Carver 400 MY engine RPM issue

[mjk1040]

Cpoint; Is it possible there may be a screen at the fuel pump intake that could contain particles or the fuel cooler? It appears you are progressing since you are up to 3,000 rpms! I too could not find any other filter in line after the spin on water separator/filter for 7.4l Mercruisers. Is your pick up in the tank screened? If you cut the old filter apart and not finding particles. I would lean toward possible bad fuel line somewhere restricting max fuel flow when needed. APITA, but may have to dismantle entire fuel system from tank to fuel rack looking for an issue. I feel for u!

[hausherrs]

Ive got a question, now that I think about it. If I turn the key on does the fuel pump stay on? Or does it just prime until the engine starts? I need to drain the stbd tank and was thinking maybe I can disconnect the hose at the oberg and run it into a tank.

This engine still running bad. It will only contribute at idle. Try to throttle up and it just falls on its face. I think my pickup is clogged. I can see junk in the bottom of the tank.

[waybomb]

How was the anti-siphon valve?
Also, I did not think pick-up socks were still being used. If you see the bottom of the tank, do you see a sock on the dip-tube end?

[km1125]

Source of the post Ive got a question, now that I think about it. If I turn the key on does the fuel pump stay on? Or does it just prime until the engine starts?

It will only prime the system and then shut off if the engine is not running

[mjk1040]

I do not know 4 certain, but would believe after looking at the parts listing for the fuel system it would continue pumping unless it had a pressure switch within the fuel system. I saw none unless it's controlled by the onboard computer in the newer models. Then again it could be internally controlled in the electric fuel pump? Similar to your fresh water pump! But if you are still having fuel issues I'm afraid you are going to have to trace out the entire fuel system looking for an issue. Could all the crap you have discovered so far gotten into the fuel pump or fuel regulator and be causing your rpm issues? I'm hoping you find it soon.

[Viper]

Hausherrs, did you manage to find the problem yet?

[km1125]

Source of the post I do not know 4 certain, but would believe after looking at the parts listing for the fuel system it would continue pumping unless it had a pressure switch within the fuel system.

I believe it's an ABYC requirement to cut power to the pump unless the engine is running. It will allow for a prime, but then shutdown if the engine is not running. Carb units did this with an oil pressure switch but EFI units usually have the computer control it.

[Viper]

Source of the post

Source of the post I do not know 4 certain, but would believe after looking at the parts listing for the fuel system it would continue pumping unless it had a pressure switch within the fuel system.

... Carb units did this with an oil pressure switch but EFI units usually have the computer control it.

Computer controlled based on input from oil pressure sensor.

[hausherrs]

Source of the post How was the anti-siphon valve?

I didnt get to check it this weekend because of new development. See below. Also, I cant see that far down with my bore scope. Its not the highest quality unit.

Source of the post Hausherrs, did you manage to find the problem yet?

Not sure. I found a problem though. Parts ordered.

This weekend I took the family to the boat and before we headed out I wanted to clean the oberd and replace the recor. So I did. The oberg didnt have much of anything in there. The recor was nasty. I replaced it and put everything back together. I turned the fuel back on the fuel started gushing from the area of the oberg. I shut the fuel off and sopped up the half gallon of fuel from the bilge and tracked the source.

The hose was cracked right at the crimp fitting where it attaches to the oberg. I think maybe this has been cracked for a while because I didnt put much of any stress on the line, At least not enough to crack it like that.

I am starting to think that theres been somewhat of a hole there for a while. And im starting to think that with the fuel pump running its sucking air into the line causing the engine to run bad. I dont have any pictures but theres always been a strange brown spot under that oberg like it was leaking for years. But I have never found it to be wet. So I figured it was something that the previous owner found and repaired.

Anyway, I ordered two new hoses. One for each engine. This hose was gray. And it seems soft. Unlike the dirty side of the oberg that feels rigid like a wire reinforced fuel line. I bet someone had that hose repaired and they used some cheap fuel line. The replacement factory hose was only about $45 shipped.

Im going to remove the fuel pump today and get that hose out. I want to inspect the condition of the fuel pump to determine if I should replace it. Its not going to be easy getting it out so I would rather put a new one in while this one is out.

From what I can tell ill have to remove part of the septic plumbing to make room for me. And ill have to remove the lower pump and drive belt that is blocking me from getting to the fuel pump mounting plate.

Wish me luck! Or give me pointers

Thanks,

Steven

[cpoint]

Steven I think I can understand you more than anyone Been dealing with fuel issues for second year now myself Had the engine worked on, practically paid for a new engine. And fuel tank issues with crap in it, that seems to still be there...