Fuel starvation continues

[Lhaney1]

03 opti 225 sn ot701189

I been plagued with fuel starvation issues all season. Has led me to learn a lot and replace a lot of components in the fuel system. I previously found I had a broken reed on the #2 cylinder and seeing how the case pressure from that cyclinder helps drive the lifter fuel pump I thought I had the problem solved for sure.

Well the mech fuel pump(recently rebuilt) still won’t pull any vacuum. Actually if I pull the supply line off while the engine Is running a little fuel and air spritz out of the pump in port like it’s actually pressurizing the supply.. The gauge I used to test the system stays around zero even when the supply line is pinched inches before the pump and I run the motor up to 2000 rpm. I can never feel a vacuum on the inlet port.

The crankcase is pulsing strong so it’s not a reed. (Comp check is good) The pump is assembled correctly. I have cleaned the vst(and needle) and it all all seems fine.

Any ideas before i buy an entire new mechanical pump? I don’t see any housing cracks and the checkvlavess and diaphragm seem fine but something is not working correctly.

Btw. The issue is only at coming off idle after sitting. I can cruise all day long. If I shut it off for 20 minutes, idle for a min, and then try to hit it... there’s no fuel. Pump the ball tight , and off I go.

Any insight is greatly appreciated

[Sunny Jim]

The question will be asked- Are you 100% sure you rebuilt the pulse pump properly?

[Lhaney1]

99.999% :). To be honest I have rechecked it 3 times as it sure seems like the issue. It is put together correctly. If the checkvalves are cupped or not sealing for some reason i can’t tell. I took pics of the assembly process as I was discussing with others. Everyone agrees it looks to be correct when comparing to manual. The valves look fine and aren’t cupped and seal when I blow on it. Seems like it should be simple find , but I’m lost

[Sunny Jim]

Can you substitute a portable fuel tank for the onboard one, connect it directly to the fuel pump and run the motor? That would eliminate fuel line problems up to the pulse pump. Also, I don't see anything about inspecting/changing your fuel lines, primer bulb. Also, as I have done this, are you sure that the hoses connected to the pulse pump were put back onto the right ports? That's it for me. Wait for the big guys to comment. Good luck!

[EuropeanAM]

Be glad to look at those pictures if you like.

Double check the gasket behind the pump to make sure it is sealing the reference port properly.

Also- keep in mind that if the needle/seat are closed, you can't pull a vacuum on the inlet side. Pump must be able to move LIQUID from the inlet to the outlet side.

One other question- is this a BUILT-IN fuel tank, or a portable tank you are using? What type of lines/bulb do you have, and did you use (IMPORTANT) an OEM Mercury/Quicksilver Rebuild Kit in the pump (aftermarket may or may not function properly).

[Lhaney1]

I’ve done about every test on the fuel system. Aux tank included. The bulb is new oem. Lines are new. I have 2 built in tanks. But I don’t think thE issue is boat side. The rebuild kit was seirra 18-7817. A test I did today was to hook a vacuum gage up directly to the pulse pump. I know the vst was empty as the motor was starting to stall and I shut it off. With a vac gage hooked up I cranked the engine and the needle didn’t even register. I’ll try to upload some pics for all to see but pretty sure the assembly is correct. Maybe someone can notice if the valves are looking faulty. I tried to make the bay needle get stuck when I had the vst apart and couldn’t. Also seems weird that it happens after running fine and then sitting a short period of time without pumping the ball( needle wouldn’t be engaged) Has anyone ever had a fitting be cracked on the pump? That’s the only thing I can think of st this point.

[Lhaney1]

https://m.imgur.com/a/2DE9ruf

pics here if this works. Kinda new at the imgur thing

[Lhaney1]

Don, your comment about not using aftermarket kits got me thinking. So I bought the seirra one cause it was available amazon prime and was trying to address the issue quickly back in April haha. Anyway I went back and looked if anyone reviewed and had issues with the seirra kit. A couple did...not out of the ordinary but something I noticed was a review about the kit missing a rubber gasket for the one of the check valves. The complete kit came with the center pins, 2 plastic discs and 2 rubber discs(and diaphragms/gaskets). The pump I took apart and all the instructions I found online just has the plastic discs so I assumed the rubber ones were for a different assembly....there were a few other parts and a gasket that were obviously for a different pump that uses the same rebuild kit. Do you know what I am talking about? Are the rubber “gaskets” required for the check valve function when using this kit?

[Savage]

Get the Genuine Mercury Marine kit.

[SilverFox579]

Get the Genuine Mercury Marine kit.

^^^^

I ordered a water pump kit for my 2.5L Optimax from European Marine 6:51am Aug 13th and it was in my mail box 3pm Aug 15th, via USPS no less, AND from South Carolina to Washington state. I can't get shipping response like that from west coast companies nor the other side of WA. Why I always buy my parts from the fine folks at European Marine.

[Lhaney1]

^^^^

I ordered a water pump kit for my 2.5L Optimax from European Marine 6:51am Aug 13th and it was in my mail box 3pm Aug 15th, via USPS no less, AND from South Carolina to Washington state. I can't get shipping response like that from west coast companies nor the other side of WA. Why I always buy my parts from the fine folks at European Marine.

thanks. I’ll sign up and start using them. I’ve only posted a couple times on this sight and both times have received a helpful comment from them. Good enough reason right there....and ThAt is some some fast shipping!!! Hopefully it solves my issue finally. I’ll report back if it does but it sure seems likely at this point. I believe I basically created a problem with the pump rebuild before I discovered it was a broken reed and then once the reeds were fixed the faulty pump repair is still lingering.

[Lhaney1]

Put in the original OEM check valves and all is running perfectly. Pulling 4” vacuum.. Have a oem kit as a spare in route but couldn’t wait. So the aftermarket non oem valve either has a different design requiring use of the rubber check valves or it was just faulty all together.

[EuropeanAM]

We don't use "rubber" in the check valves anymore (those went away a LONG time ago).