I have been plagued with some intermittent low oil pressure indications since November. First time was day two of my two day trip across South Florida. 1st engine start of day showed no oil pressure. Shut down after 10 secs. Tried again and same thing. On the third start, oil pressure came up and was fine all day.
A couple weeks later, had low oil pressure on start up, and this time it did not come up with repeated start attempts. Added a qt of oil (which was not low, but near the lower line of the "safe zone"). Oil pressure came up on the next start. This made me quite worried it could be the oil pump, or the oil pump inlet screen assembly. Online forums showed some 5.7 Chevy truck engines could have that problem.
Another week later it happened again, but this time, a couple attempts would show the oil pressure come up and then drop down to zero after a second or two. The next attempt the oil pressure came up and stayed up for the rest of the day.
So I was hoping it was a sensor problem, as the oil pumps are extremely reliable. I ordered a new oil sender, and in the mean time, I borrowed a mechanical oil pressure gage and connected where the oil sender was. To my relief, the mechanical gage showed the oil pressure jump to at least 40 psi on every engine start without any hesitation.
I decided to install a Tee connection with both a mechanical gage hooked up in the engine compartment, and the oil sender going to the VDO cluster. My VDO cluster has been very reliable up to this point, with the exception of a blown fuse one time.
Indications today with both gages attached, showed normal oil pressure reading on the mechanical gage, and indications on the VDO that would erratically change anywhere between normal, low, or zero. Whenever it is zero, or nearly zero, I also get the Low Oil Pressure Idiot Light, and audible alarm. So despite the issues that VDO clusters often have, I am still suspicious of the new sensor, or the wiring. The sensor is a single wire type. It was a Volvo part, not aftermarket.
Anybody have further diagnostic suggestions? Know what the resistance values are for normal oil pressure (and zero pressure)?
At least I can go boating tomorrow and with the mechanical gage, I know I have proper oil pressure because of the mechanical gage, but I will probably have to pull the fuse on the VDO cluster so it doesn't sound the alarm the whole time.
_________________ ![Image](http://tinyurl.com/yc6eyl36) "Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX tow: 2017 Honda PILOT EXL-AWD prev. boats: '87 Chaparral 198CXL 4.3 OMC Cobra '69 Jetstar 16ft Ski Boat, 115hp Yamaha '68 Aluminum Jon Boat, 3hp Sears '64 Water Wings
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