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davewfo

HELP 04 Malibu VLX no power at fuel pump.

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davewfo

Hey Guys

Need some help a good friend just purchased a 2004 VLX Malibu with 430 hours. 

When he looked at the boat I wasn’t able go with him when they test drove the boat, They took the boat on the test run it ran fine and then died after a little bit. They sat for about 10 min and it started back up. There wasn’t much gas so they assumed it was out of gas. 

So we replaced the following once he got the boat home. 

   -  Replaced Fuel filter

   -  Filled tank with fresh tank of gas. 

We took out the boat after and filling it up with gas and filter change. It ran fine for about 10 min then died and we couldn’t get it to fire up again. We checked the fuel rail schroder valve and it had a little bit of pressure, but not a lot. Then we tried to crank it over and it never seem to pressurize the fuel rail ( Ended up getting it towed in 🙁). 

So we assumed it was the fuel pump so we ordered a new and installed it today. Engine cranks over and never starts checked the fuel rail again and no pressure. So we checked for voltage and there was no voltage with the key on. 

- We jumped the fuel pump with 12 volts it comes on like normal and pressurized the fuel rail. 

- We tried to start with the engine with manually putting power to the fuel pump. Engine cranks and doesn’t start. 

Question: What else should we look at or try ??

Question:  Is there a circuit breaker for the engine ? Or is there only the push buttons near the driver seat.

Question: Any other ideas that we could try ?

Thx

Dave

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davewfo

Does anyone have a engine wiring diagram for 2004 Malibu VLX ? 

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formulaben

Take a look at my revised No Start Toubleshooting Guide.  Here is an excerpt that you might find helpful...I would change the oil pressure "switch" just to be certain that's not he problem.

 

INDMAR (CHEVY) ENGINE START UP SEQUENCE

Fuel Rail Pressurization:

When you first turn the key to the "on" position (aka “key up”), the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Schrader valve on the fuel rail near 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. 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.

 

 

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davewfo
7 hours ago, formulaben said:

Take a look at my revised No Start Toubleshooting Guide.  Here is an excerpt that you might find helpful...I would change the oil pressure "switch" just to be certain that's not he problem.

 

INDMAR (CHEVY) ENGINE START UP SEQUENCE

Fuel Rail Pressurization:

When you first turn the key to the "on" position (aka “key up”), the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Schraderalve on the fuel rail near 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.  

 

Great info do you know if the oil pressure switch is a standard switch ?  The wire to the oil pressure switch was a little loose when we were looking at it yesterday. Can you typically get a new switch at the auto parts store for a LT1 assuming yes ? 

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electricjohn

What engine do you have?  I have wiring diagrams.

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davewfo
1 hour ago, electricjohn said:

What engine do you have?  I have wiring diagrams.

Electricjohn: Its the standard Monsoon 340 HP. 

 

 

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formulaben
3 hours ago, davewfo said:

Great info do you know if the oil pressure switch is a standard switch ?  The wire to the oil pressure switch was a little loose when we were looking at it yesterday. Can you typically get a new switch at the auto parts store for a LT1 assuming yes ? 

Go to the local parts store with the old one and tell them it's off of a 1999 Chevy Suburban with the 350cu engine.  It should be a match.

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electricjohn

You have a fuel pump fuse and fuel pump relay.  Both have to be good so the computer (ECM) can turn on the fuel pump, which it does by activating the relay.  You also have an ignition fuse and ignition relay.  Both have to be good so the ECM can power up the fuel injectors and the fuel pump relay.  The ignition relay activates when you turn the key to the run position.  Notice that the power that activates the fuel pump relay comes from the ignition circuit.  The fuel pump relay is activated by the ECM grounding it.  

All these fuses and relays are under a cover on the rear of the motor.  The oil pressure switch has nothing to do with any part of this sequence on a Monsoon motor.  It will only activate a limp mode and sound the beeper.

Sorry, but I have no way of posting my diagrams.

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formulaben

Oops, sorry I missed the part about you jumping the pump and no fire...

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Dhurt8955

Did you ever get this figured out I have the same problem jumped the fuel pump and it works ok but still won’t start, someone talked about the oil pressure switch might be the problem but someone else said it has nothing to do with it

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tvano

see "INDMAR (CHEVY) ENGINE START UP SEQUENCE" within this thread.

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