Mechanical Fuel Pump

[hugh777]

Good Morning,

I have a 1990 7.4/454 VP that is raw water cooled. She starts and will rev up when it is not under load. Under load she sputters and will not push the boat up to plane - feels like she is starving for fuel. What are the signs that a mechanical fuel pump has failed?

My oil has a gas smell to it and at the end of last year I had some gas in my bildge. No visable signs of leaking fuel at all - but there was gas in the bildge.

Your thoughts please. Thank you.

 

[mkast]

Re: Mechanical Fuel Pump

What are the signs that a mechanical fuel pump has failed?

Usually the clear hose routed from the fuel pump to the carburetor has fuel in it.
You might want to diagnose this problem instead of installing an electric fuel pump.
If there is fuel in the bilge, how will an electric pump help? More fuel in the bilge?

 

[Blk-n-Blu]

Re: Mechanical Fuel Pump

When the Marine fuel pump fails there is a hose / tube that dumps fuel directly into the carb/ intake. Gas in bilge = BOOM. Could also explain gas in oil but you must have a leak to get gas in bilge.

 

[Blk-n-Blu]

Re: Mechanical Fuel Pump

You may want to look at the "Adults Only" thread at the top of this forum page and check out Dons troubleshooting guide on fuel systems. Good Luck

 

[UNSUREBOATGUY]

Re: Mechanical Fuel Pump

Last fall when I first bought our boat, I found fuel in the oil-enough to thin it out a little and read overfull on the dipstick. It was also having other symptoms of a bad fuel pump so I ordered a new one. When I took apart the old one, I found it had a ruptured diaphragm. Replaced the fuel pump with the new one and it works great. No more fuel in the oil and she runs like she should. I have a much smaller engine (Merc 3.0) but I would guess the rules should still apply. Good luck.

Aaron

 

[UNSUREBOATGUY]

Re: Mechanical Fuel Pump

Oh, I replaced the fuel line from the tank to the pump as well. Made me feel better. Steel line from the pump to the carb was still good on mine, but might be worth a look (fittings, etc.) since you will have it apart anyway.

 

[hugh777]

Re: Mechanical Fuel Pump

Thank you. I'm not puting a electric fuel pump in. I was looking for some tell-tale signs of a bad mechinical fuel pump.

 

[hugh777]

Re: Mechanical Fuel Pump

Aaron,

What other symptoms were you having before you replaced the fuel pump?

 

[UNSUREBOATGUY]

Re: Mechanical Fuel Pump

Other than the fuel in the sight tube as mentioned, to me (not an expert by any means) your other symptoms seem to match what I had and seem to point towards the pump. I'm not sure if this is likely, but it looked to me that the way the diaphragm was ruptured on mine, it may have been pumping fuel into the block where the little actuator arm thing goes in, as well as through the sight tube into the carb.

 

[hugh777]

Re: Mechanical Fuel Pump

Thank you Aaron.

 

[skydiven8]

Re: Mechanical Fuel Pump

Where is the "adults only" tab?

 

[Bondo]

Re: Mechanical Fuel Pump

Where is the "adults only" tab?

Ayuh,... Right at the Top of this forum..... Or Here...

Hugh,... You need to Read This,+ quit dewellin' on the fuelpump...
Then if you still think it's the fuelpump,... Read This...