No start/dies when warm

[daveg734]

I have an 89 4.3 mercruiser. It has an electric fuel pump with an oil pressure switch. After the engine warms up for awhile it will suddenly die of fuel starvation. If I try and restart, it will do nothing but crank. I primed the carb yesterday and it worked for awhile but the situation repeated its self. I checked the spark with a timing light and it it is getting spark. I bypassed the fuel pump relay and it still wont start. The oil pressure gauge is showing zero. If it sits for awhile it will show oil pressure and restart when cranked. I thought it could be a viscosity issue with the oil. I changed oil and filter. I am about out of ideas. Could there be air trapped in the T fitting where the oil pressure switch and sender are? This issue just doesn't make any sense to me.

 

[daveg734]

Primed the bowl after a cool down (both myself and the engine) and it fired up. Died again. primed bowl. Ran and died again. Repeated enough times to realize its a fuel delivery problem.

Carb and filter are brand new. Lines are freshly bent. Fuel pump could use an upgrade. Is there anything before the pump that could be causing issues? Its an 89 four winns sundowner 205.

 

[hoowahfun]

Check your anti-siphon valve and your tank pick up tube. Sometimes there's a fitting before the anti-siphon valve with a screen in it that can clog with debris over time.

 

[Bondo]

Is there anything before the pump that could be causing issues? Its an 89 four winns sundowner 205.

Ayuh,...... Welcome Aboard,...... Hopefully there's a canister type fuel filter, 'n a tank fulla clean fresh gasoline,.....

To diagnose yer issue, find, 'n change the fuel filter,.... but don't just toss the old 1, drain it into a clear container, 'n examine it's Contents, for anything but clean fresh gasoline,.....
Then hook up a container of clean fresh gasoline, directly to the fuel filter,.....

If it starts, 'n runs, the tank or fuel is the problem,....

 

[daveg734]

I tinkered for a few more hours. Run, idle and rev are fine. If I shut it down and try and restart its having issues part of the time.

The carb and filter are new rebuilds out of the box today.

I ran the pump into a clear container. Clean looking gas. No air bubbles and decent pressure. (I used that gas to prime the bowls after it died)

It is starting to run better and didn't stall the last hour I messed with it. However I did have the not wanting to start issue due to lack of fuel.

I believe it is something to do with the parts store fuel pump. Possibly the internal regulator or bypass causing the fuel in the lines to drain back. I removed the line to the carb yesterday and it was dry.

I have been wrenching for several decades and this is a very curious situation.

 

[daveg734]

Finally had some free time and took her out for a lake test.

Same results. Would run out of fuel on a couple occasions requiring a bowl fill to get it restarted.

I tore into the feed lines from the tank. Removed anti siphon valve and the check ball/spring were like new. Still shiny stainless and moved freely. Removed the feed tube and noticed the screen on the end was clogged with looked like hair or fur (possibly fiberglass strands?) Whatever it was, it is gone now and everything is clean and reassembled. Hoping to take it out again this weekend. With any luck this will resolve the fuel starvation issue.

Thanks for all the help and advise.

 

[hoowahfun]

Sounds like that was your issue. Let us know how it turns out.

 

[daveg734]

So far so good.

Lake test tomorrow.


All in all I have to admit I was a 4.3 skeptic in this boat at first. I assumed it would be underpowered and have difficulty getting on plane. This 2 brl 4.3 alpha one with a 19 pitch seems to be the ticket in this boat. I am going to collect some gps data tomorrow and start fine tuning this combo. I assumed at first I would be swapping a motor and drive, but this boat should be just fine with its current power plant combo.

 

[daveg734]

I took it for a run today and it was fine for the first couple miles. It started acting funny so I headed back to the marina. I was halfway down the channel when it died. I opened the engine cover and the fuel pressure gauge read zero. i cranked it for a few and nothing. I primed the bowl several times and limped it to the dock. Every time I looked at the gauge it was zero.

I am going to have to pull the feed lines once again and see if the screen is clogged.

 

[daveg734]

Does anyone have a link to a good "how to" on the process to clean out the tank? I will probably change out the anti siphon just to rule that out as well.

 

[daveg734]

Ended up being a corroded wire at the ground ring terminal. As soon as I went to disconnect the wire it slipped out of the shrink tubing at the terminal. Lesson learned. Always check the simple stuff first.

 

[Jofayc]

I’m having the same stalling issue with my 1984 Mercruiser 140. I’ve replaced the coil and fuel pump with no success. Did you have a chance to test the problem after fixing the ground wire? Thanks!