5.0L Mercruiser Alpha Gen II: no gas to carb

[Txbassman83]

Please understand I am not a mechanic and may seem like a novice.

I am not sure what year the motor actually is but the serial# is Serail# M031816.
The boat is a 2001 Glastron ski/fish with a Mercuiser 5.0L Alpha Gen II.
It has been sitting for 2 years in storage and I have having issues getting it to start. In the past even with it sitting for few months up to a year, it would always start after 3 or 4 attempts and would run smoothly. I use Sta-bil fuel stabilizer with every fill-up.

I removed the top of the air intake and it is not getting any gas pushed to the carb and there is no smell of gas. I can spray starting fluid in the air intake and it will fire immediately. When I turn the key (alarm sounds but not trying to start it), I don’t hear the fuel pump run but I cannot remember if it is suppose to “come on” at that point or only when attempting to start the engine.

I did changed the Fuel/Water separator filter which was full of fuel when I removed it. I filled the new one with gas when I installed it. The engine still did not fire and still no gas to the carb. I unplugged the fuel pump and jumped it directly to the battery and the pump runs but no gas to the carb. I did check the voltage at the fuel pump wire harness and there is no voltage when the key is simply turned on. When trying to start the engine, the voltage fluctuates between 10.78 to 11.23 or so. I started looking at the starter and its solenoid and the connections looked rusted and I thought the 90 amp fuse may be bad due to the rust. I cleaned each connection and the fuse. The fuse had continuity so I reinstalled it but still not gas to the carb when trying to start it.

I assume that my fuel pump is bad (run but not pump) or the metal fuel line from the pump to the carb is clogged or the carb has issues. Note that I have never overhauled a carb and don’t really know what I would be getting into.

Questions:

1. Using the serial# M031816, can someone lookup and confirm my engine year, model and such?
2. Should the fuel pump run when simply turning the key on (alarm sounding)?
3. Is 10.78 – 11.23 voltage proper for operating the fuel pump?
4. Does anyone have any suggestions what to do next?

Thanks a bunch.

 

[alldodge]

Howdy
Thanks for the SN, and your motor is probably an 2000 or 01, just depends on when the manufacture bought the motor. In any case all good and you model was made from 1998 to 2001

Take the line off the carb and place it in a container. Then crank the motor to see if you get gas to come out

If you see gas come out, then remove the large nut where the fuel line was connected and check the strainer filter inside it (item 4)

https://www.mercruiserparts.com/bam/subassembly/31837/2697/90

The pump will only run when cranking or after the motor starts and oil pressure builds. It sounds like it working correctly, just need to figure out why no gas in the carb

Here is your motor
https://www.mercruiserparts.com/5-0l-2-bbl-gm-305-v-8-1998-2001-0l0

 

[Scott Danforth]

Please understand I am not a mechanic and may seem like a novice.


It has been sitting for 2 years in storage and I have having issues getting it to start. In the past even with it sitting for few months up to a year, it would always start after 3 or 4 attempts and would run smoothly. I use Sta-bil fuel stabilizer with every fill-up.

after 2 years not even Sta-bil will keep your fuel being fuel.

what is in the tank is no longer fuel. most likely you need to clean out the system starting at the gas filler and work your way to the carb.

in addition to checking the pump to see if its working like AD mentioned, your pump could be gummed up.

most likely the anti-siphon valve is stuck from your fuel turning to varnish

the carb needle and seat could be stuck

make sure your battery is fully charged

 

[Txbassman83]

alldodge: Thanks for the info about my engine. A couple of weeks ago when I was trying to determine the gas issue I was going to do exactly what you said but I could not get the nut to budge. It looked like and felt like I was going to ruin something. That gas line is a metal line so I can't point it anywhere even if I do get it disconnected. Also isn't that the high pressure side of the pump so the gas will have some force behind it.

Do you think the voltage at the fuel pump is adequate at 10.78 and 11.23 volts?

 

[Txbassman83]

Scott: That is what I am afraid of is that I varnish as fuel now. You mentioned that the pump's anti-siphon valve could be stuck. Do you know of a way to clean it out and possibly freeing the valve? What about pouring something inside it to melt the "varnish"?

I would like to know what I actually have in the tank but I don't know if that is feasible.

 

[Bondo]

You mentioned that the pump's anti-siphon valve could be stuck. Do you know of a way to clean it out and possibly freeing the valve?

Ayuh,..... Welcome Aboard,....... The anti-siphon valve is the tank's outlet hose barb, not in the fuel pump,.....

 

[Txbassman83]

Bondo: Thanks for the education.

 

[alldodge]

alldodge: Thanks for the info about my engine. A couple of weeks ago when I was trying to determine the gas issue I was going to do exactly what you said but I could not get the nut to budge. It looked like and felt like I was going to ruin something. That gas line is a metal line so I can't point it anywhere even if I do get it disconnected. Also isn't that the high pressure side of the pump so the gas will have some force behind it.

Do you think the voltage at the fuel pump is adequate at 10.78 and 11.23 volts?

Get the line off and place any flexible line over it so the gas goes where you want it to go

 

[Txbassman83]

alldodge: I am back in town so I'm looking at the boat tomorrow or rather today. You said that the fuel pump only runs when cranking but I was speaking with my son and wife and they both said they remember hearing a hum when the key was turned on. I assumed that was the fuel pump. We don't hear any hum when the key is on now. If that wasn't the fuel pump then what would that have been?

 

[alldodge]

Don't know what your hearing when the key is turned ON but it shouldn't be the fuel pump, its not wired to run that way. Maybe the blower or other accessory

The key turns ON by the key and the purple wire goes hot. The oil pressure switch is open and no power goes to the pump. Key is turned to start and power comes from the Purple/Yellow on starter post D, Post D is hot only while starter is cranking. Once motor starts running oil pressure builds and oil pressure switch closes which turns pump back ON thru the purple wire.

 

[Txbassman83]

Woke up this morning and realized it’s the blower to clear the fumes. Not sure if I heard that three weeks ago when I was looking at it.

 

[Jcris]

Hey txbassman,
sounds like you’re getting good advice. You should probably take the fuel hose off at the tank and make sure the check valve is not stuck closed. You may need to soak that carb inlet fitting with some “ PB blaster” or similar to get it to loose. Don’t damage that fitting or the threads on the carburetor. There’s a filter in there that could be part of the problem. Test that pump first, once you get flow from the pump then you can focus on the carburetor. If the pump checks out I would pull the carburetor and inspect it. Which will mean breaking it down enough to see what’s going on. Carburetors can be intimidating but once you’ve had them apart a few times you will see they can be fairly straight forward. This is an experienced group that has been through it all. Good luck

 

[Jcris]

Also,
10.78 volts seems low but I think it’s fine for the pump. You should also load check the starting battery. Pull it if need be and have it checked at your local parts house

 

[Txbassman83]

The fuel line connection to the carburetor would not budge. The corners were starting to round on the connection. I’m running out of time so I guess I have to take the thing in to get an estimate on whatever’s going on with it. Thanks for the help guys. I’ll post back when I get some information. May even be asking for donations. Ha ha.

 

[alldodge]

Try to take off the pump side of the line, might be easier
I've gotten some off that were rounded by using a pair of vise grips

You do need line wrenches to work on them
https://www.amazon.com/line-wrench-set/s?k=line+wrench+set

 

[Txbassman83]

I finally am able to get back to working with my boat to get it operational again. I pulled off two of the large water hoses in the front of the engine and there was rust looking sediment in both of them. Since it’s been sitting for couple years I’m assuming there’s rust buildup in the water cooling system. I’m not sure how that will affect the Engine cooling but wanted to ask you guys what steps that you would recommend for the situation. Example: change out water pump. Thanks so much.

 

[alldodge]

If its just surface rust then there should be no issue, try to run and see if things leak

 

[Txbassman83]

I was watching a video about removing the manifold and riser on each side and checking them for rust issues and such. Didn’t know if that Is something that is a routinely done or not.

 

[Bondo]

I was watching a video about removing the manifold and riser on each side and checking them for rust issues and such. Didn’t know if that Is something that is a routinely done or not.

Ayuh,.. 'bout every 5 years on boats runnin' in saltwater, with raw water coolin',.....

No reason to in freshwater,.....

 

[Txbassman83]

I am in the process of changing out my impeller. When cleaning up the corrosion under the bottom gasket, the paint chipped completely off so that the raw metal is exposed. Should I clean that up as best I can and repaint that with oil base paint? Or do you think I should just put it back together as is? Appreciate your thoughts.