Engine Won't Start/No Fuel Pump Voltage

[widowmaker]

2003, 5.0 L MPI, Bravo 3
Here's what I did. For pre-winterization I always change the engine oil and gear lube. At the dock and on the lift with the outdrive submerged I started her up to heat the engine oil, everthing normal, ran a few minutes, engaged the drive to warm gear lube up a bit. Shut her down, and replaced gear lube, normal.... Then I pumped out the engine oil at the dickstick tube with my brass hand pump, during which the pump body rubbed up against a wire/connector on the back of the alternator and caused a small spark. The plastic on the wire is rubbed away but the wire still has continuity to the alternator. Anyway I drain all the oil&filter and replace with new.

Then I turn the key to ON, hear the normal 1 beep, but there's no fuel pump run/whine sound for the normal 3-5 seconds. I turn key to start and she just cranks but no start. There's no fuses blown, no voltage at the fuel pump connector when I turn key to on. The gear lube level is a littel low, I put in 2 Qts. Is there an oil pressure switch in the circuit. It's getting cold.. HELP!

 

[Powderfinger]

The pump may be wired via the alternator and if so, one of two things may have happened. When you shorted out the alternator terminal, one of the DC diodes in the alternator burnt out, or maybe the pump itself was damaged by the short. Whenever a short occurs from a direct grounding of a live circuit, something usually always "blows"...Fuse, breaker, diode, or a motor component (winding) in the affected appliance, in your case the fuel pump.....

I'd start with popping the alternator off and having it tested. Hope this helps you....

 

[widowmaker]

Thanks for the reply. I have a mechanic coming out Wednesday. Hopefully he can figure it out. With no voltage getting to the pump I hope its only the alternator shorted out. Will update results later.

 

[Powderfinger]

Let us know how you make out....It'll be interesting to know what exactly the problem was.... :smt001

 

[Lazy Daze]

An easy, free check is the kill switch by your throttle. Be sure it's in the "run" position - flip it on/off a few times. If for nothing else, doing this eliminates possibilities.

 

[widowmaker]

Thanks but I did that too. Also played around with the shift switch. Everything seems OK. Supposed to be 26 degrees Thurs night. I may have to float the rear end to help keep her warm until I can drain the engine and do the pink thing.

 

[SeaRenity]

I had the exact issue with one of my engines. It turned out to be a fuel pump pressure regulator. It is a small black cube looking part located on top of your engine-- very accessible and easily changed. I purchased the part for about 39.00.
I hope this helps you

 

[widowmaker]

SeaRenity,
Do you have any other information on this fuel pump pressure regulator? My mechanic didn't show-up or call yesterday, or today, so I on my own. I took off the top cover over the intake area and saw a small black cube near the main engine circuit breaker area. Is that it? Do you know how to check it? Thanks I'm just trying to get as much info as I can.
Ted

 

[widowmaker]

Update... The 2 "mechanics" checked it out last week. I met with them at the boat and after a few checks they thought it "might" be one the relays on the top of the engine. They switched them around still no start but thought they may be interlocked..they were available at NAPA $62 and I swappped them out with still no luck. They said if that didn't work they would have to take it in to their shop and trace it down using the electrical drawing.

Problem is our lake is low right now and I can't get the boat off the lift, 5' draft. So anyway I winterized right there by draining block and filling with pink (good stuff)through the radiator hoses. No fogging of engine though.

I think I'll pull the alternator next and have it tested as Powderfinger suggested. I can still test it without starting the engine so I won't have to re-winterize. If that doesn't work I'll wait til spring.

 

[widowmaker]

Just an update, ;ast month I pulled the alternator and had it checked at a local alternator & starter shop. It checked out OK. I'll have to wait for a few warm days and check a few other things. I'll run 12 volts to the fuel pump to see if it works. It's my understanding the fuel pump only works to pressurize they cylinders tohelp start the engine, then after the engine runs the pump turn off. It is also my understanding there is a fuel pump pressure switch/regulator that controls the pump. Does anybody know more about the pressure switch, what it looks like and where it may be located. No I don't have service manual.

Thanks, Ted

 

[Fun Times]

It's my understanding the fuel pump only works to pressurize the cylinders to help start the engine, then after the engine runs the pump turn off. It is also my understanding there is a fuel pump pressure switch/regulator that controls the pump. Does anybody know more about the pressure switch, what it looks like and where it may be located. No I don't have service manual.

Thanks, Ted

Hello Ted, Since you have a MPI system, your engine does not have a fuel pump pressure switch, It's controlled by the PCM via time then RPM. Below should help give you an idea.

STARTING MODE​

When the ignition key switch is turned to the on position,the ECM turns on the fuel pump relay and the fuel pump builds up pressure for a few seconds, then turns off until the ECM sees an RPM signal of 300 + RPM while in the crank position from the key switch. The ECM then checks the Engine Coolant Temperature (ECT) sensor and Throttle Position (TP) sensor and determines the proper air/fuel ratio for starting. The ECM controls the amount of fuel delivered in the starting mode by changing how long the injectors are turned ON and OFF. This is done by pulsing the injectors for very short times.

RUN MODE
​

When the engine is started and RPM is above 300,the system operates in the run mode. The ECM will calculate the desired air/fuel ratio based on these ECM inputs: RPM, Manifold Absolute Pressure (MAP) sensor, Intake Air Temperature (IAT) sensor and Engine Coolant Temperature (ECT) sensor .Higher engine load (from MAP) and colder engine temperature (from ECT) requires more fuel, or a richer air/fuel ratio.

FUEL CUTOFF MODE​

No fuel is delivered by the injectors when the ignitionis OFF, to prevent dieseling. Also, fuel pulses are not delivered if the ECM receives no distributor reference pulses, which means the engine is not running. The fuel cut off mode is also enabled at high engine RPM,as an over speed protection for the engine. When cutoff is in effect due to high RPM, injection pulses will resume after engine RPM drops slightly.
​

ACCELERATION MODE​

The ECM looks at rapid changes in Throttle Position(TP) and provides extra fuel by increasing the injector​

pulse width.

DECELERATION MODE​

The IAC is similar to a carburetor dashpot. It provides additional air when the throttle is rapidly moved to the​

idle position to prevent the engine from dying.

 

[Here For The Party]

I have the 8.1 but i understand your engine has the same basic electronics, if this is so there are 2 fuses in the wiring harness on top of the engine. There is one fuse specificlly foor the fuel pump. I had a simular issue and my mercury guy directed me right to them and it was a .20 cent fix and we were done. They were on the starboard side on top behind the pcm.

 

[widowmaker]

Thanks for the replies.
I hope it's as easy as the fuse thing. I'll look for those and try that when the weather breaks. If not that, then could it be the PCM? 9 degrees here tonight...I miss FL.

 

[widowmaker]

Update on the problem. Took it to my local non-dealership mechanic. He traced the problem to the main computer on the engine. A new computer cost about $1,700, holy crap. He said his friend had a boat with the same engine and shorted out the dipstick to the alternator too, so it's not just me, bad design. He said they ran a separate wire circuit off the key "on" switch that provides power to the fuel pump and solenoid when the key is "on". I said lets go for it. For $250 he got it done. Starts right up and runs great. You have to remember to turn the key to "start" right away as the pump runs in the on position. All in all for a diagnosis and repair $250 is not bad.
Hope this helps someone else some day.

Have a great summer.
Widowmaker

 

[rgl1100]

I have the 8.1 but i understand your engine has the same basic electronics, if this is so there are 2 fuses in the wiring harness on top of the engine. There is one fuse specificlly foor the fuel pump. I had a simular issue and my mercury guy directed me right to them and it was a .20 cent fix and we were done. They were on the starboard side on top behind the pcm.

I'm hoping you might contact me at rgl1100@msn.com. I think I'm having this exact problem and I just wanted to ask you about these fuses. I've located a schematic that shows a 20A yellow fuse located behind the PCM but it doesn't say what its for. I'm assuming this may be the fuse to which your referring.