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270 stalling at times

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Hypocolemicshock

New member
Have this recurrent issue with my 1990 Crusader 270 with quadrajet carb and 1500 hours. It’s happened yearly the past 3 years and I’ve felt I fixed the issue then the next year at some point in the season it returns. Just trying to think of things I need to check while it’s on dry dock waiting for season in April. When running at 3200 rpm after about 45 seconds it will drop rpm to 2800 then 2600 and eventually stall if I don’t back off the throttle. I can run it at 22-2400 rpm after this occurs with no problems but as soon as I go back to 3200 rpm it will do it after about 45 seconds. When it does stall it fires right back up. No problems with my other engine and both utilize the same tank. First year it did it I changed the ignition module, seemed to fix it for about a year then it recurred. Changed plugs and put a new fuel pump in and problem seemed fix until the end of this last season. Changed fuel line and removed floscan from that fuel line as it is the only difference between the engines I can think of. Of course after doing that it ran the 8 miles to storage perfectly. My thoughts are that my “fixes” were just coincidental as they are different items but then the problem recurring almost a year later. Any thoughts on what else this could be?
 
I had a similar problem.....it was my ant-siphon valve located at the connection at the fuel tank. At high RPM the engine would eventually quit and after sitting a bit it would restart when the pressure was off the ant-sipon valve.
I went through changing parts on the engine and "thought" many times it was fixed but the problem kept coming back at varying times during cruise.
If one engine runs fine and the fuel is all from one tank then the question I have is....does your system have TWO anti-siphon valves .....one for each line going to each engine ?? My engines are the same as yours but I do have two tanks and each has a anti-siphon valve for each fuel line to each engine.
 
willow said:
I had a similar problem.....it was my ant-siphon valve located at the connection at the fuel tank. At high RPM the engine would eventually quit and after sitting a bit it would restart when the pressure was off the ant-sipon valve.
I went through changing parts on the engine and "thought" many times it was fixed but the problem kept coming back at varying times during cruise.
If one engine runs fine and the fuel is all from one tank then the question I have is....does your system have TWO anti-siphon valves .....one for each line going to each engine ?? My engines are the same as yours but I do have two tanks and each has a anti-siphon valve for each fuel line to each engine.
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That was one of the things I checked but when I removed what I thought was the anti siphon valve there were no internals to cause obstruction.
 
So you only have one valve.......not two outlets from the tank, one for each engine. ??

In my boat the anti-siphon valves are connected to the head of the two fuel tank outlets and then the barb was pushed into the fuel line hose and clamped.

Mine were just the the simple valve with a ball bearing and with a spring in in front of it so the fuel pump suction had to pull the check ball off its seat by overcoming the spring pressure...mine had gunk on the spring and the spring would not fully collapse and the engine starved for fuel and eventually quit. I'm guessing that the gung dried a bit, the spring opened a bit and the engine would start again, run for awhile and then the spring became stuck again and the engine stopped....again..

I was into close to $1000.00 in changing parts when I finally checked the anti siphon valve and for less than $4.50 the problem was solved...Actually $9.00 as I changed both to be on the safe side.:D
 
Had some people think it was the anti siphon valve given it will run for almost exactly 45 seconds perfectly before acting up. Once it starts I need to drop rpms to 22-2400 and will run fine. Took my back deck off to check the anti siphon out. Took off the barbed connector and wasn’t an anti siphon. Each engine has a separate pickup hose about 8” apart. I didn’t check the one for the other engine since it was running good. Seems to start acting up when I’m in good chop but once it starts it doesn’t matter if it’s flat out or not. Probably put on 300 miles or more between the times it starts acting up each year.
 
I'd suggest you really troubleshoot the problem to finds its cause vs guessing what to change next.
That said, it sounds like its more of a fuel delivery issue than spark...and could be the problem engine is fed from the tank with the longer pickup and the crud that has accumulated in the tank is collecting on the screen at the bottom of that pickup tube.
 
If you have to call the mechanic, let's hope they have the background for thi type of issue...they can be real bears to find due to the intermittent nature...
 
makomark said:
If you have to call the mechanic, let's hope they have the background for thi type of issue...they can be real bears to find due to the intermittent nature...
Click to expand...
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that’s been the annoying part with this issue. I’m unsure if I actually fixed it or if just given the duration of time it took me to fix it was what actually allowed the issue to resolve.
 
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