P0171 in 3 miles
#42
03-25-2015, 03:33 PM
I recall you saying the fuel filter was rusty and feared opening a can of worms, but it's something you're going to have to deal with somewhere down the road. It would be much more convenient to deal with in your driveway or a shop than along the side of the road. You should check fuel pressure at the Schrader valve on the front of the fuel rail. Pressure should be about 45-55 psi after connecting the gauge and turning the key to the "on" position. After starting the engine pressure should not drop more than 1 psi with increased rpm. You can pickup a cheap fuel pressure test gauge from Harbor Freight Tools for around $20. Fuel pressure problems can be caused by a clogged fuel filter, fuel pressure sensor, fuel pump, fuel pump strainer, or fuel pressure regulator. The regulators have been known to be a problem with the 3800 engine. Your going to need to check that pressure to know your on the right track. Be sure to relieve the fuel pressure before connecting the gauge by removing the gas cap and putting a rag around the Schrader valve and depressing the "tit" in the middle. Hope this helps.
Last edited by plumbob; 03-26-2015 at 09:29 PM.
#47
03-26-2015, 09:19 PM
Harbor Freight does have them, described as "Fuel Pump Tester", but based on reviews they seem to be a POS. Looked closer at the Auto Zone "Fuel Pressure Testers" and the $24.99 doesn't seem to have the Schrader valve fitting, but there are others for $44.99 and $49.99 that do. You will likely find them at any auto parts store.
Last edited by plumbob; 03-26-2015 at 10:41 PM.
#50
03-30-2015, 06:12 PM
You might be able to find a parts house that rents them. Not sure if Autozone does or not. Pressure should be between 45 and 55 psi, probably 50psi, and should not vary more than 1psi with increased or decreased rpm's.