95 Malibu echelon fuel problem please help

[Iamthebigdog]

I have a 95 Malibu echelon 350 EFI throttle body. It runs fabulous until I turn it off and sit on the lake for an hour or so. It then starts up fine but dies after running for a couple hundred yards. Then it does not start due to a lack of fuel. The water/fuel separator is only half full of gas, but the vapor reservoir containing the electric fuel pump is empty. If I pour gas into the vapor reservoir, it again starts up and runs fine. Here is a list of what I have done: (sorry but I don't know the exact mechanical names for everything)

1 replaced the mechanical fuel pump

2 replaced gas line

3 pulled tank and cleaned out ( it was not dirty) as well as the uplift tube in the tank ( it was also fine)

4 tested the air valve at the tank

5 tore apart and cleaned the vapor reservoir including the float, chamber, jet, screen on electrical pump, new seals

6 changed water/ fuel separator

I am at a loss on what else to try even after reading many of the prior posts. This problem seems to be very intermittent making it that much harder to diagnose. I keep looking to the mechanical fuel pump due to the water/fuel separator being almost out of gas ( I don't know if it should be completely full) . I don't think it is the electrical pump as the reservoir is out of gas. So it seems that the reason that it starts and runs for a couple hundred yards is that it is using up the fuel in the vapor chamber and once that gas is depleted, it stops running. Why is the vapor chamber running out of gas? Could I have gotten a bad mechanical fuel pump? I always thought a mechanical fuel pump either worked or did not work...no in between. Should I bypass or add an in line electric pump? Can someone PLEASE help me to make my boat the reliable workhorse that it has been for years???

Edited June 24, 2013 by Iamthebigdog

[Sethro]

You are experiencing classic vapor lock symptoms. I have resorted to blocking my engine cover up when sitting for extended periods, as well as running the blower for a while. Skidim.com has a kit to solve the issue, but others have outsourced the parts to make there own kit for about 1/3 the price. I haven't done it yet, as I typically ski at a private lake with little down time. But, it's on my list to do some day.

Skidim kit

[Sethro]

Sorry, just read your post again and see you already have a mechanical pump prior to the high pressure electric pump? If not, where is it located? As far as mechanical pumps either working or not, my buddy just finally found the problem on his carbed indmar and it was the mechanical pump. His symptom was starving (boat would die) at high rpm, other than that it ran great.

Edited June 24, 2013 by Sethro

[Iamthebigdog]

My Malibu gas flow is as follows: fuel tank - up lift tube - gas line - water/fuel separator - mechanical fuel pump on the engine block - line to vapor chamber- out of vapor chamber via the electric pump to the injectors. As I mentioned, I already changed the mechanical pump, obviously for no reason as I have the same problem...unless I got a bad fuel pump. Again, I thought a mechanical fuel pump either worked or didn't. I obviously still have gas in the vapor chamber as it usually starts and runs for a short spell. However, yesterday it would not even start at all after sitting. After adding fuel to the vapor chamber, I was on my way. I have cleaned or replaced everything from the fuel tank to the water fuel separator. I am at a loss and really don't know what to try next. Are you still going with a vapor lock? I have had the boat for 13 years and only stared having any problems last summer

[Steve B.]

Vapor lock. I also have the mechanical after the electric. Extremely common issue. Little hotter than usual in your neck of the woods ?

When you sit, prop the engine cover to release heat. Run the blower for about 10 minutes before you start engine. Add ethanol treatment to your gas. Are you getting gas at a new place ?

Steve B.

Quick edit...what temp thermostat? If 180, change to 160.

Edited June 25, 2013 by Steve B.

[Iamthebigdog]

Temp is in the 90's but this is where I have lived with the boat since ownership. I buy gas all different places. One correction, my mechanical pump is before the electric. I will check the thermostat but still do not understand why this is happening now after all these years. Does anyone think an inline electrical fuel pump in place of the mechanical fuel pump to be a solution?

[Steve B.]

At the very least, try the above. And, as you come to a rest, let the engine idle for a minute or so before shutdown. Then prop that cover up a few inches.

Also for verification, do a search on vapor lock.

Edited June 25, 2013 by Steve B.

[MountainRob]

Definitely sounds like vapor lock. I wrapped all of my upper fuel lines and the fuel pump in heat shield tape, and it solved the issue for me. You can buy it on Amazon.

[Iamthebigdog]

If I wrap the lines, change thermostat if needed and the problem still persists, is the next best solution to put in an in line electric fuel pump? If so, would you want the pump on a separate switch or wire it in so it always runs when the ignition is on? Where would be the best place to run the wires to? Thanks to everyone for their input! I don't want to be a pain in the ars, but I want to fix the problem...not prop the motor cover open, etc. I want it fixed-thanks

[malibuparadise]

If I wrap the lines, change thermostat if needed and the problem still persists, is the next best solution to put in an in line electric fuel pump? If so, would you want the pump on a separate switch or wire it in so it always runs when the ignition is on? Where would be the best place to run the wires to? Thanks to everyone for their input! I don't want to be a pain in the ars, but I want to fix the problem...not prop the motor cover open, etc. I want it fixed-thanks

FWIW, if you have an electric fuel pump, my 98 carbed mc does and it has a low oil-pressure switch wired into the ignition circuit, i.e., if the engine stops, oil pressure drops and at 5psi the fuel pump "safety" circuit opens and the pump is deenergized; a good thing with a box-covered engine. Not sure this is applicable here. My 93 skier has a mechanical fuel pump (no need for such a switch) which I thought was bullet proof too, SO I'm so very interested in this thread to cut off any vapor lock ? problems at the pass that I might have here in Hawaii with pretty warm temps all year long (ahh....sorry folks.....)

I'm just finishing off a major bu drydocking and now is the time to mod if necessary. I have a photo collection of the interesting journey so that will come when I can write up the finer points of the project (to me anyway).

Hardly any ski inboards here and we "course" ski (+ etc.) all year long under rainbows. Sad (not) but true. RETIRE in paradise and join us. ;-)

[SFD]

I disagree on the vapor lock.

I have the same engine and went thru similar symptoms -

Just checking through things so you are not spending cash -

Did you install the correct type of fuel line hose? Is it collapsing?

Is the screen and fuel line IN the gas tank clear?

Is the vent line clear at the gas tank?

Is the screen and line clear from the water separator to the VST tank clear?

Is the vent line clear on the mechanical fuel pump?

Is the vent line clear on the VST tank ( vapor separator tank ) ?

Is the pump working in the vapor separator tank?

[Iamthebigdog]

yes to all of the above except the fuel line collapsing. I have gone through all lines, screens, the pump is working, and replaced fuel lines with proper lines. what problem did you find SFD?

Edited June 26, 2013 by Iamthebigdog

[Woodski]

Based on your posts it sounds like the electric pump is losing it's prime. Is the vent line for the mechanical pump clear, is the cam for the mechnical pump working or actuatling the pump itself as the engine turns over? Any leaks at the vapor cannister.

[malibuparadise]

I disagree on the vapor lock.

I have the same engine and went thru similar symptoms -

Just checking through things so you are not spending cash -

Did you install the correct type of fuel line hose? Is it collapsing?

Is the screen and fuel line IN the gas tank clear?

Is the vent line clear at the gas tank?

Is the screen and line clear from the water separator to the VST tank clear?

Is the vent line clear on the mechanical fuel pump?

Is the vent line clear on the VST tank ( vapor separator tank ) ?

Is the pump working in the vapor separator tank?

Vapor separator tank (VST)? 93 350 mercruiser skier, don't have right?

[Iamthebigdog]

yes I do have a VST (Vapor Separartor Tank) with a float inside next to the electric fuel pump (all inside the VST). (95 merccruiser EFI throttle body fuel injection) The electric fuel pump is losing its prime because the VST is out of gas! Why is the VST running out of gas? This is the enire problem. All vent lines look fine...blow thru them all with no problem. Seems that this forum is having quite a debate on whether it is a vapor lock issue or not. I am from the old school that if something worked for 12 years and does not work now under the same conditions, something is broke and needs fixin'. Sure wish I new the answer. If there are any more ideas out there, please let me know-BIGDOG

[Sethro]

Fuel pressure regulator? I'm not very familiar with the Mercury.

[Iamthebigdog]

Suppose to be in the low hundreds this weekend. Wrapped all upper fuel lines, made sure vacuum lines were clear and thermostat is stock at 160. Well see what happens. Still waiting for other ideas if this doesn't work...not a lot of feedback on adding an in line electrical fuel pump. Thoughts????

[JasonK]

Could it be the added ethanol at the pumps causing vapor lock? Have you tried running premium or maybe the sta-bil ethanol additive?

Prop the engine cover and keep the blower running to see if the problem goes away. If it goes away, then it's probably the newer fuels causing vapor lock.

Maybe try re-tightening your hose clamps on any fuels lines. Or bypass a filter. I think I had a bad water-separating fuel filter before.

[Woodski]

Looking over your post again, have you checked the anti siphon check valve on top of the tank? Sometimes they corrode and stick. Again, my comment on the mechanical supply pump having an issue based on your statement that the electric one is downstream from that. I think if it were only vapor lock it would not go the couple hundred yards before quitting as that fuel would have been boiled due to heat soak.

[MikeD13]

Was there ever any resolution to this?

[inis25]

Had a similar issue in a 95 malibu 10 years ago or so. Tried multiple additives but the problem still occured. switched over to only using ethanol free gas and have not had any issues since. 

[PURDUEskier]

If you have a vapor separating tank (VST) like the OP then check the 1994 Malibu Echelon thread from March 30th about the diaphragm installation.   I am not familiar with the 350 but the 454s with the VST had the exact same issues and that solved it.