O/T While we're discussing electric fuel pumps....

As I understand it, in normal function the fuel pump is supposed to run for a couple seconds when the key is first turned on to pressurize the system to start the engine. Then, once it is running and gets oil pressure, a switch attached to the oil system turns on and lets the electric fuel pump run. The reason for this is to shut the fuel pump off if the engine should quit(lose oil pressure) in a crash.

Problem with ours is, the pump doesn't run for the two seconds or so when the key is first turned on. You have to crank the engine until it builds oil pressure before the fuel pump will run and let the engine fire up. Sometimes it takes up to 30 seconds of cranking before oil pressure builds up enough so it'll go.

What's the problem here? Is there a relay that might be bad, or does it need a new ECM? It started doing this after jumpstarting a tractor. Didn't run at all then until a new fuel pump was installed.

I didn't realize that the oil pressure switch bypassed the relay....figured if the relay was bad it wouldn't run the pump at all.

So, it's gonna get a new relay and hope it's not the 'puter.

If it IS the 'puter, I don't really want to put the $$$ into it....this is an old beat up work pickup with a gazillion hard miles on it that never sees much highway duty. Would it be ok to wire up a bypass around the oil pressure switch to a pushbutton switch so that I could manually run the fuel pump for a couple seconds before I start it?

Truthfully too, there's not much chance this vehicle's gonna ever be in anyone elses shop....it's used for fencing here on our ranch 40 miles from the nearest town and regulated to off-highway use only. Frame's been broken and welded, body's beat to heck, and it'll likely live here without leaving till it's completely dead and then get used for parts, not traded off to some other poor unsuspecting soul.

Thing is, the engine runs great, transmission shifts solid, so we just keep using it. The cobble job was just to keep from having to sit and crank the heck out of the thing every time we have to start it.

Hopefully, the relay fixes it! I'll report back if I get to town to pick one up in the next week or so. Thanks again!

When you turn the key "ON", the 'PUTER cycles the pump on for a couple of seconds, using the fuel pump relay.

When you turn the key to "START", as soon as the 'PUTER realizes it's getting pulses from the ignition pickup, it again turns on the fuel pump relay.

If the fuel pump relay is bad, or there is a problem in that circuit (or the 'PUTER), there is a backup system, the oil pressure switch, that is also capable of turning on the fuel pump, once the engine has cranked long enough to build up oil pressure.

So, your problem lies in the fuel pump relay or the 'PUTER or associated wiring between the 'PUTER and the fuel pump relay.

The OIL PRESSURE switch is working as it's supposed to, providing the backup means to tuen on the fuel pump after some cranking, or the truck wouldn't be starting at all.

Start by listening under the hood for the fuel pump relay to click in and out, while someone else turns the key on. (The relay is located under the removable electrical cover on the upper RH side of the firewall.)

If you hear the relay "click", it's contacts MAY be bad, or if it doesn't click, it's coil may be bad, or the 'PUTER, or wiring, as previously mentioned.