I have a 94 Topaz and suspect I have a failing fuel pump. The two symptoms are: (1) the car runs well most of the time, but at high rpms I occasionally get pinging, (2) when idling in drive, the engine seems to vibrate more than it should. About the vibrating, if I put it in neutral, rpms go to around 850 rpms, and it's very quiet and the vibration goes away, but in drive it drops to 700-750rpm and vibrates (I can feel it through the steering wheel). At first I suspected the pinging was due to carbon deposits inside the engine, so I put in a couple bottles of higher quality super concentrated fuel injector cleaner at two different fill ups, this seemed to smooth it out somewhat, so I figured it was getting a routine injector cleaning which helped anyways, along with removing carbon as the bottle claims. The more I read on the internet, if the fuel pump is not putting enough pressure into the system, this will cause a lean mixture and maybe pinging. I suspect this is what is happening at higher rpms. At lower rpms, a lean mixture can make it run rough (the vibration). I tested system voltage, at idle in park is 14.53 V, in drive the same, with headlights 14.44 V, with A/C 13.12 V, so I imagine the fuel pump is also getting this voltage, and at this point I am ruling out insufficient sparking voltage (coil problem). I "tested" the fuel pressure regulator as other people suggest (remove vacuum hose to see if there's fuel coming into the intake manifold and there's no fuel coming through) so I'm assuming that it is working as well.
Before going out and buying the pump, I'd rather test the fuel pressure in different driving conditions (idling and highway speed), and I've seen testing kits that have a hose and mechanical gauge, but I can't use this on the highway. So my question is, if I'm using the right fitting to ensure a tight seal, is there a problem with attaching the fuel pressure sender on the fuel rail at the "Pressure relief valve" according to Haynes manual (Schrader valve)? It seems a logical place to put it since it would be measuring the pressure the injectors are seeing, and wiring would be simple right through to a gauge inside. I've seen others put the pressure sender BEFORE the fuel pressure regulator, but as I understand it the pressure may fluctuate while driving, which is why the fuel pressure regulator is there, to keep a consistent pressure for the injectors, and I really want to see what pressure the injectors are getting.
I will put a new fuel filter and PCV valve in, they are about 20000 miles old, although I don't suspect the fuel filter as being a problem as I always but quality gas (Shell or 76) and 89 octane. Other information on the car: just passed 100000 miles, always routine oil changes, Bosch Platinum 4+ spark plugs (ran a lot better), K&N air filter (WOW! LOTS MORE POWER AND MILEAGE! Everyone ought to have one), new cap and rotor, plug wires 20000 miles old, recent water injection for removing carbon deposits (also helped, seems there's less pinging overall so I'm happy, lots of dark grey steam that stank of carbon came out while doing this). Last year took a road trip on old, bad cap and rotor, still got 30mpg on what Ford says should get 27mpg, I attribute this to the K&N and the Bosch plugs. Can't wait to test it again now with the new cap and rotor. Recently checked the plugs and they look fine, a light grey and no other deterioration, two electrodes look like they spark more often than the other side or one side is exposed to a hotter part of the chamber, which is interesting