Trojan Boat Forum

Hi, I have 1985 454's. 350 HP. One of my engines began stalling and had difficulty starting last fall. I'm now trying to get the issue resolved. Basically, the engine will start and run roughly. I believe it is fuel starvation. If I try to throttle, it may rev up but often times it just stalls. I can hear a lot of air hissing through the carb air intake ports. Is that normal if it is fuel starved? Steps I have taken. 1
1. Changed Spin on fuel water separator.
2. Sight tube on fuel pump is empty.
3. Pulled the inlet to the carb and turned the engine over. Had good fuel flow – I do not think it is the pump
4. Pulled the carb filter – It was nasty. Changed it out still have the problem.
5. Pulled the carb filter again. Seems to have more crud.
Bottom line I think I have some crud in the fuel that is clogging carb filter. Not sure if that is the only problem though. When I try to throttle up, I get louder hissing through the carb. Any ideas anything else to check?

Updated
Compression Check:
1: 142
3: 130
5: 130
7: 135
2: 130
4: 127
6: 122
8: 135

A little gap between high and low but right and no stuck valves. About 980 hours on the engine.

I switched carbs but it was too late to run. I will try in the morning. Other fuel filter looks pristine after 1 year so I really think it may be the gas in the starboard tank.


Port engine is running fine but does have a separate fuel tank and no crossover

If it will run up on starting fluid or gasoline poured directly in the carb throat its a fuel issue.... if not its likley a spark issue. The carb swap should tell you more as long as you are geting proper fuel pressure to it. A homemade fuel pressure gauge can verify equal fuel pressure on the good engine and this one too.

Fought a similar problem on my 454 (Chaparral) - ended up being too much fuel pressure from the fuel pump where the pressure regulator had been ruined by E-Gas. I swapped carbs, etc. just like you and finally found too much pressure was overcoming the floats. Can only have about 5-PSI (7-PSI max I believe).

Can you hook up a small portable tank with a squeeze bulb and take the existing fuel and fuel pump out of the equation?

+1
Hook up portable fuel tank and primer ball to isolate the ship's fuel system and fuel pump.

I have had this similar problem on rochester carbs. it could be the power valve sticking. try starting the engine , it if is running really rough, lightly tap on top of the carb over the inlet / bowl with a screw driver handle or other hard plastic tool and see if the idle smooths out. if so, get a rebuild kit and do a minor rebuild.

Update:

I changed the spin on filter and I switched the carbs. The engine ran for a few seconds and then started doing the same thing. I can keep in running if I pump the gas on and off. I think it's the accelerator pump on the carb jetting extra fuel. I sprayed carb cleaner around the intake manifold without much effect, a shot in the throat of the carb and it picks right up. The carb inlet filter was gumming up again. The carb filter cleaned right up with some carb cleaner and air. The crud seems a little jelly like and I think it is just gumming up the carb filter, causing starvation.

I've started changing the risers and elbows because they are due so I won't be able to test again for a little bit. Is there any way to clean the fuel in the fuel tank? I probably have about 30-40 gallons in a 125 gallon tank.

How would I go about setting up on a portable tank?

Scott,

I went through a similar issue a couple of years ago. Try using your crossover valve and see if running off the other tank eliminates the issue. The anti-siphon valve is a prime suspect.

The valve is what the copper lines threads into at the tank. It doesn't "look" like anything but a fitting until you remove it. Mine was clogged up and limited me to about 1,500 rpm's.

Bob

bob I think he said there is no crossover valve.

Bob,

No crossover connection. If I had them before they have long since been removed. I will try to get to the tank connection and pull it off. Did you climb back on top of the muffler to get to it? Looks a little tight

Scott, no factory x-over valve under the cockpit floor? Mine is roughly centered just behind the battery cover. Ok, I'm sure you would have seen it by now.

The anti-siphon valve is more forward of the gas tanks. If you put one foot between the engine and bulkhead you can reach it or slide the engine hatch back a couple of feet and you can reach it by laying on the deck.

Do you still have the factory copper fuel line running from the top of the tank? The tank end is the valve and the other end goes to the crossover valve. Even if you have new lines or a slightly different configuration, they couldn't easily change the output on the tank. That's what you're looking for.

Bob

I had a friend that was having a similar issue and had gone through a couple of mechanics before he asked me to take a look.
I hope this pic turns out as I took it with my phone, but here is what I found.


Yes, those are legs sticking out of the end of the anti siphon valve.
That is exactly how it looked when I unscrewed it from the tank.

Nice. Dead Critter

Thanks Bob, I actually have Hoses with threaded fittings running from the fuel tank to a spin on filter bracket mounted on the stringer. From there it is hard fuel line to the suction of the Pump (Bypasses old canister filter. and hard fuel line to the carb. (That's from memory, there may be a section of hose between the spin on filter and the pump)

On top of the tank are some fittings, a valve and then the hose starts. I have a separate pickup from the same tank for the generator. I have a similar arrangemnt from the port tank and I've traced the lines and the tanks do not x-conn.

When I bouht the boat the setup was the same but i had the fuel lines replaced as part of the acceptance survey as the old rubber was going bad.
I'll try to get some pictures

what about a loose connection or a friction/rubbing pinhole between the tank and the suction side of the fuel pump.

If it was high in the system it may not leak but could be a source of air on the vacuum side.

.............................shot in the dark ?


RWS

I pumped 20 gallons of gas out of the tank. I now have a rig to connect to a portable tank. I am trying to get a test run in this week on the portable tank but have to finish some other work as well. I'm not really sure hwo much gas I have remaining in the tank. i suspect that I had more than I thought as the fuel gauge is still reading at or above a 1/4 I can't really trust the gauge though.

I tried to pull the anti-siphon valve. I just don't have good access to the top of the tank I was able to get the fuel line off but the shutoff valae and anti-siphon valve wouldn't budge with the limited wrench room I had. I didn't want to break anything. I did put carb cleaner right at the anti-siphon valve and soaked it good. Hopefully that will free up any deposits that may be there.

Time has been really short to work on this but I appreciate the continued feedback. I will report back on any progress.