Faulty engine alarm

Discussion in 'General Discussion' started by 7 Palmas, Oct 9, 2019.

My engine alarm goes off for seemingly no reason

  1. How to fix?

    0 vote(s)
    0.0%
  2. Faulty engine alarm

    0 vote(s)
    0.0%
  1. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    My engine alarm goes off for no apparent reason. Mercruiser 97, 7.4l, MPI, Bravo 3.
    When cruising my alarm sometimes goes off and rpm cuts out for a few seconds. Temp is normal and I've replaced the alarm sensor twice. What's going on?
     
  2. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Steady beep, double start up beep, continuous intermittent beep ?
     
  3. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    And...

    What alarm sensor did you replace? There are multiple.

    Does the RPM only cut-out when the alarm is sounding? What RPM's were you cruisng at and what do the RPM's drop to?

    There's only a couple things that would cause a "limp" mode.

    7Palmas... do you have a MEFI-2 system? In your model year, you might... which I believe means only a solid horn and even less things that are monitored. Temp, pressure and drive lube, I believe.
     
  4. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    Steady alarm and engine revs drop only for a few seconds.
     
  5. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    Replaced Temp and Lube sencors.
    Rpm does cut out usually cruising at higher RPMs only for a few seconds then picks up again sometimes to a higher RPM than I started with. It looks like it drops to 2000RPM.
    Yes I believe I have the MEFI-2 system.
    My mechanic has done the diagnostic hookup (in the shop) and found no errors. He's is leaning towards disconnecting it.
     
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    The more info you give the better. Answer some of LD's questions in post 3, and anything else that might help.
     
  7. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    Steady beep
     
  8. Sublimetime

    Sublimetime Active Member

    698
    Oct 22, 2007
    clifton nj
    420 da
    454
    Change out the oil pressure sender, or short it out while at cruising rpm and see if it causes the rpm to drop as you indicated. That might be the culprit.
     
  9. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    All 3 of those sensors work on a ground trigger. Try disconnecting them and testing them 1 at a time.
     
  10. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    I have shorted out the the oil pressure sender and alarm still goes off.
     
  11. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
     
  12. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    That was the gear oil sender I shorted
     
  13. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    Thankyou I'll let you know how i go but it won't be till spring now. Just to let you know Oil Pressure gauge reads normal and so does Temp Gauge. I've disconnected gear lube container and alarm still goes off.
     
  14. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    What the gauge reads means nothing, it's what the ecm sees. You now know it isn't the lube bottle.
     
  15. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    Ok
     
  16. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    Do all the gauges die at the same time when the engine cuts out?
     
  17. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    No Oil Pressure and Temp gauges read normal.
     
  18. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Had the same thing..turned out to be a failing systems monitor...basically false alarm.
    Note my engine is a 1995 7.4 carb, so not quite as modern as yours....
    Old school analog gauges are the best monitor you can get, temp, pressure, etc. they do not interpret anything, just show you the facts of what the engine is doing.
    I had to disconnect my systems monitor and just watch my gauges, which is what I do anyway.
     
    7 Palmas likes this.
  19. 7 Palmas

    7 Palmas New Member

    12
    Jul 8, 2019
    DA 270 1997, GMC Sierra, Humminbird
    7.4 mercruiser Bravo 3
    Thanks Keysohana, I will consider doing that. Did your engine revs drop as well?
     
  20. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    No, the engines ran great with the alarms going off, when I removed the systems monitor board, I found it was bad.
     

Share This Page

Show Sidebar