ahickman

Bought an 87 Runner 22RE, 5sp. and am working out all the bugs. After replacing an upper ball joint this morning, I started working on my list of electrical repairs. Both the fuel gauge and temperature gauge are not working. I have checked both temperature and fuel senders with an ohm meter. Both fall within FSM specs. Checked the wiring from the sensors all the way up to the comination meter in the dash. Checked that both gauges respond to applied voltage (e.g. needle moves with voltage). Everything seems to be in order, but neither meter moves. Tried wiggling the connectors/wires on the back of the combination meter. No effect. Per the FSM, there should be a few volts on one pin of each gauge. No such luck, Kinda stumped as to what to check next. Suggestions????

yayfortrees

Do you have voltage to the sending units?

ahickman

No. On the single wire attached to the coolant sensor, I read 0 V. Likewise, the fuel gauge reads 0 V.

abecedarian

grounds?

ahickman

For the coolant sender, the intake plenum serves as ground, right? The brass casing for the sensor is in direct contact. For the fuel sender, ground is good also. Stumped.

abecedarian

circuit is:

battery > ignition switch > gauge > sending unit > ground

no?

I'm away from my diagrams so forgive me.

ahickman

Yeah, looking at the FSM it should be that simple. I am tempted to put battery 12V on the top-side of each gauge. If the gauges do not respond, then I am tempted to move on to the next repair item.

abecedarian

I know it's never that simple. Parallel resistances and the like.
But I'd think you could check for the appropriate voltage / ground potential at the gauges' respective terminals- both gauges should have the same V+. Both should have different resistance to ground. And the resistance for each gauge ground return should be relatively equal to the resistance across each sending unit to ground.

ahickman

Thanks. Daylight is here and things are warming up. Heading out to give it another whirl. Thanks.

Hadmatt54

Your truck is an 87 and the wiring may be the same or different from an 86 which is the wiring diagrams that I will be refering to. Depending what options you have on your truck the testing procedures will vary. Do you have full instrumentation (Tach, Oil pressure gauge, water temperature gauge and fuel gauge, volt gauge, brake light, etc.) or does your truck have a combination of gauges and idiot lights (oil pressure light, temperature gauge and fuel gauge, alt light , brake light, etc.)? The reason I ask this is because all of the gauges, lights, etc. in your dash are connected to a common Buss and are fed from the 15 amp engine fuse, so I'm going to ask a couple of stupid questions, is there continuity across this fuse and have you verified 12v from the fuse to the combination meter (terminal A (white connector)11 yellow wire). If none of these lights are coming on when you turn the key on, then you do not have 12v. feeding the combination meter. If you do have 12v. then:- The 86 FSM that I have checks the gauges for a Combination meter with a tach using a 3.4 watt 12v. bulb in series with the sender lead to ground, so obviously these gauges need some resistance to ground in order to work. If you have a combination meter without a tach the tests use an analog dc voltmeter. My FSM does not have any test procedure where you directly ground the sender lead to test the gauge, so it would stand to reason a dc. voltmeter does not have the proper resistance. On the fuel gauge you have three terminals (Ig, Fu and E) and on the temp gauge you have three terminals (Ig, Tu and E), the FSM provides definite resistance specs between each of these terminals for both gauges.
Fuel:- Ig-Fu approx. 83ohms, Fu-E approx. 156 ohms, Ig-E approx. 239 ohms
Temp:-Ig-Tu approx. 135 ohms, Tu-E approx. 138 ohms, Ig-E approx. 273 ohms
Ig is the 12v. source, Fu and Tu go to the senders of each gauge, E is a common between only these two gauges and it connects to terminal A4 (22re 5 spd & 22r) or terminal A5 (22re auto & 22rte) white/black wire that goes to ground under the left kick panel.
If you are only having problems with these two gauges and everything else seems to be operating properly, then this may be the common link, check for continuity between E on both gauges this will verify that the printed circuit is ok between them. Check for continuity between E and any body ground, if everything else is ok this should reflect as poor or non continuity. Lift the ground under the kick panel, check for continuity from E (combo meter) to the ring terminal to verify the wiring. If this ground circuit is intact clean the ring terminal and the body metal where it connects and reconnect, hopefully this solves your problem. If it doesn't you will have to get into replacing parts.

ahickman

Answers:

1. My truck has a combination of idiot lights and gauges. Speed, fuel and temperature are the only gauges.
2. Looking at the FSM, all idiot lights and gauges are fed by the same 12V bus. Despite the fact that most of the elements are working, I did check to see that the 12V was being supplied at pin 11. Good to go.
3. I unplugged both sensors and checked for voltages between pins using a DC voltmeter. Nothing!
4. Checked continuity between E pins and is good.
5. Terminals A4/5 on the FSM I am using goes to the back door detection/EFI. Sure?

Aaron

Hadmatt54

I have both a Factory Service Manual and a Wiring Diagram manual for 86 4Runner/Pick-up, but there is some discrepancy between the two and the Combination meter Plugs is one such case. What the wiring diagram book calls connector "A", the FSM calls that same Connector "C". Why this is so I can't explain, but I also have a FSM and the Wiring Diagram Manual for an 89 4Runner and it does the same thing.
I assume that you are looking at section BE 26, if so look at wire C 4 or C5. One of these should be a white/black wire that goes to the left kick assuming that Toyota didn't change the colors from 86 to 87.
Turn to the wiring diagrams in the back of your FSM. Go to diagram 2 (top left corner) pane 6 (center of diagram under picture of combination meter) This diagram will confirm wire color and where the ground point is made. If your 87 is the same as my 86 there is a white/black wire that ties the Temp and Fuel gauges together and connects to ground point "a". On the bottom far left of this diagram it describes ground point "a" as "located under left front pillar".
If our wiring diagrams are not the same this diagram will point you in the right direction. The 87 may be different; on my 89 this ground was brown and it connected to the reinforcement pillar that the steering column bolts to and ties to both sides of the cab.
Good Luck!

86yotafirsttimer

i just purchased a 86 yota pick up 22r carbed 4x4 5 speed im a mechanic but new to these old yotas i bought without the fuel and temp gauge working where do i begin on solving this problem

yotarover

have fun

93toyrunner2

Download the FSM from the link in my signature, and open your own thread for your question in the "Newbie" section.

Hadmatt54

Post #10 is straight out of the FSM and wiring diagram manual for an 86.

ahickman

Should have mentioned that the fix to my fuel/temp gauge issue was related to the fuel sender unit. I found that sections of the wound wire which the slider moves along was severly rusted and caused an open circuit. I cut those sections out and soldered the ends to get continuity.

humboldtMUD

was wondering if you could elaborate a bit more on your fix, whats this wound wire, you took the sender out of the tank to get to it?. my temp and fuel gauges just stopped working sounds like same problem

humboldtMUD

never mind fixed it

Hadmatt54

Elaborate please!
Some other person may be searching for an answer to the same problem you had.
What did you find and how did you fix it?