Tweet
My 1996 PCM GT40 Pro Boss 5.7L EFI engine has only 290 hours and starts with first key turn always. This weekend it ran great. I tied up for about three hours, when I started it up to head to the ramp, out of the blue the engine is basically not operable. The idle is very erratic, and when throttled up, there is a delay in revving up, it starts to rev, then threatens to quit unless I throttle back; I have to throttle up and down to get the revs up at all, but they don't stay. Shakes the whole engine when in gear. There is also an erratic, knock every few seconds, sounds like the port valve cover area, but I can't feel anything if I put my hand on it. I'm pretty sure it's a knock and not a backfire. I ran it in the driveway last night without the flame arrestor and it def seemed to be a knock from inside the engine. If I try to work it up to higher revs, it stalls out, and also when I return back to idle it'll stall, unless I give it little pokes above idle speed. And it knocks like I said. Kind of a metallic knock, like something hitting the valve cover (not saying that's what it is, that's just what it sounds like. Sort of a hollow sound if that makes any sense)
I replaced the plugs and drained/replace the fuel, removed and cleaned the flame arrestor (though I lost that when I set it on my car bumper then ran an errand…trying to source a replacement.) I also drained the fuel cell, and removed it. The filter didn't stay on the high pressure pump, it was stuck pretty good in the bottom of the fuel cell. There also was some corrosion around the bottom of the high pressure pump, I'm guessing from water settling in there when the boat is idle all winter, but the bottom/inside looked clean. Thinking that maybe the filter was really clogged and causing my problem, I replaced the fuel cell without the filter and tried running the engine briefly...problem didn't improve any.
So...that's about as far as I can go, unless anyone can give me some ideas based on my vague description:
1. Not a gradual decline...it was running great, then on start up three hours later, was a dog, just like that.
2. Idle is erratic
3. Quickly throttling up stalls it out
4. A knocking sound in the engine.
4. Working the throttle up from idle back and forth can increase the revs, but it's not smooth at all, and won't maintain high revs.
5. When I was returning to the dock on Sunday, working in and out of idle speed to keep moving slowly, when engaged with the prop the engine shook quite a bit as well. Not as much when in the driveway in neutral, but still a shaky.
I have ordered new ECC and Fuel relays; new spark plug wires; an FCC filter and O-ring, and the FCC high pressure fuel pump hose that I've heard can get cracks in it. Even if not the problem, all those items won't hurt to be replaced on a 15 year old engine.
I have also been advised to test the high pressure fuel pump, which I'll do next. If that's the problem, could that lack of fuel cause the knocking sound?
Thanks a ton in advance for any help you can give.
I replaced the plugs and drained/replace the fuel, removed and cleaned the flame arrestor (though I lost that when I set it on my car bumper then ran an errand…trying to source a replacement.) I also drained the fuel cell, and removed it. The filter didn't stay on the high pressure pump, it was stuck pretty good in the bottom of the fuel cell. There also was some corrosion around the bottom of the high pressure pump, I'm guessing from water settling in there when the boat is idle all winter, but the bottom/inside looked clean. Thinking that maybe the filter was really clogged and causing my problem, I replaced the fuel cell without the filter and tried running the engine briefly...problem didn't improve any.
So...that's about as far as I can go, unless anyone can give me some ideas based on my vague description:
1. Not a gradual decline...it was running great, then on start up three hours later, was a dog, just like that.
2. Idle is erratic
3. Quickly throttling up stalls it out
4. A knocking sound in the engine.
4. Working the throttle up from idle back and forth can increase the revs, but it's not smooth at all, and won't maintain high revs.
5. When I was returning to the dock on Sunday, working in and out of idle speed to keep moving slowly, when engaged with the prop the engine shook quite a bit as well. Not as much when in the driveway in neutral, but still a shaky.
I have ordered new ECC and Fuel relays; new spark plug wires; an FCC filter and O-ring, and the FCC high pressure fuel pump hose that I've heard can get cracks in it. Even if not the problem, all those items won't hurt to be replaced on a 15 year old engine.
I have also been advised to test the high pressure fuel pump, which I'll do next. If that's the problem, could that lack of fuel cause the knocking sound?
Thanks a ton in advance for any help you can give.
Comment