOT, which means I need to go drive around with the thing hooked up to the fuel rail and taped to my windshield, right? Is it safe? Can I wait until the engine gets hot with that setup?

I guess the question is: what should I definitely avoid doing to be safe and not burn my car to the ground?

Man I don't like to play with fire

Aggravated4life

First install the gauge when the car is COLD...you hand tighten it down on the rail after you take the cap off.

Then with a pair of pliers, tighten the gauge a little more til it feels tight and then prime the fuel rail by turning the key on and off a few times while waiting a few seconds before doing each key turn...this should bring the fuel pressure up to 38-45 psi depending on your car.

If no leaks, then start the car and let it run, watch the gauge and be sure it doesnt leak...

Check the entire line too, the gauge and the valve you screwed on to the rail...if all checks out ok and you feel confident its not going to leak,
tape the gauge to the windsheild and do a warm p the car and do a few WOT runs so you can monitor the gauge.

Is there a reason you need to do the gauge test?
Is there a possible problem you suspect?

Most of the time I can run the engine at idle and crack the throttle open by hand and watch the gauge at WOT and part throttle and etc and its usually enough to convince me whatever im looking for.

When you turn the key off, the fuel pressure should not drop down fast...it should hold, then slowly bleed off after a long time.

If it does, theres a chance the pump is allowing it to leak back or the FPR isnt holding pressure etc.

Let us know how it goes...yes its scary about fire..which is why I start on a cold motor first.

Have a fire extinguisher close by at all times..but dont worry so much..you have to literally unscrew the gauge off almost half the way before gas spurts out.

BTW, dont take the gauge off on a hot engine.Let it cool down for a few hurs first and use a towel around when its cooled to catch any gas that may come out when taking the gauge off.
I know you thought this but its a reminder.

GlockLT4

What he said ... [img]http]//www.corvetteforum.cc/ubb/biggrin.gif[/img].

nickd

All those warnings are for the MFR to cover thier *** , don't let them scare you-lol.
I have done this many, many times before. I prefer to only hand tighten the fitting on the schrader, personally I would never tighten it with a wrench, aside from the fact it's not necessary you may end up damaging some of the threads on the valve as well as the o ring seal inside the test gauge fitting. You should be able to get it more than tight enough by hand.
Whatever makes you feel comfortable though.
Otherwise do like Bill said.

vim LT4

Reading those posts made me a lot more confident I hand tightened the thing on the valve, turned the ignition on a few times and checked for leaks; turned the engine on and let it idle and checked for leaks; grabbed a fire extinguisher, went out into the world and did my readings. So far, no fire!

Bill's86Coupe, my engine is running lean and we're trying to figure out why

Thanks all!

Vince.

ham

I see you've already done it but for those who might be interested the ignition point of gasoline is over 500 degrees. I was also concerned when I had mine dyno'ed because when I arrived, I had to plug the gauge line into the rail before the pressure had had time to fall. So while trying to get the threads started, I spewed gas all over the intake (and my hands). I was obviously worried, but the dyno guys acted like it was no big deal so I went ahead and just dried up the fuel with a rag afterwards. After that, I did some searching on the net and found numbers ranging from 486 degrees to over 800 degrees was the ignition point. If the engine coolant was around 200 degrees, there's no way the top of the manifold could be anywhere near 480 degrees. I would think that most under the hood fuel fires are caused by wiring in the engine compartment or plug wire spark igniting the fuel.
Just my .02 & 1/2.

JasonL

Good info ham. Just wanted to add that I seem to remember reading that exhaust gas temps of piston engines were around 600 degrees? Something to keep in mind [img]http]//www.corvetteforum.cc/ubb/smile.gif[/img]