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  1. #1

    Default Often stalls when coming off plane

    1996 V/P 454ci with a DP-S1 with OEM fuel inject system. All injectors were tested about 1 year ago.

    We had this long block put in by a friend a couple years ago and we average 25 hours a season here on Lake Erie. If I come off plane and don't feather down the throttle it tends to stall and there is even a bounce into low rpm even when I take it slow. Seems to idle just fine auto about 800 rpm around the marine but it will stall every now and then at dock when warm.

    New filters this season and the issue is slightly worse this early summer.

    Being F/I I assumed everything was mapped and not much control like an old carb engine. Thoughts on what I DIY like me can check before I make this an issue with a mechanic that won't have time to look at it anyways for 2 months in my area!

    Thx.

  2. #2
    Join Date
    Jun 2014
    Location
    Arizona
    Posts
    206

    Default Re: Often stalls when coming off plane

    Not really enough info, but water entering the cylinders when your bow goes down and stern goes up is a possibility. Do you have thru-transom exhaust? Any flappers installed in the exhaust system? How quickly/easily does she re-start once stalled? Fuel starvation for some reason when the bow dips down is another possibility. Has fuel tank level been similar each time? How full are they typically when this happens?
    Last edited by Chris Rohde; 06-21-2022 at 05:37 PM.

  3. #3

    Default Re: Often stalls when coming off plane

    Quote Originally Posted by Chris Rohde View Post
    Not really enough info, but water entering the cylinders when your bow goes down and stern goes up is a possibility. Do you have thru-transom exhaust? Any flappers installed in the exhaust system? How quickly/easily does she re-start once stalled? Fuel starvation for some reason when the bow dips down is another possibility. Has fuel tank level been similar each time? How full are they typically when this happens?
    I'm sure my word choice was poor. Rather then saying coming off plane I should say more todo with a quick drop in RPM from cruising (2800-3000 rpm) down to idle. If I don't take it down in a linear fashion it seems the low RPM (thus fuel?) or idle just isn't enough to sustain the demand. I don't believe it has todo with the true angle of the boat.

    Oil has always looked good (no water in system) and continues todo so. The exhaust is OEM through the outdrive. I know I have read that these setups were once prone to back flow of water and some recommend higher risers. I've always been very nervous of this and thus take the boat down at a speed that the stern wave doesn't over power the transom and cause any issues but if I just go a wee bit to quicker then usual it's 50/50 it will stall. I can feel it and give it some gas (little) to solve the possible stall scenario.

    Being the system would have enough fuel in the flow system I would think it would be some time before fuel starvation would be a factor. Fuel in tank is good and the sender was new when we restored the boat a couple years back. It's level at 1/4, 1/2 and 3/4 has been verified with a measuring device for accuracy.

    So what I'm hoping at this point is someone with experience has seen similar issues and know this system and or F/I and knows of what it needs in it's ripe old age.

    to answer the one question. it restarts quickly. The boat can sit months and start in 2 sec and it starts in 1 sec from a stall. On rare occasions (1 in 20) it can be harder to start after running it for a few hours and being in port and then needing to leave. Seems like it might take 5-10 sec of start engagement to get it going.

    Lastly, it seems slightly gassy for a fuel injection system and no noticeable slick on the water. We've checked and double checked for any leaks in the hard or soft lines and confidence is high there is no leak in the fuel delivery system.

    That's all I Know!

    EDIT: I will add as it's going to be another post but the tach is getting very inaccurate at times too but I believe this to be unrelated. it's a new farina gauge (2 seasons) and for the last two seasons it's has it's moments that (again) I'll share in another post later even after I check all the connections and grounding points.

  4. #4

    Default Re: Often stalls when coming off plane

    My guess is idle air circuit.

    When you pull back on throttle all the way you starve the engine for air...idle air circuit will compensate to keep engine running. If it isn't working, no air, no combustion. Bumping the throttle back open a little provides enough air to keep it running.

  5. #5

    Default Re: Often stalls when coming off plane

    Quote Originally Posted by nomagic View Post
    My guess is idle air circuit.

    When you pull back on throttle all the way you starve the engine for air...idle air circuit will compensate to keep engine running. If it isn't working, no air, no combustion. Bumping the throttle back open a little provides enough air to keep it running.
    It very much feels like a air (vs fuel) issue especially since it fires right back up.

    What variables and inputs does this curcuit have that might be getting wrong values...or is there a possible air leak giving a bad value. I know with these boat systems (especially VP) there is very little DIY troubleshooting out there. it's not bad enough to take to a mechanic but I know a guy who can prob look at it in the end of the season if needed as he has all the factory readers.

  6. #6

    Default Re: Often stalls when coming off plane

    Small score...I found this document for the 5.7...not sure what year but there is an IAC control function test at the bottom I can try.

    5.7Gi-E info.pdf

  7. #7

    Default Re: Often stalls when coming off plane

    nice, but the quick and dirty, for me anyway (and i'm not a mechanic and it will show but have wrenched my own stuff my whole life..61 years now)...

    ..is to find the IAC valve. It will be a plunger type thing that meters air past the throttle plate. that plunger/valve must move...you should be able to easily move it. if it doesn't move you've likely found the issue. hit with some kind of lubricant/penetrant...get it moving.

    The diagnosis attached does not seem to address a stuck valve which is very common in a marine environment where an engine doesn't get used often.

  8. #8

    Default Re: Often stalls when coming off plane

    OK, so I decided to have a look at the engine this weekend while at the boat and believe identified the IAC valve here hanging on the starboard side of the intake. With the boat idling at port I pulled the connector and she died. Get get a chance to hit it with lube due to some time constraints so that will be my plan on Thursday.

    In the mean time who can help me source this unit so I can price one if needed? I see no markings or numbers on the unit and my engine has been always a bit of a mystery with all the local pros I've dealt with. The plate wasn't on the original engine and then we replaced it with a long block. I found a plate later in the bilge so cruddy it took some work to read the numbers but we think we got:

    Product Number: 3868604
    Serial Number: A925839 (not 100% sure on 2nd digit)
    Engine code might be : GSiPLK (or GXiPLK)
    P = power steering
    LK = 96-97 year
    (Type DP-S1 1.68) for the outdrive although I know this has no bearing on this project.
    Last edited by carboncow; 06-27-2022 at 04:10 PM.

  9. #9

    Default Re: Often stalls when coming off plane

    Ok, looks like that is a throttle position sensor and not the IAC!

  10. #10
    Join Date
    May 2010
    Location
    DC Burbs/Maryland Eastern Shore
    Posts
    2,419

    Default Re: Often stalls when coming off plane

    I'll throw in that jacking back the throttle is bad practice. You should always lower speed gradually and well in advance of entering low speed zones.
    On of the bad things that can happen is reversion where your stern wave rapidly crashes into your transom causing water to back up into your engine.
    Practicing the ancient art of ren-ching

  11. #11

    Default Re: Often stalls when coming off plane

    Quote Originally Posted by o2batsea View Post
    I'll throw in that jacking back the throttle is bad practice. You should always lower speed gradually and well in advance of entering low speed zones.
    On of the bad things that can happen is reversion where your stern wave rapidly crashes into your transom causing water to back up into your engine.
    Nobody ever said I was "jack back" the throttle so at lot of assuming going in this post that brings nothing to the resolution.

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