2007 Merc 5.0 TKS stalled at speed, had to be towed

[nola mike]

Fyi, looks like the tks switch may be different. I can't link ATM, but manual #41 has 2 switches (which one are we talking about?). It appears that the 2nd switch is different than the warning switch on the older models. And like I said above, this switch feeds the icm whereas the older ones didn't

 

[haglunde]

Fyi, looks like the tks switch may be different. I can't link ATM, but manual #41 has 2 switches (which one are we talking about?). It appears that the 2nd switch is different than the warning switch on the older models. And like I said above, this switch feeds the icm whereas the older ones didn't

Just got the TKS manual supplement and I see what you're talking about. There is a yellow wire oil pressure switch tied directly to the ICM. From the initial testing I've done with a smart buddy, it looks like we're not getting power to the fuel pump. But the fuel pump is functional- we hot wired it directly from the battery and it runs.

 

[alldodge]

The pump gets powered direct from the starter when cranking and thru the oil pressure switch when motor is running

 

[haglunde]

So we were just starting to get the diagnostics narrowed down when a new problem popped up. We are blowing the the 20amp ignition fuse (red wire). Then the diode smoke itself. The only things we did was to remove and replace connectors at the oil pressure switch and fuel pump for testing. And apply direct power to the fuel pump to ensure it worked without dependencies. Now the motor will run for a short while, then blow the 20 amp. When running, we tug on as much of the wiring harness as we can reach without issue. I did find a previous post where the temperature switch was blowing the 20 amp and the diode, which is instructive. But this now seems like a second problem not related to the first.

 

[alldodge]

Diode over heat and 20 amp fuse blows, sounds like the TKS module

Apply 12V thru a fuse to TKS and ground the other lead to see if fuse blows

 

[haglunde]

Could a bad fuel pump be causing this many issues?

 

[Scott Danforth]

Could a bad fuel pump be causing this many issues?

test the fuel pump. have to do the diagnostic work to determine what is wrong before firing the parts cannon.

 

[alldodge]

Could a bad fuel pump be causing this many issues?

I doubt it because you said the diode was overheating (Post 2 pic). If it was shorted out you wouldn't be able to turn the motor off. Blowing the fuse and diode getting hot leads me to the TKS module

 

[haglunde]

test the fuel pump. have to do the diagnostic work to determine what is wrong before firing the parts cannon.

If I have to pull the pump to test it, I will probably just replace it as it's buried behind the water separator and under the alternator. One of my frustrations is that you have to unplug things to test them and then they're not in a normal state. Is there a way to test it without pulling it to see if it's electrically within bounds?

 

[haglunde]

I doubt it because you said the diode was overheating (Post 2 pic). If it was shorted out you wouldn't be able to turn the motor off. Blowing the fuse and diode getting hot leads me to the TKS module

And this test would be a fused 12v direct battery connect to the module with a ground lead as well, correct? Is there a meter test?

 

[Scott Danforth]

hook wires to it and run it test..... tells you if the pump works or not can be done in-situ

then see if the pump is getting power test.....tells you if the wiring/controls works or not.

 

[alldodge]

And this test would be a fused 12v direct battery connect to the module with a ground lead as well, correct? Is there a meter test?

Yes, + and -

Meter
TKS Module Resistance
Ambient temperature 21° C (70° F) 35-45 Ohms - -6.6 ° C (20° F) 55-70 Ohms

 

[rickasbury]

Ayuh,.... Welcome Aboard,...... There should be a fuel pump switch on the portside of the motor's block, aft of center, way down low, just above the oil pan,.....
That oil pressure switch powers the fuel pump, when the motor is runnin',......

When starting, the fuel pump is powered by the outboard side tiny terminal on the starter's solenoid,.....

That's what that little wire is for...thx!

 

[haglunde]

The shop has the boat now all winterized and shrink-wrapped. It runs fine when first started so they were able to do the oil, lower unit and antifreeze. This saga will apparently continue in spring. Thanks, all--

 

[alldodge]

Dang