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Discussion Starter #1
Hi - I'm the proud owner of a mostly running 1987 Suburban, with 6.2 of course. This is my first GM diesel so I have a few questions to get it fully on the road.
The oil pressure gauge and temp gauge don't work, so i bought new sending units. However, the wiring connectors seem different. Did I get the wrong ones, or do I have to "adjust' the wiring to connect? Especially the temp sender old one seems to have 1 wire, but the new one has 2 pins for connectors. I did just buy these at the local parts store, so if that's no good where is the best place to order parts from? I know a lot of times you get what you pay for, so I don't mind spending a little more to buy GOOD parts...
Also I found your fantastic reference lit section, but I'm old school in that I like to have a printed manual to hold in my lap before I crawl up underneath my rig. What are the recommendations for the best one I can buy? I know Haynes, Chilton, etc usually aren't the best on details, so I'm hoping there's one or 2 good ones out there that are a little better. I'm sure I'll have more questions as I dig into this thing. Thanks!!!
 

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Welcome to DieselPlace

Be sure to look in the FAQ located at the top of the 6.2L page. It has all the goto info you seek including manuals you can download and more:

(y)
 

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Welcome!

This is a valuable forum and you're going to get a lot of use out of it.

The oil pressure sending unit should be a single blade connector.

The coolant temperature sensor is a two terminal connection.

You have the right new sending unit, but I bet you're looking at the wrong unit on the engine.

I'm guessing that you're looking at the sensor on the drivers side of the block near the front. That is not the temperature sensor that goes to the gauge, that temperature sensor is part of the glow plug controller system.

The temperature sensor that goes to the gauge is located on the passenger side of the block towards the rear.

Hope this helps somewhat.
 

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Incorrect, 6.2 is a single wire sensor. Driver head at the front.
The passenger rear is the one for the glow plugs. It is a thermal switch, and very hard to find and expensive these days.

Oil pressure sender is a single wire sender behind the driver head.
 
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Discussion Starter #6
Hmmm, did it change from year to year? I'm looking at the driver's side head, the wire closest to the front. Sensor body feels the same (I haven't taken it out yet since I'm not sure) but it has a single wire that slides onto a T post, not a spade lug. This is on a 1987 version, if that makes a difference. This is the one I have, from Advance Auto, note the 2 pins for a plug: Ecatalog
 

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Discussion Starter #7
Paddy looks like you posted just when I did. The ones in that catalog page all look like the one I have. Problem is I just have one wire, with a very different plug on the end. Any idea what kind of adapter or what the other wire is supposed to be?
Thanks,m
 

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Paddy looks like you posted just when I did. The ones in that catalog page all look like the one I have. Problem is I just have one wire, with a very different plug on the end. Any idea what kind of adapter or what the other wire is supposed to be?
Thanks,m
Look at the rockauto page again.

There is one with a single spade connector that is labeled "switch."
 

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Discussion Starter #10
OK, had a chance to do some wrenching this afternoon. replaced the oil pressure sender, which was a giant pain to get to, and no difference.
:(
So I unplugged the driver's side sensor wire, and no difference there either. Plugged it back in, and unplugged the passenger side 2 wire sensor, and no difference there either.
So basically, with the key off, Oil pressure is pegged, and temp gauge is pegged. Turn the key on, and oil pressure needle drops to 40. Crank & run, needle is back pegged, although it does wiggle a tiny bit every now and then.
No matter what you do, temp needle never moves. So I'm thinking maybe it's not the sender anyway, and I may have 2 bum gauges? Does that sound right? or maybe a pinched wire somewhere? Is it worth tracking down new replacement OEM gauges or should I just upgrade/replace? Thanks for all the advice.
 

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FWIW LMC Truck sells replacement OEM style gauges without having to buy the whole cluster...

I have no skin in the game, I'm just a satisfied customer of theirs...

The pic finally loaded... that's a late model sender, two wires, one for signal, the other for ground back to the computer. Having a seperate ground makes teh sender more accurate for ECM's and such, eliminates corroded ground straps, rusty blocks, etc. Solid copper (well, stranded) from inside out to the sender and back...
 

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Hi NC Burb,
in case you have a faulty gauge, then you don't need to replace it! The original Delco gauges for the diesel trucks are different from the gas trucks and they are an absolut rarity and very hard to get!!!!! So don't throw it away!!! There is a very simple way to repair it. I had the same issue and i learned a lot. So just disassemble the instrument cluster and remove the gauge. On the back of the gauge you see a ceramic resister attached to the gauge. Disassemble the resistor. The resistor has a color. Now you need a multimeter. Measure the resistance (ohm). GM has a chart with all the colors. Each color has a unique rsistance. For example the color brown has 78 ohms or dark green has 90 ohms. But you need only to know if there is a resistance when you measure it or not. In case there is no resistance, then the resistor is broken and you have to replace it with a new one from the same color.
The same thing are with the temperature sensor and oil pressure sensor. you just need to measure the resistance on them.
So for the truck years 1979-1990 the coolant temperature sensor has a resistance of 1365 ohms when the coolant is cold. When the coolant is boiling it has 55 ohms. On operating temperature (200°F) the resistance should be around 96 ohms.
The oil pressure gauge for the truck years 1978-1990 has a resistance of 1 ohm at 0 psi. 80 psi would be 88 ohms. But when the engine is in idle you have around 35-40 psi oil pressure and the resistance should then be around 40 ohms.
 

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Discussion Starter #13
oh wow, I am flashing back to my circuits course lab in college...should have paid more attention. :)
I guess I will pull the cluster and the gauges, they're not doing any good right now anyway. thanks for the tip, I'll have to dig in some more!
 

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i
oh wow, I am flashing back to my circuits course lab in college...should have paid more attention. :)
I guess I will pull the cluster and the gauges, they're not doing any good right now anyway. thanks for the tip, I'll have to dig in some more!
if you have more detailed questions, just ask me. I gained lots of experience the last years when i rebuilded my truck. So i'm happy if i can share my knowledge now with somebody who needs help.
 

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Discussion Starter #15
thanks. So do my symptoms mentioned above in post #10 sound like bad resistors? or wiring short or something else? I guess I have to start somewhere and start tracing things out. Thanks,
 

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thanks. So do my symptoms mentioned above in post #10 sound like bad resistors? or wiring short or something else? I guess I have to start somewhere and start tracing things out. Thanks,
yes, according to the symptoms it could be that. After so many years in service is the chance high that they are broken. In my instrument cluster i had also two broken resistors. But the gauges itsself are almost indestructible. Further you can check if the ground from the instrument cluster is bad. That ground is bolted on the sheet metal about 3 inches on top of the fuse box behind the wiring harness.
 

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thanks. So do my symptoms mentioned above in post #10 sound like bad resistors? or wiring short or something else? I guess I have to start somewhere and start tracing things out. Thanks,
Start by going through all of your grounds. Remove each one, clean the contact points, and then reinstall.
Replace any that are in questionable shape
 

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I'd slap a mechanical gauge in it and be done with it.
 
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Welcome to the forum 'Burbman. Like mentioned above, you've come to the right place for accurate and experienced information, on this long lost engine. Keep the faith, and don't give up. Once your Burb is tuned in, you'll love it for (if nothing more) the fuel mileage, and simplicity.
 

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Once upon a time, I fixed the problem of inaccurate stock gauges...

 
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