5.7l EFI with cool fuel and fuel in the sight tube?

[thumpar]

Today we were out and just siting about 12 miles out from the launch. When we went to move the motor didn't want to start so I checked it out. There was fuel in the sight tube. I disconnected it from the flame arrestor to get it started and we high tailed it back to the launch. The sight tube goes to both the mechanical pump and the cool fuel electric pump. Is it possible for the cool fuel system to dump fuel in the sight tube or is the definitely the mechanical pump?

 

[Fun Times]

Ah thumper, sorry to hear of your running troubles today. Yes it's possible the VST (Vapor separator tank) could also spill fuel into the flame arrestor from a bad fuel pump diaphragm or stuck float, needle and seat. #'s 3 thru 6. Or it's the mechanical pump diaphragm.

http://www.mercruiserparts.com/Show...inbr=1953&bnbr=130&bdesc=VAPOR+SEPARATOR+TANK

Your parts catalog if needed.
http://www.mercruiserparts.com/selec..._nbr=809500+95

PS, you can buy just the top cover O-Ring (^^^ not listed ^^^) vs buying the whole O-Ring kit. Look up Merc part number 25-803831. It's good for general clean up and inspection. While you're in there, Carefully clean the filter, you'll be glad you did. http://forums.iboats.com/forum/engin...ce-over-repair

Let us know, good luck.

 

[thumpar]

Thanks for the reply and links. I am going to try to see which sight tube the fuel is coming from later today when it cools off a little. I picked up an impact screwdriver. Thanks for that link I probably would have stripped the screws out.

 

[thumpar]

I started it on the trailer just now and it ran like normal with no fuel in the sight tube so I am leaning toward the VST being the problem. We are loosing light so my plan is to break the VST open in the morning and see if I can find a problem. The only thing I have to add is that when we had the problem it was around 95F out and the temp was just a tick past 175F on the gauge. It cooled down but it surged a couple hundred RPM every once in a while on the way back.

 

[Fun Times]

Hum, The VST's are notorious for running hot and causing vapor lock on hot days. You still wan to CARFULLY clean the filter and inspect everything the best you can. You should be amazed at what the filter looks like vs what it should look like. A dirty filter could play a part in the vapor lock symptoms of the VST. Good luck.

 

[thumpar]

Is there an alternative to the VST system? I am going to go take it apart here in a few minutes.

 

[alldodge]

I have the VST and agree with fun times about the vapor lock issues. So far with non-E10 fuel no more vapor locks. The tank can be disassembled and cleaned but I did not take the filter screen off. Stated you can take it off if your real easy but if it breaks you have to replace the hole tank, so I didn't. Stills working just fine.

To replace the VST you can install the cool fuel system which can be the 1st gen with the high pressure pump installed below the port motor mount and keep the mechanical fuel pump. Or replace both the mechanical and VST with the latest gen of the cool fuel assembly which contains both low and high pressure pumps. That being said you need to re-plum the lines.

Edit: also may need to add an additional relay and fuse for the dual fuel pump setup

 

[thumpar]

I took it apart. The screen was not bad at all but cleaned it. When I took the diaphragm apart is was so bad that my finger turned black when I touched it and can't wash it all off. I think I found one of the issues.

 

[thumpar]

Not the best picture but you can tell it is see through. The only thing holding it together is the mesh inside.

 

[Fun Times]

Yes I see the holes, thanks for the photo. That would do it.

 

[thumpar]

Luckily I found one not to far from me. It is about an hour and 15 minutes away but it will keep the wife happy. Going to pick up the kit now.

 

[thumpar]

It's alive. After a 2 1/2 hour trip to pick up the parts and then a trip to pick up the locktite she is back up and running. Thanks for the advice Fun Times. We will be on the water tomorrow.