Thunderbolt IV

[tpirate]

I am working with a 4.3 Alpha one (SN OC 753728) with thu nderbolt IV ignition. Lost spark did the trouble shooting guide and determined the issue to be the distributor sensor. Thanks for the info.

During this process I found the gray wire to the tach. Disconnected and terminal connector wrapped with tape. I haven't tried connecting it as I'm waiting on the sensor. Any thoughts as to why it would be Disconnected?

Also, I found a blue/white wire disconnected. It was run with a blue wire which was connected to a sensor on the port side of intake beside the distributor(oil sensor maybe?) Any idea where the blue/white wire should be connected?

 

[Bt Doctur]

just a guess the tach was causing an issue running the motor,does the tach work now?
Blue in that area is the oil pressure sensor and the Blue/white(tan) may be for the "no oil pressure sender"

 

[tpirate]

I haven't tried the tach yet but, will see what happens once I get the distributor sensor installed.

Not sure where the no oil pressure sender is.

Os that even necessary if I'm showing good pressure on my oil gage?

 

[Scott06]

I haven't tried the tach yet but, will see what happens once I get the distributor sensor installed.

Not sure where the no oil pressure sender is.

Os that even necessary if I'm showing good pressure on my oil gage?

The low oil pressure switch will either be on top of block by distributor or down by the filter. The sender is for the gauge , the switch makes an audible alarm when oil pressure is low. Depending on the year the alarm system for merc sounds for low oil pressure, high engine temp, and low drive lube level (alpha gen2 and newer only).

when you start it will beep until oil pressure gets up. Someone may not like that and have disconnected it. Is it necessary no but not bad to have working. This happened to me a few weeks ago. Was skiing picked up some weeds and going along at basically WOT on way home... I regularly scan my gauges but basically instantly my temp shot up to 200, alarm was first indication I had of high temp. I would have noticed a bit later but the alarm got my attention to shut it off.

 

[tpirate]

The sensor is next to the distributor. The blue wire is connected at the top. Would the blue/white wire attach at the same terminal? I attempted to attach a photo but it won't load.

 

[alldodge]

As @Bt Doctur mentioned, most likely your Blue/white wire is actually a Blue/Tan and goes to the oil pressure switch.

The Blue goes to the oil gauge sensor
The Blue/Tan goes to the oil switch.
Edit: scratch the fuel pump comment, Tan/Blue sounds the alarm if oil pressure is lost

Double edit: I need more coffee
Tan/Blue , Tan with a Blue stripe is used for alarm

 

[tpirate]

10-4, the blue/tan is for the alarm. It's been disconnected since I've owned the boat so not sure where to stick it. Sounds like it goes on the same terminal as the blue wire ?

 

[Scott06]

10-4, the blue/tan is for the alarm. It's been disconnected since I've owned the boat so not sure where to stick it. Sounds like it goes on the same terminal as the blue wire ?

no goes on a switch not sender completely different functions. Switch just opens and closes electrically speaking at a given pressure (4 or 7 psi) , sender changes resistance over a pressure range (ohms) to gauge gauge moves based on ohms signal it gets. If you dont have a oil pressure switch there may be extra connectors in the harness. My merc had an extra ground lug in it for I think a mercathode that the boat didnt come with

 

[tpirate]

no goes on a switch not sender completely different functions. Switch just opens and closes electrically speaking at a given pressure (4 or 7 psi) , sender changes resistance over a pressure range (ohms) to gauge gauge moves based on ohms signal it gets. If you dont have a oil pressure switch there may be extra connectors in the harness. My merc had an extra ground lug in it for I think a mercathode that the boat didnt come with

Okay. That makes sense. I'm thinking there's no switch to attach it to.

Thank you

 

[nola mike]

Okay. That makes sense. I'm thinking there's no switch to attach it to.

Thank you

Might not be. What year? The '89 I pulled my accessories from didn't have one.

 

[tpirate]

It's a 1990 Chaparral

 

[tpirate]

The low oil pressure switch will either be on top of block by distributor or down by the filter. The sender is for the gauge , the switch makes an audible alarm when oil pressure is low. Depending on the year the alarm system for merc sounds for low oil pressure, high engine temp, and low drive lube level (alpha gen2 and newer only).

when you start it will beep until oil pressure gets up. Someone may not like that and have disconnected it. Is it necessary no but not bad to have working. This happened to me a few weeks ago. Was skiing picked up some weeds and going along at basically WOT on way home... I regularly scan my gauges but basically instantly my temp shot up to 200, alarm was first indication I had of high temp. I would have noticed a bit later but the alarm got my attention to shut it off.

I got the sensor installed, and she fired up with the bump of the key.....I decided to attach that wire from the tach that I found taped up. The boat wouldn't start. I could see the tach moving while cranking. I disconnected the wire and it was difficult to start and ran rough for a few seconds. Once it was idling smoothly again, I cut it off and it went back to starting easily and running great. What's going on with the tach? Would it be worth running new wires?

 

[alldodge]

It's common issue with Tach and time. The Tach is shorting out and needs replaced.

Reason it ran ruff is motor had excess gas that need to burn off from not starting

 

[nola mike]

Could also be the wire to the tach. You can connect it at the coil and disconnect at the tach. If it runs ok your tach is the problem

 

[tpirate]

Could also be the wire to the tach. You can connect it at the coil and disconnect at the tach. If it runs ok your tach is the problem

Thanks, I'll give that a try.