Engine dies suddenly but starts right back up

[jrd_mon]

Have a volvo penta sx v6 that has started dying randomly while out on the water. The engine just shuts down completely. It happens at slow speeds in no wake zones as well as higher speeds (30 mph). It starts right back up though without any problems and without me doing anything special. Seems to have full power when I hit the throttle. Any guidance would be greatly appreciated! Thanks!!

 

[Don S]

Re: Engine dies suddenly but starts right back up

Without a full model number or serial number of your engine, an answer is impossible.

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Sorry for the delay in responding to the question. Been a wild few weeks! Anyway, it is a Volvo Penta 4.3 GL. I hope that is what you were looking for. I've taken the boat out since my original post. The problem seems to be getting more frequent and serious. Last time I had it out I was pulling a tube with 3 kids on board. Not going real fast but good enough for a fun ride. The boat started to lose power at random times. Eventually it died a few times but started right back up until one time it died and wouldn't even try to turn over for about 15 minutes but still wouldn't start. I tried starting it every 5 minutes or so and finally after about 40 minutes it started up and we made it back to the launch with out problem and with plenty of power. It acted like nothing was wrong. When I got home it started right up in the driveway. I checked the fuel in the fuel filter and it seemed fine; no water separated out or anything. There was a little bit of sediment that came out of the filter but that was it. I've looked at the distributor and it appears to be new (I just bought the boat this summer from a family member who swore it was working perfectly last summer.) I'm going to put a new fuel filter on since I've already got the old one off but I doubt that's going to fix the problem. I had one guy say it must be the fuel pump but I really don't know. Let me know if you need to know anything else about the model of the motor. Thanks!

 

[Maclin]

Re: Engine dies suddenly but starts right back up

My first take is it is an electrical problem. Loose or broken wire to the coil, something like that. Since it is a family member and no one is trying to scam anyone I would ask them a little more about what they have done or did just before you got it, things like that. Maybe someone was in there and leaned on a wire, or had to remove something to get at something else, that kind of thing. It could help pinpoint a physical area of the engine or any other part of the boat where a wiring issue could lie.

It could be the unit inside the distributor aging, or cracked wires there also.

When on the water and it dies I would look down the carb and push the throttle a few times to see if the accelerator pump squirters give the same good full streams all the way thru the stroke to see if the carb has fuel. If the streams falter or vary after a couple of strokes then the fuel bowl may be drained indicatiing a problem with fuel delivery. You have an electric fuel pump that will only get power while the engine is running. There are some components there that can fail or have wiring problems. A relay is involved as well as a special output from the alternator. If those are not to spec or broken then the fuel pump will not get reliable power.

Also I would want to check the spark by removing coil wire from distributor cap and have some one crank it while you hold the end close to a ground.

Just be ready to do these diagnostics on the water if/when you go out again to help eliminate or illuminate problem areas.

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Thanks for the advice. I'll take a look at some of those things this weekend hopefully. Just for my curiosity, I took my battery down and it turns out its gone bad. Would that possibly explain the problems I've been experiencing with random stalling and loss of power? It's an easy fix so I hope that's all it is.

 

[Maclin]

Re: Engine dies suddenly but starts right back up

That certainly is a factor. Clean or replace all of the large gage wire terminal ends, negative and positive, at the battery and the starter and the engine block. A shorted battery can drain alternator power also, cause low voltage even when running.

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Replaced all the spark plugs and fuel filter as well as the battery. A mechanic friend of mine also said to put some carb cleaner in the fuel tank which I did. Took it out Saturday and it worked perfectly for a couple of hours. Not just about as we were getting done for the day it died. When I'd turn the key it would start up but as soon as I let go of the key it would die. Had to get towed in and when I got home it still wouldn't stay running although it would stay on as long as the key was in the "start" position. Do you think this is a new problem or the same problem I started with at the beginning of this thread? I'm hoping it's the ignition switch going bad. I've also read some threads that suggest the oil pressure safety switch could cause this problem. Any suggestions besides those two items? I'll start testing the switch tonight.

 

[Maclin]

Re: Engine dies suddenly but starts right back up

This is one scenario that could be relative to you situation, involves the ignition coil positive terminal power circuit...:
Engine starting then running with key in Start/Crank position then dying when returned to Run could indicate a problem in the coil ballast circuit which powers the coil via the positive terminal. Ballast resistance is bypassed when cranking so it starts, then when key returns to Run there is no power to the coil due to bad ballast resistor component or wiring. In normal Run conditions battery voltage is run though a ballast resistor of some kind. If this component or circuitry has a problem then it will only get power when cranking when that circuit is bypassed.


regarding Oil pressure safety switch...:
The oil pressure safety switch/circuit affects power to the fuel pump and is probably not your exact problem. Your system does not use a safety switch but has another mechanism with same intent, however your symptoms would be different if it was a fuel pump power issue. Your engine would run for a little bit with key in the Run position until the carb bowl ran dry, then Starting/Cranking would bypass the safety circuit and give power to the pump while cranking and enough fuel would get in to run a little bit again, lather-rinse-repeat kind of thing.

 

[Don S]

Re: Engine dies suddenly but starts right back up

You never did post the full model number of your engine. Don't know what ignition system you have without knowing.

Since it dies when you let off the key, with the engine off, turn the key on and check to see if you have voltage on the purple wire of the ignition switch.

regarding Oil pressure safety switch...:

Volvo doesn't use that, Mercruiser does.

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Thanks Don! I'll check the purple wire tonight. I was hoping Volvo didn't use the OPSS since I was having a hard time finding it!

 

[Don S]

Re: Engine dies suddenly but starts right back up

Get the full model number or the serial number of the engine too.

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Checked the ign. switch by connecting the neg. probe to the battery and pos. probe to the purple wire with the key in 'On' position. I got 12.7V so it seems like the switch is good. I was really hoping that was the problem; easy and cheap to fix! The model is SX-M and serial # is 4202034172. Where should I go from here?

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Last night I tried starting the motor again with the same problem where the engine would start with the key in start position and then would quickly die when the key went to the on position. I noticed the wires attached to the switch were pretty oxidized. So I took off the ign. switch, cut the ends of the wires off, re-stripped them, and put them back on the switch. Now the engine is staying on without any issues. Could that really have been the problem? Oxidized wires preventing a good connection? There's an obvious difference now. We'll take it out tomorrow and see what happens. Hopefully everything goes well. Can't beat a free and easy fix if that's really what it was!

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Took the boat out for another short trip today since the boat started up fine and pulled a wake boarder without any problem but when we shut off the engine to switch boarders, the engine wouldn't start back up. We finally did get it started and it ran real well back to the boat launch. We thought about trying to keep going but then it died again and we couldn't get it started back up. Everyone on the dock kept saying it was vapor lock. Don't know much about that. The engine did seem to start up again when the key was in the start position but wouldn't stay going when the key was in the on position. Getting frustrated with this problem. Have an appointment with a local mechanic shop on Friday if I can't figure out the problem before then. Thanks for any advice you can offer.

 

[Jeepster04]

Re: Engine dies suddenly but starts right back up

Does this engine have an electric fuel pump? Doesnt the fuel pump only run when the engine is running OR youre cranking the boat? Maybe something is going on causing the fuel pump to only pump when the key is turned.

Far as I know, Vapor lock means the fuel is so warm in the fuel lines that its turning to a vapor. Our Volvo does this when its really hot out and I really don't know what we can do to fix it. It will only do it once after the boat has been ran and then sits; like stopping to swim for example. Once you restart it and get on plane, it will sputter and most often die. It'll usually start right back up, sometimes requiring extended cranking.

 

[Don S]

Re: Engine dies suddenly but starts right back up

I'v been asking for 2 months for an ENGINE model number or serial number and so far I have gotten a serial number for the outdrive only :facepalm:

He must not want help very bad.

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

Don - Quite the opposite. I'm definitely looking for help as evidenced by my repeated postings over the last few days trying to keep this thread active. Apparently I don't know where to look for the engine model number or SN. I'd be happy to get that for you if I knew where it was located.

Jeepster - You're describing exactly what we're experiencing. It's got to be something along the lines of vapor locking. I noticed about 3 - 4 inches of the fuel line was sitting directly on the engine block so I've rerouted that line so it isn't touching anything now. I'm also going to try not shutting the engine off for a few minutes after pulling someone. We didn't have this problem in the spring when it was a little cooler. Has to be related to the heat. Going to give it another try tonight.

 

[Don S]

Re: Engine dies suddenly but starts right back up

Apparently I don't know where to look for the engine model number or SN. I'd be happy to get that for you if I knew where it was located. .

Then you should have said something instead of just ignoring the question.

http://www.volvopentastore.com/mall/template/store/volvopenta/help.html

 

[jrd_mon]

Re: Engine dies suddenly but starts right back up

I thought I had answered the question and was not aware the number I provided earlier was not the one you were looking for. I will post the correct information tonight or tomorrow as soon as I can.

 

[Don S]

Re: Engine dies suddenly but starts right back up

When you go back to the boat try this too.
Last time I had you turn the switch to run and check power to the coil, basically, do it again but slightly different. Start the engine, and when it dies, don't touch the key, just go check power to the purple wire on the coil again.
The switch may not reconnect the ignition when coming back from the start position.