1999 ox66 225 fuel pump ground issues

[dieseltruck]

first off id like to say im sorry if the same post is out there new to this so bare with me...i have a 1999 225 ox66 trying to find out if the voltage regulator/resistor controls the ground to the fuel pump under 1200 rps's? and if so if the voltage regulator/resistor is bad will it drop out the ground to the fuel pump.. i turn key on fuel pump buzzzes for about 3-5 seconds pressure's the fuel rail motor will start run for about 15 seconds then stalls used meeter to find im loosing the ground to the fuel pump used jumper rite befor stalling to ground fuel pump and motor stays running...can anyone help with my issue thanks to all responces

[99yam40]

I am fairly sure Rodbolt or someone else with the knowledge will chime in at some point so be patient,
just make sure you are giving all your motor info and what all you have found/done already as he does not like to beat around the bushes to see what he can flush out of you.

[rodbolt17]

the ECU controls the ground.
the resistor is only in the circuit until about 1100 RPM to reduce pump operating voltage to about 9V.
above about 1100 the resistor is not used. this gives it a two speed pump.

myself I think the ECU is removing the ground due to another fault.

[dieseltruck]

ok thanks for the responce.. im kinda at a loss now it will reve up but looses the ground at idel i can ground the pump and it idels fine. what direction would you think i should look next? i have pulled and cleaned the vst tank and screen i have replaced all 3 LP pumps i have installed new plugs.i have pulled and cleaned the 02 sensor. i thought for sure on iboats i saw a post were you said the voltage regulator/resister controled the ground to the fuel pump below 1200 rpm's then the pump ground is controled by the ecu above 1200 rps's. what else would tell the ecu to drop the ground at idel? thank you for any help you can provide....andy

[rodbolt17]

the regulator rectifier is vastly different than the fuel pump resistor.
the regulator rectifier is located on the stbd side the pump resistor is located on top of the hrottle body assy.
the ECU selects either the resistor as the return path OR the bypassing the resistor all RPM dependant.
the resistor is quite easy to check, simply unplug it select ohms on your DVM and check it.
also check the circuitry leading back to the ECM pins.
also test the fuel pump current draw again using your DVM only now set up for amperage.
it should draw less than 4 amps, much more and its overloading the ECU.

[dieseltruck]

hey rod i had a short time to mess with it today found it did not want to run long at all.checked and had no power at the fuel pump this time..checked the fuse by the big relay rechecked power at fuel pump now im getting close to 15v now motor will start and run longer than it has in awhile around 3-4 min it has a few hicups now when its ideling then soon it dies acts like its running out of fuel. while it was running volts at the fuel pump was 8.8 8.9v it seemed like the ground held in this time i guess im gonna have to break down and have a tech look at it... i pulled the plug to the resistor use my dvm on oms i had 1.1 not sure what the specs are for it. like i said i have pulled and cleaned the vst tank and screen all 3 new LPfuel pumps new plugs pulled and cleaned the 02 sensor it may be an electrical issue...thanks for your responce and help..andy

[99yam40]

what did you find that caused the no voltage?

15 volts seems high for a 12 volt battery that is not on a charger

[dieseltruck]

I pulled the fuse by the big black relay put back together it is on charge it is plugged in to the on board charger. While the motor was running I was getting like 8.8 to 8.9 volts I tryed checking the amp draw on the pump dvm not sure if of was working rite was getting like .4 -.8 amps like I said it ran longer this time with some hicups but still acted like it was running out of fuel until it stalled it fires rite back up. Need to put fuel pressure gauge on it to check pump psi may not be enough psi at idel would the resistor have impact on voltage to pump at idel causing low fuel pressure? Maybe u or rod can answer that and thank u for trying to help me.......Andy

[99yam40]

Did you read this? He said it should be about 9v
How did you measure the volts at pump? To motor ground or to wires at pump?

the ECU controls the ground.
the resistor is only in the circuit until about 1100 RPM to reduce pump operating voltage to about 9V.
above about 1100 the resistor is not used. this gives it a two speed pump.
myself I think the ECU is removing the ground due to another fault.

I think You may need to monitor fuel pressure , volts at pump, and amps maybe to see what is going on.
May have a bad connection to pump or ECU removing ground or bad connection at resistor

[dieseltruck]

I checked the voltage at the wires on the pump its self and yes your rite I'm very close to the 9v at the pump. I'm going to get a fuel pressure gauge today and maybe check all connections I know I need atleast 35 psi at the pump I'm just not sure y now its running longer before stalling and the hicups now it kinda sounds like the lp pumps they are brand new but I guess one or more could be bad from factory compression I think is good 100-105 on all 6 cylinders maybe we will figure this thing out you guys are big help and I thank u very much....

[jb123]

i too had this issue saturday , whereas pump would drop pressure and stall, i applied 12v to pump both ways to ensure pump was working and it seemed fine all day yesterday but i think itll be back... let us know what you find out.

[dieseltruck]

this has been a on going issue it started on the water would run around fishing then try to hit another spot fire it up and stall like it was running out of fuel.now all of this is happening in the yard on the hose.im pretty sure its a fuel issue and im pretty sure its electrical causing it. found i was loosing the ground used jumper to ground the fuel pump motor runs but i dont let it run like that long due to i dont want it to mess anything else up. after pulling and checking the fuse by the big relay/looks like a big fuse block now it runs longer but still ends up stalling like its running out of fuel.i did not have time to check it with the fuel pressure gauge today but thats the next step to see if the psi is droping and if it is what is causing it to do so..ijust want to say thanks to rod and 99yam for there input and help i wish i had more knolege on this but ill keep posting with my progress and please posting back if any ideas of this issue would be a big help...thanks to you guys.

[jf123]

Try moving and pulling on the main harness. There are factory splices in that harness that fail.

[jb123]

in the main/10 pin? serious?

[rodbolt17]

on that OX66, the ign system is old school alternator driven CDI.
will generate spark as long as the flywheel is turning.
if ECU voltage drops it automatically goes into ECU bypass and continues to spark only now its locked at 7* BTDC.
however if your dumping ecu voltage the fuel control system quits.
most sensor failures will lock base ign timing at 7* BTDC.
some will lock it throughout the RPM range others will allow it to advance.
most all will fix fuel rich at low speeds.
some will fix it lean above 4000 RPM.
remember the ECU is the ground path via the ECU for the fuel pump.
two of the blue wires in the ECU connector control this path.
one selects the resistor as the path the other selects a straight ground.
below about 1200 the resistor is in the circuit and drops pump operating voltage to about 9V.
above 1200 or so it selects a straight ground.
however if the pump trys to draw more than about 5 amps the ECU will overload and quit.
a failing,sticking or stalled pump will increase the current draw.
easily measured though.
wont be the first tech I ever saw change a fuel pump only to have the same issues.
however I have only seen one ECU failure on an OX66 that wasnt oil related.