When is the bowl full?

[High Hopes]

Hi guys,

I have a manual override switch on my fuel pump. It is a push button. When I haven't run the engine in a long time, I hold the push button down to activate the pump. This eliminates the need to crank the engine to raise the oil pressure to active the pressure switch to turn the pump on. I thought the push button was a pretty slick idea. The switch is located near the pump so I can listen for a change in the pump noise after it fills the carburetor bowl and carburetor needle valve closes.

But I have run into a snag. For some reason, my pump now sounds the same regardless of fuel flow. Or maybe sometimes the bowl is already filled when I push the button so I don't hear the change in pump noise that I expect.

The last time I tried to start the engine, I had trouble. The engine wouldn't start. Part of the troubleshooting drill is to check for fuel. I wasn't sure the pump was working, so I pulled the fuel line off the carburetor end. This is messy, smelly, and a little bit dangerous. I always get gas on my hands.

So, I was thinking of adding a fuel pressure gauge between the pump and the carburetor to detect when the bowl needle valve closes. Has anyone blazed this trail ahead of me? Is there a way to check for fuel delivery without getting their hands wet with gasoline?

-Steve

[romantic comedy]

I feel cheated. You just stopped the story. Was it getting fuel? Did it start?

Why are you so concerned with the fuel pump? Is there some problem. Mostly they work or they dont. (mostly) Why do you want to know when the float valve seats?

if you only get fuel on your hands, you are doing great. I get it everywhere, usually in my face too.

Remember that you can use starting fluid to check if it is getting gas. Don recommends it!

[ndutton]

I have a similar feature with my pump Steve. After a long layoff I'll give the system a 5 second prime and start her up. If the pump isn't pumping the engine will starve itself easily within a short time at idle. One time I absentmindedly left the fuel shutoff valve closed and started the engine on residual bowl fuel only, two other times with a faulty OPSS. In all cases she fast idled somewhere around 60 - 80 seconds and died.

[Dave Neptune]

get the gage

Steve, I have been pushing for preassure gages in line for a long time now. I have mine mounted between the polishing filter and the carb. I also have a shut off mounted "on the gage". I found this to workout quite well as the gage has many mounts available and the gage was attached via a "tee" fitting. One port for the gage and the other to the carb.
A permanant mounted gage surely eliminates a lot of guess work when trouble arrives. I just mounted a cheap S/W zero to ten PSI unit. I use the mechanical pump and it sits around 2~2 1/2 psi, when the preassure "holds" the bowl is full.

ave Neptune

[joe_db]

I do have a pressure gauge, but I don't watch it to start the engine. My prime switch is out with the rest of the engine controls. I usually hold it for about 20 seconds or so and that does the trick.
Thread creep, but my spring fuel project consists of:
1 - Switching to an electrical sender fuel pressure gauge and putting the gauge out on the panel with the other gauges.
2 - Changing the fuel pumps from series to parallel. It has been mentioned on this forum that having 2 pumps will do me no good if a checkvalve sticks in one of them if they are in series.
3 - Adding a switch on the panel for the second pump. Right now I use the fuses to control which one is on.
4 - Adding a return line and valve for priming and polishing.

[High Hopes]

I feel cheated. You just stopped the story. Was it getting fuel? Did it start?

Why are you so concerned with the fuel pump? Is there some problem. Mostly they work or they dont. (mostly) Why do you want to know when the float valve seats?

if you only get fuel on your hands, you are doing great. I get it everywhere, usually in my face too.

Remember that you can use starting fluid to check if it is getting gas. Don recommends it!

LOL - Sorry to leave you with a cliff hanger. Yes, I got is stared, but I don't know why. I pulled the plugs; they looked nasty. Dumped a bit of gas into the cylinders, put the nasty plugs back - dick. Ran off the West Marine, spent $20 for 4 plugs . Dumped some gas in the cylinders, installed the new plugs and she fired up.

So, I guess it was the plugs, but really the old ones should have done something - a pop or two. That is why I want a way to know if the carb is delivering gas. The plugs didn't seem wet when I pulled them. So maybe it just took a long time to get gas into the engine? - maybe the plugs were the problem? I am trying to figure out how to figure out what really happened.

Gas in the face - I haven't managed that yet, but have gotten enough gas in the bilge and on my clothes that I started to pray that I wouldn't make any sparks. I don't like that feeling - not the praying, that was ok. I'm just not into self-immolation.

I will check out starting fluid. I have never used it. Is this ether in a spray can?

Steve

[High Hopes]

I have a similar feature with my pump Steve. After a long layoff I'll give the system a 5 second prime and start her up. If the pump isn't pumping the engine will starve itself easily within a short time at idle. One time I absentmindedly left the fuel shutoff valve closed and started the engine on residual bowl fuel only, two other times with a faulty OPSS. In all cases she fast idled somewhere around 60 - 80 seconds and died.

Whoa! I don't think I have every started my engine on a five second pump. Hmm... maybe something else is going on. I'm talking about a minute or so before I hear the pump change its pitch.

[edwardc]

LOL - Sorry to leave you with a cliff hanger. Yes, I got is stared, but I don't know why. I pulled the plugs; they looked nasty. ...

To me, this says that you have been running too rich. Does it start easily, with just a little choke? If so, you're probably too rich. Our updraft carbs normally should require full choke to start cold, and should require the choke for about the first 30 sec or more.

Plugs that are running in a proper mix should be light tan or gray, and dry, with no crud buildup. Try adjusting your mixture. You may need to tweek the timing at the same time to get a proper idle rpm.

[ndutton]

Steve,

A minute or so is a tremendous amount of pump time to fill a carb bowl. I'm thinking there's more to it. I'm plumbed with a return line to the tank so I can use my pump to purge a fresh filter and I can draw a dry filter full in a minute.

My practice of a quick prime is on principle only, I have no evidence it's even needed. Tell you what, I'll stop the practice and see if there's a difference. I've always advocated there's enough residual fuel in the carburetor bowl to start and run the engine for a minute without any pumping.

[joe_db]

I only need the prime because I run the gas out to shut down at the end of the day. For restarts during the day the engine catches in about 2 seconds.

[ndutton]

I hope my math is correct.

A very rough calculation with the carb bowl volume and the spec flow rate of the electric pump results in an estimated 5 second pump time to fill the bowl from a dry start. That does not take into consideration reduced flow rate due to float valve orifice size or other system restrictions so if we arbitrarily apply a 3X fudge factor we're still only at 15 seconds.

As discussed on a recent thread, I'm not one who chooses to run the carb dry at shut down.

[sastanley]

I just use the bale on my mechanical fuel pump to prime the system after a long lay-up until my fuel pressure gauge (in the same place as Dave Neptune's, in between the polishing filter & the carb) reads 3 PSI and vrooooom!.

Even without a gauge, once the system is pressurized the bale won't move the diaphragm any longer so you can tell the system is pressurized with fuel.

( i know, I know...this does not help)

[High Hopes]

To me, this says that you have been running too rich. Does it start easily, with just a little choke? If so, you're probably too rich. Our updraft carbs normally should require full choke to start cold, and should require the choke for about the first 30 sec or more.

Plugs that are running in a proper mix should be light tan or gray, and dry, with no crud buildup. Try adjusting your mixture. You may need to tweek the timing at the same time to get a proper idle rpm.

Hi Ed,

You may be right. My engine never burns lean. Vacuum is low at cruising speed; it lugs a bit. I need a faster turning prop. And come to think of it, it has been a l-o-n-g time since I adjusted the carb.

Some of the crud I was speaking about was actually rust from water which had collected on the head around the plugs and crept down the threads to the points.

This is what happened. The boat has a deck leak; we had lots of rain; I was away from the boat for about four months; the cabin flooded; black slime formed on the cabin sole; every surface was moldy. With all the moisture, the head started to rust, too. It was new a few years ago.

Anyhow, the engine was started and run till she got up to temp, flushed with fresh anti-freeze, and put to bed for the winter, again. Never a dull moment.

I am off to the boat tomorrow to look for deck leaks again. The weather man promises rain which is good for finding leaks. The last time I was out there, I pulled the log transducer (a paddle wheel gizmo) out of its through-hull fitting. This makes a two inch hole for the bilge to drain to the outside, so I do not expect to see anymore water in the cabin this winter.

Thanks -Steve

[High Hopes]

Steve,

A minute or so is a tremendous amount of pump time to fill a carb bowl. I'm thinking there's more to it. I'm plumbed with a return line to the tank so I can use my pump to purge a fresh filter and I can draw a dry filter full in a minute.

My practice of a quick prime is on principle only, I have no evidence it's even needed. Tell you what, I'll stop the practice and see if there's a difference. I've always advocated there's enough residual fuel in the carburetor bowl to start and run the engine for a minute without any pumping.

Hi Neil,

Now I am wondering if the change in fuel pump noise has anything to do with anything at all. Maybe it has nothing to do with the flow through the pump. Maybe it does. Maybe the fuel filter contents flows back into the tank and the pump has to suck enough to fill it again. The filter is mounted about mid-tank level. Maybe this needs to be lowered. Maybe the petcock, which is mounted higher than the tank, leaks air into the lines. Maybe, maybe, maybe.

Neil, I would like to know what happens without any priming. Thanks. I can't say why I thought the bowl should needed filling at all.

[High Hopes]

I only need the prime because I run the gas out to shut down at the end of the day. For restarts during the day the engine catches in about 2 seconds.

Hi Joe,
After the initial start for the day, all is well with me, too. The initial startup is the killer.