'86 Jimmy 4in Lift, 40’s, tons, 8.1 Swap- 700r4 said PNNNNN

[GWeakland620]

Another small setback found tonight. While laying out the wiring harness, I noticed I couldn’t find the plugs for my throttle body. After some research I found that I do not have the correct throttle body for my truck. Once I checked google images, I found the correct TB with my plug on it. So I’ll be trying to trade that out tomorrow at work.

May the record show that although I am saving money, I would not go this route again by piecing this swap together.

 

[GWeakland620]

Oil Pressure gauge part number is "D1819A - Oil Sending Unit (AC Delco)". And you also need to get "PT2326 - Oil Sending Unit Connector (AC Delco)" which is the plug for that sensor, it only has 1 wire coming out of the plug. Then all I did was splice the one signal wire from the original oil pressure plug in my original harness to that new connector, and that was it.

For my temp gauge I bought this: "TS6469 - Temp Sending unit (Napa part number)" and pulled the plug out of the port on the driver head (some people have had problems getting the plug out and had to drill it out, mine just unscrewed without issues luckily) and attached the factory temp sensor plug to it and that's it!

So how does the engine monitor oil pressure? Or does it?

 

[Kay86K5]

Another small setback found tonight. While laying out the wiring harness, I noticed I couldn’t find the plugs for my throttle body. After some research I found that I do not have the correct throttle body for my truck. Once I checked google images, I found the correct TB with my plug on it. So I’ll be trying to trade that out tomorrow at work.

May the record show that although I am saving money, I would not go this route again by piecing this swap together.

View attachment 330966

After I did the Tilden route vs trying to piece it together, it literally was the same amount of money in the end but took way more time to piece it together. It's a little more up front to buy a package, but saves a crazy amount of time in the end. Just depends on how you want to do it. If you're on a tight budget and can't drop a larger amount in a lump sum then go the piece together route, but don't think it's really going to save you much in the end (money and time included).

So how does the engine monitor oil pressure? Or does it?

I'm pretty sure the ECM is getting oil pressure from a different source. The sender I referenced is just to get your square body gauge to work. If you think about it, the way I put it together my gauges telling me what the motor is doing is completely separate from the ECM and the input it's getting for what the motor is doing.

 

[campfire]

Why bother with a separate gauge and sender if you can just pull the info from the ECM?

I assume you'd be pulling OBD2 info already, so why not skip the extra analog wiring?

 

[campfire]

And if you're not using OBD2 info, why would you even bother with a delightfully modern engine?

 

[Kay86K5]

Cause the square body gauges are already there, and it cost me little money to get them to work on the modern motor instead of having to buy a more expensive system to pull from the ECM (aka, Dakota digital gauges). ECM is handling running the motor and if it ever stops running and throws a code, you can still easily pull the code and research what's happening. The gauges are just a quick reference guide to the basics of what's happening with the motor. In my opinion, no real reason to spend extra money on fancy digital stuff there when the stock analog gauges will work just fine

 

[Glen Canyon]

Why bother with a separate gauge and sender if you can just pull the info from the ECM?

I assume you'd be pulling OBD2 info already, so why not skip the extra analog wiring?

I kept mine all factory gauges, used the temp sender from the old engine, mine is a 77 so it has a mechanical oil gauge and the factory tach works ,total cost 0 $

 

[Kay86K5]

I kept mine all factory gauges, used the temp sender from the old engine, mine is a 77 so it has a mechanical oil gauge and the factory tach works ,total cost 0 $

Yeah, all I did was the temp sender (pretty much a factory BBC one) and the specific Oil sender and plug to get the 8.1 to work. I don't remember off hand, but I don't think I spent over $30 to get all my factory gauges to work. It doesn't make sense to me why people spend crazy money on gauges. To each their own I guess

 

[ZooMad75]

Yeah, all I did was the temp sender (pretty much a factory BBC one) and the specific Oil sender and plug to get the 8.1 to work. I don't remember off hand, but I don't think I spent over $30 to get all my factory gauges to work. It doesn't make sense to me why people spend crazy money on gauges. To each their own I guess

The ecm does not need an oil pressure signal to run the engine. In a stock truck it took the info to send the information to the cluster via serial data.

Outside of shutting the fuel pump relay due to no oil pressure (like after a rollover) the ECM will work without the signal. I can't remember if the gmt800 truck did kill the fuel pump for a rollover or not. I'd have to look it up.

 

[Glen Canyon]

The ecm does not need an oil pressure signal to run the engine. In a stock truck it took the info to send the information to the cluster via serial data.

Outside of shutting the fuel pump relay due to no oil pressure (like after a rollover) the ECM will work without the signal. I can't remember if the gmt800 truck did kill the fuel pump for a rollover or not. I'd have to look it up.

When I built my harness I just removed the oil pressure wiring and all works fine.

 

[campfire]

Cause the square body gauges are already there, and it cost me little money to get them to work on the modern motor instead of having to buy a more expensive system to pull from the ECM (aka, Dakota digital gauges). ECM is handling running the motor and if it ever stops running and throws a code, you can still easily pull the code and research what's happening. The gauges are just a quick reference guide to the basics of what's happening with the motor. In my opinion, no real reason to spend extra money on fancy digital stuff there when the stock analog gauges will work just fine

I'm not advocating spending a mint on fake digital gauges. But an OBD2 reader is now a $7 item. Everybody should should have such a reader on hand for diagnostic use. So why not put it to work reading engine information while you drive?

 

[GWeakland620]

I'm not advocating spending a mint on fake digital gauges. But an OBD2 reader is now a $7 item. Everybody should should have such a reader on hand for diagnostic use. So why not put it to work reading engine information while you drive?

You still have an OBD2 port for diagnostics. Just not the large amounts of money to run a cluster off of the ECU.

 

[ZooMad75]

I'm not advocating spending a mint on fake digital gauges. But an OBD2 reader is now a $7 item. Everybody should should have such a reader on hand for diagnostic use. So why not put it to work reading engine information while you drive?

What's easier to read on the fly? A 2" diameter gauge with large numbers and big needle or a scan gauge with a digital readout 1/2" tall by 3" wide?

Not saying you shouldn't have a way to read engine data, but while driving you need easy at a glance not squint to read info.

 

[Truckman4life]

Some where I have an old automotive wiring book and it specifically talks about digital vs regular gauges and how the regular gauges are the way to go for racing and also to turn them in the mount so that the needles all point straight up to the 12 o'clock position at the normal operating place for that gauge so that when racing you can glance down quickly and just see if they are all at that spot without having to interpret any data.

 

[campfire]

What's easier to read on the fly? A 2" diameter gauge with large numbers and big needle or a scan gauge with a digital readout 1/2" tall by 3" wide?

Not saying you shouldn't have a way to read engine data, but while driving you need easy at a glance not squint to read info.

Yeah, that's true for gauges you watch closely. Oil pressure is a gauge most people never even notice. We are weird folks around here.

 

[GWeakland620]

Before this swap, the oil gauge was the only one that worked haha.

 

[Kay86K5]

The ecm does not need an oil pressure signal to run the engine. In a stock truck it took the info to send the information to the cluster via serial data.

Outside of shutting the fuel pump relay due to no oil pressure (like after a rollover) the ECM will work without the signal. I can't remember if the gmt800 truck did kill the fuel pump for a rollover or not. I'd have to look it up.

I know in my old 96 K2500 with an L29 454 it had the function of killing the fuel pump if the ECM read low oil pressure, cause it happened to me that the oil pressure sending unit went out, and the truck wouldn't fire...no fuel pump. So I changed the fuel pump and it did nothing. Did more research and decided to change the oil pressure sending unit, and it fired right back up.

I'm not advocating spending a mint on fake digital gauges. But an OBD2 reader is now a $7 item. Everybody should should have such a reader on hand for diagnostic use. So why not put it to work reading engine information while you drive?

Yeah, we're talking about two different things here. You're talking about being able to scan the ECM to read codes, clear codes, and see vitals of the vehicle. And yes, those are cheap and easy. I have one I bought off amazon that was $20 that plugs into the OBD2 port and then into my laptop. I downloaded the software and can do all that from my laptop.

We're talking about getting gauges setup inside the cab for when you're driving around. Yes, you can get digital gauges that pull from the signal the ECM is getting to run gauges, but those are pretty expensive as you start searching around. In the case of square body trucks, as we've mentioned above, it take minimal time and money to just keep your stock gauges and have them work. Therefore for little money you still have properly working gauges and can still pull data from the OBD2 port with a cheap scanner

 

[Smokinthehippies]

I know in my old 96 K2500 with an L29 454 it had the function of killing the fuel pump if the ECM read low oil pressure, cause it happened to me that the oil pressure sending unit went out, and the truck wouldn't fire...no fuel pump. So I changed the fuel pump and it did nothing. Did more research and decided to change the oil pressure sending unit, and it fired right back up.



Yeah, we're talking about two different things here. You're talking about being able to scan the ECM to read codes, clear codes, and see vitals of the vehicle. And yes, those are cheap and easy. I have one I bought off amazon that was $20 that plugs into the OBD2 port and then into my laptop. I downloaded the software and can do all that from my laptop.

We're talking about getting gauges setup inside the cab for when you're driving around. Yes, you can get digital gauges that pull from the signal the ECM is getting to run gauges, but those are pretty expensive as you start searching around. In the case of square body trucks, as we've mentioned above, it take minimal time and money to just keep your stock gauges and have them work. Therefore for little money you still have properly working gauges and can still pull data from the OBD2 port with a cheap scanner

not disagreeing with any of that, but the best cheap way to ibd2 gauge is to get a dongle that sends to an old phone and download the app. Pretty sure Ben has it on his truck @Babaganoosh

 

[GWeakland620]

not disagreeing with any of that, but the best cheap way to ibd2 gauge is to get a dongle that sends to an old phone and download the app. Pretty sure Ben has it on his truck @Babaganoosh

Wouldn't be the easiest to use if you typed with your middle finger or something...

 

[ZooMad75]

not disagreeing with any of that, but the best cheap way to ibd2 gauge is to get a dongle that sends to an old phone and download the app. Pretty sure Ben has it on his truck @Babaganoosh

I've got an obd2 dongle that works with my phone through the Torque app. Again great info, but even on a good size phone the data is a hell of an eyechart to read when I'm driving. I'm not saying it's my eyesight either, but it requires focus to look and see the screen. Focus that really needs to be on the road.

I typically will look at it for the data when I'm stopped or while somebody else is driving. Once the 8.1 goes in I'll tie it to my iPad I use in my Blazer for a bigger screen to view on. It's mounted out of my normal line of sight so I'll not pay much attention until I'm stopped.