Engine Stalls when fuel is below 1/4 tank

[somat84]

I have a 1988 4.3L 175 HP OMC. When I run at WOT with a 1/4 tank of fuel or less the engine intermittently losses power and wants to stall. I can keep the engine running if I throttle down, and even get back up to speed before the engine wants to stall again. I assumed there is water in the tank which gives me a bad fuel gauge reading. Or the fuel in the tank may be sloshing around making me suck in gas and water causing the engine to want to stall. I filled the tank the engine continued to do the same thing. Could this be because there was still air or water in the fuel lines, or maybe because filling the tank mixed the water and fuel? I have never experienced any issues with a tank over 1/4 full until now, but I have never filled with gas on the water and ran the boat immediately. Typically I fill the boat on the trailer which would let the water and gas separate if there is water in the tank. Any help or suggestions are appreciated.

 

[hard-3]

Re: Engine Stalls when fuel is below 1/4 tank

I had the same problem , the fuel pick up was not on the bottom of the tank and it actually had 1/4 tank on fuel gauge but would not pick up fuel in tank. it would run at level but die when nose up . all fuel running to back of tank and not sucking up in pick up. my fix was never get below 1/2 tank. Sounds like you might have a bunch of crap in fuel tank. if you can get to fuel sender unit take it out and siphon tank bottom off. get one of those siphon pumps with a squeeze bulb like you use to fill kerosene heaters with and suck out. change your water seperator also you may have bunch of junk in it. let it set a while to allow water to seperate and go to bottom. nose up on trailer to get it to go to back of tank. siphon into clear glass jug to see if your clean. keep going until you get clean gas. Marinea gas tanks are known for having water in them .

 

[sarantis]

Re: Engine Stalls when fuel is below 1/4 tank

Your solution is exactly as described above.In my same situation i got rid of the grid you 'll find at the metalic straw that leads inside the tank because this way the crasp stays there until you clean the tank but without it stays to the filter which is easy to replace.

 

[Bondo]

Re: Engine Stalls when fuel is below 1/4 tank

Ayuh,....

And,...
Checking/ Changing the Fuel Filters will tell you if you have a Water Issue.....

 

[somat84]

Re: Engine Stalls when fuel is below 1/4 tank

Thanks guys, I will start by changing out the fuel water separators. Can I attempt to pump the water out of the tank through the fuel fill neck?

 

[somat84]

Re: Engine Stalls when fuel is below 1/4 tank

Where do I find the metallic straw leading into the tank? I like the idea of removing the grid from it. Does anyone have any illistrations or link to online procedures? My boat is a 1988 Wellcraft 190 Classic.

 

[Bondo]

Re: Engine Stalls when fuel is below 1/4 tank

Ayuh,....

At the top of the tank, the Fuel Outlet fitting....

The Hose is clamped to the Anti-siphon valve,....
The Anti-siphon valve screws into an Elbow....
Remove the Elbow,+ the siphon Tube is attached to the other side....

 

[drpboston]

Re: Engine Stalls when fuel is below 1/4 tank

I'm actually having the same problem with my 1988 4.3 L OMC. Was on a trip where I was doing alot of idling (river cruising) for literally hours. Just prior to that filled up at a Marina. ON way back from river locks, in open harbor, wouldn't open up at WOT, stuttering got worse and worse until she would only run at idle.

Just rebuilt the carb last month and was running like a top.

Plan on changing the water/fuel filter first. I also know there is a small filter element in the Rochester 2bbl where the fuel line enters. I didn't change it because I didn't know how it came out. I assume its stuck, unless there's a secret to getting that filter out.

How can I tell if I have water in my line when I take out the old fuel/water separator? Also, is there a screem or grid I should be cleaning out as well? I know it's an aluminum tank and not fiberglass.

 

[achris]

Re: Engine Stalls when fuel is below 1/4 tank

I'm actually having the same problem with my 1988 4.3 L OMC. Was on a trip where I was doing alot of idling (river cruising) for literally hours. Just prior to that filled up at a Marina. ON way back from river locks, in open harbor, wouldn't open up at WOT, stuttering got worse and worse until she would only run at idle.

Just rebuilt the carb last month and was running like a top.

Plan on changing the water/fuel filter first. I also know there is a small filter element in the Rochester 2bbl where the fuel line enters. I didn't change it because I didn't know how it came out. I assume its stuck, unless there's a secret to getting that filter out.

How can I tell if I have water in my line when I take out the old fuel/water separator? Also, is there a screem or grid I should be cleaning out as well? I know it's an aluminum tank and not fiberglass.

Start a new thread... don't hi-jack others and start confusing things....

Chris..........

 

[somat84]

Re: Engine Stalls when fuel is below 1/4 tank

I will work on the fuel system today. I wont have the boat in the water until Sunday but hopefully all goes well. I will be sure to give an update.

 

[drpboston]

Re: Engine Stalls when fuel is below 1/4 tank

Sorry man, didn't mean to hijack. I am just having the same EXACT problem as Somat on the same EXACT engine size and year. Thought I'd commiserate and brainstorm a little.

 

[somat84]

Re: Engine Stalls when fuel is below 1/4 tank

I changed the fuel water filter and took the boat out over the weekend. All was great for the first 1/4 tank for gas then the stall issue started again. The only good news is, my dad was with me so we tried to trouble shoot the issue. A few things to point out:

1. We took the air filter / spark arrestor off the carburetor and clearly saw the engine was getting no fuel when it wanted to stall. This eliminated the "water being in the gas" theory. If the issue was water, I am assuming we would have at least seen something squirting in the carburetor.

2. I removed the main gas line from the fuel pump (which is a cam fuel pump, not electric), gave the engine a quick crank and could very clearly see a healthy squirt of fuel coming from the pump. This doesn't necessarily mean the pump is good but I am hoping to rule the pump being bad out for now.

3. I then removed the fuel line from the carburetor to inspect for a potential block. There is a brass conical shaped filter type element in the fuel line when I removed it but there was no debris.

So I am lost. I am assuming the fix will be something cheap and easy once I determine the problem but their in lies the trick. There may be a block in the main fuel lines running from the tank to the filter and pump, or the accelerator pump in the carburetor may be bad. The issue is more prevalent under a higher load but the issue got worse as the day went on. It became difficult to keep the engine running even at a, close to idle, speed. Anyone have any ideas what the issue may be?

 

[ziggy]

Re: Engine Stalls when fuel is below 1/4 tank

ya could try running on a remote fuel tank with some nice, fresh, clean fuel in it... that'll elminate everything prior to the fuel pump.... replace your fuel filters for sure. ya could pressure test your fuel pump to see if it is within specs. or here's a dandy thread that ya might find a good read.....http://forums.iboats.com/showthread.php?t=167561

 

[hard-3]

Re: Engine Stalls when fuel is below 1/4 tank

check the anti-siphon valve on the fuel tank outlet. if its rusty it will not flow right. sounds like a fuel delivery issue check out fuel line from tank pickup to fuel pump. get some brass fittings and put a fuel pressure gauge between the fuel pump and carb. should have 4.5-6 psi when running.
If not then either restriction between fuel in tank and fuel pump or bad fuel pump. try running on outboard tank connected to inlet of fuel tank. if probs go away then trbl is in fuel tank,anti-siphon or fuel line.


keep the fire extinguisher handy while troubleshooting fuel problems
cause _ _it happens.

good luck

 

[somat84]

Re: Engine Stalls when fuel is below 1/4 tank

Thanks guys, that is an excellent idea, running from an external tank. I have to admit, I feel kind of stupid not thinking of that myself. Would it be ok to run with the muffs on the engine or should I run it under a load? If it is truly a fuel issue, I don't think it would matter if there is a load present. If the issue does turn out to be dependent on a load, that opens up a whole other box of questions.

 

[hard-3]

Re: Engine Stalls when fuel is below 1/4 tank

run under load to test. if it is a vacuum issue it probably won't show up under no load condition. here is a fuel pump test proceedure from Summit racing

FUEL PUMP TESTING per ACTRON fuel pump tester
CAUTION: Use extreme care in disconnecting
fuel lines. Catch all gasoline in a container and
discard. Leaking gasoline is a serious fire
hazard.
Initial Inspection
Before testing, check tightness of all fittings and
connections.
Check the rubber fuel lines at the fuel pump for
deterioration, such as splitting, cracking and
spongyness.
If leaks are evident in lines or fittings, repair or
replace as necessary. If leakage is detected in the
pump at the diaphragm flange, in the sheet metal
cover, or in casting breather holes, replace the
fuel pump. Check fuel level and remove any kinks
in the fuel line. It is not necessary to remove the
fuel pump for any of these inspections.
Procedure
1. Disconnect the fuel line between the fuel pump
and the carburetor and attach the vacuum gauge
hose to the fuel line, using adaptors as necessary.
(See Figure 10).
NOTE: The fuel in the carburetor fuel bowl will be
sufficient to run the engine for these tests.
2. Operate the engine at idle. Hold gauge at
carburetor height and note the reading. Stop
engine and re-connect fuel line.
Test Results
Compare the observed reading with the
manufacturer?s specifications. If specifications are
not immediately available, fuel pump pressure
can be considered satisfactory if it is between 4
and 6 PSI, with lower readings for smaller displacement
engines. If pressure reading falls outside
this range, consult the manufacturer?s specifications
before replacing the fuel pump.

VOLUME TEST
1. Operate engine with fuel line connected to fill
carburetor fuel bowl. Stop Engine.
2. Disconnect the fuel line at the carburetor and
connect a flexible hose to the fuel line using the
adapter as shown in Figure 11. Insert the other
end of the hose in a proper gasoline container.
3. Have an assistant start the engine. While holding
the gasoline can, carefully collect the discharge
from the fuel pump for exactly 30
seconds. The assistant must count off the time
precisely and turn off the engine after the 30
seconds to get an accurate measurement. Reconnect
the fuel line to the carburetor.
4. Remove the gasoline from the engine area.
Pour the contents of the gasoline can into
another container marked off in fluid ounces
such as a kitchen measuring cup. Record the
fuel quantity.
5. After taking all measurements, return the fuel to
the vehicle?s gas tank.
Test Results
Consult the manufacturer?s specifications for required
fuel delivery rate. If specifications are not
readily available, use the following table as a guide.
Engine Displacement Ozs. Collected
(CID) (30 seconds)
Up to 225 8
225 to 350 11
Over 350 16
If the above conditions are not met, replace or repair the defective components