Perkins diesel runaway....

Discussion in 'Main Morgan 38 Sailboat Forum' started by schlepper, Jul 8, 2019.

  1. schlepper

    schlepper John m. Harrison

    Joined:
    Aug 20, 2012
    Messages:
    275
    I just went on a trip from Bradenton down to Captiva and back. On the day we started our trek back, we motored for about a mile, just about to enter the ICW when the motor accelerated like I had kicked the throttle forward, then idled back to where I actually had it, then accelerated wildly like I had firewalls the throttle at the helm.... I knew it was a runaway so I quickly scrambled below, removed the steps, then air breather and put a teak block I had over the intake and she shut down.... I immediately put out the jib and then the mainsail to keep us moving forward and away from the sandbars we had just cleared. I noticed I had a pile of black oil in the plastic tray underneath the engine and there was oil splatter on the top of the engine and before I could shut it down, I noticed oil gurgling out of the oil filler cap.... I was in shock, i had changed the oil about 10 running hours before, complete with new filter and I had replaced both fuel filters PLUS did a fuel polish/tank cleaning. I let it all cool down and just enjoyed the sail and cracked open a beer... what the heck.
    So about 2 hours later, I went back below, wiped off the engine, put some paper towels in the oil now pooled in the forward end of the tray and in checking the oil, I had far more oil than I had placed in the engine at the time of oil change and upon checking it after our first day of the trip, the oil level was normal.
    I cranked the engine up, at the ready with my wood block but it started like normal and sounded just fine. I had been running high oil pressure readings at the gauge for a long time but never have had any problems for the 5 years or so it's been like that and my mechanic didn't seem to think it a problem. When i checked the oil pressure upon restarting the engine, the pressure at idle was about 10 on the gauge instead of the usual 60-70. At 1500 it went up to about 20. We motored and motor-sailed the next 2 days of our journey back home and it ran fine, never repeating the runaway scenario.
    When I cleaned the oil up in the tray, it was obvious it is diluted with diesel. I am thinking the gurgling in the oil cap was the overfill situation of diesel in the oil filling up the valve cover and going down the valve lifters and causing the runaway. The IP was rebuilt about 2 1/2 years ago. The lift pump was replaced about 6 years ago, and I have not had the injectors off, but when I crack each of their steel lines at the injector, the engine dies down and when I re-tighten, the RPMs go back up to normal.

    Anyone else have this happen? It ran flawlessly after this episode and after finding the spade fitting on the oil pressure sending unit was slightly loose, upon snugging it up, the oil pressure ran right at 40, middle of the gauge, all day yesterday after I noticed and tightened the wire fitting....
     
  2. dave_a

    dave_a Dave Ahlers

    Joined:
    Aug 15, 2006
    Messages:
    750
    John, if you have a Perkins...
    The mechanical lift pump has an internal diaphragm. If it starts to leak it can add diesel to the crankcase. Causing the runaway problem you had.
     
  3. schlepper

    schlepper John m. Harrison

    Joined:
    Aug 20, 2012
    Messages:
    275
    Thanks Dave, a couple of years ago, I had to have my IP rebuilt as the engine was smoking terribly, rough, stumbling, etc.. The mechanic I had take care of it, talked me into a Foley spin on secondary fuel filter fitting to get rid of the canister/cartridge style OEM filter. After I replaced the lift pump, which I happened to have a spare still in the sealed plastic bag and Perkins part box, the engine still would sound like it was going to rev up as I got it started after bleeding, etc.. I had already changed the oil and filter so the oil has no diesel dilution. The engine would not restart after I did the bleed each time, even after it had already cranked and run albeit with 'RPM spikes' from idle to 1000-1500. The solution was that the spin on filter housing converter had vibrated loose and was allowing air into the fuel filter head, and given enough time, would build up air and thus the 'no re-start' even after the initial bleeding and starting. Now it runs great, holds excellent oil pressure and the oil analysis that I had done after the runaway showed no ominous metal content in the oil sample... the Perkins 4-108 can be temperamental at times, but dang, these things are tough and solidly built. I plan to take it out late next week to get see if the lift pump has the diesel in the oil issue squared away.
     

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