System Check troubles and Tach.

[FishhawkNWO]

I had posted this question in another thread but figured instead of hijacking that one that I would start a new one here. Thank you to those that already offered inputs on the topic.

If anyone has a tach they would like to sell please keep me in mind.

I purchased a boat last summer and started it for the first time yesterday after sitting all winter. It has a 1996 evinrude 50hp. The tach has system check with the 4 warnings.

My first concern was that I wasn’t getting a “beep” when the ignition was turned on which lead me to find that the tach wasnt working. The tach was unplugged. While plugged in the motor would not start. With it disconnected it ran fine. After plugging it in again the tach got so hot it melted pin 1 and it pulled out from the gauge when I went to remove the connector.

After checking voltage on the harness side with the ignition in the on position there is 12V being supplied to pins 1,4, and 8. Previous owner said he didn’t know anything about it.

A member already explained which each pin does thanks @Chris1956

“Pin 1 is purple wire, should have ign +12VDC

Pin 2 is black wire, ground all the time

Pin 3 is grey wire, is tach sender

Pin 4 is tan/yellow from VRO pump, should not have voltage. Should ground to indicate "no Oil" alarm

Pin 5 tan/black is low oil in reservoir. Will ground when low oil.

Pin 6 -Tan- is overheat, Will be grounded when engine overheats.

Pin 7 is tan/orange. Is "system Check" alarm. indicates fuel restriction on V6 OBs only.
Pin 8 is tan/purple, will supply voltage to horn. Probably if you fix pin 4, that will get fixed.

So I would look for melted wires near VRO pump, allowing purple to short to tan/yellow”

I followed the wiring and found where it connects to the VRO pump in the motor. There are no spots that I was able to find where the tan/yellow wire would be in contact with the purple wire.

A few questions:

1. Why would the tach stop the boat from being started?

2. Are there any other areas that might be giving 12V input to pin 4?

3. What would cause pin 1 to get so hot? (Although the entire tachometer got warm and is probably smoked now)

Was so excited to take my family out for a boat ride and this stuff happens. Tis life.

Thanks in advance.

- FishhawkNWO

 

[dingbat]

Guessing your gauge is shorted internally and needs replaced.

FWIW: pin # 4 is normally closed in operation

Test # 2 from the book.
With ignition switch on, check voltage between pin #1 (purple) and pin 2 (blk) . If battery voltage is present replace gauge

 

[Chris1956]

To add to what Dingbat said, which I thought confusing. If the gauge doesn't work, and you have voltage on pin 1 and ground on pin 2, the voltage supply is good, therefore the gauge is bad.

Also, I think the tan/yellow wire will be open when oil is being pumped by the VRO pump. Test 9 says to connect the tan/yellow to the black (ground wire) and see if the gauge shows the "no oil" light. Consequently when the tan/yellow is not grounded, there will not be an alarm.

Did you find any wires melted in the harness?

FWIW, I expect your system check gauge is bad. However, you need to get the alarm circuits working before replacing it.

For now you may be able to use the tachometer function. Your wiring harness may have ring terminals on the purple, black and grey wires. The sys check gauge had corresponding posts for them.

 

[FishhawkNWO]

Good morning,

As always thank you for the replies.

I was able to find a thin green wire behind the inline fuel filter that the insulation was melted. This thin green wire was part of a cluster with:

Green
White/tan
Black/tan
Big green
Big blue

When I found voltage at pins 1,4,8 I had the negative on pin #2.

Voltage supply is definitely good to pin 2, my concern is if I buy another gauge and connect it with voltage at pin #4 that it gets smoked too. At over $200 a pop it is an expensive test. I’m determined to figure out what is causing voltage supply to pin 4.

Does anyone have any recommendations on where to find a PDF service manual? The photos I’ve found have been pieced together but would be great to have a full manual.

Regards

 

[dingbat]

Good morning,

As always thank you for the replies.

I was able to find a thin green wire behind the inline fuel filter that the insulation was melted. This thin green wire was part of a cluster with:

Green
White/tan
Black/tan
Big green
Big blue

When I found voltage at pins 1,4,8 I had the negative on pin #2.

Voltage between pin 1 and 2 is a ground fault with in the tachometer. All bets are off after that

 

[Faztbullet]

If there is any short on the purple wire it should blow the fuse on engine. I would disconnect rectifier/reg at engine and retest.

 

[FishhawkNWO]

Voltage between pin 1 and 2 is a ground fault with in the tachometer. All bets are off after that

I did two tests, one with negative on bus terminal of fuse block, other with negative on pin 2, both tests showed 12 volts at pins 1,4,8. This was on the harness side.

All bets off meaning?

 

[Faztbullet]

If in my shop this is what I would do:
1) Disconnect rectifier/reg
2) Disconnect VRO harness
3) Check pins again for voltage
There is nothing in that wiring that will keep ignition system from working.

 

[FishhawkNWO]

Here are the results from unplugging VRO

Ignition on VRO plugged in:

Pin 1: 12V
Pin 4: 12 V
Pin 8: 12V

Ignition on VRO unplugged:

Pin 1: 12V
Pin 4: 0V
Pin 8: 12V

I did a continuity test on the VRO between the purple wire and the tan wire and it showed continuity. Therefore safe to say VRO needs to be pulled, inspected, repaired, and/or replaced?

Motor is still running as it should.

Thanks

 

[Chris1956]

That cluster of green, black/tan, white/tan is for PTT trim sensor. Big green and Big Blue are PTT motor wires.

Pin 8 is power to the horn. It should sound a beep, when power applied to system check gauge. Power should then disappear on that wire.

Clearly power is getting on pin 4 very near or in the VRO pump. I would inspect wires up to when they go into VRO pump. I do not know if you can repair/replace the no oil warning module in the VRO.

 

[dingbat]

All bets off meaning?

You are not dealing with simple relays. You have logic control (ICs) in both the gauge and vro pump.

A blow logIc control module, as evidenced by 12V on pin 1, could short the control internally causing the erroneous readings your seeing.

VRO is a simple magnetic pulse counter. Power supplied to the VRO at the vro connector thus the reason you lost 12v on pin 4 when disconnected the vro connector.

 

[FishhawkNWO]

Hi everyone, I’d just like to firstly say thank you to anyone that took the time out of their day to help a newbie out. It was very much appreciated.

After doing the continuity test and finding that pins 1 and 4 had continuity at the VRO I suspected it was time to pull it. Miraculously my neighbour heard me puttering away and HE HAD A SPARE VRO! I pulled mine, and noticed the electronic module of the VRO could be removed. The pump my neighbour had given me had slightly different mounts. I pulled the module off mine, checked the part number and it matched the module on the pump my neighbour had. So I just switched over the modules. I did this because the pump that was on my boat was working fine, it was only the module that was acting up.

Below is a photo of the module I pulled. You can see a bubble in the top left where I suspect it shorted and heated up.