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TBI oil pressure switch ?'s

bluejeep

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TBI oil pressure switch ?\'s

Having troubles with my TBI (88 motor) and was told by a shop to change the oil pressure switch. I went to take the old one off and the extension/elbow piece that it screws into broke off at the block, back beside the distributor. Dealer wants $25 for this extension/elbow. Anybody know what size the threads are that screw into the block? I want to use some common brass fittings for $5 and hook it up once I get the old piece out, and want to be prepared with the correct fittings to get it hooked back up. Thanks in advance... /forums/images/graemlins/1zhelp.gif
 

azblazor

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Re: TBI oil pressure switch ?\'s

I believe it's most likely 1/8" NPT - but there are definately variances - even between same years. I just replaced my daughters 89 and they listed 2 different sizes for that year. Her's was the 1/8.
 

bluejeep

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Re: TBI oil pressure switch ?\'s

How much do they vary, any idea? It's visually easy to tell the difference between 1/8 and 1/4 NPT. I was thinking it looked like 1/8" NPT, but I wanted to see if anybody knew for sure. Any idea what that other available size was? Thanks for the reply.
 

azblazor

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Re: TBI oil pressure switch ?\'s

Well if it looks like it's 1/8 it probably is. But if it were me I would take it apart first. Isn't it already broken?
 

bigburban383

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Re: TBI oil pressure switch ?\'s

Yeah, just remove it and take it to the hardware store. Your gonna have to remove the distributor to get to it.
 

bluejeep

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Re: TBI oil pressure switch ?\'s

Yeah, it's already broken and yeah, it's under the distributor. I was just hoping to stop at the hardware store on the way home from work....
 

dyeager535

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Re: TBI oil pressure switch ?\'s

All the blocks I have ever seen are 1/8" front and rear oil fittings, and most of the time, 1/4" above the oil filter.

I'm sure there is SOME variation, but 1/8" front and rear seems to be the most common. Some early blocks didn't have the 1/4" above the oil filter drilled/tapped.

There are a few different sending unit/switches out there, Napa's "Echlin" catalog is fun to look in...lists how the connector needs to be pinned, what the values of the switch or sender are (0-90 ohms for example) functions, and 1/8", 1/4", etc. in most cases.

I started out with a seperate oil pressure sender and switch, but with that catalog, found one out of a slightly newer GM vehicle that was 1/4", and did both functions, with one 3 wire connector. Just an idea.
 

bluejeep

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Re: TBI oil pressure switch ?\'s

Got the broken off piece out last night and it appears to be 8mm x 1.0 threads where it screws into the block. I've ordered the replacement from GM, but I'm pretty sure the switch itself is 1/4" NPT where it screws into the elbow fitting.
 
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