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Indmar 320hp - Hot Start Problem


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Hi,

Hoping someone can help with this frustrating issue. I have a Malibu Sunscape 2006 Indmar 320hp LCR fuel injected with around 150hrs on the clock and recently its been having trouble turning over when hot. The engine always turns over first time every time when I take her out cold, the problem is when we go out for a ski the engine gets up to temp & we decide to go in for lunch or take a break for 20+ mins. The engine will kick over as normal but after 30 seconds to a minute it will start to couch and will cut out. Attempting to restart the engine from this point will do either of two things. 1 - it will turn over and run very rough in idle, engaging gear will cause cut out. 2 - engine will attempt to start but no ignition (you can hear the fuel pump and the starter motor going but no spark). Normally if I squeeze the fuel lines with my hands and let it sit for 5 mins it will start up, have a bit of cough and then we are away again. However, on my last outing I couldn't get the engine to kick back over for 45+ mins and eventually got towed back to the ramp.

I was able to successfully replicate this at my house using the water hose (hopefully means its easier to diagnose) just by getting engine up to temp, turning off and letting is sit for 30 mins.

I often have the blower on but this doesn't seem to make a difference. Note that this issue has only started happening recently.

I have read some good posts in this forum but none seem to be exactly what I am experiencing. The boat is booked in at the shop to diagnose the problem but Im concerned its going to be an ongoing niggling issue so looking for your advice.

Thanks!

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Hi Denny,

Thanks very much for your quick response. I have heard of the vapour lock issues but lots of people are saying different. Why do you think it would have started all of a sudden?

Do you know of any documentation of how to install this second pump?

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I've got almost 500 hrs on my Monsoon & only seen the vapor lock issue like twice. It was pretty easy to nail down too. I took a rag & drenched it in the cooler ice water. Then stuck it right on top of the fuel pump. After about 10 seconds all the symptoms you just described disappeared..... completely. The engine was running fine after running rough, slow to start, or even no start.

I can't explain it. But I run the blower almost all the time to try & combat it. When I saw it, the engine was hot, like we had been at idle speed for maybe 15 or 20 minutes, low RPMs, and the weather was hot, in the 90s. We had stopped for a bit & cut the engine for maybe 5 or 10 minutes when I tried starting it. I figured that was the hottest the engine would ever get... I've read where the condition is caused by the engine's heat heating up the fuel in the fuel lines, creating a bubble, almost a vaccuum, that the fuel pump was having a hard time to overcome, so it was delivering fuel at an erratic rate, mixed with hot air.

Good luck getting over it. Like I said, I just run the blower a lot. Figured it was a good thing no matter how you look at it.

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Thanks appreciate the response. When I replicated the issue off my water hose the fuel pump was not even hot, nor was it that hot in the engine compartment to where the fuel would boil.

Im wondering if you think crappy fuel would be the cause of this issue. All the recent issues have been on the same tank of fuel from when I filled up last time and have been on a few outing recently still getting through this full tank. Do some fuels boil or vaporise sooner than others?

If so, whats the best way to drain the fuel tank?

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Also, i forgot to mention, I have a fuel filter with water separator. The bottom part of this filter looks to be full of clear fuel (Im guessing thats the water). Should this be emptied out? Would this be causing any issues if its full? I can upload a photo if that will help...

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You definitely should empty out the water separator - there's usually a twist valve on the bottom of the bowl. But that's likely not the cause of your hot start issues.

As you probably know, the hot start issue is a problem because the temps around the fuel lines and pump get so hot when the engine is shut off and the fuel is stationary in those lines (rather than cool fuel coming in from the tank...), and the fuel begins to vaporize. If the fuel system was pressurized like a cooling system on a car then this wouldn't be such a problem, but they aren't so workarounds have to be devised. Temporary stuff like putting a cold rag on the fuel pump is good stuff in a pinch but you don't want to have to rely on that as a regular process. So, net, there's really two ways to lessen the vapor lock issue: a) cool the fuel while it's sitting stationary in the fuel lines after the engine is shut off, or b) keep the fuel circulating prior to re-start. You have an advantage with a fuel injected engine as there's a return line back to the fuel tank and thus recirculation isn't too tough to accomplish (no such luck with carb'd engines as there's no fuel return line). You can try to cool the stationary fuel in the lines prior to re-start but this gets complicated pretty quickly as you need a source of cool temps and a heat exchanger (and you need to circulate it as well). Personally, I would engineer a fuel recirculation system so that the fuel the pump and injectors are getting when you re-start is cool fuel from the tank, not hot fuel that has been sitting in the supply lines while the engine has been shut off. This typically involves adding a couple electric valves so you can T-off the supply line right at the pump and T-into the return line downstream of the injectors, and adding a fuel pump in between the two valves. This is what I've seen at least, and it works. That aux fuel pump should not be located in the hot engine bay obviously.....

Incidentally, the boiling point of gas varies somewhat across the different suppliers, and the presence of ethanol is not helpful either. The gas you have in your tank may have a slightly lower boiling point than gas you've had in the past, or perhaps your local gas dock (or station) is now supplying fuel with a lot of ethanol.

Hope that's helpful.

ps. a really BIG blower can lower engine bay temps enough to lessen the vapor lock issue but it has to be a big one.....the usual stock ones simply don't move enough air to make a meaningful difference.

Edited by CliffB
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i was told that an injected engine should not be fed through a fuel/water separator.

i'll see if i can find where i gained that info but it would only cost a couple of bucks to buy a couple of hose barbs to bypass that filter as a test.

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i was told that an injected engine should not be fed through a fuel/water separator.

i'll see if i can find where i gained that info but it would only cost a couple of bucks to buy a couple of hose barbs to bypass that filter as a test.

Correct, they can introduce air into the fuel system, that's why Indmar does not put them on stock

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Sounds like a prime example of vapor lock to me as well. I think I know the physics of it (fuel turns to vapor in the lines because of excess heat) but I can't say why it's so intermittent. I've had it happen a few times after hard runs as well as moderate runs, I've also not had it happen after surfing for hours in 95 ambient air. I personally think it has alot to do with the quality of gas, but can't really back it up with any facts. I just put a rag on the lines nearest the fuel pump, pour a water bottle on the rag, and drive away 10 minutes later like nothing ever happened.

Edited by Ndawg12
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It does sound like vapor lock. Did you change gas stations recently, or did the one you go to up the ethanol level?

Try some ethanol treatment stuff. Are you in southern hemisphere, or very hot where you are at?

When I prop the engine cover a couple inches while sitting, it seems to have stopped the probem.

Steve B.

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It's funny, I had vapor lock issues on a 94 MC Prostar 205 a number of years ago. I can't tell you how many guys, mechanics, Indmar techs, etc. told me that a Chevy 350 with Throttle Body Injection could not get vapor lock.

In the end, I called the guys at Skidim.com & they suggested a $13 fuel line insulation kit. Keep in mind this is a much different engine & fuel system than we're talking about now, no computer control, much lower fuel pressure, etc. But I installed this insulation kit on the fuel lines that are over the intake manifold & near the engine. And I never had the vapor lock issues again.

So when someone tells me that it's not possible for the blower to make enough difference to cool the motor, yet we have been successful in evading the problem by simply running the blower for almost 2 years now..... including trips to Hells Canyon & Lake Shasta where it was in the 100s for days...... Maybe it's all coincidence..... or maybe it's cheap insurance & worth a try.

You should also try new gas if you think all the problems are related to this particular tank of gas.

Edited by Bill_AirJunky
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I would look just above your oil filter you will find a pressure switch It is screwed into the side of the block. Mine has two wires at the end. You can unscrew it from the block and flush it with a cleaner. Its a pressure switch if it is hanging up it will cut spark to your engine. I found this to be the culprit and it did just what you are describing. The boat I worked on started cold every time but would give us problems well hot or even cut out just after take off well worm. I flushed one with gas as I had no cleaner at the time. It worked fine but its not a good practice to use gas for cleaning just for safety reasons. blow it out and reinstall it put the wires back on and give it a go.

I am betting you will be fine. the switch is not very costly if you wish to replace it but cleaning has worked every time for me.

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It does sound like vapor lock. Did you change gas stations recently, or did the one you go to up the ethanol level?

Try some ethanol treatment stuff. Are you in southern hemisphere, or very hot where you are at?

Wow, thanks to everyone for their responses, its very much appreciated. I am now pretty confident it's to do with the fuel in the tank. I realised that this issue has only been happening on this tank of fuel and one other 12 months back. I also remembered that on both occasions I put in standard unleaded fuel as that was all they had at the station (and it might have been crappy unleaded at that). I normally run premium unleaded (either 95 or 98 octane). The tank is a 1/4 full at the moment so I am wondering should I try and drain this fuel or or what ethanol treatment would you recommend or do I add some premium fuel to the tank. Its sounds to me that this fuel is boiling sooner than the premium one...

Correct, they can introduce air into the fuel system, that's why Indmar does not put them on stock

In regards to the fuel filter, should I change this over do you think to a standard fuel filter without water separator? I will defiantly be empting the bottom tonight.

I would look just above your oil filter you will find a pressure switch It is screwed into the side of the block. Mine has two wires at the end. You can unscrew it from the block and flush it with a cleaner. Its a pressure switch if it is hanging up it will cut spark to your engine. I found this to be the culprit and it did just what you are describing.

This sounds very promising and will take a look at this tonight. Thanks very much.

Thanks again all. I will be sure to update the progress.

Edited by rdog
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A failed engine coolant temperature (ECT) sensor will cause what you are experiencing. When it fails, it tells the ECM that the engine is 32*, when it is really 160.

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A failed engine coolant temperature (ECT) sensor will cause what you are experiencing. When it fails, it tells the ECM that the engine is 32*, when it is really 160.

Thanks. Where abouts would this be located and what does it look like. Are they easy to replace?

Like this one? http://www.bakesonline.com/detail.aspx?ID=1798

Edited by rdog
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Yup, that's the one. It is usually located on the top of the engine in the front, near the thermostat. It is easy to test with a multi meter. You can buy the part at an auto-parts store for half that price.

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Yup, that's the one. It is usually located on the top of the engine in the front, near the thermostat. It is easy to test with a multi meter. You can buy the part at an auto-parts store for half that price.

Thanks very much. Im going to try replacing this & putting some ethanol treatment in the fuel to see how it goes.

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I fought vapor lock for 4 years on my 06 Monsoon. Tried every trick in the book. Blower on, insulate lines, put extra bilge blower blowing directly on pump,new pump,regulator, lines. Seemed better after new fuel pump and regulator install but problems reoccurred within a year. Cold water squirted on locked up pump usually did the trick to get her back up and running. In the end, I added the secondary low pressure Carter fuel pump before the Stock fuel pump and that did the trick for me.

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I use "Lucas" safeguard Ethanol treatment. The bottle says E-10, E-15, E-85. They recommend only a few ounces in a tank. I over do it, but I haven't had the problem since using that, and propping the cover open when partying after skiing,

One thing I've noticed, you can really feel the heat of the engine escape under the engine cover, especially after 15 or 20 minutes, it's like wow, a lot of heat coming out !

If you feel confident, I think I'd change the existing gas. With a known good, low ethanol level fuel.

Good luck, keep us posted.

Steve B.

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