5.7L Merc, Long cranking before start up.

[Bchristie9]

I am just curious if anyone has ran into this issue. I have a 2000 5.7L merc that has a carb. What i have found is when i go to start it cranks for a about 10seconds then fires right up with no hiccups. Happens cold or hot. While cranking it doesn't even try to fire. Sometimes after only shut off for a minute if will fire up instantly but not all the time. Another thing that i have noticed is after cranking just before it fires the dash will beep real quick and then starts up instantly after the beep. Once the engine fires it rungs great. Boat is a 2000, 205 crowline if that helps. Also after boats sits for a bit the engine compartment is a bit strong of fumes. No fuel leaks.

Thanks,

 

[Bondo]

Re: 5.7L Merc, Long cranking before start up.

Ayuh,.... Welcome Aboard,... Are ya pumpin' the throttle before ya try to start it,..??

Are ya Advancin' the throttle when ya tryin' start it,..??

Which carb,..??

 

[Bchristie9]

Re: 5.7L Merc, Long cranking before start up.

Yes i am pumping a few times before and giving throttle while cranking. Unsure of what kind of carb is on it but will take a look at that. Its almost like the fuel is draining back or a bowl in the carb is leaking out internally. Doesnt even try to sputter while cranking but when it does start it fires up real nice without a miss.

 

[Bondo]

Re: 5.7L Merc, Long cranking before start up.

Yes i am pumping a few times before and giving throttle while cranking. Unsure of what kind of carb is on it but will take a look at that. Its almost like the fuel is draining back or a bowl in the carb is leaking out internally. Doesnt even try to sputter while cranking but when it does start it fires up real nice without a miss.

Ayuh,... That may well be what's happenin',.... Gotta know Which carb you've got...

The 4 bbl. Merc/ Weber is known to do that...

 

[cr2k]

Re: 5.7L Merc, Long cranking before start up.

There should be a yellow wire with a red tracer on the + side of the coil. This wire jumps 12v to the coil during cranking so the coil will have plenty of power to fire. Pull this wire and check that it is energized during cranking. If not, your problem is a bad starter solenoid or broken wire not giving you enough power during cranking.

 

[Don S]

Re: 5.7L Merc, Long cranking before start up.

There should be a yellow wire with a red tracer on the + side of the coil. This wire jumps 12v to the coil during cranking so the coil will have plenty of power to fire. Pull this wire and check that it is energized during cranking. If not, your problem is a bad starter solenoid or broken wire not giving you enough power during cranking.

Not exactly, the yellow/red striped wire goes to the slave solenoid and starter solenoid for cranking the engine only. Not connected to the coil at all.

There is a Purple wire with a yellow stripe that goes to the oil pressure switch on the 2000 engine to power the fuel pump during cranking, but nothing to the coil on that model.

 

[fishaman]

Re: 5.7L Merc, Long cranking before start up.

I had 2 5.7 engines with Weber (or, the same, Edelbrock) 4 bbl carb, and both had this problem. Only in my case the cranking was required when I was away from boat for a week or more, otherwise started right up. One of them had mechanical pump, and I do not know solution in this case. For the other one (with electric pump) I had "shorted" the oil pressure switch with a momentary "ON" switch. Before starting after a long break, pushed the button for about 10 seconds with ignition on, then it fired right up.

 

[Bchristie9]

Re: 5.7L Merc, Long cranking before start up.

I have a 2 bbl carb on this engine, also mine has a electric fuel pump. So the engine needs to see oil pressure before it gives power to the fuel pump? I will also try once i have it back together to jump oil pressure switch just to see if it fires right away. Mine only has to sit for a minute or two after running and it cranks for a bit before it fires again. Thanks for the help. Any suggestion helps.

 

[dubs283]

Re: 5.7L Merc, Long cranking before start up.

So the engine needs to see oil pressure before it gives power to the fuel pump?

sort of...

during engine start/cranking, there is a circuit that "bypasses" the oil pressure switch and provides 12 volts to the fuel pump

once the engine starts and is running, the crank circuit wire stops providing power to the pump and the oil pressure switch provides the power

it may be the wire that provides power during cranking has an issue and is the cause of your problem, you can check the circuit with a voltmeter at the fuel pump connection during cranking

 

[Don S]

Re: 5.7L Merc, Long cranking before start up.

Fuel is probably not your problem. After running, and then setting for a minute, the carb is full of fuel. Even if the pump didn't come on there is enough fuel in the carb to start the engine and run for a good 15 to 20 seconds.

Another thing that i have noticed is after cranking just before it fires the dash will beep real quick and then starts up instantly after the beep.

That beep is making me wonder.
Try this. Make a jumper wire with an aligator clip on each end and hook it from the positive terminal of the battery to the + terminal of the coil and see if it starts normally. You will have to remove the jumper to shut the engine off.
I'm thinking something possibly a corroded/loose terminal in the ignition system (purple wire). When it beeps is when contact has first been made.

 

[grewvin1]

Re: 5.7L Merc, Long cranking before start up.

Just to add to the thread, have 2, 5.7L with Rochester carbs new rebuilt all is in good order choke plugs cap and such. When away for the week have to pump throttle 2 or so times advance throttle 1/4 crank for 5-8 sec. stop pump throttle one more time advance stick 1/4 will fire right up. As one that grew up with carb, cars each one seems to have there own quirks. Same issue on starting my Cessna after a couple of days sitting.

 

[rthomas]

Re: 5.7L Merc, Long cranking before start up.

My marlin has always been the same way, I've had 3 different carbs and two different ignition systems over the years with no difference in starting, my tolly has basically the same motor/carb/ign as the marlin starts with a tap of the key warm or cold. I think it might be because of back pressure in the exhaust system from having to push it so far down in the water because the marlin will start just as easy as the tolly when its out of the water.