5.0 TKS will not start

[mdaddy]

Mercruiser 5.0 tks will not start... 1st thing I noticed is that the untial alarm (the loud anoying alarm) doesn't come on anymore when ignition 1st turned to on position.... removed fuel line from carb and and no fuel is being pumped when attempting engine start.... by passed fuel pump connection, apollied 12v and pump worked... also oil pressure switch (ops) receiving 12 volts. Question: is the ops normally open or closed when ignition off? I removed my ops and it read OL multimeter (mm) across the 2 connectors. What am I missing?

 

[QBhoy]

Is your lanyard connected properly and securely ? Trade mark signs of it.
best of luck.

 

[alldodge]

apollied 12v and pump worked... also oil pressure switch (ops) receiving 12 volts. Question: is the ops normally open or closed when ignition off?

No power to the fuel pump from the oil pressure switch until pressure comes up, its normally open connection for fuel pump

Start power comes from the starter small outside terminal Purple/Yellow wire.


Other diagram

 

[alldodge]

So far as the alarm not coming ON, look for the other oil switch below the distributor with Tan/Blue wire

 

[mdaddy]

So, 1. the ops is open until the ignition is turned to start then the starter activates and tje ops closes to send power to fuel pump?
2. All Dodge, I will check ur suggestion tomorrow.
Thanks guys and I'll respond with outcome asap.

 

[Bondo]

So, 1. the ops is open until the ignition is turned to start then the starter activates and tje ops closes to send power to fuel pump?
2. All Dodge, I will check ur suggestion tomorrow.
Thanks guys and I'll respond with outcome asap.

Nope,...... The switch closes when there's oil pressure,......

Before there's oil pressure, the fuel pump power comes from the outboard tiny terminal on the starter's solenoid,.....
But only when the starter is engaged,.....

 

[mdaddy]

ok thanks guys, it was a loose wire so now it starts with fuel reaching carb. which brings me to my original problem. The boat will crank but will not stay running maybe 1 out of 10 times. I recently rebuilt the carb due to boat sitting up for a few years. I'm thinking either idle circuit or problem with enrichment module to begin with. Any suggestions

 

[alldodge]

Is the enrichment pin retracted when cold?
Once warmed up does it idle fine?

 

[mdaddy]

Yes and I have the fuel line disconnected from the carb and no fuel is being fed to the carb so I think there is a problem in that circuit.... ignition-starter-oil pressure switch-fuel pump. Anymore ideas AD?

 

[mdaddy]

the engine does turn over fine but no start

 

[mdaddy]

AD, is the oil pressure an open circuit as well?

 

[Rick Stephens]

First thing to do is apply power to the outside small lug on the starter solenoid - the yellow/purple wire. This is to see if the fuel pump spins up. I do that at the beginning of every season to prime my fuel lines and carburetor. I just use a screwdriver from the top lug on the solenoid with is direct from the battery. You should hear the pump start up. If not, then you have a bad fuel pump or the fuel pump wiring is not connected - hot or ground sides.

If the pump spins up, then next is start tracing the power to the pump. With key on, you should have power to the oil pressure switch on the purple side.

Rick

 

[alldodge]

Going back to this comment

So, 1. the ops is open until the ignition is turned to start then the starter activates and tje ops closes to send power to fuel pump?

When motor is cranking the is a purple/yellow wire which connects to the small terminal on the outboard side of the starter solenoid. This wire feeds 12V to the fuel pump while the motor is cranking. Once the motor starts and oil pressure builds up, then the oil switch feeds the fuel pump

 

[QBhoy]

This is exactly what happens when the lanyard toggle switch is moved. No ignition alarm and won’t fire. Just a thought on simple terms.