140 Mercruiser fuel issue

[Boater Craig]

So I've got a '86 19 foot Citation with a 140 Mercruiser in it. The boat has always been good to me - and hasn't given me much trouble - til this year. Ran great last year - not that I used it too much with rainy weather. Only problem I've had is the hessitation that everyone talks about going from idle to full throttle... but have dealt with it. This year I went to get it prepped and ready to put in the water - did and oil change and went to start it.... and nothing. It turns over but just won't catch. I pour a little gas down the carb and it fires up and then stalls out. Seems to be starving for gas - checked the filter at the carb - and it's clear and clean - and dry. So I checked at the fuel pump - checking that filter - and it was also on the dry side. I know there's gas - and checked the line coming into the pump by blowing through it into the tank - and can hear bubbles in the gas. I'm thinking it's the pump - but I talked with a shop and he said they don't usually go bad - but I'm stumped. I don't know what else to check - any help would be great.
thanks

 

[myoldboat2]

Re: 140 Mercruiser fuel issue

from my merc manual's troubleshooting section...

Fuel System Lean

Cause / Special Information
1. Empty fuel tank
2. Fuel shut-off valve closed (if equipped)
3. Vapor lock / 3. Engine will not start after warm engine shut down
4. Automatic choke / 4. Stuck open, wrong adjustment
5. Fuel tank vent plugged / 5. Engine will start initially. After a short time of running,
engine will stall and will not restart for a period
of time. Can verify it is a vent problem by running
engine with filler cap loose. Fill cap will act
as a vent.
6. Air leak on suction side of fuel system / 6. Sucks air into fuel system reducing fuel volume
7. Plugged or pinched fuel line
8. Fuel pump / 8. Low pump pressure

the manual gives the procedure for testing the fuel pump, but it involves a special fitting and a gauge. you may be able to find out the flow rate spec on the pump.

try to divide and conquer... detach the fuel line going into the fuel pump and attach the line from a different external fuel tank. if it works, one of your lines is blocked or your fuel tank vent is clogged. be very careful and follow all the precautions in the manual.

 

[OldDriver]

Re: 140 Mercruiser fuel issue

Key word you used there my freind is "usually". But on occasion they do go bad. If it's an electric fuel pump, diconect the hose from the carb and let it pump into a glass jar. A but if it's electric, be sure it's getting power 1st.

 

[1980Galaxy]

Re: 140 Mercruiser fuel issue

just because fuel pumps USUALLY dont go bad, doesn't mean that they don't. i have a mechanical fuel pump and it went bad last year. just food for thought

 

[jimmytee]

Re: 140 Mercruiser fuel issue

change the pump... I thought mine was pumping, but once I changed it, I realized how weak it was....easy to change, and no problem since then...

 

[myoldboat2]

Re: 140 Mercruiser fuel issue

btw, you should read the "3. HOW TO: Testing your boats fuel system" thread in the adults only section... more good info from Don S.

 

[fishrdan]

Re: 140 Mercruiser fuel issue

btw, you should read the "3. HOW TO: Testing your boats fuel system".

^^^ Yup

I wouldn't go swapping parts hoping to stumble on the problem without troubleshooting and diagnostics first.

You said the carb's fuel filter was dry (no fuel) and then blew through the fuel line and heard bubbling in the fuel tank, but did you check the fuel line for cracks? I had the same problem on my boat and I even blew through the fuel line and heard bubbling in the tank,,, but there was a crack in the rubber fuel hose causing the pump to suck air instead of fuel.