Gas in crankcase

[bankermike]

Put a new (rebuilt) 4bbl quadrajet on my 5.7 litre mercruiser alpha one. The only way I could get the engine to run higher than an idle was to manually hold the choke closed with my hand and then the engine would run at higher rpms. I guessed that it needed a new pump. They did'nt have the exact fuel pump at O'Reilly's but sold me one which they assured me would work. Installed the fuel pump and low & behold the engine would run at higher rpms but I could'nt get it (the carb) adjusted to idle. While running the engine at around 3000-3500 rpm I noticed oil coming out of the dipstick. I shut down the engine and then noticed a large black oil and water stain on the ground where the exhaust was coming out. Motor was hooked up on muffs.
Upon checking the oil level, it was running over and mixed heavily with gas. The engine never came close to running hot, as I kept a close eye on the temp guage.
Is it my carb? Is it my fuel pump? Did I a blow a gasket or something? I don't know where to begin.
Thanks for anyhelp.

Michael

 

[Haut Medoc]

Re: Gas in crankcase

My guess is a faulty fuel pump......
You do know that you cannot substute an automotive fuel pump for a marine pump, correct?
Even though it will bolt on......
Anyway, gas in crankcase = bad fuel pump....

 

[Fishermark]

Re: Gas in crankcase

A couple of things...

First, why did you originally suspect a fuel pump? I would suspect a poorly rebuilt carb myself.

Second, did O'Reilly's sell you a marine fuel pump? Or just "one that would work"? You need to be certain to only put marine parts on the engine for safety reasons. (Others will chime in with words like "boom" and "big explosion." )

The gas in the crankcase sounds like it is coming in from a ruptured diaphram in your fuel pump. I doubt seriously that you could get that much fuel in the crankcase merely from a carb or stuck needle valve - it would have to run down through the rings in such quantities that your engine wouldn't be able to run.

EDIT - Looks like we were posting at the same time! d

 

[Bondo]

Re: Gas in crankcase

EDIT - Looks like we were posting at the same time!

Ayuh,..........

And,....... It looks like you're Both Right to Me..........

 

[bankermike]

Re: Gas in crankcase

No, I was not aware that I had to have a special marine fuel pump. I'm sure they sold me an auto fuel pump. I did tell them the fuel pump I needed was for a boat. What's the difference between the two?
I suspected I had a faulty fuel pump because the carb seemed to be "starving for fuel".
I don't think I was having the gas in the crankcase trouble until I installed the new fuel pump. Do you think it is a faulty fuel pump or is just the wrong type? If my original fuel pump was'nt bad, why was the carb "starving for fuel" and why would the carb advance to higher rpm's after putting on the new fuel pump?
Thanks for the help.

Michael

 

[Haut Medoc]

Re: Gas in crankcase

That one could have been bad, too......
I'd wager that you can find the correct fuel pump right here on iboats......
That or your nearest Mercruiser dealer....
Or maybe Napa.....
If you go local, be sure that it is marine rated......
Using an automotive is not only dangerous, but illegal.....
If you get stopped by the Coast Guard, you will get a ticket.......
Put the proper fuel pump on & post the results & we will take it from there......
Don't forget to change your oil, gas thins it out & it loses it's lubricating abilities......

 

[bankermike]

Re: Gas in crankcase

I've been searching trying to figure out the correct fuel pump to put on but I'm having some difficulty. The fuel pump that came off the motor is a Carter 0-3000. My engine ser.# is OD458981. I think maybe it's the 18-7283 fuel pump but I'm just not sure. I don't want to buy another one that's not the correct one. can someone please help me out?
Thanks!

Michael

 

[Gary H NC]

Re: Gas in crankcase

See if this is the same pump?

http://cgi.ebay.com/ebaymotors/Merc...701457QQihZ005QQcategoryZ124104QQcmdZViewItem

 

[sabastianunf]

Re: Gas in crankcase

You can actually call merc and they should be able to give you part #'s just make sure you have the block # and year built handy. Also can order parts off thier website - they just ship from your local merc dealer.

 

[LuckyPenny]

Re: Gas in crankcase

I ran into the same problem last year. DO NOT run the engine until you change out the fuel pump. PERIOD it will make a very very very loud bang if you do. Any Chevy 5.0L or 5.7L automotive pump will fit.
First of all, does the fuel pump you installed have a vent hose leading to the carb? if not it is automotive. Marine pumps have two diaphrams should the primary fail the secondary will allow you to get enough fuel to get home, but not at WOT.
If you need a cheap fuel pump look at ebay. Do not use an automotive pump.
Another point is that if you do blow up; and you will, your insurence will not pay off.

 

[bankermike]

Re: Gas in crankcase

The fuel pump I installed DOES have a vent hose going to the carb. At lease that is where I have it connected, as that is where it was connected on the old pump. The guy at the parts store called it a vaccum line.
Maybe the reason I could'nt get the new carb to run at WOT on the old fuel pump was because it was working on the "back-up" diaphram?
I going to try my local NAPA store this morning. The nearest Mercruiser dealer is over a hour away from the small town I live in. I'll make sure to get a Marine pump. Maybe I'll have better luck at NAPA than I did at O'Reilly's.
Thanks again

Michael

 

[180shabah]

Re: Gas in crankcase

You should have better luck, NAPA carries Sierra parts.

 

[bankermike]

Re: Gas in crankcase

Five minutes in NAPA & they found the CORRECT fuel pump. They'll have it first thing in the morning. I spent over a hour at O'Reilly's Sat. afternoon only to get the wrong pump.
I'll install the correct pump tomarrow afternoon and hopefully that will cure my troubles.
Thanks.

Michael

 

[Fishermark]

Re: Gas in crankcase

Good luck with it - let us know how it goes.

 

[bankermike]

Re: Gas in crankcase

Bad news. I put the new fuel pump on and I'm still having the same problem with the carb. The only way I can get it to run is by holding the choke fully closed. It will idle and run at higher rpm as long as the choke is closed but as soon as it opens it dies like it is starving for gas. I took the new rebuilt carb off and sent it back to the company I bought it from and they're going to replace it with a new rebuilt one. At this point I'm not sure it is the carb, as I was having basicly the same problem with the old carb. Any Ideas? I should have the new carb back sometime next week. If that does'nt work, I don't know what to do.
Thanks for your help.

Michael

 

[ziggy]

Re: Gas in crankcase

might be time to test the fuel system. here's some info dons posted on that....

http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=24;gtid=1107009

 

[bankermike]

Re: Gas in crankcase

Thanks for the info Ziggy but I see a couple of problems with these tests....I can't get my engine to run at WOT...I don't have a dynamometer and I don't think I can convince one of my buddies to lean into the bilge and hold the choke closed with one hand while holding on for dear life with the other while we zip across the lake at WOT (60+mph). Any volenteers? At this point, I would let you drive & I'll hold the choke and take the readings if we can get her to run 60+ like she used to.
Seriously though, thanks for all the help.

Michael

 

[sabastianunf]

Re: Gas in crankcase

Sounds stupid but have you tried adjusting the mixture needles on the carb and do you know how to do it properly? Is this an automotive carb or a marine? Are there any open vaccum leads where the carb could suck air in through? Are you sure you are getting a good seal around the base of the carb? Are your fuel filters new and clean - there is one before the fuel pump and a small one at the connection at the carb and is your gas fresh?

 

[ziggy]

Re: Gas in crankcase

when was the last time ya gave it a minor tune up? are ya sure the elec. side of things is up to snuff? points, plugs, wires, condensor, cap, rotor, timeing, dwell, maybe you dont' have carb or fuel pump problems. yer symptoms are wouldn't start and runs poorly if it does start. maybe yer floodin real bad because ya have to keep chokein it because of another issuse.

if the carb is flooding, causeing fuel to spill into the oil. some ideas might be.
needle and seat worn or damaged
float adj. incorrect
leaky float
carb gaskets leaking
auto choke defective or out of adj.
excessive fuel pump pressure,
clogged flame arrestor.

i may be out a line. but a new carb and fuel pump havent helped it seems.... so i'm trying to think of something different.....hope ya find yer problem and have a good day...

 

[Reel Poor]

Re: Gas in crankcase

If your holding the choke closed to get it to run right it's starving for fuel. Two real possibilities, Carb problem or a vaccum leak. May be an intake gasket or carb baseplate gasket. The quadrajet carb gaskets are bad about comming apart when they are removed. The little solid rings that make up the bolt holes will sometimes stick to the intake when you remove the gasket. Check that they are not still on the studs before installing the new gasket. Also before installing the carb make sure the gasket fits the baseplate of the carb properly, as well as the intake.

If it's a proper marine set up there should be no vaccum hoses or sources to contend with.