Fuel problem. Opinions??

[Darren J]

I was just thinking that the only parts not replaced or bi-passed from your tests is the tank itself and that first internal line, so it must be either of those. It would be good to eliminate that line as a possibility before cutting floors or tanks.

I assume you have bi-passed the fuel filter/head etc. It would be disappointing to find there was something solid (like a dislodged piece of the old fuel lining that was breaking up) that is jammed in the head at a bend or something. Possibly sufficient to restrict flow from time to time if it moves. But maybe its lodged sufficient that it does not clear through.

I guess, given it is intermittent and seems to clear itself for no obvious reason, you would want to be sure you really have eliminated all possibilities. For example, when it ran fine on the jerries, were you using any part of the existing system? If you did, you would assume that part of the system is ok. But it may not be the case. By the time you connected in the jerries, it is possible the original system may have come good again if you simply reconnected it, it may have then got you home also without trouble. I guess just because it all ran on them doesn't necessarily prove the problem was back in the system from there.

[gofishin]

Is the primer bulb getting sucked flat?

Yes, first question that comes to mind.

For the times when you had to come home on one donk, did the motor just die/not perform, or did it come good and die repeatedly?

Does the new tank have a sender unit installed? If so, swing arm or vertical/plunger type?
Cheers
Brendon
P.S. Drilling holes in the pickup tube will reduce the tank's useable volume, as it will suck air/vapour once the fuel level drops to/reaches the highest hole!

However , if you drill a few holes say 6 - 10mm higher than the bottom of the pickup tube, this will tell you if it is a hard flat object or a flexible plastic/fabric etc that is causing the blockage. I say a few because you want the total area of the holes to be equal to (or within 85% of) the pickup tube I/D.

Edit; sorry, started typing a while ago before a lot more replies came about.


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[tunaticer]

Sounds to me like there is a large fish scale in the tank.
Old payback method that usually results in them selling the car/boat. Anyone got the shits with you?

The fish scale drifts about in the tank and eventually goes near the pickup and seals it off completely at a totally random timeline.

What diameter is your pickup line?

OMC tanks have a fine mesh end about 35mm long to a 6mm pickup line.
Possible that it might be large enough to feed your engines and possible you might be able to push it through the pickup line and into the tank. It will solve the problem if it is a fish scale.

It is not a piece of rag if the primer bulb sucks flat.

[Fed]

I used to get salt clogging the mesh in the breathers that was sort of intermittent and would often disappear by itself, could have simply dropped off while trailering.
It wasn't a 100% clog just a restriction but enough to flatten the primer bulbs at speed, I'm guessing you've looked up their bums like a CSI. You hinted around checking the breather but did you actually try it with the fuel cap released?

Had a car that did the same thing and it turned out to be a rubber hose spout floating around inside the tank & also breaking up, it looked like an old fashioned rubber fuel hose spout from a servo pump. I used to have to disconnect at the fuel pump & blow back into the tank then be good to go for a day or a month. Car was a fibreglass kit car and the tank was built in under the back deck so I was reluctant to cut the back deck out... it was like winning lotto when I found it.

[ShaneC]

The tank has no sender unit, I use an old fashioned dipstick to gauge the fuel level. Fed I have pretty much eliminated the breather, it is protected by a shroud to stop salt getting in, but the breather as a whole was not changed when the tanks were and I never had the drama prior to the new tank. Tunaticer, mate plenty of people have the shits with me at any given time but I am not sure any of them would stoop to those levels. That scenario has crossed my mind many times and cant be eliminated outright, but its still got me buggered what the object is. I am interested that you say a piece of rag would not suck the primer flat though. Do you think enough fuel could get through a rag to run the motor?? That being the case it makes Wardys idea of a piece of stainless wire through the pick up a very feasible one to give a go.

[rtp1984]

Hey Shane.
Where do you fill?
through the deck I assume if you check fuel level with a stick.

Could you set up a temperary pick up through the filler cap.
This would then draw your suspect to it, you would nearly be able to unscrew the cap and pull the object out still sucked on the end of the pick up, or at least be able to look through the filler cap and see what it is

[ShaneC]

I fill up through a filler in the gunnel mate. The idea of drilling a hole through my filler cap and making a pick up that was much larger than what I have did cross my mind thinking I may be able to pick the object up so it would remain in my filter. Sounds good in theory but I discounted it as unpractical.

[Darren J]

If you do resort to cutting the deck/tank, maybe fit a second pick up, and run it as well as the original, as in draw from both pick ups. They can't both get blocked together, if there is some physical separation between them.

Would be interesting to run the boat as normal, when the problem next occurs, undo a fuel fitting, blow back into the tank (to dislodge the suspect blockage), connect and see if the problem immediately clears and fails to return.

[Bremic]

My parents had similar problems with their car. Went on for several years, would happen every couple of days and then no problem for months. The old man tried everything he could think of until he eventually pulled the fuel tank out. He found a bit of wax paper in the fuel tank, something like a bubblegum wrapper. After that, no more problems. Would have thought the wax paper would have broke down in the petrol, but there you go.

[trymyluck]

My parents had similar problems with their car. Went on for several years, would happen every couple of days and then no problem for months. The old man tried everything he could think of until he eventually pulled the fuel tank out. He found a bit of wax paper in the fuel tank, something like a bubblegum wrapper. After that, no more problems. Would have thought the wax paper would have broke down in the petrol, but there you go.

Heard of people using a tallyho paper in the fuel tank as payback for whatever reason. Apparently they don't breakdown and float around until they get sucked to the pickup.

Mark

[ShaneC]

I would suggest that would be a great get back. But the problem started as soon as the new tank was fitted so I would not think the bloke I paid $5k to do it would hold a grudge.

[John Buoy]

Silly question I know but is bulb is fitted with correct direction of flow Shane ?
Can you fit a clear filter close to tank as this will show you whether fuel is flowing.
Mostly though it does sound like a tank blockage !

[scottar]

If you do end up putting a hole into the tank as an access, why not put it directly over or as near as possible to the pick up - that way it should be an easy sighting/retrieval of the blockage if the issue re-occurs. I would try the bit of wire and the bore scope first.

[gofishin]

The tank has no sender unit, I use an old fashioned dipstick to gauge the fuel level ...

Well that rules out this as a source. Why I asked was some years ago there were two types of faults with typical plunger senders causing this exact problem!

I have also seen this problem caused by a bit of careless removal of masking tape on the tank pipe risers in a cat. i.e. to stop crap entering the tank while the floor (and tank risers) was glassed up/over. Then when the guy fitted the hoses, he was careless and lazy!

It could be anything, but I would try a few things before getting the pneumatic tools out for the tank.

A simple schematic of this tanks fuel system, showing all line components and bits that have, and the hose which has not been replaced might help people get their head around the problem a bit better, and prompt a few more suggestions.

How many baffles/chambers does the new tank have? I guess at least 2 baffles. Where is the filler in relation to the pickup?

Does the problem occur at all tank levels, or more prevalent when 1/2 full or nearly empty etc? This should tell us if it is a buoyant 'thing', or just wafting round etc.

Where about was the previous hose delamination, at the tank, or closer to the donk?

From your previous comments (no tank vacuum/hissing from fuel cap but primer bulb sucks flat) we can totally rule out a breather issue.

...This is what I am going to do. I have a guy with a big petrol sucky thing coming around next week. I have made up a spear that can go to the bottom of the tank thats much bigger than the pick up to quickly drain the tank and hopefully pull something out of it. ...

Is his 'big sucky thing' rated for a continuous duty cycle Shane? Where/how were you planing on using the spear, down the filler opening?

The problem with this is that you are sucking from a different part of the tank.

We know that it is most likely a foreign object blocking the pickup. I would first look at using a continuous pumping process with your mates pump.

Can you get to the pickup easily, and unscrew/withdraw it? From previous comments I assume so. If so unscrew it and leave it sitting in place. Suck out of it through a primer bulb, then filter, then pump, then back into the filler pipe (assuming it is up the other end of the tank).

This will create a continuous process were you are drawing the object to the pickup. When the bulb sucks flat you know it is on the end of the pickup. Hopefully with pump still running you can carefully pull the pickup out and find your problem.

I have made a few assumptions here, and depending on answers to above this may not work.

Typing on an iPhone is giving me the sh!ts, so enough for now.

Cheers

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[Aussie123]

Trying to replicate this issue is nearly impossible as it happens so randomly.
I remember one trip it occurred about 5km offshore from 1770 with full tanks.
It's happened with half a tank of fuel and a quarter of a tank and anywhere in between.
We could burn 1000 liters or more between events as well.
Just when you think the problem has gone away it comes back again and nothing seems to trigger it like certain tank levels, weight in the boat or sea conditions.
I still think the tank has a foreign object moving around between the baffles and occasionally it finds its way to the section with the pickup.
I have been through the system numerous times and magyvered it numerous times to get us home on both motors and it really is annoying.