Installed new fuel pump--now gas flows out of overflow at shutdown.

[cheburashka]

1974 Glassply, 140 Mercruiser.

I decided to install a marine fuel pump, even though the boat originally had a pump that drained into the bilge. The new pump is a Carter M60601. I can't find any information on it through Google, but the parts store I go to had it in a catalog, listed as the proper fuel pump for my engine and it does have the overflow tube.

After installation and priming, I got the engine running but it shut down very quickly. I went back to the engine bay and found a lot of fuel had shot out of the overflow and onto the valve cover. Fuel also appeared to be draining out of the main jets. I put on a known good carb with a new needle and seat and good float height, and the same thing happened. There are two conditions that create the overflow. One is shutting down the starter after prolonged cranking, and the other is when the engine has been idling, but begins to run rough. I'm not sure if it's the rough running that's causing the overflow, or vice versa

Is it possible that this fuel pump is putting out too much pressure for the needle/seat on the Rochester carb?

Is it possible that this

 

[Fishermark]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

found a lot of fuel had shot out of the overflow and onto the valve cover.

Fuel shot out of what overflow? The clear line from your new fuel pump? If so, then your pump is bad. Also, if so, that line goes to your carb - not your valve cover.

If you're talking about a different overflow... then I'm not sure which you're referring to.

 

[cheburashka]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

Sorry about that. The fuel bowl overflow--a brass tube with an angled cut on it that sticks out above the choke butterfly.

 

[Fishermark]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

Might be time for a fuel pressure check. You say the carb is a "known good one" - it certainly sounds like a stuck needle valve to me. Maybe some dirt got in when you changed the carbs. Hows the filters look?

 

[chiefalen]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

If i remember right you should have between 4-6 pounds for the fuel pump.The new one giving you more?

 

[cheburashka]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

The highest fuel pressure I get with this pump is 4psi. It holds pressure with the engine off, which leads me to believe that the float valve is doing its job. If there were a leak, wouldn't that let the pressure out of the line?

I've inspected the float valves on both carbs, and they seem to be in very good shape, and clean.

I'm not sure how the overflow works on these Rochester carbs. If the tube above the choke butterfly is an overflow, where is the inlet? Does it only feed from the top of the float bowl, or is there another part that might feed into it?

 

[Don S]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

If the fuel is coming out of the overflow from the fuel bowl, and you only have 4 psi on the pump, then you have carb problems. Either the float doesn't, or there is dirt in the needle and seat, whatever it is, something in the carb is causing the problem. Not 4 psi of pressure from the pump.

 

[cheburashka]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

I checked it with the fuel line disconnected and it runs like a champ. Once the fuel line is re-connected, it overflows again.

Both of these carbs were rebuilt last season. The fuel pumps, power valves and other parts are all fine, but both carbs appear to need new needles and seats. Is it the ethanol in the gas that's doing this? If I wipe the rubber tip of the needle on a clean white cloth, I get black residue and that doesn't seem right.

Is it possible to get just the needle and seat, rather than the full carb rebuild kit? Are there aftermarket needles and seats for the Rochester carbs that are a bit more reliable? I remember buying ball-bearing-style inlet valves for the SU carbs on my MGB, and they took care of some pretty serious sticking problems.

 

[chiefalen]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

I'm going to ask what may seem like a question from left field, The floats holding air? Had that problem in older cars the floats rust out, have fuel in them instead of air.

All it takes is one little pin hole in the float. Thats a twin carb setup? Not to many of them around.

Might be the only solution is to go with a new manifold with a new single carb setup. E-bay has one i think not to expensive used setup with the carb on it already.

Just a suggestion I hate to spend money also but might be the only way.

good luck let us know how you made out.

 

[tommays]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

i will go out on a limb and say check the fuel pressure as we are assumeing the new pump is good , i am sure a few bad ones have sliped out

 

[cheburashka]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

It's a single carb setup--regular Rochester two barrel. By "both carbs" I meant the one on the boat and the spare. The floats are good.

I checked the fuel pressure, but the kit I have is set up for fuel injection as well as carbs, so it may not be particularly accurate in the lower ranges.

I have an inline fuel pressure regulator. I'll put it into the system and see if lower pressure does the trick.

Still looking for a source for just the needle and seat. Anyone successful at finding these items by themselves?

 

[thumpar]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

If it didn't happen with the original fuel pump I would look there first.

 

[chiefalen]

Re: Installed new fuel pump--now gas flows out of overflow at shutdown.

The original pump on the boat when you got it was not the original pump that came from merc.

Someone put a auto pump on there. Damn unsafe I say. Sooner or later we would have heard about the explosion on the news.

How did you measure the new pump pressure?

That overflow hose clear, or full of gunk. The one from the carb to the pump.

When you rebuilt the carb. did you soak it good in cleaner overnight?

Than blow it dry with compressed air.

35 year old boat hmmm some carbs. just can't be rebuilt.