Help with testing a fuel pump

[Oldman]

Still trying to figure out my P0171 code.
I've decided it's probably a weak fuel pump.
In order to make sure this is in fact the problem, can you folks please tell me exactly how to test the fuel pump with a fuel pressure tester. I do not have a scan tool. I tested it a month or so at idle and reported my findings here (45), but you guys told me that I needed to rev it up or remove the vacuum line from the regulator or something else.
If you guys could please tell me exactly how to conduct this test, I would greatly appreciate it.
I will be using a simple pressure tester that the auto parts stores have as a loaner tool.

Thanks in advance for your help.

[justdave]

Uhhh...the loaner/rent-'em fuel pressure gauge kits come-WITH instructions (sometimes on a CompactDisc that 'should' be in the plastic box, but which the store may have decided to keep behind the counter). The testing procedure IS posted elsewhere on this site; a simple search will find it. (Most experienced folks on Forums will not respond to questions whose answer may include SAFETY issues.) ALL of the fuel-pressure testing kit makers ALWAYS include instructions with their kits, with Safety Issues listed first, and Warnings about flammable fuel, Eye-protection, etc (to prevent user mishaps, and, make any lawsuit attempts afterward impossible).
I will add another warning: a previous user of a kit may have removed/lost/damaged the special rubber seal inside of the connector that usually screws-onto an engine's fuel-rail test port; check it CAREFULLY with a strong light and magnifying glass as needed to be certain it will seal the high-pressure connection BEFORE you attach it (or have the store's clerk check it with you watching). ANY under-hoods fuel leaks are very dangerous.-----If you still cannot get the correct testing procedure, post another followup request, with specific questions about the info you may still be missing.-----As to the engine-vacuum connection atop a fuel-pressure regulator: when starting, the engine is turning over relatively 'slowly' (compared to at-idle RPMs) and needs much-less fuel to get it running (than it requires for powering down the road). Regulators were designed to deliver less-than full-rated pressure...UNTIL the engine is actually running smoothly. ONLY when it is running smoothly (not coughing and sputtering, for instance), a cold engine generates about 16 inches Hg vacuum, which causes the fuel-pressure regulator to deliver it's specified pressure. This design is kind of a backup-plan safety system, to avoid flooding an engine that has some kind of recent problem/parts-failure. (Remember, excess fuel, ANY fuel, is dangerous...modern fuel-injection systems use high-pressure fuel systems which are potentially even more dangerous than those in older cars.) *By-the-way, when fully warmed-up, usual engine vacuum = 20 inches.

[Oldman]

Thanks,

I will have to say this is undoubtedly the most extensive, detailed non-answer I believe I have ever seen on this forum.

You win the prize!

Actually, it's just good to get a response.

I was starting to think that everyone had died or something.

[Oldman]

Thanks everyone for your overwhelming response to my cry for help!

Whil waiting for a response, my car actually died on the side of the road. BAD FUEL PUMP!! Only place I could go to get one without transportation was a junk yard. $30.00! Runs better than I can ever remember. Apparently, a fuel pump can go out gradually where you don't actually notice the decrease in performance.

Great to have it back and running like it should.

Hopefully, I can erase the codes and see if the P0171 code comes back.