Fuel Pressure Problem 1994 PCM 5.8 Ford

I have a 1994 Sport Nautique with the early TB Injection. With Ignition on / Engine off Fuel Pressure at TBI Shrader Valve is zero. Fuel pumps both run for approx. 4 seconds when ignition is first switched on. If starter is engaged during this initial 4 second period engine starts and runs fine, fuel pressure is 13 when running. However, if starter engaged after first 4 seconds, engine will not start - no fuel pressure. Now that I know trick of starting imediately, starts and been consistent. But... this engine has a bad habit of not starting between skiers, and has left us stranded. I think I have not seen the last of this problem. Dealer said I should have fuel pressure whenever ignition is on. Do I have: a) worn out high pressure fuel pump/check valve, b) bad Engine Control Unit computer or c) no idea what I am doing? Any help here is greatly appreciated.

Sounds like your system has fuel pump controlled by the computer (ECU). You can always take it out of the equation by rewiring the pump control circuit.

The dealer is wrong about having pressure whenever the ignition is ON. USCG regs require a shut-off function on the pump, just like the auto's have that inertial switch controlling their pumps.

The rewire circuit uses an oil pressure controlled switch - SPDT. the NC contract connects to the COMMON terminal when no pressure exists and the the NO terminal makes contact once oil pressure build up. The COM terminal goes to the pump, the NC contact goes to the starter solenoid, and the NO contact goes to the
+12V at the coil (upstream of a ballast resistor, if present). The switches are readily available and are the three terminal type. Most have a 1/8" NPT fitting on the end.

Thanks MM.
I assumed the fuel pumps were controlled by the ECU too and your rewire sounds like a terrific solution. I see that I currently have two oil pressure sending units on the same plumbing just above oil filter, each with a single wire, both look stock. One sending unit is a can the size of a golf ball (for gauge?), the other is real small (murphy switch?). Could I possibly already have an oil pressure murphy-switch? I assumed ECU would use engine rotation to allow fuel pumps to run not oil pressure? Trouble is I get no fuel pressure when cranking starter, only during first 4 seconds of ignition on and when engine is running.
Is the SPDT rewire a marine or auto part? If I rewire as you advise, can I use the small existing oil pressure sending unit? Where else would this second sending unit be going?
Thanks in advance.

They use oil pressure to drive the switch for it serves a dual purpose...if the oil pressure drop, the engine stops due to lack of fuel....kind of a self preservation concept.

Most ECU controlled systems will only run the pump for a few seconds when the key is switch ON. to get the pump to run again, the key needs to be cycled or the engine started. Many ECU's use the oil pressure switch AND RPM > 300 to turn the pump on.

The rewire suggested has been around since electric fuel pumps. You can get the switch in either flavor. Use the "boat Parts' link above, click the "more parts/choice" and then open the sierra catalog. scroll down in the left box for electrical, click it to open that section and scroll down to the oil pressure switches. the SPDT has number OP72533. The typical 'buzzer' switch is shown as OP22900. The sender units - for the gauge - are on that page, too.

Can you use what's there? - don't know as you haven't ID'd exactly what you have. Maybe, maybe not.

One word of caution - be careful about eliminating something that may feed the ECU. You can improvise a 'dummy sensor' if necessary. Best to check the factory manual if available. If the dealer you mentioned before can show you (or let you copy) the wiring diagram, you'll know what you can/can't change.

Thanks again MM -
I will test the existing oil pressure sending unit, if that's working properly, then proceed with the rewire you suggest. What do you mean by 'dummy sensor', a toggle switch? The local dealer couldn't find a diagram for my model of TBI. I am rigging a bypass at the "4-second relay" timer just so I don't get stranded out in the lake until I get a permanent fix. Your advise has gotten me way down the road toward happy boating. It's much appreciated - will keep you posted.

"Sending units" typically connect to gauges; sensors to computers.

I was getting at some ECU's don't like to see "no sensor" or they may set a code. Many times, they can be tricked and made happy with a fixed resistor thus the 'dummy sensor' label. whether you MMay need this or not is driven by the specifics of your engine/ecu configuration.

if you ground the oil pressure wire and the pump stays on you know