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Thread: Inboard hard to start when warmed up

  1. #1

    Question Inboard hard to start when warmed up

    I have a 2001 Volvo Penta 5.7 EFI in a Seasport that has been slowly developing starting problems once the engine is warmed up. Starter cranks for 3-5 seconds before the engine fires and exhaust smells of unburnt fuel. On a cold start, it fires without hesitation. Engine runs just fine throttling up and at normal cruising speed. It has fresh gas and I changed out the fuel filters and it still has these symptoms. Engine temp is a steady 175 degrees. Seems to have all the classic symptoms of vapor lock, but this is fuel injecte Any suggestions for DIY before I haul it off to a mechanic? Thanks

  2. #2

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    Could be vapor lock in the fuel lines. I've experienced this on vehicles.

  3. #3

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    Could be a sensor that is not feeding back the correct engine temp to the EFI unit causing the fuel injection to be dumping more fuel then is needed on a hot start. That could be why it starts easily when cold, but "floods out" when warm. The sensor may only be needed during start, and factored out of the system once the engine is warmed up and running. Can you pull the codes off the EFI unit? Not sure what would be needed on a GM engine, but it should be fairly easy to do. Codes should be similar if not identical to a car or truck. Good Luck.

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    replace the engine coolant temperature sensor. (Note: there is usually a separate coolant temperature SENDER ), which sends the temperature to the gauge that you see, so you see the correct engine temp, but the EFI is being told a different temp by the SENSOR, and flooding the injectors with fuel (because it is likely being told that the engine is still cold).


    Make sure to differentiate between the two, and replace the sensor.

    I have had this identical problem, with symptoms exactly as you describe. and replacing the ECT sensor solved the problem.



    Edit: You should be able to pull the sensor and check the amt of resistance to see if it is within specs if you can find the specs in the FSM, but I think you can pretty well assume it is faulty.

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    The resistance check can be performed while the ECT is installed, matter of fact it is best to do so then use the temp gauge as a reference . Check coolant levet first of all to be sure ECT is in direct contact with coolant, if there is no direct contact ECT will read cooler than actual engine temp most times. Or you could just replace it, they are not expensive.

    Another possibility is the crank sensor is beginning to act up, often the first signs of intermitant failure is a hot soak/start.

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    I had similar symptoms on my 2005 Seasport. Compression check revealed two dead cylinders - exhaust valves. Head gasket kit and valve job had me back in the water a couple weeks later.

    Its amazing how "well" it ran on six! If it wasnt for the heavy gas fumes I might have kept running it.

    Probably worst case - but it wouldnt hurt to check the compression.

  7. #7

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    Hey thanks for the good advice on things to check. I pulled the ECT sensor. Reads about 2800 ohms at room temp. Dunked the sensor in some hot water about 200 degrees and it went down to about 500 ohms. I have no idea what the spec range is on these sensors, but it seems to respond to changes in temp. No scaling or deposits on the sensor either.

    Compression test will have to wait a few days but any other ideas to check out would be greatly appreciated.

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    the fact that the ECT responds to changes in temperature means nothing except that it doesn't violate the laws of physics. Of course resistance will decrease when it heats up. You need to find out what the resistance specs are, or buy a new one, and test it to see if it reads differently. You will not see any visible clues because the coil is inside the sensor. You have verified that the coolant is full? A compression check is reasonable protocol if you have been losing coolant.

    From looking at the ECT spec. chart for my toyota pickup, for comparison, 500 ohms is a bit too high (i.e. cold) if you really had 200 degree water, it should have read more like 300.

    Of course your sensor is probably a bit different than the one on the chart I referenced linked HERE, but I bet it isn't much different, if at all. My 2 cents is still to buy a new sensor.

  9. #9

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    I'm a self admitted simpleton on using a multitester, but if I set it to 20K scale and it reads 2.8, isn't that 2800 ohms? The ECT sensor is definitely fully immersed in coolant. I had to plug the hole when I pulled out the sensor. I'll keep responders posted on updates once I figure this one out. Thanks again for all the help.

    BTW, I've managed to avoid boat mechanics for 10 years, doing all the routine stuff myself. Any recommendations on a reliable mechanic you know of in Anchorage that might help me on this one?

  10. #10

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    possibly leaking injectors, very common on multitec style injectors , if you can pull the fuel rail and injectors
    then pressurize system and watch for drips

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    The shotgun approach of replacing parts, even when using educated guesses ,to see if it fixes the problem can work but many times it can end up costing more in the long run. Your best bet is to find someone with a rinda tech box or diacom software to diagnose the problem correctly. The software can display all the sensor values, trouble codes, power balance tests to isolate problems to individual cylinders ect. That being said, ECT sensor failure would be a possible culprit, especially if you motor seems to be running rich and burning more fuel than normal, leaky injection.or o ring is another possibility so is a failing crank.or cam sensor or.............

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    I ditto what WEST had to say ...

    I had a very similar situation with my 2003 Osprey with the volvo penta 5.7 gi. The duo prop out drive had the wrong props, causing the engine to lug, thus high cylinder temps and burnt exhaust valves, good cold starts terrible hot starts. After we had a valve job and changed out the props so that we could develop full rpm at wot, by the book, no problems in the last 4 years .... good luck

  13. #13

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    This may be the case for my engine too. I've replaced the distributor cap, rotor, and fresh spark plug wires. Took off the exhaust manifolds and risers. The seawater side of the cooling jackets were pretty toast. Note to self: replace risers and manifolds about every 6-7 years, not 11 years. Once I get it back up and running, I'll do the compression test.
    I dropped a prop size a year after purchase of the boat for the same reason. Thanks for your suggestions.


    Quote Originally Posted by ocnfish View Post
    I ditto what WEST had to say ...

    I had a very similar situation with my 2003 Osprey with the volvo penta 5.7 gi. The duo prop out drive had the wrong props, causing the engine to lug, thus high cylinder temps and burnt exhaust valves, good cold starts terrible hot starts. After we had a valve job and changed out the props so that we could develop full rpm at wot, by the book, no problems in the last 4 years .... good luck

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    You do not need to get it running to do a compression test. Now is the time. The exhaust manifolds are out of the way. If you have not changed them for 11 years, I imagine that bad compression is what you will find. I am very surprised that they lasted that long without any other issues. I would not go more than 5 years without changing them. Just not worth the "savings" (Learned this the hard way)

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    Quote Originally Posted by Soundfisher View Post
    You do not need to get it running to do a compression test. Now is the time. The exhaust manifolds are out of the way. If you have not changed them for 11 years, I imagine that bad compression is what you will find. I am very surprised that they lasted that long without any other issues. I would not go more than 5 years without changing them. Just not worth the "savings" (Learned this the hard way)
    I've been debating doing the compression test on a cold engine and how that might effect results. The VP shop manual and every internet site I checked says to bring the engine up to operating temp before testing. This has me wondering whether to wait until I have the exhaust system back up. I can't find any information on compression deviation between cold and warm engine.

    Flushing with freshwater followed by salt neutralizer after every trip bought me a little more time on my exhaust parts, but you are right, why get cheap when the end result can be wicked expensive. Kind of bugs me that they can't engineer something better than cast iron with saltwater running through thin walled narrow passages.

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    A comp test at normal operating temp will give a higher result, but testing while the engine is cold if perfectly acceptable. If you have results of 115-125psi or better cold, rings and valves are in good order. If you have low psi you can squirt a little oil into the cylinder and retest; an increase indicates worn rings- no effect indicates a valve issue or worse depending on intial value. A burned valve, broken valve spring (often noisy), broken rings or a hole in a piston would manifest as a constant dead miss in the affected cylinder.

    However, a hot start problem is not a compression issue if cold starts are normal. An exception would be minimal valve clearance that becomes unacceptable once hot, but this would lead to a burned valve if not caught and corrected in quick order. The chances that enough cylinders are such to create this issue are very, very unlikely with a hydraulic valve train.

    Leaking fuel injectors would cause a hard start or rough run whether cold or hot due to over rich in one or more cylinders and loss of fuel rail/injector pressure. If the issue is not resolved on the next hot start, try cycling the key to on -then off then on and crank to start- if improvement is noted then I would suspect a fuel prime issue- culprits would be fuel pump relay, fuel pump, restriction in fuel line (not likely if engine runs well once started), poor electrical connection due to heat loss/resistance.

    Another likely cause is an ignition failure when hot, normaly the ignition control module or pickup coil in the distributor; often when these fail when hot a stalling/shutdown occurs until the component/s cool enough to allow the intermitant electrical break to close. This is easy to check by looking for spark at the plug wire to plug connection during failure- no spark = ignition failure someplace.

    A hot start problem is most often the result of an electrical failure of some nature when cold start is otherwise normal.

    The symptoms you describe indicate either a too rich fuel condition or a lack of ignition (poor spark)-both result in excessive unburned fuel out the exhaust.

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    One of the cheapest, most easy way to diagnose or trouble shoot is a compression test. If the readings on the comp. test are good, then get into the technical stuff. The comp test is a 1/2 hour job that is full of info. So easy, even a caveman can do it.

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    Quote Originally Posted by Soundfisher View Post
    One of the cheapest, most easy way to diagnose or trouble shoot is a compression test. If the readings on the comp. test are good, then get into the technical stuff. The comp test is a 1/2 hour job that is full of info. So easy, even a caveman can do it.
    Update: Good news, the compression on the cold engine ranged from 150-200 psi. Should get new risers this week and get them installed. Time to check to see if the parts replaced so far have resolved the delayed warm start problem. I didn't mention before (too embarrassed), but the contacts inside the distributor cap were pretty green. At least this issue has got me paying closer attention to overall engine maintenance.

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    That sounds like excellent news. Pushing 200 though makes me wonder about your gauge? That sounds too high. I would try again with a different gauge. If all seems well then as I stated before now is the time to get into the more technical stuff. I am still surprised at the amount of time you got out of your manifolds. Sounds like a good tuneup is in order though. If the comp is that good, and fairly close to (+/- 10%) of each other, sounds like you should have a few good hours left in her. Good luck to you.

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    Quote Originally Posted by Soundfisher View Post
    That sounds like excellent news. Pushing 200 though makes me wonder about your gauge? That sounds too high. I would try again with a different gauge. If all seems well then as I stated before now is the time to get into the more technical stuff. I am still surprised at the amount of time you got out of your manifolds. Sounds like a good tuneup is in order though. If the comp is that good, and fairly close to (+/- 10&#37 of each other, sounds like you should have a few good hours left in her. Good luck to you.
    The poor ignition (weak spark) inability to ignite the fuel properly leads to sooting/carbon buildup which will produce high compression values. After the engine is running properly again and for long enough to burn out the deposits, compression values should even out and drop some.

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