94 Malibu Echelon LX TBI Dripping Fuel

[MikeD13]

I've got a 94 Malibu Echelon LX with the 350 Magnum EFI Tournament SKI.  I've been having this issue for about 2-3 years and its now to the point, where i can count on it to not start in a heat soak condition.  It will crank up and run great on a cold start.  I can run the boat for hours and it never stalls, sputters, or acts up in anyway.  I'll turn the boat off, let it sit for 5 minutes and she'll crank right back up no problem.  However, if i get to operating temp, then let it heat soak with the dog house down for 30 minutes, it will not start.  I'm in DFW and this past saturday the temp did not get above 85 degrees F outside.  The temperature gauge never registered above 145 and I ran it hard. I used a laser temp gauge and when pointed at the thermostat housing, the temp never exceeded 145, so i believe my temp gauge is accurate.

I intentionally replicated the issue 3 times Saturday and each time i noticed that immediately at the 30 minute mark, the gas would drip out of the TBI rather than spray.  NOrmally, i can remove the coil wire and crank it over several times and then it will start.  I did have to pour water on the VST and fuel lines at one point in order to get it started.  Again, once its running, i can shut it off, then immediately start it back up with no issue.

This engine has a mechanical fuel pump which then routes to the Water Separator, which then routes to the VST(Vapor Separator Tank).  THis VST contains an electric fuel pump.  There is a supply line from the VST to the TBI then the TBI back to the VST - so no fuel line back to the gas tank.

I've completed the following in the last 3 months:

1. Swapped distributor  cap, rotor, plug wires, ignition coil

2.  REplaced the Thermostat with a 160 degree quicksilver.  Replaced the tranny cooler and impeller (cleaned impeller pieces from old tranny cooler hose.

3.  wrapped the VST and gas lines with thermo tape.

I've ordered a fuel presser gauge to check the fuel pressure at the supply line before the TBI under the heat soak scenario - if this issue is indeed vapor lock, what should i expect the fuel pressure to read?  I've also ordered the thermostat temp gauge - both the 1 wire for temp gauge and the 2 wire for the computer.  I read that if the 2 wire is not reading correcting resistance, it could relay false info to the computer.  

The only things i can think that could possible be the issue are:

1. vapor lock - not sure why it is so much worse over last 3 years

2. TBI needs rebuilding - i run seafoam consistently in the gas.

3  VST electric fuel pump is weak. 

I'm curious if anyone has experienced anything similiar.  If it is the VST fuel pump causing the issues, i'm considering bypassing the mechanical fuel pump and VST and installing and in-tank pump with a return line back to the pump.  I"m not sure which fuel line and fittings to use at this point tho.  I've not been able to verify if braided AN fuel line is marine grade.

I've thoroughly enjoyed posts related to this topic and appreciate everyone's help.  

Mike D

[tex599]

It sounds like your flooding the engine from the fuel dripping down the throttle body.   Not sure if this is an indmar motor or not, but I had 95 Mastercraft with the indmar (might have been a PCM) and the fuel pressure regulator went out and caused this issue.  You can also check the injectors, they could be bad as well.   My other thought would be the ignition coil, when they start to fail, heat just makes them worse.  Most of the time a mechanical fuel pump either works or doesn’t. You can have a weak diaphragm, but your pressure gauge will tell you a lot. 

[Woodski]

@MikeD13:  Use the search function on this site to read up on other similar threads that include some solutions.  Also, a reason for deteriorating hot start performance would certainly be wear and tear on the fuel pump and perhaps your fuel that may have more ethanol content compared to previous.   Your most recent issue may be fuel related, have your local stations gone to the summer blend yet, if not a harder start would be the result.

[96Response]

If you are having fuel drip into the engine after it is turned off then that would cause a flooding situation same as a carbed version with a stuck float. I.m not a 100%  on how the exact pressure and timing of the injector , but i would suspect if fuel is dripping out, then the injector nozzle is not closing. No fuel should drip ever. it should only be a spray. I can tell you that if the engine backfired one time it usually takes out the injector. they are mostly plastic and cannot handle the flash of heat. I have all the components in a box that i removed when i went to a Carb. If you need anything let me know. You can have whatever you might want or need. I will never go back to TBI ever. To unreliable.  I have a 96 Response and had so many issues with the TBI that i went back to old school carb. it is very easy to do and cost under a $1000.00 to do it correctly. It is reliable and makes more power than the TBI ever did, Starts and runs better as well.