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oil pressure buzzer & engine hesitation, will not go over 2800 RPM's 2003 injected 5.7

cctowboat1

New member
It stated doing this once in awhile, now all the time. The engine starts fine, when I give it a little throttle the alarm goes off for 10 sec and stops, more gas same thing until I get to about 1500rpm's then it stays on. The oil pressure gauge tells me I have good oil pressure. Engine runs fine till I get to 2000RPM and then every 10 seconds the RPM's drop about 1000RPM's for a second and then go back up for another 10 seconds and does it again. It will not go over 2800RPM's from half throttle to full throttle. I had someone put a diagnostic tester on it and was told it is telling me no oil pressure. I checked the sensor and switch and the two wires were broken off the terminal, great found the problem...NOT....put new terminal on the two wires and hooked back up, same thing. One of the wires looked like it had a clear cover at a spot where I could see a thin wire? I changed fuel filter, cap & rotor, and cleaned the water/ fuel separator. still did not solve the problem, switched the ECM's from the other engine, no luck, bought a Sierra oil pressure switch and tried that, not sure if switch was bad and if this one would even work. Any one got any ideas or suggestions?
 
While our boat does not seem to be set up exactly the same way, we experienced an issue very similar to this when we purchased our boat and took it out for the first time on our own. What we found was the oil pressure was low in the transmission. I would encourage you to check the fluid levels there. It might not be the issue, especially because it seems it is engine related but it is certainly worth a shot especially as this is almost exactly what we experienced.
 
The oil pressure sender (larger of thetwo gizmos on the “T” fitting) sends an analog signal to thegauge and is not connected to the ECM (engine computer). Be surethat the gauge is acting normally. If so, you have oil pressure. Theswitch on the other side of the “T” is connected to the computer,and it is telling the computer that you have inadequate pressure. Ithink it is a “dumb” sensor, either on or off. I have neverexperienced it, but according to the manual, this is the cause of thecomputer cutting back the rpm of the engine. You can search Googlefor MEFI 4 Diagnostic Manual and download one. Great tool fortrouble shooting. If you have changed the switch it could be abroken wire or a bad connection on the J1 plug going into the ECM(manual will tell you which wire at that end). A little time with anohm meter and you should find it.
 
Could also be the wrong switch...

concur on getting the diagnosis correct, especially if the ECU is entering power reduction mode...
 
Anyone know the part number for the switch, I can seem to only find one that looks like it R020015A but it says for bigger engine 8.1
 
I would check the wire for continuity from the switch to the J1 plug into the ECM before I invested in another switch. Disconnect all power to the engine. Then disconnect the sensor wire at the switch end and see if you have it ungrounded at the plug end. Then ground it at the switch end and see if it is now 0 ohms to ground at the plug end.
 
CaboJohn, Which # plug in the J1 Plug, I could only find oil pressure imput in the J-2 plug at J2-20 in the diagram but there is no wire or connection there. what should I be looking for in the J1 Plug
 
Not sure what you are seeing or what diagram you are looking at. Page 5-36 of manual shows oil pressure input to computer as plug J1-4, wire colored blu/white. Page 5-29 shows oil switch connected to computer by blu/wht to J1-4. So that ties. Other wire from switch is green to ?? (likely ground but ask an expert, I am not sure but with a meter could figure it out). Page 5-28 shows oil pressure sending unit with a light blue wire, presumably going to the gauge on your dash. Don't see any yellow or green with yellow on either the switch or the sender.
 
I was looking at the wrong one I guess, but when I look at this one http://www.crusaderengines.com/manuals/L510005C.pdf - my pages seem different than yours 5-36 shows me diagram for Injectors + 5-29 shows me a blank page + 5-28 shows me twin engine harness? - Page 5-40 show's me the J-1 plug and the Ji-4 shows me blue/white for "general warning 2 (oil pressure) input" still looking for other pages - there's 347 pages in this manual
 
Your manual is same as mine except it seems to be a later version with a few additional pages (mine does not have the twin engine harness, although that is the setup I have). Looking at your manual, page 5-31 shows the oil pressure switch with blu/wht going to J1-4. And as you found, page 5-40 shows the plug with the blu/wht connected to J1-4. Page 5-30 shows the oil pressure sender to the gauge as lt blu. I would check the blu/wht for continuity back to the J1 plug. If that is good, figure out if the switch is normally (when not seeing oil pressure) closed or open. If open, wire around it so it is closed and see if your problem goes away. Then you know the problem is the switch. If closed now, then disconnect and see what happens. If that does not do it, figure out what the green wire does (or should do). I suspect it is a voltage source but am not sure and I am not familiar with the method used on the schematic. It would be easier if my boat was not 3000 miles away right now.
 
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