Soft shutdowns until it doesn't start anymore

[pdecker]

I think I have a fuel starvation problem but can't figure out how to fix it. Last month, I tried to finish my migration down the ICW from Annapolis to Fort Lauderdale. As I got within about 50 miles of my destination, I started having soft shutdown problems. The engine would putter out, but I could usually restart it. I found I could prolong the running time by giving it less throttle. Finally, it wouldn't start at all.

I replaced the fuel filter in my Racor water separator and made sure there was no water in the fuel. The old filter wasn't dirty, and the engine still wouldn't run. I checked the flow from the two-year old fuel pump, and didn't get anything at first. I jumpered out the oil pressure safety switch (OPSS), and heard the familiar clicking sound, but no flow.

Then I "primed" the fuel system by filling the Racor bowl with gas, and then the pump would produce ample flow. I reattached the hoses to the engine and it would start and run as long as there was gas in the Racor bowl. When the engine stopped, I checked the bowl and it was empty. I replaced the fuel hoses and repeated. Same thing -- it runs as long as there is gas in the Racor bowl. I cannot put a priming bulb in my lines because the West Marine Superstore here does not have a bulb for the large diameter fuel lines I have.

Finally, I checked to see if there is a problem with the fuel tank vent by trying to run it without the fuel cap on the tank. Same as before. I'm running out of options. I rechecked the tightness on all the hose clamps in the fuel system.

Could the old Racor water separator have an air leak? The o-rings are fine.
Could the aluminum fuel tank be plugged with junk at the bottom?

Phil
S/V Catmandu

[romantic comedy]

seems that you narrowed it down.

You can remove the racor.

Blow back into the tank to see how much resistance there is, and maybe clear the obstruction.

Hook up another tank to make sure the problem is what you think it is. you can by pass the racor, or even the pump. Can use an outboard tank, or a bleach bottle. Use a few feet of fuel line and attach the bottle higher then the engine. Gravity will keep the engine supplied.

I would also do a rebuild of the carb. To be sure.

[Dave Neptune]

Checks on the boat.

Have you checked for fuel flow by "pumping into a can"? Do this at the carb end of the fuel line. A simple fuel pressure gage at this point would let you know if it is delivery or in the carb itself. If you get a slow flow check all fittings and clamps first and then recheck. No change check/replace polishing filter first then look to the Racor. If you have flow but no pressure may be the pump itself. Some electrics have an internal screen that can plug and a check valve that can be compromised.
Certainly sounds like lack of fuel and the less throttle and it takes longer to sputter out pretty much confirms that, now just where or how is it restricted.


Dave Neptune

[joe_db]

I had some issues like this and tracked them down by getting 3 gauges. I had one fuel pressure gauge, on vacuum gauge on the inlet of the Racor, and one on the outlet. What I found out eventually was my fuel fill hose was disolving and dropping bits of rubber into the tank. They would clog the fuel tank inlet and starve the engine of fuel, but then drop off when the engine was shut down. Without all 3 gauges you could not figure this out. Normally the only gauge is on the output side of the filter and it looks like a clogged filter.

Also I think you mentioned air getting in. Make sure the Racor seats well and that the fittings are well sealed.

NOTE: Do not get liquid filled gauges. I found out the hard way they give incorrect readings when heated or cooled substantially.

[edwardc]

Another "stuck ball"?

This sounds a lot like a problem I had several seasons ago, discussed elsewhere here. Cliff-notes version: it was the fuel pump. Clicked and moved some fuel, but didn't have the needed volume. Would run but eventually stall. Less throttle made it run longer but still stalled.

Turned out it was the check-valve ball inside of the pump. It was sticking to its seat. I was able to effect a temporary repair by opening the pump (the bottom twists off), removing the screen, and pressing on the ball with a fingertip. It freed with a "click" and then moved smoothly. After reassembly, it pumped mad volume, and the engine ran fine.

Unfortunatey, after a few weeks, it stuck again, so the only permanant fix was to replace the pump. Still, it's an easy fix to try, and might get you out of a jam.

[CalebD]

do you know what is at the bottom of your fuel tank?

[pdecker]

I think I isolated the problem to the carburetor

I appreciate all your comments, and I'm trying all the diagnostics that don't cost money first. I think it might be the carb. Here's why.

First, I tried blowing into the fuel tank to try to clear any blockage. It was very, very difficult to blow anything. However, I could easily suck. I didn't suck very much since I didn't want to gargle with gas, but perhaps there is a check valve in the line. Anyway, I don't think it's a blockage in the fuel line.

Then I bypassed the Racor water separator, made sure all the hoses were tightly secured, and tried to start the engine. As usual, it cranks really well but didn't start. I got a few coughs when I completely closed the throttle, but nothing else. (Of course, the raw water intake valve is closed while I'm doing all this.)

Then I bypassed the fuel pump and put the fuel intake hose in a jerry can held above the engine. Still it didn't start, so I conclude that the carb doesn't have enough suction to even pull the fuel downhill. I reattached the fuel hose to the fuel pump. I noticed the fuel hoses during all these procedures were dry after trying to start, so no fuel was flowing.

So, I think there must be gunk in the carb. I'm ready to order a carb rebuild kit. I have not had the carb rebuilt in over ten years. Is there anything else I should try for cheap before I mess with the carb?

Phil

[Dave Neptune]

Whoa

pdecker, dry lines mean no fuel flowing and no fuel flowing is not the carb.

Note the carb does not and is not capable of sucking fuel in!!!!

Do you have an electric or manual fuel pump?

Dave Neptune

[pdecker]

It's electric

I have a two year old electric fuel pump. It clicks when I turn on the engine with the OPSS jumpered out.

pdecker, dry lines mean no fuel flowing and no fuel flowing is not the carb.

Note the carb does not and is not capable of sucking fuel in!!!!

Do you have an electric or manual fuel pump?

Dave Neptune

[Dave Neptune]

When it clicks do you get any fuel flow?

Dave Neptune

[JOHN COOKSON]

Note the carb does not and is not capable of sucking fuel in!!!!
Dave Neptune

+1 and another +1
Fuel is pumped to the carb. It does not suck fuel into it.
Get the fuel pump pumping fuel then go from there. You may have a defective fuel pump or some sort of blockage tank ->fuel pump.
Once you get fuel to the carb then you can figure out if you have a carb problem or not.

TRUE GRIT

EDIT: POST #1000!

[romantic comedy]

I would rebuild the carb, since you are doing all this.

It is easy to see if the carb is not working. Just hook up a gravity feed tank. This can be very simple. Just a gallon jug with a hose. Set up a siphon feed.

[ndutton]

Shameless plug

As the discussion develops I can't help but think of the fuel pressure feature Don required for the EWDS, would have pointed in the direction of fuel delivery instantly.

[pdecker]

Great comments. When I first started to diagnose this a few weeks ago, the fuel pump pumped when the Racor water separator was manually filled with fuel. When I check for fuel pump flow without pre-priming the system, it doesn't pump anything.

Question: Is the electric fuel pump self priming or not? If not, how would I prime it? I can't add a priming bulb inline because my fuel hoses are of a larger diameter than the largest bulb fitting. Whenever I manually filled the Racor, the engine would run until the Racor bowl is empty.

[Dave Neptune]

Leaks or the pump

pdecker, do you know what type of pump? If your Racor is above the carb you were gravity feeding until it ran out so I would not consider the carb.

You either have a faulty pump or an air bleed leaking into the line before the fuel gets to the pump. These small electric pumps pumps so little volume that just the tiniest bleed will stop the flow(THE SUCTION TO THE TANK) cold!!!

I strongly suggest you check each fitting and clamp and check all sealing surfaces on the Racor. If it were mine I would not even fuss with the old fuel lines I would replace them. If you install a CHEAP small fuel pressure gage in front of the carb after the polishing filter if so equipped your questions will be answered by the gage. The gage will always be there to check whenever something goes amiss, just look and see~~that eliminates a lot of diagnosing time right there!!!

Dave Neptune