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Engine Dies

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CrazyWalt

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Merc. 5.7 carborated year 2000

Merc. 5.7 carborated year 2000. Engine starts up and idles for about 30 seconds then dies as if starving for fuel. Changed fuel filter. Disconnected fuel line to carb and cranked engine and fuel pump sprayed fuel. If I start engine and give it gas it still dies as if starving for fuel. What do ya'll think?
 
"THERE IS ALSO A SAFETY CONTAC

"THERE IS ALSO A SAFETY CONTACT SWITCH ON THE TROTTLE ASSEMBLY ITSELF, IF IT STARTS AND YOUR TRYING TO GIVE IT GAS BY PUSHING THR CONTROLS FWD. OR REV.EVEN A LITTLE, IT MIGHT BE CLOSING THE CONTACTS.AND THE ENGINE WILL NOT KEEP RUNNING."
 
The choke butterfly should be

The choke butterfly should be just closed when the engine is cold before starting.
When it starts the butterfly should open about 1/8 to 3/16 of an inch within a second or two.
If it opens more than this the engine will lean out and quit or bog.
Once running the choke heater should open the choke to completely vertical within about 5 minutes or so.

Rod
 
"Rod, this may be my problem.

"Rod, this may be my problem. Today while trying to figure it out I was watching the choke, trying to figure out how it worked and I'm pretty sure it opens all the way up, in fact I don't remember it ever shutting. How do I fix and what could have caused it because boat ran fine a few weeks ago until I had starter troubles. Since then I had starter rebuilt, changed battery to ground wire, changed battery to starter wire, changed sparkplugs. I didn't touch carb. Is this something that just wears out?"
 
"The choke heater my need adju

"The choke heater my need adjusting. After a few years they can get out of adjustment.
It's a boat after all; if anything can go wrong, it will.

Is it a 2 bl or 4 bbl carb? Quadrajet, Weber?
There may be a black round plastic housing on the end of the choke shaft outside the main body of the carb. If so, this is the heater.

There will likely be 3 screws around the edge that hold the cover on. These should be loosened and the cover rotated so as to close the choke. Just enough so it just closes at normal room temp.

Then try it out. It may take a tweak or two to get it just right.

Rod"
 
It's a 2 bl. Not sure on t

It's a 2 bl. Not sure on the rest. I will fiddle with with the heater tomorrow if I have what you described.
 
"Btw; the choke heater if it a

"Btw; the choke heater if it as I described, is electriclly heated. So after a few minutes it should get warm, and the choke should open. If it stays cold and the choke does not open, the engine will choke out and die due to rich mixture. This means the heater coil inside it is likely shot.

Rod"
 
"New results. If I start my e

"New results. If I start my engine and keep the key turned with my hand all the way to the right the engine runs perfectly and idles great. I held it there for over 10 minutes and then let it go... about 30 seconds later engine died. guess by holding the key to start position I was bypassing the oil pressure switch and the fuel pump was pumping into the carb and engine was running fine. Where is this oil pressure switch? I followed the positive and negative wire from the fuel pump and it goes into a black housing with blue ends...comes out of that housing as a purple with yellow stripe wire and a ground wire...purple with yellow goes to something on carb (black and round)....ground wire goes to a bundle of wires taped together to rear of engine (to ground it I guess). I googled oil pressure switch to see one and I don't see it yet....And when I find it, do I replace it?

Also, when I changed my starter I hooked the yellow and red wire to S and yellow and purple to the other side...Was this right? If I switch them is my problem solved?"
 
"So let me get this right:
Yo


"So let me get this right:
You are disconnecting and changing stuff without the benefit of a wiring diagram, or making sketches or notes?
Good plan!

Aside from this, it sounds like your starter is wired correctly.

Here is something to try that should determine if the oil switch is operating correctly.
The oil pressure switch is mounted at the port side rear just above the oil filter or adapter.
It has a purple wire and a pur/yellow wire attached.
If you jumper these two wires and she runs OK, the problem is the switch as you suspect.

Rod"
 
"purple with yellow goes t

"purple with yellow goes to something on carb (black and round).."
That black round thing is the choke heater I mentioned earlier.

Rod
 
"Found the pressure switch...t

"Found the pressure switch...thanks...and I haven't gone disconnecting anything and changing things yet, just wondering if I should. And I thought that may be the heater. Rod, I appreciate it and will let you know what happens when I jumper it."
 
"I jumpered those two wires an

"I jumpered those two wires and engine still died after about 30 seconds. I cranked it back up and held key to start again and she ran fine...let it go and died in about 30 seconds. I know its wiring. I just don't know where. I had starter rebuilt and put it back in before this started happening. I have the yellow and red hooked to the S, yellow and purple on the other side, Two 6 or 8 gauge wires (one red and one orange) go to a white box (I guess a fuse) and hook to the same post as the wire to the battery. What do you think Rod?"
 
"Holding the key in the start

"Holding the key in the start position for 10 minutes!!! The starter wasn't turning was it?

It sounds like the ignition switch may be the culprit; either defective or the ignition switch or the starter is wired wrong.

uhoh.gif
"
 
"CW;
I had a close look at th


"CW;
I had a close look at the wiring diag for your motor in Merc SM24 (which you can download BTW using Bondo's handy backdoor link.)

The strange thing is that it does not show the fuse that you mentioned, though other diagrams in the same SM do show the fuse. Maybe it was not used on the 5.7 for some reason.

The yel/red should be on the small S terminal.
The pur/yel should be on the other small terminal (not sure how it is marked).
The heavy red battery cable should be on the large B terminal.
The lighter red and the orange wires should be attached to the fuse on the B terminal.

It sounds to me like you have the starter wired correctly as per the diagram; unless I have misunderstood what you have said.

Why not try a tap into the pur/yel wire that feeds the fuel pump and connect a 12 volt test light to it. Then start it and see what the light does. This should tell a story, about whether and when your fuel pump is getting power.

If its not getting power, use the test light to see if the purple wire feeding the oil pressure switch has power. It should be powered when the key is on.

If the pur/yel wire to the pump is not getting power, or is intermittant, that may also explain why the choke is wide open. That same pur/yel circuit feeds the choke heater and without power the heater won't heat. Someone may have opened up the choke adjustment so the engine would not die when warmed up. Just a guess.

I hope this all makes some kind of sense.

Rod"
 
I also agree with Guy that the

I also agree with Guy that the key switch may be faulty if the power to the purple engine circuit is intermittent. They get kind of funky after a few years. It is a boat after all.

You could try a test light on the I terminal of the key switch. It should be hot with the ignition on. Wiggle the key and see what it does. The light should be steady with the key on.

Rod
 
"OK Rod....Here are the light

"OK Rod....Here are the light test results:

Purple/Yellow wire to fuel filter---only powered while key is all the way to right like starting, when engine starts fuel filter loosing power.
Purple wire feeding oil pressure switch---has power when key is turned on
Key Switch---the light is on steady with the key on when touching the Ign. terminal of the key switch.

I don't know what to do know...but I guess the fuel pump is loosing power after startup. Whats next?"
 
"CW;
I thought we might have


"CW;
I thought we might have lost you there; but who could blame you?

OK; so here is how I would logically deduce where your trouble is.
You say your key switch and purple wires at the engine have power when they should, so there is no trouble to that point.

Did you try the pur/yel wire to the fuel pump WHEN THE ENGINE IS RUNNING?
It will only be hot when the key is in the start position, unless the engine is running, when it should remain hot (due to the oil pressue switch closing).

If you mean that the pur/yel wire to the pump was dead WITH THE ENGINE RUNNING, then that almost certainly means the oil pressure switch is pooched.

Rod"
 
"The pur/yel wire to the fuel

"The pur/yel wire to the fuel pump was dead while the engine was running...But yesterday I jumped the oil pressure switch and engine still died.

There is a purple wire and the pur/yellow wire going into the switch. I unhooked them, got a piece of wire (like 14 gauge) and connected the circuit and the engine still died after same amount of time...unless of course I held the key to the right.

I'm gonna go do this again real quick; be right back."
 
"CW;
In that case the only ot


"CW;
In that case the only other possiblity is a discontinuity in the pur/yel wire somewhere between the oil press switch and the fuel pump.

Try this: Jumper a wire from the post of the switch where the pur/yel wire attaches, to the pur/yel feed to the fuel pump, and try it. (Leave the purple wire connected to the oil press switch.) If it runs OK, there is your proof. If not, I am going to go have a stiff shot of Scotch Whiskey. Actually I might anyway.

Rod"
 
Ok jumpering the oil pressure

Ok jumpering the oil pressure switch got me same light test and results....light on while starting only...light off when engine is running.

But I also did a light test with the switch unplugged and got same results...light on while starting.....light off when engine is running. I did not expect power to go to the fuel pump with the switch unplugged.
 
"Rod,

I tried jumpering lik


"Rod,

I tried jumpering like you said with no luck, same results. However, with the switch disconnected, if I connect a wire to the end of the purple wire and connect the other end to the pur/yel wire (but up next to the fuel pump) then it works as it should. What did this do different then jumpering the two together right there at the switch."
 
"CW;
What your test did was e


"CW;
What your test did was effectively jumper the switch and the pur/yel wire from it to the pump.
So logically either the switch or the wire from the switch to the pump is bad. It pretty well has to be one or the other.

If you put your test light on the pur/yel terminal at the pump, does it stay on with the engine running as it should? If so, then the switch is good. Then jumpering from there to the pump feed should allow the pump to run.

When you did your jumpering test before, you did leave the black wire connected at the pump, right? This is ground and must stay connected.

BTW, send me your fax number and I can fax the wiring diagram to you.
Rod"
 
www-alt.mercurymarine.com/mnet

www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/24/24covr1.pdf

Thanks for that offer but I found it online...my engine is page 4E4 in mercurey Service Manuel 24. I left the black connected and just did a splice into the pur/yel wire. We struggled through this one. I really appreciate everything. I'm so tired of chasing little purple wires around my Merc.
 
"Wiring issues can be a big PI

"Wiring issues can be a big PITA.

Take heart though; you could have had a dealer waste hundreds of dollars changing first the pump, then the oil press switch, then god knows what else; while it was a wiring thing all the time.

Good luck.
Rod"
 
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