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Loganruss34

Fuel pump not getting power

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Loganruss34

So I’m new to the Malibu boats got a Malibu sportster for little to nothing doing some work on it as it’s been sitting, I have two questions. Is there a fuel pump in the tank, next question is since the pump on the side of the motor is not getting power I saw on a earlier form that it is the oil pressure sensor. Where exactly would that be I’ve been told it’s by the oil filter and then on top of the motor it has the 350 carbureted motor in it. Thanks for the help! 

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formulaben

I can't say for certain it is EXACTLY the same as yours, but these Chevy 350 small block engines haven't changed a lot.  No, there isn't a fuel pump in your tank unless it has been modified (unlikely.) 

The 2 oil pressure sensors are located down low on the engine: for a v-drive this is on the forward right (starboard) side of the boat, for direct drives it's the aft port side of the engine. Note the bigger "barrel" sensor is for your dash only; the other one sends a signal to the ECM to allow the fuel pump to run if it sees positive oil pressure, around 6psi...at least that's how I understand it on fuel injected engines, so YMMV. 

Anyhow, it's a super quick fix, just make sure you DO NOT use any teflon tape on the unit, as the threads form the negative connection of the circuit.  You can buy a "marine" version or just take your old one to the auto parts store and get a direct replacement.

2r289lk.jpg

 

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MalibuNation

There is a relay that controls the fuel pump that can go bad.  Replacing the reply is a cheap thing you can try to see if that fixes your fuel pump not getting power.  MN.

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tvano
3 hours ago, MalibuNation said:

There is a relay that controls the fuel pump that can go bad.  Replacing the reply is a cheap thing you can try to see if that fixes your fuel pump not getting power.  MN.

no start troubleshooting document may be of help.

the following comments apply to my '04 lcr, ymmv.

@MalibuNation's fuel pump relay is next to two other relays (ign and starter) above the ecm on the rear of the engine.

all three relays are alike so you can swap your suspect fuel pump relay (green wire in the relay harness) with another relay to see if the symptoms change.

note that there is a fuel relay fuse that could be an issue, too.  it's located near the same panel w the relays in a capped connector that does not look much like a fuse holder.

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mcgreg

Thought i would mention a similar fault that cuts off power to fuel pump in case you’re probing of the oil pressure switch does not pan out. 

The safety lanyard switch on the dash board that you are spose to hook to your life jacket, should it go bad, will cut off power to the main purple ignition wire, in turn cutting off power to the fuel pump. You can test it by bypassing the lanyard switch. Simply remove the 3 wires from the switch and wire nut them all together. 

Before pulling out all yr hair, check out this quick work around. Good luck!

Ps, Sure would be great if Malibu would publish the wiring dgrm, but I've never found one.

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electricjohn

it's a carbed engine,  no relays or ECM.

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cla10beck

On the carbed engine, there is a third oil pressure switch that will only supply power to the fuel pump if over 5 psi.  It is in a different spot than the two pictured above.  They have been known to fail.  See the below comment from enginenut:

 

There should be an oil pressure activated switch by the distributor. This is referred to as a fuel pump safety switch and depending on the vintage will have two or three wires. If it is a three wire switch there will be a red wire that goes to the fuel pump, a purple wire from the wiring harness and an orange wire that comes from the starter solenoid. When you are cranking the engine, the orange wire will get power from the starter solenoid (only gets power when cranking) The orange and red wires are connected together internally in the safety switch and the fuel pump should run. When the engine starts, the orange to red connection in the safety switch opens and the connection between the purple wire (always hot when the key is on) and the red wire is completed which keeps the fuel pump running. The three wire switches were somewhat problematic so we switched to a two wire switch.

With the two wire switch, the orange and red are on one terminal and the purple is on the other one. During the crank cycle, the orange wire is powered by the starter solenoid so the pump runs during cranking. When the engine starts, oil pressure closes the circuit between the purple (hot with ignition on) and the red/orange connection. The red wire supplies power to the pump and the orange wire just dead-heads at the solenoid.

Electric fuel pumps are wired this way so the pump will not run with the key on and engine off which is a Coast Guard Regulation. The see if the pump is working, you can temporarily run a jumper between the purple and red wires and turn the key on. The pump should come on. If it does, the pump is probably OK and the switch is bad. There is a three wire to two wire switch replacement kit, Indmar P/N 496007 that has everything you need to replace the three wire switch with the better two wire switch.

 

 

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Flyandboat

cla10beck,

I was reading your post. Very good information.  I have a 2001 Response that has sat unused for 2 years. I am getting no fuel. Pump is good i bench checked it. no current to pump. Just found bad lanyard switch. BYPASSED  it and still nothing to pump. Everything else has current. By the way new battery. Had to pull starter. Does orange wire have to be on starter solenoid for pump to work? Also spent hours tracking the two wires coming from the pump connector. Black wtth white stripe was good continuity. Gray was not good. Fuses are all good. Traced backwards from EFI and lost continuity going through heavy batch of wires over trans. I jumpered the wire and have continuity. Does the gray wire change over to something else? Can I wire the pump from the ignition? Does the pump always run or have a pressure limit switch? It is one of those pumps with a return to tank. 

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formulaben

There should be a fuel pump relay in there.  If it sat for 2 years then maybe it's sticking or is corroded.  See below:

 

Verify fuel pump cycle (3-5 seconds) at key on. Note that the fuel pump does NOT cycle if the emergency engine shutoff switch (lanyard) is removed. This 'pre-run' fuel pump cycle charges the fuel rail which should provide enough fuel to start the boat. After the engine starts, power to the fuel pump is provided by the oil pressure switch. A bad oil pressure switch or insufficient oil pressure will shut down the fuel pump. (Engine should/could run for a short period then die.) There is a fuse and a relay dedicated to the fuel pump. The power for the fuel pump originates at the large (red buttoned) circuit breaker in the engine room, goes to the fuel pump's 20 amp fuse, then to the fuel pump relay, then to the pump. The control of the fuse pump relay is activated via the ECM by a green wire with a white stripe. The fuses and relays are mounted on the underside of the ECM cover, which is mounted on the back of the engine. The ECM turns the fuel pump relay on for a short period when it sees an ignition input from the keyswitch (called keyup) and will turn it back on when it sees a distributor reference signal (input) from the distributor module, during cranking and run.

 

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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cla10beck

Formulaben provided more info that I ever could.

 

My reference to the oil pressure switch that activates the fuel pump is only for the carburetor engines of those years.  That switch is replaced by the fuel pressure reading to the ECM in the EFI versions.

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formulaben

I wish I could recall who/where I got that from, but can't take credit for it...hat tip to "that guy" whoever he is. 

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