Fuel delivery issue

[ziggy]

Re: Fuel delivery issue

yep, i don't know what that cluster is. it's not like mine. and don't look like the book. the book did have something 'similar' to what he's got. not exactly though. hence my questioning of what he's got.

i hate to say, but mine is like it came from the oem in '75. fuel in and fuel out. plain and simple and dangerous... a cater fuel pump.

 

[paul ages]

Re: Fuel delivery issue

Glad I got some conversation going!

It's a '68, and as far as I can tell there were a few changes between then and '75. that said, it could very well not be stock.

I plan to add clear line from the pump to the carb, as it will be nice to see whether fuel is flowing or not when the problem happens. The safety line... it's below the diaphragm, right? I don't believe I have an opening down there for one.

I forgot to mention fuel pressure testing. When working well, it tests at the carb end of the line to be at the upper end of specs, 4.2 PSI if i remember correctly. When the problem occurred, we connected the test gauge and got a fluttering nothing there. The spot I'm venting is where the water separator was before I bypassed it. In other words, tank-->junction (was separator/filter)-->pump-->carb. After venting at this location, pressure resumed at the carb end of the line.

The tank "vent" is the overflow tube to the side of the boat. I didn't measure it when I pulled it to check that it was clear, but it's probably 3/4"-1" I.D. I'm starting to suspect that that pump diaphragm may be going, which would explain why it only acts up under high demand, but it seems that any perforations would result in fuel in the oil, no?

I'll likely open the pump up monday morning for inspection. I don't think the lady will be happy about any shop time this weekend...

 

[baldy1]

Re: Fuel delivery issue

I had an old Mercury outboard that was doing the same thing or close to it. The boat had two built in tanks. Long story short, I took the pick up screens off and put in-line gas filters in the fuel lines coming out of the tank. I soon discovered that junk, in this case dried up silicone was doing the plugging. I since put in a bigger water seperator filter in. Someone had the bright idea of hard piping with abs plastic the main fuel fill lines, and the sealant got into the tanks. It has been fixed the right way.

 

[gozierdt]

Re: Fuel delivery issue

You eliminated the fuel/water separator, but I'm wondering if the rubber line from the tank to the separator is collapsing under high flow conditions? Did you check that line by blowing into it, or using a vacuum source on it? It's possible that the inner layer of the hose has separated from the outer layers and is collapsing. A long shot, but it's always good to replace old hose (if you haven't already) with new hose that can resist the ethanol in the current fuels.

I also don't understand that loop around the pump at all. The pump should just pump fuel endlessly around the loop. There must be a check valve. It looks like the loop fitting on the left of the picture is longer than the right? Hard to tell. If it was mine, I'd pull that line off and see what's going on with it- just so I knew. And fuel pumps aren't very expensive. I'd put that on the "immediate replacement" list (plus from what's been said above, you'd get the safety benefit of having the safety line in case the diaphragm ruptures, once you add that safety line).

 

[paul ages]

Re: Fuel delivery issue

You eliminated the fuel/water separator, but I'm wondering if the rubber line from the tank to the separator is collapsing under high flow conditions? Did you check that line by blowing into it, or using a vacuum source on it? It's possible that the inner layer of the hose has separated from the outer layers and is collapsing. A long shot, but it's always good to replace old hose (if you haven't already) with new hose that can resist the ethanol in the current fuels.

I also don't understand that loop around the pump at all. The pump should just pump fuel endlessly around the loop. There must be a check valve. It looks like the loop fitting on the left of the picture is longer than the right? Hard to tell. If it was mine, I'd pull that line off and see what's going on with it- just so I knew. And fuel pumps aren't very expensive. I'd put that on the "immediate replacement" list (plus from what's been said above, you'd get the safety benefit of having the safety line in case the diaphragm ruptures, once you add that safety line).

I blew into the line with compressed air. I should replace the hose, I've just been avoiding it if not necessary, as I can't reasonably replace everything on the boat at once, though it has felt like I was going to have to at times...