Genset - sudden jump in oil pressure?

[Beausoleil]

What would cause a sudden jump in oil pressure - from about 45psi (normal) to about 110psi?

The last couple of times I ran my Westerbeke BTD-7.6 genset, after about an hour or so of runtime, I noticed that the oil pressure had spiked. The load on it at the times I noticed it was about 15A (1st) and 25A (2nd). Both times I was charging the batteries (125A and 75A chargers) while running the Spectra DC (14A max) watermaker, and running the electric hot water heater (120V 1500W). The chargers had tapered off, so the majority of the load was the HW heater. The genset powers two 30A legs on the AC side, with the 125A charger on one, and the 75A charger & HW on the other. I don't think the electric side of things is the cause - just putting it out here for completeness.

The genset's fairly new - 276 hours on it. I did recently change the oil, filter, and heat exchanger zinc. I double-checked to make sure I didn't overfill the oil sump. What else should I look at? I'm running the genset as I post this - 25 minutes and the oil pressure's normal - 45psi, load on it is currently 30A - 50%. As an FYI - I know the genset is typically under-loaded, but later this month I'll finally install the two A/C units (12k & 16k BTU).

Any ideas? The engine temp doesn't change, or the perceived loading on the engine (no noticeable change in sound). Could it just be a failing oil pressure sensor?

[skipmac]

I would check the sender first myself and also the gauge. Not a pro mechanic so not sure but I believe you can screw in a portable gauge or tester to verify the pressure. Also check the wiring going to the sensor and gauge to make sure nothing is loose. Otherwise I guess you would have to swap out the parts to confirm that part of the system is functional.

If you verify that the pressure is spiking I do not think that high a pressure would relate at all to load. I would focus on blockage or restriction in the oil system. Since you just changed oil and filters I would start there. Maybe put in another filter in case that one has a problem. Check to make sure you didn't lose a washer or o-ring into the system.

[GordMay]

Originally Posted by skipmac

... I would focus on blockage or restriction in the oil system. Since you just changed oil and filters I would start there ...

Indeed.

[Beausoleil]

Well, after speaking to a diesel tech at R. B. Grove down here in Florida, and he thinks it's the pressure sender. Since the oil filter mounts horizontally and has only a gasket near the outer edge (like normal), he's inclined to think it's the sender since he can't think how the gasket could have worked loose - plus I'd see oil leakage. He thinks the cause is the sender, since those seemingly have a higher failure rate in his experience. I have two which were included in the initial spares pack that came with the genset, so I'll check that first, once the genset cools down. I'll report the results back here later...

[GordMay]

Test your gauge & sender, per this post:
http://www.cruisersforum.com/forums/...sting-645.html

[perchance]

If the guage and sender check out then it is probably the pressure relief valve that is sticking.

[Beausoleil]

I re-terminated the sender wire at the sender end, and the problem hasn't re-occurred. I'll see what happens over the next couple of days.

Thanks for the info, Gord - both the new and old sender tested fine.