Fuel Pressure Test

gulls@play · **Posted:** Mon Nov 28, 2011 3:58 pm

Can anyone tell us how to check our fuel pressure? We're thinking we may have a bad fuel pressure regulator. Port engine won't run. Looks like the test gauge is pretty cheap so we want to test it ourselves.
Thanks in advance!

Borchik · **Posted:** Mon Nov 28, 2011 7:35 pm

What engines?

ric · **Posted:** Mon Nov 28, 2011 7:50 pm

If it's fuel injected.. you should be over 30psi. Not sure on what engine you have. Some have test ports that looks like a tire fill nipple on the fuel rail. Others you have to splice a gauge in.

If it's carb, you gotta splice a gauge in. Should be over 4psi.

gulls@play · **Posted:** Tue Dec 20, 2011 8:30 am

Its fuel injected. Thanks!

gulls@play · **Posted:** Mon Jan 02, 2012 4:14 pm

Tested the fuel pressure this weekend. We put te tester on the slow pressure test port first. Gauge showed zero when the key was just switched on. We could hear the fuel pump working when the key was switched on. Tried to start the engine the gauge went up to about 10 psi after a couple of turns. We tested the high pressure and it was around 52 psi and went to 60 psi when we tried to crank the engine. Anybody got ideas on what the problem is? We have 5.0L gxi-e engines.

298VISTA2000 · **Posted:** Mon Jan 02, 2012 4:37 pm

You might want to see if your check valve (a/k/a anti-siphon valve) to the gas tank is too tight because that will keep fuel from properly flowing. I had fuel delivery issues with my generator and my tech changed the plug(s), fuel pump, fuel line and finally discovered that the check valve to one of my gas tanks was way too tight for the gen's fuel pump to deliver a proper fuel supply. It shouldn't be too long for some of the technically inclined owners that know their stuff to respond because I don't even know if I am barking up the right tree.

gulls@play · **Posted:** Tue Jan 03, 2012 11:44 am

I meant to add this in my previous post. We have also noticed a small amount of fuel floating on the water since this has been happening.

ric · **Posted:** Tue Jan 03, 2012 12:04 pm

Well, if it's the GXIE it should be multipoint fuel injection (8 fuel injectors) and it should be at least 30psi at the fuel rail.

gulls@play · **Posted:** Fri Jan 06, 2012 4:50 pm

Well since there was no pressure at the low pressure pump when the key was turned, we will have to assume it is the low pressure pump that has failed. The plan will be to replace the fuel cell unless anyone has an other ideas about what it could be.

GTBecker · **Posted:** Fri Jan 06, 2012 5:13 pm

gulls@play wrote:

Well since there was no pressure at the low pressure pump when the key was turned...

According to the GM EFI Diagnostic manual, the low-pressure system check is ""Crank or run the engine; on all models, look for a minimum of 6 +/- 2 psi while cranking or at idle, or 5 +/- 2 psi at wide open throttle".

I believe the engine must be turning for the low-pressure pump to operate.

Edit: on my 5.7GSi (throttle body injection), the low-pressure pump also runs for two seconds when the key is turned on, before start, to assure there is fuel in the reservoir for the high-pressure pump to work with. Yours are different engines but might be expected to do the same. Still, if you see 10psi when cranking, my guess is that's normal.

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Fuel Pressure Test

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