Good Morning! New the forum...new to Toyotas...recently picked up an 87 4runner for my son's first vehicle for $1500. We have 10 months before he's driving so a little time to do a lot of stuff. The floor pan, spring mounts, cab mounts and frame are all solid. It runs and drives. The 5 speed shifts fine and t-case seems to be working. The body and interior are rough but it's the coolest beater in town! This is going to be an AWESOME educational experience for the both of us as neither of us are mechanics.
One issue we've encountered is the temp and fuel gauge not working. Figuring the temp gauge was more important, we started there. After verifying continuity between the gauge and the temp sensor we discover no voltage to the gauge. After some head scratching and deciphering the crappy diagrams in the Haynes manual we discovered voltage to the temp gauge is actually fed through the fuel gauge??? Upon removing the fuel gauge we discovered no continuity between the terminals on the back of the fuel gauge. We (gently) manually manipulated the fuel needle a handful of times and suddenly started getting continuity through the terminals. Once we plugged it back in and energized it both the fuel gauge and temp gauge started working.
Now however, the gauge only works when you tap the back of the cluster a few times. Once it's deenergized it stops working until you tap the back of the cluster. Looking on line for replacements I can only seem to find used gauges on ebay without any assurance it's actually a working unit. Anyone have advice on fixing the existing gauge or finding a new replacement? As I mentioned no one is ever going to confuse me with being a mechanic and this is my first experience working on any type of gauge. I guess I could try some WD-40 and blow it off gently? I usually fix everything with WD-40 and duct tape.
TIA for any advice!

 

Most here would recommend the factory service manual(FSM). I also strongly encourage the Toyota EWD manual(Electrical wiring diagram) You can sometimes find on eBay at an ok.
price. It's a gold mine of info you don't get in the regular FSM.
Everyone has their own approach, but if this was my recent acquisition, I'd go around and note everything not working. Create a list.
Then I'd start removing every non-Toyota item that's been added over the years, including any aftermarket wiring. If the factory wiring has been cut or spliced I'd repair the connection by solder and shrink tube.
The most common areas to look for add-ons would be the battery, under the driver's side dash, behind the radio, and both kick panels.
If you see previous repairs to the factory harness try and evaluate the quality of the repair and re-do if needed.
posting some pictures may help in accessing possible concerns. And don't use WD40. If you need to clean connections try brass brushes, steel wool, etc.

 

Jimkola thank you for the advice! I'll look for the FSM and wiring diagrams immediately.
Regarding the wiring, everything looks factory and to be in pretty good shape. The only non-factory addition is a stereo and a front bumper. The previous owners really didn't abuse it but they did use it.
This is going to be a great journey!

 

If you remove the connector from the water temp sender and ground it does the needle go all the way up? The sender is about 1/2 way back on the intake manifold, and sits vertically. The senders on the front of the intake do monitor water temp, but the give info to the ECU, not the gauge.

 

It does as long as we have continuity across the fuel gauge to the temp gauge. Before we discovered there was no continuity through the fuel gauge the needle did not move when the lead to the temp sender was grounded.