View single post by JH12947
 Posted: 12-06-2024 11:04 pm
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JH12947

 

Joined: 07-14-2022
Location: Penticton, British Columbia Canada
Posts: 56
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 Tom - The 3 terminal switches (such as an Echlin OP6610) can be wired such that the normally closed (S) terminal takes power from the ignition "start" wire on the solenoid to provide power to the pump until the pressure is high enough at which time it closes the contacts with the switched normally open terminal for running. I've pasted below an excerpt from a thread on the OpelGT.com forum that fully explains the operation. I have this setup on my Opel, and it works well, but in that car the OP drops right off when the engine is shut down.

Safety Switch contacts are "switched" by engine oil pressure ONLY:
1. CO/Common/"P"/e-Pump (+) Power
2. NC/Normally Closed/"S"/Ignition switch "Start"
3. NO/Normally Open/"I"/Ignition switch "On/Run"

1. Key in 'ON/RUN' position, engine off, no oil pressure, safety switch is static/unswitched (NC_CO NO): 12V available at safety switch NO/"I" contact, but not at NC/"S" and CO/"P" contacts . . . e-pump stopped.

2. Key in 'START' position, starter turns over engine, oil pressure rising, safety switch is static/unswitched (NC_CO NO): 12V available at NC/"S" and CO/"P" contacts to power e-pump . . . e-pump running.

3. Key in 'START' position, starter turns over engine, oil pressure rises to ~7PSI, safety switch is switched (NC CO_NO): 12V source for CO/"P" contact (e-pump power) is switched from NC/"S" to NO/"I" . . . e-pump running, engine starts.

4. Key released to 'ON/RUN' position, engine running, oil pressure above ~7PSI, safety switch stays switched (NC CO_NO): 12V source to CO/"P" contact (e-pump power) remains connected to NO/"I" by oil pressure . . . e-pump running, engine running.

5. Key is in 'ON/RUN' position, engine stops, oil pressure drops below ~7PSI, safety switch is switched back to static (NC_CO NO): CO/"P" contact (e-pump power) is switched back to NC/"S" by lack of oil pressure . . . e-pump stops due to no 12V at safety switch NC/"S" contact . . . ignition key not in 'Start' position!