Mercruiser 43 L stern drive Fuel pump Question

"Hello,

I have recently b

"Hello,

I have recently been going thru my mothers boat its a 1994 euroline with a mercruiser 4.3 L v6 sterndrive with a weber 9600s 4 barrel carb electric fuel pump, in hopes to bring it back to life. it was bought new in 95 from the boat show used a dozen times or so, then sat for the last 12 years. All in all besides mildew and mold that all washed off the boat is still like new, I got it a new battery, changed oil + filter, drain gas put in fresh, new filter/ seperator, opened up cap cleaned it up, took out all the plugs cleaned them up and tryed to start it engine would not even turn over so after some checking I benched the starter to find out it needed a new one, after replacing the starter, it turned over, and the altenator was stuck, I wenched on it to losen it up, then after using some starting fluid and gas down the carb. and cranking for two whole battery charges nothing, I decided that the carb needed rebuilding so I rebuilt it and put it back on got it to start twice only to die after seconds it seamed like the carb was not getting gas so before I took off the carb again I checked the fuel pump again I had all ready put a hose on the line and turning it over a gas had come out but this time around nothing and there is 12v, but to think about it I never heard anything from the pump. So I hooked the 12v to it and nothing, so i decided to replace it during this I relized that there is 12v to the the conector all the time even with the key off I thought that it might have been the small terminals on the starter solinoid were switched but after taking them both off ther was still 12v at the pump conector so I am thinking that the old pump burned up because of being on all the time My question is should there be 12v even with the key off at the fuel pump? and dose the yellow/red and purple/yellow on the solinoid have to be on a certin terminal ? couldthe oil switch be stuck keeping 12v to the pump?"

"Here is a schematic I hope it

"Here is a schematic I hope it helps...




"

"Thanks for the speddy reply,

"Thanks for the speddy reply, yup thats how its wired but I still have 12v at the fuel pump conector all the time key on or off? is this right?"

No. FP gets 12 volts from a k

No. FP gets 12 volts from a key activated starter solenoid until oil pressure builds up which activates the fuel pump relay.

So with wire even off the sta

So with wire even off the starter solenoid there is still 12v at the fuel pump with the key off do you think the oil pressure switch might be stuck giving the pump 12v power all the time? Again Thanks for the help it is greatly appericated

"Re: "oil pressure switch

"Re: "oil pressure switch might be stuck"

Good place to look... just remove the connector from the oil pressure switch to see if +12 goes away... BTW... if that's the case, its a safety hazard as well."

Either way there should NOT be

Either way there should NOT be 12 volts to the oil pressure switch when the key is OFF.

Disconnect the large connector at the engine wire harness and recheck. This will seperate the dash from the engine.

If 12 volts is still present then there has to be a wrong wire or short at the engine. If not then it is the dash wiring........

Thanks to all of you I will tr

Thanks to all of you I will try all either later when I get off work or tommorow and post the results thanks again

"Hello again

well I tried

"Hello again

well I tried the oil pressure switch and with the wires off there is 9 volts left those off and dissconected the large conector from the dash to the engine and there was still 9 volts so with no wires fro the pump the purple/yellow one and the yellow/red one to the starter, none to the oil switch and the large conectoe disconected there is still voltage at the fuel conector guess my question is is there supposed to be any voltage with the key off at the fuel pump conector?"

"Another thought, Could some

"Another thought, Could some thing in the altenator be shorted? makeing voltage at the pump wire? Cause it was rusted stuck and I had to break it free with a wrench so it would spin I am so lost here."

That was the wrong connector.

That was the wrong connector. You want the big round one on the engine. Look close at the starter for corrosion on the wiring connectors.

Sorry that is the connector I

Sorry that is the connector I ment the one right by the engine I just put the starter in its a brand new one and the conectors were cleaned. So there is supposed to be no voltage at the pump with the key off?

No voltage is correct. Check

No voltage is correct. Check the starter connections; there may be one barely touching another. Since it is 9 vdc that leads me to believe there is a high resistance short. Does the fuel pump have a relay?

"Not touching for sure, and I

"Not touching for sure, and I do not belive there is a relay the digarm above that kghost provided is the excact diagram for my boat"

"It sounds as if:
a) the

"It sounds as if:
a) the wires to the starter are not correct, i.e., the purple/yellow one goest to the wrong place...or..
b) While the starter may be a correct mechanical replacement, the connections to it are incorrect, i.e., not exactly the same as the original one...or...
c) There is an internal short in the starter back feeding 9V to the purple/yellow wire.

With the key off, the post on the starter that the purple/yellow wire connects to should have zero volts on it."

"First chesk to see which wire

"First chesk to see which wire has the voltage
at the Oil pressure switch, purple with yellow or purple?

If it is the purple then the altenator is suspect.
If the purple has the voltage then the voltage should be present at the choke (+) and the coil (+).... This would mean that your ignition circut is live all the time......


If it is the purple with yellow wire than a short is suspect. Most likely at the starter solenoid

The altenator has 12 volts from the battery/starter soleniod all the time. (orange wire)
If the alt is shorted then it could be feeding back thru the purple wire."

Both of the small terminals on

Both of the small terminals on the starter meter 0v I have the purple/yellow (fuel pump wire) and the Yellow/red ( ignition wire ) not conected and the wires to the oil pressure switch not conected and the main engine conection not conected and there is still voltage at the pump I'm stumped

purple yellow has 9v I will ch

purple yellow has 9v I will check the purple on the oil switch do you sugest removing the orange and see if it gose away? I will go test now again thanks you guys for all the help I have been messing around with this for 2 weeks

The 9 vdc is the key; somethin

The 9 vdc is the key; something is dropping the 12 vdc down. I've seen green corrosion growing several inches and cause a dead short.

"right now as it sits the star

"right now as it sits the starter only has the red,red,orange to one of the lage terminals and the black that comes from the starter to the solinoid both the purple/yellow and red/ yellow are taped off the oil pressure switch is taped off both wires, I also removed the altenator, and the large conector from the front to the engine is unpluged and there is still 7-9 v at the fuel pump conector and retating wires like the wire to starter not connected and oil pressure switch also not connected"

"Peter

What is this black

"Peter

What is this black wire you speak of??

There is no black from the starter to anywhere.

The only 16 guage black wires are from the wire harness and go to the slave solenoid, choke, interupter switch and to the fuel pump connector.

There are also a couple of others but should not matter in this case.

The altenator also has a black wire. (10 guage)

Please recheck and try to be specific on colors and where connceted.

Also do one more thing.

Disconnect the battery and recheck.
If disconnecting the battery kils the voltage then you must have a short to ground somewhere!!!"

"Hi,

Sorry the black I me

"Hi,

Sorry the black I ment is the wire that gose from the starter to the solenoid it is the wire that grounds the solenoid I think it comes on the starter already, I have disconected the battery and left just the postiive to see if there was 9v and not matter what I do there is 9v unless I totaly disconect the battery also the only wires are the 3 on the large terminal that are conected, Do you think either the slave solenoid or the breaker could be causing this? do you have any idea how I would go about testing if they are ?"

Are you saying you disconnecte

Are you saying you disconnected the negative terminal from the battery and there is still 9 vdc at the pump? If that is the case then disconnect all the alternator wires. If it goes away then the capacitor on the alternator is holding a charge. You don't have multiple batteries do you?

"Peter

Contact me thru my

"Peter

Contact me thru my email, click on my member name to get my email. I will give you my cell number and speak to you about this, It would be better if you are at the boat so you can answer my questions."

Sorry I ment I tryed that not

Sorry I ment I tryed that not voltage if either of the battery wires are conected


Kghost Will do thanks

"good news it would not stay r

"good news it would not stay running but I jumped out the oil switch and she stays running. I still have that ploating voltage though 7 volts when key is off it has to be a short because the purple/yellow only gose to three places fule pump, starter solenoid, and oil switch and with that wire off all 3 places it should not be getting voltage from anywherem, before I pull the harness out dose any one have any other ideas? the loom is covered with electrical tape and not the easiest to get at so it would be best just take it out and unravel it"