rebuild mech. fuel pump on mercruiser 470.. works?

[dccordell]

Hey guys, been looking around for a replacement mechanical fuel pump for my mcm 470. I've just about settled with the idea of buying a new one ($$!), but I would first like to consider the option of rebuilding the old pump. I found what appears to be the replacement diaphragm from the mercruiserparts.com website. Is the diaphragm pretty much the only part that wears out on these things, if the arm (that rides the cam) is still in good shape?

Not trying to take a short-cut here, but I wouldn't mind saving over a hundred bucks for the same thing in the end.

Here is the link to the parts catalog, it is down on the list between items 19 and 20, part number: 49089A1.

Any ideas? Is this a smart idea, or best to just go with a new one? And if a new one, anywhere else to look other than iboats and ebasicpower? Cheapest is around $145, new.

Thanks!

 

[ziggy]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

imho, if the mercruiser service manual says it's rebuildable and parts are available, go for it. i did on my rebuildable fuel pump. i just R&Red the diaphram.

ya don't say what year ya got. but if it's an older fuel pump. like on my '75, it may not be a marine fuel pump. won't have the 3rd line going back up to the carb. if it don't have that. then i'd think buy the new marine one.

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Oops, yeah forgot the year... It's either a 78 or 79, leaning toward the 79.

It actually does have the 3rd line to the carb, but when I hooked it up, even with the diaphragm wore out, it doesn't push any fuel up the clear line. This may be normal, I don't know for sure. It's my understanding that when the diaphragm is out there should be some fuel going up the tube?

The PO had capped off the mechanical fuel lines and put in an inline elec. pump from the auto store. Not safe... and it got super hot when powered on! So I'm trying to get it back to factory setup. Just wasn't sure if anybody ever actually rebuilt their mechanical pump... glad to know it's been done!

What is the best way to get the lines full of fuel after reinstalling the pump? Just crank the motor? I have no idea how fast the pump can move fuel so wondering if there is a quick way to fill up the bowl and lines before cranking.

Thanks for the quick reply... Glad I'm not the only one up browsing on a Saturday night! haha

 

[stonyloam]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Make sure to let us know how it works out.

 

[telstar1]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

An outboard type primer ball is a great way to prime things. All my boats and farm equip have one.

 

[telstar1]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

oops thats primer bulb

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Interesting idea.. I hadn't thought of that. Never seen one in an I/o setup but I guess I haven't seen that many! I suppose that would help with cranking after the boat has been parked for a while, not having to turn over so much before fuel gets to the carb, right?

 

[Bt Doctur]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

"it doesn't push any fuel up the clear line"

It`s not supposed to have any fuel in it. that line,if it shows liquid means the diaphram ruptured and it carries the fuel up to the carb and not in your bilge.

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Ok I wasn't sure If it was for just went it ruptures or when the diaphragm just doesn't work any more. I guess the rupture makes more sense! Thanks.. I'll prob order the part tomorrow and give it a try unless there are any other objections?

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Ok I wasn't sure If it was for just ...

Oops! Double post..:redface:

 

[honeys money]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

I think a priming pump bulb is illegal on an inboard, better check.

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

I think a priming pump bulb is illegal on an inboard, better check.

I'll definitely have to check that out first...

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Got the parts in today... looks like the rebuild kit comes with just about everything needed to repair the pump.

However, I was unable to figure out how to remove the rocker arm pin from the pump housing to pull out the rocker arm which must be removed to remove the diaphragm. The manual is pretty vague in explaining how to get it out. When I try to pry on the "retainer", it just falls apart as if it is some really soft metal, almost like plastic, but it doesn't come off and I can't see the pin.

I can't push it out from the other side because the pin doesn't go all the way through. I don't know how I'm supposed to do this. I'm sure there is a common way to do it if they sell the repair kit. Any ideas? I just don't want to mess it up.

First pic is the retainer side of the hinge pin. The second is the opposite side of the pump showing that the pin does not come through to this side.

-

 

[telstar1]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Re the primer bulb being possibly illegal for inboards Im wondering if someone can give the reference to the reg that says this. Recently I asked a local well respected marine surveyor abt this, as well as "see thru" water seps. His take was that if theyre not in the engine compartment theyre both ok. I know Im rigged that way, have passed numerous inspections and insurance surveys, would like to know where it says thats a no no. Thx

 

[daydreamer1252]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

I am embarrassed that I cannot clearly remember...the only excuse I have is that it was 6 months ago.......but I think if you turn the pump over and look in the between the two sides of the stamped rocker there is a keeper in the middle......don't remember if it was a snap ring or cotter pin or what.....I also seem to remember (ya I guess that I could call it a memory) that I drilled a small hole that a 1/8" pin punch would fit through on the side opposite the flared end of the pin you've been working on so it could be tapped out from there....then again that could have been another project....the boat is not available to me to check until spring.....a sad thing when memory starts to fade....

Good luck

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

You were pretty much right... there is the keeper "clip" on the center of the rocker hinge pin. Needle nose pliers pulled that right off.. then I had to figure out what was going on with the plug. I found a website that went in good detail on tearing apart the carter pumps (here), even though it's not the exact same pump, it is similar in the tear down procedures. Once I knew the cap would just pop out with a little persuasion, I just took a flat screwdriver and a small hammer and got under the lip and popped it out.

Once you take the spring out from the rocker, it's easy to grab the hinge pin with needle nose pliers and slide it out.

I was concerned because I didn't get the gasket that goes inside the pump assembly I my kit. All I got in the kit was the diaphragm and the gasket that goes on the filter and bowl. Not sure if it needed to be replaced because I didn't take it apart since I didn't have a new gasket. Other than that, it all went pretty easy. Trickiest part is getting the rocker spring back on. Roll it in with some needle nose pliers and then push it onto the retainer with a screwdriver worked.

However, I'm dissapointed because even after rebuilding the pump it doesn't seem to be pumping any fuel. I put it back together according to that website and to the vauge instructions in the merc manual. Since the motor is out of the boat, I just took a piece of fuel line and ran it from the pump IN side to a jug of gas, just to see if it would pump any fuel. After turning over the motor a good bit, I wasn't seeing any gas coming out, so I took the bowl off and no gas in there either, so as far as I could tell it wasn't pumping anything. Guess I'll pull it apart again tomorrow and see if I did something wrong.

I do know that when I had it all back together, when I would rock the rocker back and forth, it would push air out of the emergency outlet only (where the clear line goes). I thought this was unusual, seems like it would be pushing air out of the oulet side if anywhere, right? Any ideas what I may have done wrong?

 

[daydreamer1252]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

There are 2 check valves in this pump you can see them in the chamber formed by the two "halves" that the diphragm fits between. The round check valves are pressed into the housing halves. If these check valves are not working....allowing fluid to pass one way and not from the other....the pump will not work......that may be the issue and certainly worth checking...I have not found any replacements for these....luckily mine were in good condition.

Glad the other idea shed some direction on disassembly.....come to think of it (or now that you mention it) the rebuild kit I got was from Mercruiser and the "cap" was an included part and that was how I knew I could destroy the old one on disassembly....:redface:...memory I had one once.....sheesh....

Good luck

 

[dn010]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Make sure all the lines are tight otherwise you'll pull air instead of the fuel. Feel the part inside the engine through the hole where the pump mounts to make sure the pump lever is actually getting operated. DON'T do this with the engine running, of course! Lastly try priming it. I have a large bulb that you can purchase from a drug store - the ones they use for babies - deflate it, put the end inside the hose or metal pipe (the line between the carb and pump), let it inflate and after a few times you'll have fuel where you need it. then hook the line up to where you took it off from. Beats the heck out of trying to siphon and then brushing your teeth! Of course, this is because the engine is out of your boat, I wouldn't recommend such a task on the water...

 

[dccordell]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Yeah my kit had a cap in it too... when I noticed that, I figured I could get it out one way or the other, tore up or not. I did see the checkvalves... couldn't really tell much from just looking at them. I wonder if I could poke something down into them to see if they are opening. I'll have to check it out when I get the pump apart. Wish the kit came with new ones... seems like it should.

Good idea dn... I may try to do something like that with a fuel line primer bulb I have laying around here, just to see if it will help. Seems like the pump should prime itself after turning over the motor for a while. I did feel inside there on the cam where the lever rides... it didn't seem to be rough or pitted or out of the way. Guess the only way to check for sure would be to somehow put an indicator against it and turn the motor over to see how far it can push the lever as it turns.

Guess if all else fails, I'll be ordering a new pump. We shall see...

 

[stonyloam]

Re: rebuild mech. fuel pump on mercruiser 470.. works?

Guess if all else fails, I'll be ordering a new pump. We shall see...

Just a note of caution: A while back someone posted that they put a new replacement fuel pump on their 470 and it wound up ruining the pump cam lobe, apparently because the arm tension was too high with the new pump. I could not find the original post, but he said he was going with a marine electric pump. His was one of the newer style pumps, but since the older ones are no longer available, that is probably the one you would have to use. When the time comes I would probably replace mine with an electric pump like this: http://www.jegs.com/i/Carter/180/P4389/10002/-1?parentProductId=1145238 add a oil pressure cutout: http://www.holley.com/12-810.asp and add marine fuel filter. In the meantime good luck with yours. Love those 470s