SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: 77Galaxie on July 06, 2015, 09:48:13 AM
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Took the boat out this past weekend to Havasu. Took a ride up to pirates from the landing and boat ran great all the way up there (was running at about 3200 RPM with an occasional pedal mashing). On the way back to the lake I switched tanks. Id like to add that I've checked all pickups and valves for suction on my tanks. The boat will start to bog down and I can pedal through it for a little bit but eventually it dies out on me completely. I can get it started after it stalls but it does the same thing. I've had this issue since I rebuilt the boat and have tried everything that makes sense to me. Anyone have any input?
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fuel pump or fuel filters been checked ???
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Fuel filters checked. Just put a new on this season. Although I put a new carter fuel pump on when I rebuilt the boat. My next thought was to buy a new stronger fuel pump. I've got a carter 5.5-6.5 psi/ 30 GPH fuel pump.
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Took the boat out this past weekend to Havasu. Took a ride up to pirates from the landing and boat ran great all the way up there (was running at about 3200 RPM with an occasional pedal mashing). On the way back to the lake I switched tanks. Id like to add that I've checked all pickups and valves for suction on my tanks. The boat will start to bog down and I can pedal through it for a little bit but eventually it dies out on me completely. I can get it started after it stalls but it does the same thing. I've had this issue since I rebuilt the boat and have tried everything that makes sense to me. Anyone have any input?
I'm feeling one of three problems. Bad fuel hose (inner line collapsed), inadequate tank venting (pulling a negative on the tank) or garbage in the pick up (may have a small screen on the puck up tube that's full of shit).
Good hunting.
GT
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I thought about the tanks not venting correctly but immediately after the boat stalled I put my ear close to the gas cap and listened for a gasp from the fuel tank. Also, I installed new fuel lines on the boat and I've had this problem since I've done that
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You could have a flapper. The inner liner tears as the hose is assembled onto the fitting. It then acts like a check valve when the flow is high enough. Then when the flow drops, the flapper returns and so does the flow.
To try and pinpoint this to a fuel delivery issue, did you look to see if there is fuel in the carb immediately after it stalls? Do you need to crank the starter a lot to get it to restart like the pump needs to reprime the carb?
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I did check the peep sights on the carb on the primary and the secondary bowls. The primary didn't have any fuel in it and the secondary one did (it stalls at high RPM). Also, the fuel filter is full when it stalled.
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Is the fuel filter on the suction side of the pump or the pressure side? I see a lot of issues with filters creating too much restriction on the inlet side of the pump, actually starving the pump for flow. However, you indicated that the problem didn't happen until you switched tanks AND only after replumbing the boat.
Check the hose connections between said tank and the switching valve.
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The fuel filter is on the pressure side right before the carb. I have 2 saddle tanks tied in at a valve. I have re plumbed all lines, checked each pickup for suction (to check for holes or cracks), checked the tank selector valve for suction, I have the new "oldstyle" fuel flip caps (I believe they vent themselves). The crazy thing is it is usually the passenger side by chance that has the problems and then I flip to the driver side and it works fine, but this weekend the driver side was giving me problems. Before this trip I did take off the venting system off the passenger side cap and switched it to the drivers side. I just cant see that that would be my problem. Seems like it is starving for fuel but it will crank up right after it stalls. I've been scratching my head over this for quite some time. And also there could have been a problem before that was never solved, but I got this boat off my grandpa and he doesn't remember much about it anymore. only the horror stories I don't want to hear about it! :(
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If it is a venting issue, it recovers before you can investigate or try to restart the engine. That means there is just enough restriction to stall fuel flow.
A little joke from my pump systems class; pumps don't suck, they blow! That means all pumps work better on the pressure side than on the suction side.
Fuel is pushed into your fuel pump by atmospheric pressure inside your vented fuel tank and a reduction in pressure created by the fuel pump. In order for flow to occur, this differential in pressure must exist. If no air can enter the fuel tank, as the fuel level drops, the volume above the fuel level increases, and the pressure inside the tank drops. Once the pressure (or lack of pressure) in the tank drops, the vacuum in the tank equals the vacuum on the suction side of the pump, flow stops.
There is probably just enough restriction on the vent to where once the engine stalls, atmospheric pressure returns. Fuel is being consumed faster than air can flow into the tank.
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So you think my best bet is to tap some vents in the filler cap somehow? Also would it behoove of me to get a better fuel pump seeing that I probably have the minimum in my boat now?
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So you think my best bet is to tap some vents in the filler cap somehow?
If I am understanding you properly, It sounds like your problem follows the switching of the vents AND while operating on the good vent, there is no ussue. The problem will most likely manifest itself only when using high volumes of fuel for extended periods of time. If that is in fact true, repair the vented cap as they were intended to function.
Kinsler has the following to say regarding fuel tank vent size:
The tank MUST have a vent. Large amounts of fuel volume are being removed from the tank. This volume must be replaced or a vacuum may be formed inside the tank, causing the fuel to be ‘locked’ inside. Scenario – a straw in a drinking glass: put a finger on the end of the straw and lift it out of the liquid; the straw retains the liquid until the finger is removed and allows air in.
NOTICE: Fuel tank and cell manufacturers may NOT offer a tank that is properly configured for your application.
Too large of a vent will not hurt anything, too small may cause the pump to cavitate, resulting in an inconsistent fuel supply or damaged engine parts. Remember when altering a vent by adding length (hose), installing a roll-over valve, or a filter, the vent may require a larger inside diameter (see ORIFICE THEORY on Pages #202-203).
MINIMUM ALLOWABLE TANK VENT SIZES:
For pump sizes of -00 upto -1 3/8” (.375) inside diameter or bigger.
For pump sizes of -2 upto -4 1/2” (.500) inside diameter or bigger.
For pump sizes of -5 and bigger 3/4” (.750) inside diameter or bigger.
NOTE: When running multiple pump systems multiply the area of the above vent sizes by the quantity of fuel pumps.
Also would it behoove of me to get a better fuel pump seeing that I probably have the minimum in my boat now?
I would suggest, once you get your vent issue sorted out, install a fuel pressure gauge near your carburetor. Have someone observe the gauge while you launch hard and keep your foot in it for a minimum of 15 seconds. If your current pump can maintain 5-7PSI (with a Holley) and your Air Fuel Ratio (AFR) is within reason, I would say you do not need to upgrade. If the pressure falls off (like it does right now), I would suggest that you find the cause of that before blindly replacing parts.
Good luck,
Joe
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Okay great! Thank you for your help. Now a quick "what if" question. Lets say it is venting perfectly and the fuel pump is not the problem. Can there be an issue with ignition of some sort? I've got an Ignition Electronic Conversion kit with a pertronix coil and a stock distributer. Is there any sort of issue I can be having there?
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Okay great! Thank you for your help. Now a quick "what if" question. Lets say it is venting perfectly and the fuel pump is not the problem. Can there be an issue with ignition of some sort?
I think you can safely eliminate the ignition as the source of this problem.
My $ is on a fuel delivery issue because you said the primary float bowl was empty. Everything you said points towards that.
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I was told that the primary (front) bowl will be empty when at high RPM and since it dies at high RPM it would be empty in that case and it will be running on the rear bowl.
is this correct?
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I was told that the primary (front) bowl will be empty when at high RPM and since it dies at high RPM it would be empty in that case and it will be running on the rear bowl.
is this correct?
Not correct
Pressure is the result of resistance to flow. As fuel fills the float bowls, buoyancy pushes the float up which closes the needle and seat valve. When the needle and seat valve is closed, all fuel flow is restricted. This causes the pressure in the fuel line to come up.
As the engine consumes fuel, the fuel level in the float bowls drop along with the float and the needle valve opens, allowing fuel flow into the float bowls and the process repeats.
The float bowls should remain full at all times, without the fuel pressure overpowering the float and the needle and seat valve.
If fuel flow into the float bowls is insufficient to keep the fuel level above the jets and other metering orifices in the metering blocks/plates, the engine will lean out. If it happens while you got your foot in it, you could melt down the engine.
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Okay great! I'll get the venting issue worked out first and report back with issues if any! Thanks a lot for the help!
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Do i dare say run it with the gas cap loose? If it still does it its not a vent issue
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Do i dare say run it with the gas cap loose? If it still does it its not a vent issue
Forgot to mention that
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Sometimes we iver look the easy stuff Flusher
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Sometimes we iver look the easy stuff Flusher
Especially while writing novels on a cell phone when I should be working on my boat.
Think that thought got lost around the time he said the issue switched sides when he swapped fuel fills.
Cheers,
Joe
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Ya I thought about running it with the cap open but out there on the lake a full throttle I didn't want to take any chances on water getting in the tank or fuel going everywhere in the boat or on people!
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Or just run a line into a small 1 gallon tank to check. I changed my fuel sep to 3/8 npt, ran 1/2 fuel line, enlarged cap vent and added a spring (inside fuel line) in a tight curve. My pressure holds solid with a carter mech to a holley 850dp now.
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What size fueling are you running, from the tanks to the T to the fuel pump? Also if you have a Holley carb they have a brass filter in the bowl right where the fuel line hooks up, it might be plugged, running the boat with the caps open will determine if it is a vent problem, just don't do it in Havasu 😉
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I'm running 3/8 line everywhere. I just did a rebuild on my holley (750) thinking that was the culprit but alas it wasn't. I took the whole fuel filler assembly out of my boat today and I don't see any difference in suction between both passenger and driver side but I'm still going to tap into the side of the filler cap and but a vent line in. I just don't know where to put it where it won't get too wet. Any thoughts??
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I had a fuel issue before and had all the above is good stuff.
Another thing I want to add is some pickup tubes have checks in them which really can just end up restricting flow. I think I read you checked your pickup tube which means you can pull em out I would double check they don't have the checks.
Could be crap in tanks
Small lines (I installed larger pickups all the way to carb)
Proper vents
The gauge is great idea it will be a great tool and would be a great way to begin the troubleshooting process that everyone has mentioned so you can figure out which issue you have
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Ya, it's been a real pain in the butt. What throws me off is that it's not a consistent problem. Sometimes it's worse than others. It'll happen every time I go out but won't happen every day. Maybe once a trip. Also, I just recently took my pickups out and they don't have checks in them. I did notice that my coil was pretty hot. Does that have any relevance to my problem?
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I have seen the issue with the selector T try swapping lines or simply replace it. I think they are about $20
BAM!
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So to update you guys on this topic I took my boat out this past weekend after venting both of the tanks and putting a higher rate mech. Fuel pump in. Boat still started to stall on me on my way up to topock. I was able to pedal through it and get it to idle and then full throttle again. This happened to me about 3 times. ( I even opened up my gas cap when it was happening). After it happened for that period of the time I didn't have another problem with it for the rest of the trip. I made it to pirates cove and back no problem. Any ideas? Maybe vapor lock? Not sure where to go from here
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Haven't taken the time to read thru all the previous posts. Have you checked your float levels?
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Yes, I've done everything that I am think of myself. Just trying to get other points of views on it
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Does it happen after wot and letting off or while on wot
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How much fuel in tanks
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They're full
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Are you letting off throttle before it happens I also have a 460 and if I go wide open and just let off mine cuts out for a second
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No it'll happen while I'm hold it down and all the sudden the tack just drops and it tries to die
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I think your losing spark check your coil
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Do you have points
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I have a pertronix kit with a blaster coil. I don't think I'd be losing spark for only part of the time. Like I said it only did it to me for about 3 times consecutive and then it stopped for the rest of the day
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I'm not a expert but check for a loose wire
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I had points and mine did same thing didn't convert to pertronix I put in a assault racing he ignition and no problems since