jbraun2828

I just bought my fuel pumps a couple months ago and had 11psi at idle. So they are either left over from 2010 or they are still making them the same way. I put regulator's on and never thought anything about it.

bustag

I have an extremely stupid question and embarrassed to ask and I'm sure I'll get blasted for being a dumbass but here goes.

The brass looking vent tubes on the side of my mechanical fuel pumps are reasonably plugged with brown dry sludgy looking crap. Should these tubes be cleaned out?

Blast away. LOL

BUP

iTrader: (9)

Yes clean it out but IMO these pumps should be changed out every 5 to 10 max anyways. Today fuels are really bad and the internal side of these mech. fuel pumps form very heavy corrosion and or a form of aluminum oxcide. White or lite yellowish power.

I see this all the time and the worst are the 4 bangers - Mercs and Volvos get completely contaminated of the complete fuel system and carb. Why these apps more so than the rest - because these apps do not have water fuel separating filters installed like the V-6 and up apps. Water in the fuel really accelerates this problem by 10 times as fast.

Also will add - the problem pumps that Merc had would over stroke causing high fuel pressure, 11 to 15 psi and that is too much for carb apps. They flood / dump especially at idle. We at that time sent these pumps back but to only get another bad pump that did the samething. A thicker mounting gasket brought the psi back down to spec. We still have currently these apps running 100 % fine as we speak. just an FYI.

Griff

Yep, clean them out. It is the overflow tube in case the pump diaphragm ruptures.
The fuel will dump into the tube and up to the carb instead of dumping in the bilge.

bustag

Thanks guys thought they should be clear so I gently cleaned them out hoping I was right. Almost done with the engine room remodel Griff I think you will like it. repainted, wires hidden and loomed, new shiny diamond plate and mirrored stainless, Now if I can figure why the gen wont start I'll be really happy. Arrrrg! See you in June buddy.

mach12450

I know this thread is now well dated but I as well am having this same issue. Just put part number 862049a1 for my 502 magnum a week ago, installed it over the weekend and immediately flooding out carb at idle. Replaced needle and seat same issue, adjusted float level same issue. Checked fuel pressure and 11psi at idle. Called dealership that sold fuel pump and they have also instructed me to install the thicker gasket. After doing some research I have found that installing this gasket can create a tapping noise from the fuel pump rod slapping the pump arm. Can anyone confirm this? Most people that experienced this, called Mercruiser and they instructed them to install a Sierra pump. I called Sierra and they don't offer a fuel pump for this application. I really don't want to change this pump again as it was a huge pain in you know what, and I hate hack the stock tube up to install regulators but that might be what has to happen. Does anyone know of a good aftermarket pump that will work to replace this part number? I considered the holley marine pump but they are rated at almost 8 psi and from everything that I've read Quadrajets don't line over 6 psi at the needle and seat. Thanks for all the input if anyone is still following this.

RBOT

I too have this same issue. Just had my Q-jet rebuilt and installed the 862049A1 pump from my local merc dealer and surprise..it flooded the carb out. Does the 8M0058164 pump work for the 502's? Looking up the info on it and it states 5.0, 5.7L small blocks only.

mach12450

I have done some research and have not found any other pumps that will work for the 90-92 carbed 502 without the sea pump style fuel pump. I called Sierra and they said they don't offer a pump that will supply enough volume for the 502 at high rpm. Everyone else that has had this problem seems to have installed a regulator in line between pump and carb. I haven't had a chance to do anything yet, but later this week I'm going to install the thicker mercruiser gasket that they told me to install and will report. What really sucks is I rebuilt my Q jet and replaced the fuel pumpwith the same part number on my starboard engine 2 years ago and it was a flawless process.

RBOT

What gasket are they telling you to use? I would rather try the gasket than install a regulator at the moment.

mach12450

I'll get you the part number as soon as I pick it up. It's a mercruiser part number supposed to space the pump out from the block and cause the arm travel to shorten and lower the pump pressure. I'll let you know what the number is and how it works out this week.