'09 5.0 TKS (Carb) not running

[Nitz31]

Trouble with my '09 5.0 TKS (Carb) #1A342087. Engine died on the way back to the slip and will not restart. If I jump the fuel pump straight to the battery, it will run. I believe my issue is in the Purple/Yellow circuit that feeds the fuel pump via the oil pressure sensor. I have also just replaced the oil pressure sensor 2 days ago as the 1st known culprit for this issue. Anyone have any thoughts on this? Its a carb motor so it's pretty simple but I'm at a loss. Only thought I have is the starter solenoid could be bad because I do not have any power on the P/Y wire at the solenoid in any condition. I have been told by several people, these units 'never fail' but I keep thinking I'm the lucky one.

Edit: If I get it started when cold, it will run for no more than 5 minutes sort of until the engine warms up and then dies. I'm assuming its just burning up all the fuel in the carb.

 

[alldodge]

Probably no 12V power going to the motor. By jumping the fuel pump directly it would back feed the the motor. Being a carb once the fuel bowl is filled the motor would keep running until the fuel ran out. When you disconnect power from the pump it dies right away because it also removed power to the coil

Look for the 15 to 20 amp ignition fuse under the helm. It feeds the key switch on the purple/red wire

If fuse is blown then most likely the TKS module or the temp switch has shorted out

 

[Rick Stephens]

First is check if you have power going to the pressure switch when the key is on. Then jump it there. If it runs, then your new pressure switch ain't so good.

The outside lug on your starter solenoid should be powered when cranking. If it isn't, then you have no primer circuit. In that case the only way you get fuel to the carb is to crank long enough to build up 5 or 6 pounds of oil pressure and engage the oil pressure switch.

 

[Nitz31]

Probably no 12V power going to the motor. By jumping the fuel pump directly it would back feed the the motor. Being a carb once the fuel bowl is filled the motor would keep running until the fuel ran out. When you disconnect power from the pump it dies right away because it also removed power to the coil

Look for the 15 to 20 amp ignition fuse under the helm. It feeds the key switch on the purple/red wire

If fuse is blown then most likely the TKS module or the temp switch has shorted out

View attachment 362323

Fuses are good. And when I jump the fuel pump, it is direct to the pump so there is no back feed into the system. Only the battery and the pump plug. Thank you for the diagram. I had a thought on just replacing the P/Y wire as a test but I dont know what feeds it. Does it come from the starter or is it drawing power from somewhere else?

 

[Nitz31]

First is check if you have power going to the pressure switch when the key is on. Then jump it there. If it runs, then your new pressure switch ain't so good.

The outside lug on your starter solenoid should be powered when cranking. If it isn't, then you have no primer circuit. In that case the only way you get fuel to the carb is to crank long enough to build up 5 or 6 pounds of oil pressure and engage the oil pressure switch.

No power at the outside lug when key is on or cranking. I jumped the pressure switch and the boat ran BUT when I did this the jumper became really hot. Did this while I was waiting for the new pressure switch to arrive. Installed that yesterday.

 

[alldodge]

No power at the outside lug when key is on or cranking. I jumped the pressure switch and the boat ran BUT when I did this the jumper became really hot. Did this while I was waiting for the new pressure switch to arrive. Installed that yesterday.

Starter or pump is drawing to much current or pur/yel is shorting out

Disconnect pur/yel from starter then jumper oil switch to get it to run. It should run without the jumper once started but find out if still gets hot

 

[Nitz31]

Starter or pump is drawing to much current or pur/yel is shorting out

Disconnect pur/yel from starter then jumper oil switch to get it to run. It should run without the jumper once started but find out if still gets hot

Did that. P/Y disconnected from starter and jumped oil pressure sensor plug. Fuel pump ran but same result, jumper wire got really hot. Installed new fuel pump and got same result, so I have ruled out the fuel pump being bad.

 

[alldodge]

Once it's running, will it continue to run without the jumper?

 

[Nitz31]

Once it's running, will it continue to run without the jumper?

I will have to double check on that later this evening. I am thinking no but will confirm.

 

[alldodge]

It should, the carb is full of fuel and should run for several minutes just idling

If it doesn't then there is a short somewhere. Will need a voltmeter to see 12V with key ON (motor not running) on purple wire. Should be on one side of the oil switch and + side of coil.

If less then 12V not running, something is pulling voltage down. unplug TKS and Temp switch

 

[nola mike]

Ok...
1. Engine cranks. So Yellow/red to slave and then to starter is good.
2. Gauges presumably work with ignition on, so purple circuit is good.
3. Nothing off of the starter lug when cranking, so that's an issue. However, I'd verify it with the P/Y disconnected at the starter.
4. When you jump the pump, is the P/Y disconnected at the pump? With P/Y disconnected at starter, oil switch, and pump, engine should run normally when the pump is jumped without the jumper getting hot.
5. With all of the above, you should get 12v off the both sides of the OP switch when running.

 

[Nitz31]

Ok...
1. Engine cranks. So Yellow/red to slave and then to starter is good.
2. Gauges presumably work with ignition on, so purple circuit is good.
3. Nothing off of the starter lug when cranking, so that's an issue. However, I'd verify it with the P/Y disconnected at the starter.
4. When you jump the pump, is the P/Y disconnected at the pump? With P/Y disconnected at starter, oil switch, and pump, engine should run normally when the pump is jumped without the jumper getting hot.
5. With all of the above, you should get 12v off the both sides of the OP switch when running.

Thank you. I will check and confirm this evening.

 

[Nitz31]

Update: Boat is heading to the shop for the professionals to look at. Pulled it from the water last night and jumped the fuel pump direct to the battery (no other lines connected) to flush the motor if possible (salt water use). Able to start and run for ~5 minutes then died. Lost spark to motor. Any thoughts? I will post my repairs when I get it back to help anyone else out if I can.

 

[alldodge]

I believe you have so.ething pulling to much current.

 

[nola mike]

I believe you have so.ething pulling to much current.

Can't think of why he'd lose spark after 5 minutes of running though, unless the temp switch closing did something. Op, do you have 12v at the coil pos when you lose spark?

 

[Nitz31]

Can't think of why he'd lose spark after 5 minutes of running though, unless the temp switch closing did something. Op, do you have 12v at the coil pos when you lose spark?

Didnt check before it went to the shop.

 

[Nitz31]

OK, boat is back from the shop. Here's the answers in case anyone else may run into this issue. 1 - Oil pressure sensor was bad and replaced; 2 - Temperature sensor switch was also bad and shorting out when engine reached 130F and shutting everything else down. Even being this simple it still took the shop about 6 hours of diagnosis to pinpoint the issue. $1300 for a $70 part but problem solved and the boat runs great again.

 

[Rick Stephens]

Diagnosis is always a bear. Glad you got back running. Tough one.

 

[nola mike]

We were getting close! That goofy ass tks system strikes again...
Thanks for the update, enjoy being on the water.