STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

Mercruiser 1984 120 in a 22 foot starcraft, NOW tuned up (new wires plugs point condensor cap rotor) carb ultrasonic cleaned and rebuilt . It starts great and runs as long as I pour fuel in the carb ..oh fuel pump?? Clear line on pump running into fuel can start engine after filling carb,, No fuel flow in clear line? I am thinking the camshaft lobe that actuates the fuel pump levers worn out>??? Ever hear of this on the 120 mercs? OR someother thing? I replaced all the fuel lines (actually my buddy did ) and cleaned the tank,,HELP Please!!! Next move electric fuel pump.

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

madmans said:

Mercruiser 1984 120 in a 22 foot starcraft, NOW tuned up (new wires plugs point condensor cap rotor) carb ultrasonic cleaned and rebuilt . It starts great and runs as long as I pour fuel in the carb ..oh fuel pump?? Clear line on pump running into fuel can start engine after filling carb,, No fuel flow in clear line? I am thinking the camshaft lobe that actuates the fuel pump levers worn out>??? Ever hear of this on the 120 mercs? OR someother thing? I replaced all the fuel lines (actually my buddy did ) and cleaned the tank,,HELP Please!!! Next move electric fuel pump.

Click to expand...

Ayuh,.... I'd sooner think the fuel pump itself is dead...

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

If that cam lobe wore out... your oil would be full of metal specks in it.

What's the history here.... something that just started, or did you just get this boat?

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

That clear line is a tell tale, when there is fuel in it there is a diaphragm failure and the pump needs replacing.
To check your pump, supply the pump with fuel, pull the carburetor feed line and turn the motor. (Catch the gas, and be careful to eliminate sparks) If there's no fuel it's not working, pull the pump and inspect it.
It's a lot easier to replace the mechanical pump than it is to install and wire up an electric one correctly.
Fuel pump lobes should not wear out unless the wrong pump was on there.

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

If you are getting fuel when cranking through the fue line with it disconnected I would then start looking at the carb. Fuel float would be a good place to start. Is it adjusted correctly?

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

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Join Date: May 2009Location: Nashua, NHPosts: 1,387




Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe



That clear line is a tell tale, when there is fuel in it there is a diaphragm failure and the pump needs replacing.
To check your pump, supply the pump with fuel, pull the carburetor feed line and turn the motor. (Catch the gas, and be careful to eliminate sparks) If there's no fuel it's not working, pull the pump and inspect it.
It's a lot easier to replace the mechanical pump than it is to install and wire up an electric one correctly.
Fuel pump lobes should not wear out unless the wrong pump

I bought boat 3 years sitting oiled cylinders up let it sit new tune up parts including carb rebuild kit and proper ultrasonic cleaning. New fuel line (man was the old line ever rotten fire hazard for sure) Now new fuel pump and no suction from it ,I thought old pump was bad but new one is crap also. I put clear line on Inlet to carb from a 2 gallon jerry can to see if fuel pump sucked fuel NOTHING,No suction when i put tongue on inlet hose while engine running ,I use a bimba air cyclinder modified to safely inject fuel into the carb and fill the bowl for starting and fiddling. I am ready to go electric pump as I suspect the cam lobe (or balance cam >??whatever drives the fuel pumps worn out?_) anyhone have similiar problems? Thanx Mike

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

There is often a "fuel pump push rod" that is between the camshaft and the fuel pump. It is often in the way and can make it difficult to install the fuel pump. Did you notice it?

I know on SBC engines there is one... not sure on yours though...

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

When you say you replaced the fuel line what exactly did you replace? The clear line is not the fuel line.

Problem Found and Resolved Finally quite Obscure!!!!

Problem Found and Resolved Finally quite Obscure!!!!

thumpar said:

When you say you replaced the fuel line what exactly did you replace? The clear line is not the fuel line.

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I replaced all the fuel line from Tank to carb, installed water fuel spin filter seperator, BUT I found the prob;lem, After much screwing around the check valve in the tanl was defective and needed more than 4 psi to open up, I replaced the fitting without a check valve and ,,,fuel flow tons where before was none. I suspect problem solved too dar kto continue will finish tomorrow after work, I ghave a positive feeling bout this fiunally after all My friend AGary and I have done .Thanx all Mike

Re: Problem Found and Resolved Finally quite Obscure!!!!

Re: Problem Found and Resolved Finally quite Obscure!!!!

Put the correct fitting back in the tank. You NEED an antisiphon valve. It had one for a reason.

Re: Problem Found and Resolved Finally quite Obscure!!!!

Re: Problem Found and Resolved Finally quite Obscure!!!!

Also make sure the line from the fuel pump to the carb is a hard line.

Re: Problem Found and Resolved Finally quite Obscure!!!!

Re: Problem Found and Resolved Finally quite Obscure!!!!

You NEED an antisiphon valve?? Why? It wont run work with the one I have, It does suck one way and not the other so working as It should BUT it doesnt alow fuel to the carb, without it it sure had great fuel flow. Thanx all, Mike

Re: Problem Found and Resolved Finally quite Obscure!!!!

Re: Problem Found and Resolved Finally quite Obscure!!!!

madmans said:

You NEED an antisiphon valve?? Why? It wont run work with the one I have, It does suck one way and not the other so working as It should BUT it doesnt alow fuel to the carb, without it it sure had great fuel flow. Thanx all, Mike

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Ayuh,... It's there to save yer Life,... a Required safety feature...

Re: Problem Found and Resolved Finally quite Obscure!!!!

Re: Problem Found and Resolved Finally quite Obscure!!!!

PLEASE READ AND RETHINK REGARDING THEThis might explain some things...
http://edocket.access.gpo.gov/cfr_20...cfr183.568.htm
THIS EZPLAINS PERFECTLY, wE HAVE A FUEL SHUTOPFF AT OUR FUEL WATER SEPERATOR NOW ITS TIME TO TAKE OUR FIRST BOAT RIDE lATER mIKE AND gARY

Re: Problem Found and Resolved Finally quite Obscure!!!!

Re: Problem Found and Resolved Finally quite Obscure!!!!

madmans said:

PLEASE READ AND RETHINK REGARDING THEThis might explain some things...
http://edocket.access.gpo.gov/cfr_20...cfr183.568.htm
THIS EZPLAINS PERFECTLY, wE HAVE A FUEL SHUTOPFF AT OUR FUEL WATER SEPERATOR NOW ITS TIME TO TAKE OUR FIRST BOAT RIDE lATER mIKE AND gARY

Click to expand...

This post is very difficult to read and the link does not work. What are you trying to say? Something about not needing to meet regulations?

Re: Problem Found and Resolved Finally quite Obscure!!!!

Re: Problem Found and Resolved Finally quite Obscure!!!!

Madmans, what happens if the line between the tank fitting and the water separating filter gets cut or broken? The anti-siphon valve shuts it off at the source for maximum safety factor.

Re: STUMPED by a PUMP??? (or a camshaft? Lobe) maybe

Hm you have a vilid Point for sure. Perhaps i ca nbuy a 2 pound anti siphon valve. I did put the anti siphon fuel pickup tube in a plastic bag when i used pressurized air to clean it and also see what the heck was plugging it up? ifound some dirt a chunk of stick or bark (hard to tell but something was there) I was happy as a Pig In Poop that I finally had fuel to the carb after weeks of messing around changing pumps and scratchin=g my head . Would a lesser pressure valve be acceptable in line? Thanx Mike