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Alpha 1 Gen 2 Shift Issues

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Fritzerton

New member
Hello,

I have a 2002 Chaparral Sunesta 233 with the Alpha 1 Gen 2. The engine is a Mercruiser 5.0.

I’m having issues with it sticking in gear when going from forward or reverse to neutral. We've been fighting this for about a month and gone through the whole adjustment procedure in the service manual several times but it hasn't made a difference. I had a marine mechanic try fixing it when I was at the lake a few weeks ago and he couldn't get it any better and suggested replacing the lower shift cable. We got the lower cable replaced this past weekend and it still has the same problem.

One thing I've noticed is when I press shift interupt switch by hand, the RPMs of the engine go up a little bit then bounce up/down for about 3 seconds before it finally dies. I haven't been able to find anyone else with a similar engine to compare to see if this is normal. In normal operation on the water, when I shift to neutral, the rpm will go up and bounce then after the 3 seconds when the engine rpm drops low enough it will come out of gear just before shutting off.

The engine is the EFI model and has the switch that is normally closed so the circuit opens when the switch is pressed.

Here's a video showing what its doing when I press the shift interupt switch by hand-

Does anyone have any suggestions of what I can check next? I don't know what else to look at.
 
The shift interuptor switch should kill the ignition if held depressed.

When shifting out of forward or reverse to neutral this causes resistance on the short cable which moves the V nitch part you were pushing. This action should cause the switch to close causing a momentary (or as long as the switch is depressed) short to ground shutting down the ignition.

What i dont see is the switch itself.

You depress the switch NOT move the V notched part typically to test.

One lead from switch goes to Ignition control, the other goes to ground.

So find the switch which should be in the middle of the V notch when in nuetral and depress when running, engine should stall.

If it does NOT, confirm wires are good and all connected.
If you know how to test the switch with a meter then test it or ask someone who inderstands how to, to test it.
If all wires are good and the switch tests bad, Replace switch.
 
Did you replace it with a factory shift cable? What is idle speed ? Wondering if you can lower idle speed to help with it
 
Yes, it was replaced with the factory shift cable. The idle rpm is around 700. I’m not sure if it’s possible lower the idle. It’s EFI and from what I’ve read the idle is controlled by the ECM and can’t be adjusted.

This engine has the interrupt switch with the normally closed contacts that connect to the ECM so it doesn’t ground the ignition when it’s pressed. I believe the switch actually grounds the pin on the ecm all the time in its normal operating position when it’s not activated then opens that circuit when the switch is pressed. I’ve removed the switch connectors and checked the contacts when the switch is pressed and released and the switch is operating correctly.
 
Fritzerton said:
Yes, it was replaced with the factory shift cable. The idle rpm is around 700. I’m not sure if it’s possible lower the idle. It’s EFI and from what I’ve read the idle is controlled by the ECM and can’t be adjusted.

This engine has the interrupt switch with the normally closed contacts that connect to the ECM so it doesn’t ground the ignition when it’s pressed. I believe the switch actually grounds the pin on the ecm all the time in its normal operating position when it’s not activated then opens that circuit when the switch is pressed. I’ve removed the switch connectors and checked the contacts when the switch is pressed and released and the switch is operating correctly.
Click to expand...
didnt realize the idle speed is fixed or controlled by ecm. Re-reading your original post you said rpms pick up then it dies? Can you see spark interrupted from coil to distributor on a timing light when it is depressed manually and or with the shift lever?


also wonder if shift mechanism in bellhousing is swinging freely ? you just replaced the cable did the swivel move freely and lever on drive?

When I did my bellows I replaced the bushing and seal on shift shaft in bellhousing. I didn't fully seat the bushing so it created a little drag on the swivel which was tripping the interrupt going into gear...took a lot of effort to shift... took it off and saw this didnt move freely tapped the bushing in flush with bellhousing and all is well . Just wondering if you have something hanging up the linkage that the drive isnt getting in to neutral when the interrupt is being tapped?
 
Fritzerton said:
Yes, it was replaced with the factory shift cable. The idle rpm is around 700. I’m not sure if it’s possible lower the idle. It’s EFI and from what I’ve read the idle is controlled by the ECM and can’t be adjusted.

This engine has the interrupt switch with the normally closed contacts that connect to the ECM so it doesn’t ground the ignition when it’s pressed. I believe the switch actually grounds the pin on the ecm all the time in its normal operating position when it’s not activated then opens that circuit when the switch is pressed. I’ve removed the switch connectors and checked the contacts when the switch is pressed and released and the switch is operating correctly.
Click to expand...

As I have no experience with EFI systems I can only suggest things.

If the interuptor switch works as you describe, it still is designed to kill the ignition when depressed by hand or when functioning normal. Alpha drives depend on it to get out of gear.

So that being said, you need to confirm if you actuate/depress and hold the switch while engine is running, it ahould stall out.

With Alpha drives if one shifts out of gear to slowly the engine can stall.

What is being described is the momentary engine cut out is NOT occurring making it almost impossible to get back to neutral.
Is this correct?

If so, without a scan tool I am not sure (myself) how to determine if the ecm is getting the appropriate signal.

One other qiestion, the switch has two wires, correct?
Can you determine where they go?
Non efi, one goes to ground, other goes to ign module (Thunderbolt ignitions)
 
On the EFI models, the switch has a similar function but the implementation is handled differently inside of the ECU.

The shift interrupter switch three wires and the NO vs NC description is somewhat ambiguous...the service manual uses "activated" to describe when the shift cable moves (trips the switch) when going from in gear back to neutral...so when the switch is in the 'normal state', should have continuity between the two purple wires (on either end of the connector). When the switch is activated, this opens the connection between the purple wires...the other wire has a pullup resistor which connects to one of the purple wires...all three go back to the ECU.
 
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