PDA

View Full Version : Vapor lock or fuel pump issue??


HansenStar2002
08-11-2013, 04:11 PM
Cruising yesterday at 35 mph when engine shuts down for a second then picks back up and no other issues for the rest of the day. Get home, hook up fake-a-lake and motor won't turn over. Fuel lines were warm (travel home time was about 1 hr on the trailer). Could not get it started, batts showed 11-12 amp (2 shy of full when running but usually is what shows every time it does start). Let it sit all night in 60 degree garage. Still wouldn't fire up in the am. Hooked truck to boat batts, no change, no start just cranking strong for as long as I'd hold the key over. Let jumper system connected, pushed what looks like a pressure relief valve on one of the fuel lines to the carb (valve looks like a bike tire stem valve). Looked at fuel lines coming from FP all secure. Then I pulled the distributed cable from center of cap, re-connected it, then fired the boat right up. So, was it the pressure relief valve that finally allowed fuel to the carburaters or was it charging the batts long enough? Oh, symptoms were just like when the kill switch is disengaged.

Any help or insight would be helpful.

h20_skidog
08-11-2013, 04:41 PM
My 01 ProStar boat had similar issues this past summer. When I pushed down on that pressure relief valve going to the carburetor the fuel slowly came out. I was told that this valve should have fuel coming out of it at 35-40 psi and mine did not. I replaced the fuel pump and its been running great since.

thatsmrmastercraft
08-11-2013, 05:01 PM
Cruising yesterday at 35 mph when engine shuts down for a second then picks back up and no other issues for the rest of the day. Get home, hook up fake-a-lake and motor won't turn over. Fuel lines were warm (travel home time was about 1 hr on the trailer). Could not get it started, batts showed 11-12 amp (2 shy of full when running but usually is what shows every time it does start). Let it sit all night in 60 degree garage. Still wouldn't fire up in the am. Hooked truck to boat batts, no change, no start just cranking strong for as long as I'd hold the key over. Let jumper system connected, pushed what looks like a pressure relief valve on one of the fuel lines to the carb (valve looks like a bike tire stem valve). Looked at fuel lines coming from FP all secure. Then I pulled the distributed cable from center of cap, re-connected it, then fired the boat right up. So, was it the pressure relief valve that finally allowed fuel to the carburaters or was it charging the batts long enough? Oh, symptoms were just like when the kill switch is disengaged.

Any help or insight would be helpful.

I would take this as a clue that the coil wire was loose or corroded.

HansenStar2002
08-11-2013, 05:09 PM
Thanks for info... Oddly enough, I removed the coil wire to reproduce the problem for my wife to show her what to do after a launch with me in the boat. The boat still turned over... Isn't it impossible to start a motor without the distributor wire attached? I am not sure that the wire is bad... Other thoughts?

thatsmrmastercraft
08-11-2013, 05:11 PM
Thanks for info... Oddly enough, I removed the coil wire to reproduce the problem for my wife to show her what to do after a launch with me in the boat. The boat still turned over... Isn't it impossible to start a motor without the distributor wire attached? I am not sure that the wire is bad... Other thoughts?

Did your engine start with the coil wire disconnected? Need spark to start.

bigmac
08-11-2013, 07:01 PM
Vapor lock in a fuel injected engine with a functional electric fuel pump is extremely rare. Some techs would say that it's impossible.

HansenStar2002
08-11-2013, 08:39 PM
BigMac, true of a fuel injected system... However, my 2002 is carbureted. Thanks for posting.

Mrmastercraft - I know... Real hard to make an engine start without the distributor cap getting its jolt from the battery. I truly have no idea how it started with the lead wire off.

thatsmrmastercraft
08-11-2013, 08:50 PM
BigMac, true of a fuel injected system... However, my 2002 is carbureted. Thanks for posting.

Mrmastercraft - I know... Real hard to make an engine start without the distributor cap getting its jolt from the battery. I truly have no idea how it started with the lead wire off.

How far was the coil wire pulled out? That spark can jump a ways.

André
08-11-2013, 09:34 PM
... Real hard to make an engine start without the distributor cap getting its jolt from the battery. I truly have no idea how it started with the lead wire off.

Wow!Just wow!:huh:

JimN
08-11-2013, 09:37 PM
BigMac, true of a fuel injected system... However, my 2002 is carbureted. Thanks for posting.

Mrmastercraft - I know... Real hard to make an engine start without the distributor cap getting its jolt from the battery. I truly have no idea how it started with the lead wire off.

There's no such thing as a carbureted Mastercraft from later than 1993. You have throttle body injection. Also, the Shrader valve isn't a pressure relief valve, it's for measuring fuel pressure.

Your fuel pump is in the tank, so it can push the fuel toward the engine and that's why you can't have vapor lock. Your fuel lines were warm because the ambient temperature where they are was higher than the air temperature. If the coil wire was out by about 1/2", it wouldn't start and I would suspect that it wiggled out while it was running. BTW- you don't want to grab the plug or coil wires when someone is cranking the engine- getting a handful of 50,000 Volts is no picnic.