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Old 12-11-2011, 08:42 PM   #1
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Default ALarms Until BOTH Engines Started?

Hello!

I have an issue on my 1998 3000 SCR. I have twin 4.3L V-6's and when I start either engine, the alarm continues until I start the second engine, then the alarms stop. Also, when I turn off the port engine ignition, nothing happens until I shut down the Starboard engine, then both shut off.

All fluid levels are good and oil pressure is good. Not sure why this is suddenly happening! All worked fine until recently.

Anyone have any ideas wher to start looking?

Thanks in advance for your help!
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Old 12-12-2011, 01:59 AM   #2
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both alarm and end shut down fuctions: sound like a bad ignition switch, or someone crossed a wire under the dash, or wire poped off the ignition.

pull the panel down and check.
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Old 12-12-2011, 02:17 PM   #3
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I pulled the panel the other day and didn't notice any wires loose, I will check to see if the ignition switch is bad. What's wierd is, it allows the port engine to START fine, but won't shut down. I am going to head down there today and check lots of wires! I have been doing some reading and it appears some people say it could be a bad sensor, but not sure why it would shut down when the OTHER engine starts?

I'll dig into my wiring and se what I can find!
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Old 12-12-2011, 06:00 PM   #4
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Okay... After further investigation... The ignition switches appear to work fine on both engines. When I start one engine, the alarm howls away without stopping. If I do not start the other engine, the ignition switch will shut the engine down. This works on both sides. The problem (and the solution) happens when I start the OTHER engine. The alarm stops as soon as the second engine is started. As soon as the second engine starts, the engines will NOT shut down until BOTH engines are shut off by the key.

The EMERGENCY cut off works on both engines separately when both engines are working. this is just a WIERD problem and I am sure it is just a bad ground somewhere in the system... Only question is... WHERE???
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Old 12-12-2011, 06:20 PM   #5
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The engine alarm you are desciribing is there to verify the engine warning system is working. This should occur whenever you set the keys to the ACC. position. It should stop as soon as you successfully start the engine. On my 97 2800, when I had the stock 7.4 (454) installed the alarm would sounds constantly when the key was in the ACC position, and stop once the engine was started. When I repowered with an 8.1 496) the alarm only sounds for about 3-5 seconds when the key is set to ACC, then stops. Either is expected behavior.

I do have a few questions:

1) Are you setting both keys to ACC before starting?

2) With both keys OUT of the ignition, if you insert the Port engine key and turn the key to ACC. I would expect the alarm to sound. Once you start it, I would expect the alarm to stop.

3) With both keys OUT of the ignition, if you insert the Starboard engine key and turn the key to ACC. I would expect the alarm to sound. Once you start it, I would expect the alarm to stop.

What you describe sounds alot like expected behavior. However, I would not expect that you would need to shut down both engines to stop one engine. That makes no sense. I don't think this is a ground issue, however it does sound like someone may have wired the starters incorrectly.
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Old 12-12-2011, 06:50 PM   #6
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all the key dose is ground out the ignition to kill the engine, you have one key not doing that. if you jumped out the wire i bet the engine stops, so the key ground is faulty.

the 2nd engine wire is shorted to the first. One key should never kill two engines, trace these wires.

the alarm is secondary, the alarm only know the engine is not turing and then squels.

The 2nd engine running will turn off the alarm.

The starting curcuit is not involved, but the main power lead comes off the 80 amp fusible link that sits on the top of the hot lug on the starter.

hot wire a power lead from the battery to the key with a long wire and see if you have the same problem by jumping out the key switch.
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Old 12-12-2011, 07:11 PM   #7
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Quote:
Originally Posted by pascavone View Post
all the key dose is ground out the ignition to kill the engine, you have one key not doing that. if you jumped out the wire i bet the engine stops, so the key ground is faulty.
You certain about that Pas? I always thought turning the key to the ON and Start positions supplied 12v to the ignition circuit, and turning the key to the OFF position killed the 12V to the ignition circuit. Turning off the 12V is diffent than grounding (shorting) out.

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Old 12-12-2011, 07:19 PM   #8
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we are both right.....

a 1998 engine probily has an module that shorts or kills the ignition.

they don't run the hot lead all the way to the key switch anymore, not in cars since the 1960's.

they use a relay, and the key grounds out the relay and the relay kills the ignition circuit.
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Old 12-12-2011, 07:19 PM   #9
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Jeff, you said the port engione will start fine but won't shut down when you turn the port engine key to "Off" when the other engine is running.

Question: With the starboard engine key in the Off position can you start AND stop the port engine with the key?
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Old 12-12-2011, 07:59 PM   #10
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I'm no electrical guru but I believe we've got to get the terminology right for effective troubleshooting.

We're talking about a 12V system where the negative side is ground (opposed to a positive side ground as used in some British cars). As such only the positive side is switched. A relay, as I understand it, has 2 sides, low amperage and high. When 12V is provided (switched on) to the low side the relay closes (normally Open) it completes the circuit on the high side - providing 12V to the load.

In my mind, when you "ground" something you are, basically, shorting out the circuit. I don't believe that's how it works to kill the ignition.

Regardless, if Jeff's answer to my question above is Yes, then somehow the starboard ignition system is back feeding 12V to the port ignition system.

Dan
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