Need advice-fuel pump drive wire at oil sender??

[Randee of the Redwoods]

Ok. Short take. Engine runs fine for weeks, now suddenly now has an erractic miss joined with jumping speedo and tach. Computer codes have come bad as glow circuit, fuel pump circuit, PCM fuel circuit and fuel temp problems. Well, I had a revelation.
Riddle me this--- A while back I somehow(read-stuidity) put gas into my truck. I drained the motor, put in fresh fuel and filter and everything was fine. A few weeks after, a very minor fuel leak turned into a massive fuel leak. Problem was traced to a loose lower lock ring on the fuel filter housing leaking all over the tranny bellhousing and back of motor. The glow plug relay, oil pressure sensor, and some connections are at the back of the motor. The oil pressure sender plug was doused in fuel so I cleaned it out as best I could. Oil pressure readings have been fine all this time save for a touch of wavering in the needle. Nothing major. Or so I think...
Could it be my problem? What's the possibility that the gasoline drenched oil pressure sender/sender plug is maybe becoming contaminated? After some time of driving for whatever reason causes the fuel pump to operate erractically. So? How 'bout it? While driving one day, the truck suddenly went "loud diesel rattle" and the check engine light came on. I am now thinking that maybe the fuel pump had stopped for some reason while the oil pressure readings stayed fine.
I'm gonna mess with this scenerio by hooking in the relay to control the fuel pump. This will help the pump get the required uninterrupted supply voltage it needs and take the strain off the oil pressure sender. This way I'll know if the pump is working all the time by either installing a monitoring light or listening for the relay. I can further this by replacing the oil pressure sender plug(won't be easy, but I can try). For good measure, I'm running a new ground strap from the motor to the frame rail. This will ensure there is good voltage return from the pump to good ground.
Wanna chime in?

[NH2112]

Fuel shouldn't have any effect on the wire connections. Where I'd concentrate is in the voltage dept, making sure that there's always a rock-steady 14+V, and ensuring that all your grounds are serviceable, clean, and tight. You can't have too many grounds! Battery to frame, battery to body, battery to engine, engine to frame, engine to body, and I'd make a body to frame connection for the taillights as well. My favorite way to get good, multiple ground connections is to clean the area around a hole in the frame (say, for a 3/8" bolt), use star washers against the frame, then your ground cable(s), more star washers, then the nut/bolt head. So, in sequence, you'd put a star washer on the bolt, run this through the ground cable ends, put another star washer on, stick this through the cleaned hole in the frame, put a star washer on, then run the nut down to tighten. You could also use star washers between each ground cable connection.

[ 11-29-2005, 04:27 PM: Message edited by: NH2112 ]

[MTTwister]

Randee - search on OPS Relay - I know i've written something - and there are other threads - basically using a relay to power the pump, and the OPS merely triggers the relay. takes a big load off the weak OPS internal points.

[garre1tt]

Randy,
I had all the same problems with my 95 truck this last summer. For the eratic tach and speedo it took a new igition switch. Glow plug codes needed a new glow plug controler. The hesitation ended up a bad chip in the PCM. I did have to replace the fuel pump and the OPS.
I have been driving the truck for 2yrs and never knew you should be able to hear the fuel pump run. Drove around with a vacume guage taped to the window and if I stomped on it could get the fuel pressure to hit -2psi but still have 3.5 at idel. The IP will draw fuel on its own to run under normal driving.
don't be discuraged if it is more than one problem. Thanks to TDP it runs great now. Starting great at -5 F not pluged in.
Michael D.