Do I have a bad fuel pressure regulator?

[treverspence]

So I went to crank my boat for the first time this year and it would only stay running if I had the throttle 2/3 of the way open found a bad fuel pump also it looked like the wiring harness to fuel pump had gotten hot replaced both items went to fire boat & new fuel pump comes on & stays on as long as the key is in the on position it filled the cylinders with raw fuel before i cranked it. I pulled the spark plugs to clear cylinders of fuel now trying to figure out if I have an ECM problem, bad fuel pressure regulator or a shorted wire. Does the pump run on a timer to prime lines or to a pressure then switch off until boat is cranked? Any Ideas or advice would be greatly appreciated.

[sivs1]

did you replace the fuel filter?

[treverspence]

did you replace the fuel filter?

I replaced it mid season last year.

[sivs1]

I replace mine every year. They are cheap, so might be worth a try.

[rdlangston13]

Is this a fuel injected or carbourated motor? I know on fuel injection motors when you turn the key on the fuel pump only runs for like 5-10 seconds and if it does not see a signal from either the crank or cam sensor it will shut off. If it sees that the engine is spinning it will stay on until you turn the motor off. Also if you filled cylinders with fuel then for some reason your injectors were firing when they are not supposed to be which may indicate an ECM issue? If you have a carb then I don't have a clue.

[treverspence]

Is this a fuel injected or carbourated motor? I know on fuel injection motors when you turn the key on the fuel pump only runs for like 5-10 seconds and if it does not see a signal from either the crank or cam sensor it will shut off. If it sees that the engine is spinning it will stay on until you turn the motor off. Also if you filled cylinders with fuel then for some reason your injectors were firing when they are not supposed to be which may indicate an ECM issue? If you have a carb then I don't have a clue.

It is fuel injected my next steps will be to check the relay then check the oil pressure sensor I was told if it is malfunctioning if it is constantly seeing oil pressure the pump will continue to run.

[mmandley]

Knowing the year, make and engine you have will make this a lot easier.

The way the Chevy <Indmar> engine works on start up.

Fuel Rail Pressurization:

When you first turn the key to the "on" position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running. Test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail.

Initial Crank Action:

If you then rotate the key to the start position the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run.

The crank position sensor will send a string of pulses to the ECM in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

ECM Reaction:

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time.

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch.

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees more than 0.54 volts, it will assume the engine is flooded.

Assuming the ignition module is good the engine will "catch".

Engine "Catches":
When the engine catches, the MAF sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion.
The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM

If this does not happen, the Idle Air Mixture valve may be mis-adjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

ECM Mode:

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

Once the Oxygen sensor <if you have Cats> reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor's output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more "on time" or less "on time") to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

[kaneboats]

Dang. He took the words right out of my mouth again.

[jarodag99]

That was a SOLID post. Trying to figure out how to save this for any future troubleshooting! Open the motor box while Turning your key on (not all the way to the start position), you should be able to hear the fuel pump energize then shut off if you wait a couple seconds.


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[kaneboats]

That was a SOLID post.

Yea, every now and then the guy contributes something where we let him hang around another day.