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won't start after spring launch

edbulmer

New member
My Detroit 671s both won't start after the spring launch this year. The boat is 1986, they have been harder to start the last year. Two years ago we took it on a long trip ran great all the way. The last two years it hasn't been used much just started and run on short trips every month for a hour or so. I have added fuel treatments every winter. The fuel is 3 years old. The primary filters have been changed fuel looks perfectly clean. I just changed the secondary filters-the fuel in them was a little oily looking. Still won't start. I don't see a fuel pump in the system. Should I install one, or should I first take fuel lines lines off at the injectors to see if it is just an air lock?
 
Both no start? It's gotta be the fuel. Cant see a fuel pump? Gear driven, bolted to front or rear of engine....unless someone has done something WHACKY I've never seen before. Just follow lines from either filter. Goes like this:
Tank to primary to pump to secondary to head.
Spray WD 40 in the intake while cranking and see if they cough and sputter. DON'T USE ETHER! causes too much damage!!
If they try to fire on WD, check your fuel rack and make sure it goes to the start position (full fuel, all the way in) when you move the stop lever. Need to pull the valve cover to check. If it's wanting to run on WD and your rack goes full fuel, then your fuel load is DEAD.
SORRY FOR choppyness but I'm on my phone.
Good luck.
 
What does this mean =check your fuel rack and make sure it goes to the start position (full fuel, all the way in) when you move the stop lever. Need to pull the valve cover to check.

Also-the fuel is dead-what does that mean? Can it be that the fuel has gone bad-200 gallons. Would I have to suck it out or can I just add more?
 
After considering your problem further, I wouldn't worry about the fuel racks. I think that, since both engines won't start, that you definitely have a fuel quality issue.

You may have water...a lot of water...or...algae....or both... in your tanks.
Water is heavier than diesel fuel. Therefore, diesel will "float" on water. Your pumps pick up tube sucks fuel from the BOTTOM of the tanks. If there is water there, then water will be drawn into the fuel system first. Lots of water...no burn.

If you have drains on your tanks, try to get a gallon or more as a sample and see how much is water and how much is fuel. Do this when the water is calm so that there is no "mixing" and you can accurately determine how bad a problem you may have.

All diesel fuel will contain SOME water. And that is why, in warm climates, algae will grow in your tanks. I've seen it over as 1/4" thick slime on the walls of small sailboat tanks. It will slough off of the wall of the tank and get in the fuel lines and filters and really gum up the works.

If you have algae... or water... or both... in your tanks, you will need to clean them and the lines before starting the engines. If you try to run the engines with water in the fuel lines, you will ruin EVERY ONE of your injectors.

You CANNOT solve the problem by just adding more fuel.

I would say that you may need to ask around the docks to find experienced captains or boat engineers to get some advice about what to do for checking and, if need be, disposing of your old fuel.

Good luck.
 
What doesn't add up is the boat has been a cold climate up north the last three years, so I don't think there is any algae. Also the glass fuel filters are showing no water in the fuel.
 
With both engines down it is most likely a fuel issue. I would probably start by cracking the fuel line after the fuel pump (prior to secondary filter to make sure that it is pumping when you turn it over. If your filter change process allowed too much air into the lines that may stop teh fuel pump from operating properly. I don't think that the 671 has a manual lift pump.
 
If you are absolutely convinced that your fuel is good, then I have to agree with aliboy that you may have air in the lines. The 6 71 can be a pain to get primed after having the filters off. If, after cranking a few seconds, you remove the primary and it is not completely overflowing with fuel, then you may need to go back through your priming process. Some people crack a return line and crank the engine. I use a "blowpipe" with a one way check valve inserted into a pressure tap on the secondary filter housing. That works each and every time....for me.
 
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