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Vapor Lock - A tale of two cruises

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Hi all,

Our boating habits have changed over the last few years. We tend to wander around Lake Powell more with longer distance runs. As a result, something that I think is vapor lock has started showing up. Hot days, soak time, failure to start again until cool...all the typical symptoms. I think the story blelow and the data could eventually be helpful to others.

Below is a image from a temperature data logger attached to the lifting eye above and behind the thermostat housing. I wanted to see what the general conditions in the engine compartment were. This graph is from last weekend. If you are familiar with Powell, you will recognize some of the locations. Our camp was in Face Canyon. Here is a link to a map of Lake Powell. The time increments along the bottom are 1 hour.

On the first day, we drove quite a bit. We started out early while it was still cool at about 80F. When we were at the Cave, we idled in and let the motor idle for a couple minutes before shutting down. When we went to restart at the Cave, about 45 minutes later, we barely got the motor running, but then no problems. We didn't turn off the motor during the trips to Mtn. Sheep Canyon or at Dangling Rope Marina. Then we returned to Face Canyon. During most of the trip out air temperatuer was 90-98F. When we got back to our camp in Face Canyon, it was 107-109F. We let the engine idle for a few minutes before shutting down.

About 2 and a half hours later, we tried to restart and had little luck. We opened the hatch and the termpatures drop. We waited about an hour without luck. We closed up for the night.

Of course, the next morning the motor started right up. You can see we made a few shorter trips with a few periods of idling. Also, we did some wakeboarding with engine shutdown to put boarders in and take them out. When we made it back to the docks, we tried about 15 minutes, 30 minuntes and one hour later to start the motor. Each time with luck. I don't think the local air temperature was ever about 100F, and probably low 90s much of the time.

I've been running the blower all the time when under way. I have tried draping wert towels over the engine to reduce temperatures. Hard to know how much it has actually worked. The fuel pump does run when the key is turned to one. The throttle body injectors spit some fuel as it turns over.

A few questions.

- Is this vapor lock?

- I have the cool fuel system, but how would I check to see if I have the often discussed check valve?

- I run the blower full time, should I consider adding another blower?

- Should I just leave the blower on all day long after using the boat?

What else?

Thanks in advance

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Interesting problem. In my experience its pretty rare on a fuel injected boat to experience vapor lock. That said - throttle body injection can be a tricky animal. I would definitely agree whatever you're dealing with seems to be "hot soak" related. A couple things - you mentioned when cranking the injectors are spitting fuel. That in itself indicates you're getting fuel into the throttle body. Might be worth doing a visual on those on occasions when the engine does crank, just to see if you can tell a significant difference.

You seem to have fuel - when in "no start mode" - do you have spark? That would be my next test. If not, I'd suspect an ignition module potentially getting hot, or even condensation getting into the distributor cap (if you have one) causing issues.

Just some food for thought. If spark is good, there should be a fuel pressure tap somewhere on the throttle body or fuel line to it - if you can check the fuel pressure, might be a good test. And - just again, checking the basics - when was the last time the fuel filter was changed? If its developing resistance due to plugging, could add to the situation.

Good luck!

Ben

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Sounds like a typical IAC failure to me. Could also be voltage related. We had a very similar (and somewhat scary) situation with our 220 a couple years back. The IAC was the first diagnoses, then the voltage.

As described to me, the Fuel injection system requires a minimum voltage to start the engine (cranking) AS WELL as enough reserve power to keep the computer on. If the wiring is heat soaked and the resistance across the wire increases, the voltage could drop and the boat may not start until it cools down. No computer, no spark. No spark, no motorboat.

One new cable and we never experienced the issue again.

Vapor lock was my very first thought as well.

Good luck!

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I hope it's not the ignition module. I had it replaced last summer. The old one failed, but failed when it was hot and the motor was running at speed. Completely different feel. It's been so dry, I don't know where the water would have come from. Even the bilge is bone dry. Also, the towels were draped over the ignition module. I think they would have solved that problem. Still good thoughts.

I am planning to look at the throttle body when it works correctly. Kinda like a kid with a sore throat, if you don't look when it's normal do you really know what to look for when it hurts?

Thanks

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Sounds like a typical IAC failure to me. Could also be voltage related. We had a very similar (and somewhat scary) situation with our 220 a couple years back. The IAC was the first diagnoses, then the voltage.

As described to me, the Fuel injection system requires a minimum voltage to start the engine (cranking) AS WELL as enough reserve power to keep the computer on. If the wiring is heat soaked and the resistance across the wire increases, the voltage could drop and the boat may not start until it cools down. No computer, no spark. No spark, no motorboat.

One new cable and we never experienced the issue again.

Vapor lock was my very first thought as well.

Good luck!

Hmmm...the IAC valve is intriguing. I could pull off that repair my self. But, the symptoms don't seem to be just right. We tried to start it with additional throttle and it did not start.

Another bit of information I should have included, the fuel coming out of the injectors was more of a dribble(with droplet) or a brief straight stream. It looked nothing like this video of the injectors on the similar model engine:

Mine looked more like this:

they look pretty different. The second has anemic, weak flow.

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Fought this with the same engine. The check valve is pretty easy to spot, down by the fuel pump. Before going that route:

Dump your fuel/water filters.

Take a sample of what's in your tank and let it sit.

Water? Here's your problem - bad gas.

No water? Find someone that sells ethanol-free fuel, and you don't need to drape the engine, just put a hand towel in the bottom of the cooler. When you're stopping long enough for heat soak (1 hour minimum) drape that ice water towel over the fuel pump.

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I'd say without a scan tool there's really not a lot that your engine could (or could not) be telling you. The fuel is delivered via fuel injectors with pump pressure and pulse width timing. If your computer has another sensor that is inputting erroneous data (air flow, fuel pressure, egt, and whatever else you can add a sensor to) than the fuel flow could be diminished to a point where the engine simply can not start.

I seem to remember a thread about a loose connector at the back of the engine that could also cause a no-start condition. In fact, it may have been about one of my no-starting afternoons. I'll try to find it...

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I'm heading to the Powell this weekend to try and replicate the conditions. I'll be bringing a voltmeter to check the IAC valve. Digital thermometers to monitor for backflow to the fuel cooler. I'll also take plenty of ice and beer to cool things down.

One more question, is it possible to install the check valve in the boat is in the water or is there a real risk of inflow from the lake?

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When it will not start try advancing the throttle to full open. This will shut off the fuel flow and allow more air into the engine.

I've had issue with mine not starting when warm and this works every time.

6.2L MPI.

Not sure what engine you have as I have not seen it mentioned.

I store in Big Water and boat on Powell as well.

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Good to know. If I can reproduce a failure, I will give that a try. Sounds like that could be related to the IAC valve. Be on the look out for a boat flying up, then down the lake to create a nice heat soak at Wahweap later.

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So, I think I am a believer in the vapor lock syndrome. I monitored the temperature inside the cool fuel box, just inside the box, not actually on the cooler. We ran the boat from Wahweap up to the end of Last Chance Canyon, and back. It's roughly 30 miles each way. When we got to the our slip, we shutdown right away. For the about the first hour, the temperature rose from 96.7F to about 124F. When it leveled out at 124F, we tried to start it. It didn't start. We took a video of the injectors. Sure enough, they were barely spitting into the throttle body.

We tried opening the throttle farther which didn't help. We started keeping cool rags on the cooler, which seems ineffective at best. We also tried cooling the IAC valve, which made no difference. After an hour of trying we went to Latitude 37 for ice tea for me and gin and tonic for my son. An hour later, the cooling paid off and the motor started.

We went back out and heated the engine back up to full temp. We went back into the marina but let the boat idle in the slip for about 5 minutes until the engine temperature was about 130F. About another 15 minutes later, the fuel cooler temp started to climb and when it read 115F, i restarted the engine and let it run for another 5 minutes. We left for about an hour and came back it the motor started right up. It was still above 100F air temperature in the marine.

One more question, is it possible to install the check valve kit while the boat is in the slip?

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Just to close this out...I put in the check valve in the cooling tube coming up from the fuel cooler to the thermostat housing. It's bigger than I thought. (That what she said)

Saturday was a hot day at the lake. Easily over 100 F. Did the Wahweap to Rainbow Bridge run. While the rest of the group went up to the bridge, I watched the fuel cooler and top of the thermostat temps. The creeped up a degree or two, or three while I waited. But, the fuel cooler box air temp never went above 100F. I noticed this was the trend for every engine shutdown.

The other thing is that the thermostat housing temp was pretty constant. Without the check valve in place, I think the upper cooling parts of the engine lose their water and heat up. I think the valve could keep the engine cooler in general and prevent thermal shock at restart.

But, what do I know....

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Hey. Sometimes they do make a fix that works;). Sounds like you have solved the problems you were experiencing.

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