Wiring - ignition does not turn off

[Mechanicalmike]

Hello,

I just bought a 1981 Catalina 27 with a universal diesel. Great boat but I have a wiring bug that I think the previous owner introduced.

1. If you start and have the engine running, you can turn the key off and the engine continues to run. It will only stop if you throttle it down to idle which has to be incorrect.
2. The fuel gauge is pegged beyond full. I removed the gauge and it dropped back to normal position. When I was turning the igition key on, I noticed it went up to 1/3 tank until the key hit the On position, then it pegged out all the way beyond full again.

I suspect the two are related to ignition switch wiring. Does anyone have a diagram or pointer?

All help is greatly appreciated. I believe the gauges and ignition to be original but in very clean condition. The connectors on the back however look much newer than original. Someone was wiring.

Thanks a bunch,
Mike N

 

[Calif. Ted]

Number 1 is normal, all diesels will continue to run with key off, only way to stop is to cut off fuel or air (in an emergency). You should be stopping by shutting off fuel with a solenoid controlled by a T-handle. Turning key to off while running may damage diodes in alternator.
Fuel gauge is faulty, I've pasted troubleshooting procedure from Teleflex:
The Teleflex fuel gauge and the level sender are designed to operate on 240 ohms (empty) and 33 ohms (full). Most other manufacturers build a marine fuel level system of the same resistance as gauges and senders may be mixed at the boat builder level.
There are only three components to the system-gauge, level sender, and the connecting sender wire. The sender wire should be inspected for breaks in the copper or corroded connection to the terminals.
The fuel gauge can be inspected in the following manner. Turn the ignition on. Remove the sender wire from back of gauge. Pointer must go below the empty mark. Next, connect the gauge sender terminal to ground. The pointer must go above the full mark. If the pointer moves past both E and F, the gauge is functional.
To check the fuel level sender remove wires from sender terminal. Connect volt/ohmmeter to two sender terminals (digital ohmmeter will tend to be jumpy). Ohmmeter should read approximately:
240 ohms @ empty
100 ohms @ 1/2 and
33 ohms @ full.
If the sender is not sized properly for the tank, errors in gauge reading can also occur.

 

[Mechanicalmike]

Hi Ted,

Thanks for the great information. I will perform the tests on the gauge and see what happens.

I was amazed to hear the key was not intended to shut of the motor and that returning the gas lever to verticle really is the design. Go figure. I have been around diesel vehicles for a long time and cannot thing of a car, truck, or tractor that has that requirement. Makes sense, just the first I have heard of it. Learned two new things today.

Thanks again,
Mike

 

[Calif. Ted]

Now that you mention it Mike, I guess the mechanical fuel shut off is pretty old school engineering. Since most have a mechanical fuel pump, once started electrical no longer required. Most new trucks & stuff are rigged so when you turn off key it shuts down fuel. It is usual on our boats to have a t-handle in the cockpit that pulls a cable attached to a shut-off on the injector pump.
The key switch usually powers up everything in the control panel, gauges, blower and starter circuit. It's usually fed by a 20 amp circuit with an inline fuse taped into the main wiring loom on top of the block, that's Catalina's MO anyway.
I think and hope your problem is the gauge or bad connection on sender wire, sender is a PITA to replace. I had one that was similar to yours and happy to find it was the gauge.

 

[Mechanicalmike]

I think it may be the fuel sender. Per the instructions, I tried testing the sender unit using a volt/ohm meter. I took both wires off of the sending unit. One was in the center and the other was a ground on the cover. When I tested the ohms, I first just checked the meter by touching the two tips. It went straight to 0. Then I touched the sending unit posts. The meter went almost to zero and the needle was bouncing between 0 and 3.

So, I am thinking bad sender unit at this time. It would expain the gauge being spiked to way past full.

Does this sound correct/accurate? I do have a fuel gauge in my old Glastron power boat that I could "borrow" to swap in and see what happens to it on the Catalina. It is not a small effort to do that.

Thanks,
Mike

 

[shipwreck66]

Mike, just go get a new sending unit from West Marine for $45. I just replaced mine, first time it has worked in years. the new units align perfectly with the holes on top, just b sure and get the shortest one available, about 6 inch. To get to the unit you will need a dremel tool to make a small cutout of fiberglass that is partially covering the unit. I had to remove mine to drain the bottom looking for water, found none, surprisingly. The older tractors used a similar cutoff switch to this one, simple but effective.

 

[Mechanicalmike]

Just wanted to do the final follow up post. I installed a new sending unit and all is right it the world. Thanks for all the help.

 

[donjambur]

Engine shutoff is accomplished by rotating throttle lever past vertical to rear to shutoff fuel. My hull # is 4855 1981 C27 SR w Universal 5411 IB Diesel. Don B