Community Fixes

Verified repair solutions from SupraForums — 433 fixes extracted from MKIII threads

Priming Fuel System After Long Storage - Diagnostic Port Fuel Pump Activation

Engine will not start after fuel system rebuildFuel lines empty/no fuel pressureFuel pump will not activate with just key-onOriginal fuel pump frozen with rust from long-term storage

After a 1989 Supra sat for approximately 14-15 years, the fuel system was completely drained and rebuilt (new fuel pump, filter, strainer, cleaned tank and lines), but the engine would not start becau...

Manually activate the fuel pump by jumping the B+ and Fp terminals on the underhood diagnostic connector with the ignition key turned to ON position, which forces the pump to run and prime the fuel lines.

~5 minutesShort jumper wire or paper clipNov 2019 Forum Thread →

FIX

Brakesbeginner✓ OP Confirmed

Spongy Brakes for Years - Rear Calipers Installed on Wrong Sides

Spongy or soft brake pedalBrakes never felt properly bled despite extensive bleeding attemptsProblem persisted through multiple master cylinder replacementsProblem persisted through ABS unit replacementProblem persisted through proportioning valve cleaning

Persistent spongy, ineffective brakes despite replacing the master cylinder, swapping the ABS unit, cleaning the proportioning valve, and repeated brake bleeding sessions over the course of 8+ years.

Swap the rear brake calipers to their correct sides so the bleeder screws face upward, then re-bleed the entire brake system.

~2-3 hoursBrake fluid - Toyota/Lexus DOT 3 recommended (enough to flush the entire system)Jul 2024 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

No Power to Dash/Gauges/Windows - Failed Alternator Fusible Link

Car will not crank or start - completely deadNo power to dashboard gaugesNo power to windowsNo power to radioHeadlights still work

Car would not crank or turn on at all. Turning the key to any position (ACC, ON, START) produced no clicks, sounds, or movement. No power to dashboard gauges, windows, or radio. However, headlights, p...

Replace the failed alternator fusible link with a 100 amp bolt-in fuse (the turbo model replacement) in the engine fuse box.

~30 minutes100 amp bolt-in alternator fuse (turbo/7MGTE style)Mar 2022 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

Oil Pressure Gauge Not Working - Disconnected Sender Wire Repair

Oil pressure gauge not reading/deadLoose yellow and black wire found near distributor areaBlack connector on oil pressure sender missing its wire

Oil pressure gauge not working due to the yellow/black wire having been pulled out of its connector on the oil pressure sending unit near the distributor.

Reconnect or replace the oil pressure sending unit connector pigtail (Pico 5665PT) and slide it back onto the brass pin on top of the sender.

~30 minutesPico 5665PT connector pigtail (Amazon, ~$5-10), Sealed butt splice connector, Dielectric grease, Replacement oil pressure sending unit (optional, if original is corroded), Reproduction rubber boot cover from VintageTeqParts.com (optional, protects sender from radiant exhaust heat)Oct 2021 Forum Thread →

FIX

Transmissionbeginner✓ OP Confirmed

Driveshaft Too Short to Reach Diff - Center Bearing Mounted Upside Down

Driveshaft approximately 3/4 inch too short to reach rear differential flangeDriveshaft appeared to form a slight V-shape (not obvious when viewed from underneath)Could not bolt driveshaft to rear differential

After reinstalling the original transmission, driveshaft, and center bearing, the driveshaft appeared approximately 3/4 inch too short to connect to the rear differential. The issue persisted even aft...

Flip the center bearing support to the correct orientation so it is tucked up against the floor pan rather than hanging down.

~30 minutesNo parts neededSep 2021 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

No Start / No Spark / No Check Engine Light - Hidden Kill Switch

Engine cranks but will not startNo sparkNo check engine light at all (no blink, no constant light)Fuel pump operates and delivers 40 psi to fuel railCar was running perfectly ~10 hours prior

Car suddenly would not start despite having fuel pressure. Owner had been troubleshooting fuel pump relay and ECU signal issues, but the car had been running perfectly just 10 hours prior with no chan...

Locate and flip the hidden kill switch that the previous owner had installed under the dash.

~15 minutesNo parts neededFeb 2016 Forum Thread →

FIX

Brakesintermediate✓ OP Confirmed

Intermittent Brake Pressure Loss - Failing Master Cylinder Internal Seals

Brake pedal sinks halfway to floor during normal drivingDramatic loss of braking powerIntermittent failure - brakes return to feeling 100% firm on their ownNo visible fluid loss or leaks anywhereBrake fluid level unchanged

Brake pedal suddenly sinks halfway to the floor while driving, as if a brake line had blown. Only minimal stopping power remains from the second brake circuit. The issue is intermittent - brakes can f...

Replace the failing master cylinder with a rebuilt unit.

~1 hourRebuilt master cylinder ~$65-106 CAD (~$50-80 USD), ensure correct ABS vs non-ABS version, Fresh brake fluid for flush and bleedNov 2020 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

Engine Dies at 1900 RPM When Revving Slowly - TPS Adjustment

Engine dies at ~1900 RPM when throttle is opened slowlyEngine revs fine when throttle is opened quicklyNo error codes stored in ECU

Engine dies at approximately 1900 RPM when the throttle is opened slowly from idle (~1000 RPM). When revved quickly, the engine climbs through the rev range without issue.

Adjust the Throttle Position Sensor (TPS) position clockwise per the TSRM shimming procedure.

~30 minutesNo parts neededDec 2019 Forum Thread →

FIX

Fuel Systembeginner✓ OP Confirmed

Surging at 1500-2000 RPM After Engine Rebuild - Faulty AFM

Engine surges badly when revved above 1500-2000 RPMIdle is normal and smoothNo check engine light presentProblem appeared after engine rebuild with new rings and bearings

After rebuilding the engine (rings and bearings) on a 1991 Supra, the car starts and idles great with no check engine light, but when trying to rev the engine it surges badly above 1500-2000 RPM.

Replace the faulty AFM (Air Flow Meter) with a known-good unit.

~30 minutesAir Flow Meter (AFM) - replacement or known-good used unitOct 2020 Forum Thread →

FIX

Brakesintermediate✓ Community Verified

Rear Brake E-Brake Hardware/Spring Kit Replacement - MKIV Cross-Compatibility

Unable to find rear brake drum spring kit for MKIII SupraParts stores do not list correct hardware kit under MKIII fitmentWorn or missing rear brake hardware and springs needing replacement

Rear brake drum hardware and spring kit for the MKIII Supra (1989) is difficult to source, with most auto parts stores and RockAuto not listing the correct spring kit for the rear drum/e-brake assembl...

Use the MKIV Supra e-brake spring kit (Carlson 17393), which is a direct fit for the MKIII rear drum brake assembly.

~1-2 hoursCarlson 17393 drum brake hardware/spring kit ~$11Apr 2020 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

Intermittent No Power and No Start - Bad Alternator Fusible Link

Intermittent complete loss of electrical powerCar would not startBattery warning light on dashTachometer and temperature gauge not workingTemporarily fixed by replacing ignition fuse but problem returned after shutdown

MK3 Supra had intermittent total loss of electrical power and would not start. Replacing the ignition fuse temporarily restored power, but the problem returned after shutting the car off. When running...

Replace the 1.25A alternator fusible link (slow-burn fuse) in the engine bay fuse box.

~15 minutes1.25A alternator fusible linkJul 2020 Forum Thread →

FIX

Turbointermediate✓ OP Confirmed

Jerking and Check Engine Light Under Boost - Dry Rotted Intercooler Hoses Causing Fuel Cut

Car jerks/bucks when turbo boost comes in around 4 psiCheck engine light flashes under boost, turns off when throttle is releasedDiagnostic code 34 stored (turbocharging pressure)Car drives normally without using turboNasty smell in cabin

Stock turbo 1989 7MGTE would jerk/buck and flash the check engine light when the turbo spooled up at around 4 psi. The car drove normally in naturally aspirated conditions but would repeatedly cut out...

Replace all dry-rotted intercooler piping hoses to eliminate boost leaks and restore proper boost pressure delivery.

~4-6 hoursSilicone intercooler hose kit (eBay silicone hoses recommended as long-lasting replacement), Spark plug wires, Air filter, Thermostat (if also replacing as part of maintenance)Nov 2019 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

No Start / No Fuel to Injectors - Hidden Kill Switch Behind Radio

Engine cranks but will not startNo fuel delivery to cylinders despite full fuel rail and working fuel pumpCar starts momentarily on starter fluid then immediately dies12 volts present at injector connectors but injectors not firingDiagnostic code 14 (igniter signal - resolved separately with new distributor)

7MGE would not start. Car had spark and fuel pressure in the rail, injectors tested good with 12V present at the connectors, but fuel was not being delivered to the cylinders. Car would briefly fire o...

Locate and reconnect two disconnected wires behind the radio that were part of a previous owner's hidden kill switch, restoring the ECU-to-injector signal circuit.

~30 minutesCrimp connectors or solder and heat shrink tubing for securing the wire connectionSep 2019 Forum Thread →

FIX

Transmissionintermediate✓ OP Confirmed

Won't Go Into Gears After Transmission Rebuild - Leaking Clutch Master Cylinder Replacement

Cannot shift into any gear with engine runningClutch fluid leaking into driver footwellSlave cylinder moves clutch fork but not enough to disengage pressure plateBleeding the clutch system did not resolve the issue

After a transmission rebuild with an upgraded pressure plate (2800lb Action Clutch), lightweight flywheel, and new stock clutch disc, the car would not go into any gears. The transmission worked fine ...

Replace the leaking clutch master cylinder with a new Aisin unit, ensuring the correct style for the model year (86-90 uses flared nut fitting, 91-92 uses banjo bolt fitting).

~1-2 hoursAisin clutch master cylinder (P/N 31410-14202 for 86-90 style) ~$30 from RockAuto, DriftMotion full-length stainless steel clutch line (DM53) ~optional if replacing hard line (http://www.driftmotion.com/Full-Length-Clutch-Hose-p/dm53.htm), Brake fluid (DOT 3 or DOT 4)May 2018 Forum Thread →

FIX

Engineintermediate✓ OP Confirmed

Front Oil Leak After 7MGTE Rebuild - Missing Cam Seals

Oil trickling from front of engine behind crankshaft pulleyOil visible on exhaust side and intake side near timing coversFast trickle of oil on startupLeak appeared to originate from within the timing cover area

After a 7MGTE rebuild (resurfaced head, metal head gasket, ARP head studs, new oil pump), oil was trickling from the front of the engine near the timing covers on startup. Oil was visible behind the c...

Install the two cam seals behind the timing cover, which were missing after the rebuild.

~3-5 hoursCam seals x2 (OEM Toyota preferred, FelPro alternative), Consider also replacing crank seal and oil pump drive seal while in the area (4 front seals total)Dec 2019 Forum Thread →

FIX

Body/Interiorbeginner✓ OP Confirmed

Ignition Lock Cylinder Sticking - Worn Key Replacement

Ignition lock cylinder sticking or hard to turnKey not engaging ignition properly

Ignition lock cylinder was difficult to turn or would not operate properly

Have a Toyota dealership cut a new key using the VIN or the key code stamped on the passenger door lock.

~30 minutes plus dealership visitNew Toyota cut key from dealershipAug 2020 Forum Thread →

FIX

Electricalintermediate✓ OP Confirmed

7MGE No-Start After Top-End Rebuild - Distributor Rotor Misalignment

Engine cranks but will not startBackfire/explosion during spark plug testingStrong smell of petrol on spark plugs after crankingSlight misting of oil on plugs initially (cleared after cleaning)No diagnostic trouble codes present

7MGE engine would not start after a top-end rebuild (valves, seals, gaskets replaced, valves lapped, clearances adjusted). Engine had spark and fuel but would not fire. An explosion/backfire occurred ...

Remove the distributor, open it up, and physically align the igniter/rotor with the #1 cylinder lead before reinstalling.

~30 minutesNo parts neededOct 2019 Forum Thread →

FIX

Engineintermediate✓ OP Confirmed

Code 13 (Crank/Cam Sensor) Fix - Timing Belt Misalignment on 1JZ JZA70

Check engine light / Code 13 appearing when clutch pedal releasedNo code present while clutch pedal held downEngine ran fine otherwise with no starting issues

JZA70R Supra throwing a Code 13 (crank sensor/cam sensor/ECU diagnostic code). The code appeared only when the clutch pedal was released while in neutral, but did not appear while the clutch was held ...

Realign and reinstall the timing belt with correct timing mark positions on the exhaust cam and crankshaft sprockets.

~20 minutes to 2 hours depending on experience (OP reported 20 minutes for the belt realignment alone)New timing belt (recommended if the existing belt has been run misaligned, or if age/condition warrants replacement)Oct 2019 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

Three Warning Lights at Idle (Battery, Brake, Lamp) - DOA Replacement Alternator

Battery warning light on at idleBrake warning light on at idleLamp failure warning light on at idleWarning lights turn off between 1100-2000 RPM onlyWarning lights blink on/off when engaging clutch

After replacing a failed alternator on a 1990 Supra Turbo, three warning lights (battery, brake, and lamp failure) appeared on the dash. The lights would illuminate at idle and above 2000 RPM, but tur...

Have the replacement alternator bench tested at a reputable parts store (NAPA), confirm it is defective, and replace with a working unit.

~30 minutesReplacement alternator (Denso reman recommended over budget rebuilds), 100 amp main fuse (replace while troubleshooting, if needed)May 2021 Forum Thread →

FIX

Electricalbeginner✓ OP Confirmed

Battery and Brake Warning Lights On - DOA Replacement Alternator

Battery warning light onBrake warning light onOnly ~12V at battery with engine running instead of 13-14VRPM-dependent charging behavior

Battery and brake warning lights illuminated on the dashboard after installing a new alternator from Autozone. The charging system was only producing approximately 12V at the battery with the engine r...

Have the suspect alternator bench tested to confirm failure, then exchange it for a working replacement.

~1-2 hoursAlternator (Denso recommended over generic remanufactured)May 2021 Forum Thread →

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