Ox66 Fuel Issue

[Oyster Boat 88]

Ok guys I need a little help. I’ll give you the details and then I’m all ears.
2000 ox66 LX150 TXRZ. Doesn’t want to start easily but give it a mist of mixed gas or anything else and fires right up. All three fuel pumps and filters are new. Fuel pressure at idle is 38 psi. VST tank is full, clean and refills normally. Will idle for hours if you let it but seems to be a little rich with oil compared to its SX 150 TXRZ brother. Problem starts when you give it any fuel. Revs up for a second to about 1500 and dies. Will restart immediately after it warms up.Fuel pressure drops off to nothing instantly when you give it the gas and the voltage to the pump also goes away. If you use a jumper on the HP pump ground side to engine ground the motor stays running and doesn’t stall out. No immediate alarms when the switch is turned on. Both thermostats and temperature switches are new, engine mounted oil tank is full and switch is new. The remote oil tank pump doesn’t appear to be working is the only thing I can find wrong initially with the setup. What am I missing?

[boscoe99]

Ok guys I need a little help. I’ll give you the details and then I’m all ears.
2000 ox66 LX150 TXRZ. Doesn’t want to start easily but give it a mist of mixed gas or anything else and fires right up. All three fuel pumps and filters are new. Fuel pressure at idle is 38 psi. VST tank is full, clean and refills normally. Will idle for hours if you let it but seems to be a little rich with oil compared to its SX 150 TXRZ brother. Problem starts when you give it any fuel. Revs up for a second to about 1500 and dies. Will restart immediately after it warms up.Fuel pressure drops off to nothing instantly when you give it the gas and the voltage to the pump also goes away. If you use a jumper on the HP pump ground side to engine ground the motor stays running and doesn’t stall out. No immediate alarms when the switch is turned on. Both thermostats and temperature switches are new, engine mounted oil tank is full and switch is new. The remote oil tank pump doesn’t appear to be working is the only thing I can find wrong initially with the setup. What am I missing?

I am not understanding the voltage going away part. Are you measuring voltage on the red/yellow wire to the fuel pump?

Jumpering the fuel pump blue wire to ground, resulting in the fuel pump continuimg to run, leads me to believe that the fuel pump has voltage.

The same red/yellow wire provides battery power to the fuel injectors and the O2 sensor. Is voltage missing at those components as well?

[boscoe99]

I am not understanding the voltage going away part. Are you measuring voltage on the red/yellow wire to the fuel pump?

Jumpering the fuel pump blue wire to ground, resulting in the fuel pump continuing to run, leads me to believe that the fuel pump has voltage.

The same red/yellow wire provides battery power to the fuel injectors and the O2 sensor. Is voltage missing at those components as well?

[Oyster Boat 88]

Sorry for not being clear. There is voltage at the pump at idle. About 9v when checked at pump terminals. When the engine exceeds about 1200 the blue wire is no longer grounded. Or that is how it appears. I believe it is happening when it switches pump speeds.If I ground the blue wire on the pump then the motor does not stall out at 1200, and doesn’t drop the fuel pressure. Could this be a problem with the remote oil tank putting it in limp mode? If so can it be bypassed or disconnected to test?When running at idle speed it seems to be getting a little two much oil as well and is hard to start when cold.

[Oyster Boat 88]

I’ll swap the remote tanks and wiring harness from the other engine to see if that changes anything.

[boscoe99]

I don't think the oil tanks are involved at this point in time.

The voltage at the pump should be battery voltage/system voltage. Bad connections can result in excessive voltage drop.

[boscoe99]

The pump is grounded by the CDI but through a resistor at low RPM's. Via brown wire.

Above low RPM's the pump is grounded directly by the CDI. Via a blue wire.

I would inspect the electrical connector from the CDI that supplies the grounds to the resistor and oil pump.

[99yam40]

did you notice you mentioned CDI and ECU in that last post?
Just saying you probably did not mean to

[boscoe99]

I did not notice. Did not mean to. Fixed it. Thanks.

[Oyster Boat 88]

I swapped the oil tank from the running engine with no change as you thought. No alarms at all at this time .Then I unplugged every connector on the engine and cleaned with electrical contact cleaner. Disconnected all the grounds I could find cleaned the block and eyelets and reconnected. No change. After it warms up the engine idles down to about 900 and still smokes much more than the other engine. Should I swap the CDI from the other engine just to rule that out. I’m sure I’m missing something. The engine still seems to need a primer of gas to start when cold as well. Will it hurt to ground the blue wire from the fuel pump and run the engine at 2500 or so for a few minutes to push some fuel system cleaner through it?Takes about 4 weeks to get into a shop at the moment. Thanks for all the help so far, I’ll keep looking for the Gremlin.

[99yam40]

if the CDI thinks the remote oil tank is low, it will not allow that pump to fill the tank on the motor.

too much oil to the fuel needs to be looked at by itself.
I have no idea what controls that on this motor.

strange that you say that the VST is full, is it full when the motor dies ?
Are you saying that the pump in the VST is just stopping when the motor goes above 1200 RPM


something has to tell the CDI what RPM it is running at and to switch over to keep the pump running all the time.
.
might try hand tracing the blue wire and measuring the Ohms of that wire from the CDI to the pump.
you need to know if the CDI is giving that wire a good ground or not, and if that good ground is traveling all the way to the pump.
bad connection in-between, bad wire itself, or the CDI is not furnishing the proper ground.

[Oyster Boat 88]

Once the motor is running at idle, around 900 if you open the throttle just a little ,the engine comes up to about 1500+/- and then dies off. Maybe under 1500.If you close the throttle it may or may not stay running. During this time at idle the fuel pressure is about 38 but drops to nothing as soon as you try to rev the engine. The HPFP has about 9 volts to it at idle but looses the voltage once the motor revels up. The loss is the ground not the power. VST tank is always full and never low , so it’s not starving for fuel from the tank or low pressure pumps.I will try to rig a jumper straight from the CDI to the pump to see if a piece of wire has gone bad. I believe it’s working normally up to 1200 rpm or so but it’s not switching from the resister circuit to the CDI ground circuit . If I give the HPFP a direct ground it revs up and never dies. No alarms of any type at this point .As far as the oil goes I’m going to change the plugs and jump the ground on the pump and run the engine on the water this weekend to see if it helps to have some sea foam and ring free run through the motor. I hope this helps the cold hard start , it did wonders for the other engine on the boat. Both sat a few months and were hard to start when cold until I ran a few gallons of new fuel through the one running engine. Thanks .

[boscoe99]

Once the motor is running at idle, around 900 if you open the throttle just a little ,the engine comes up to about 1500+/- and then dies off. Maybe under 1500.If you close the throttle it may or may not stay running. During this time at idle the fuel pressure is about 38 but drops to nothing as soon as you try to rev the engine. The HPFP has about 9 volts to it at idle but looses the voltage once the motor revels up. The loss is the ground not the power. VST tank is always full and never low , so it’s not starving for fuel from the tank or low pressure pumps.I will try to rig a jumper straight from the CDI to the pump to see if a piece of wire has gone bad. I believe it’s working normally up to 1200 rpm or so but it’s not switching from the resister circuit to the CDI ground circuit . If I give the HPFP a direct ground it revs up and never dies. No alarms of any type at this point .As far as the oil goes I’m going to change the plugs and jump the ground on the pump and run the engine on the water this weekend to see if it helps to have some sea foam and ring free run through the motor. I hope this helps the cold hard start , it did wonders for the other engine on the boat. Both sat a few months and were hard to start when cold until I ran a few gallons of new fuel through the one running engine. Thanks .

Can you expand upon this please? I am not understanding a loss of voltage (power?) being related to a loss of the ground.

[boscoe99]

Once the motor is running at idle, around 900 if you open the throttle just a little ,the engine comes up to about 1500+/- and then dies off. Maybe under 1500.If you close the throttle it may or may not stay running. During this time at idle the fuel pressure is about 38 but drops to nothing as soon as you try to rev the engine. The HPFP has about 9 volts to it at idle but looses the voltage once the motor revels up. The loss is the ground not the power. VST tank is always full and never low , so it’s not starving for fuel from the tank or low pressure pumps.I will try to rig a jumper straight from the CDI to the pump to see if a piece of wire has gone bad. I believe it’s working normally up to 1200 rpm or so but it’s not switching from the resister circuit to the CDI ground circuit . If I give the HPFP a direct ground it revs up and never dies. No alarms of any type at this point .As far as the oil goes I’m going to change the plugs and jump the ground on the pump and run the engine on the water this weekend to see if it helps to have some sea foam and ring free run through the motor. I hope this helps the cold hard start , it did wonders for the other engine on the boat. Both sat a few months and were hard to start when cold until I ran a few gallons of new fuel through the one running engine. Thanks .

Can you expand upon this please? I am not understanding a loss of voltage (power?) being related to a loss of the ground.

[Oyster Boat 88]

HPFP runs and puts out 38 psi up to 1200 to 1500 rpm’s +/- a couple hundred. After that there is 12 9 volts on the + terminal of the HPFP but no continuity to ground on the - terminal of the pump so the pump simply stops and the engine dies while the VST tank is still full of fuel.It I ground the - terminal directly to the battery negative on the block then the pump continues to put out 30 psi or more and the engine runs from 0 to 4000 rpm’s and never misses or tries to shut off. So based on what you guys have taught me I assuming the Computer is cutting the ground for some reason above 1200 when it switches from the resister ground loop? Or simply a bad wire or connector between the pump and computer could cause this as well ?