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Testing is best done to obtain numbers. Then compare those numbers to standard specs in manual to see if part is good or bad. One quick test you can do that will verify:

  • ignition switch
  • ECU
  • main EFI relay
  • circuit-opening relay (fuel-pump relay)
  • fuel-pump wiring
  • fuel-pump
  • fuel-pump hoses
  • fuel filter

1... Is to disconnect fuel-hose from fuel-rail
2. Aim hose into measuring cup.
3. crank engine for 10-seconds
4. how many CC petrol did you collect in measuring cup?

5. remove fuel-rail with injectors attached
6. reconnect fuel-hose to rail
7. place little cups under each injector
8. crank engine for 10-sec
9. how many CC did you collect from each injector? Are they close to identical volumes?
10. if necessary, send injectors to Mr Injector for testing and cleaning. They'll provide you with flow-test numbers before and after cleaning.
 

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Discussion Starter · #22 ·
Sounds like a great test to try! I'm a rookie with these cars, and no master mechanic, but that doesn't sound too hard. Gonna try to get the fuel pump wiring back to factory and check out all the wiring to ECU and such as you suggested.
Thanks again!

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I have edited the post #9, as i had wrongly stated the ECU was not controlling the COR.
And i only have wiring diagram of 85, not 83.
Sorry if I have mislead people.
 

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Discussion Starter · #25 ·
When you tried to start car and it almost started... was that with manual fuel-pump switch ON or OFF?
I tried it both ways. Tried to start (some shuddering, etc) with manual FP switch on. Not much of anything with it off. And, just to reiterate, the guy bypassed the original FP circuit completely. He ran a hot wire from the fusebox in the left kick panel to the switch, then to the pump. No ECU in the picture at all.....lol.

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Discussion Starter · #26 ·
Also, I posted this on a separate thread, but gonna throw it on here also, since it may be related to the no running condition. Only the (5) fuses with pink ink on them are getting 12vdc whether ignition switch is on or not. Seems weird to me....can anyone check their car and compare notes? All accessories except the horn work fine.....Thanks!


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Have to flip image of fuses over so they match orientation of cover. Does your headlights and taillights work?

You need to remove fuse-box and look underneath to determine what's wrong by tracing all power-supply wires. I see some crimp butt-splices in lower-right, a major no-no. Shows someone has modified factory wiring. Proper wire joint requires following:
  • mechanical strength: knot wire-ends with linesman/ western-union splice
  • electrical conductivity: solder joint
  • weatherproofing: seal with adhesive heat-shrink tubing
It's done this way in pro-motorsports (F1), aerospace and military applications for performance, durability and reliability. Most likely, you'll need to remove all that non-stock wiring and restore to 100% stock wiring.

How to do proper wire-splice (can skip pre-tin step with larger-gauge wires).

Only proper wiring manual that I'll use.
 

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Discussion Starter · #28 ·
Oops....posting photo of the fusebox in proper orientation to the diagram on cover, makes it easier to see which ones are working......sorry bout that.


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Discussion Starter · #29 ·
Yes, headlights work (and go up and down). Taillights, turn signals, power accessories, etc. all work.

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Those are on other fuses not marked with pink.

1. How are you measuring for power on non-pink fuses?

2. if you pull 4x fuses for headlight and 1 for tailight, do they still work?


Horn functionality may be horn itself, horn-button on steering wheel, or wiring in between.
 

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Discussion Starter · #31 ·
Those are on other fuses not marked with pink.

1. How are you measuring for power on non-pink fuses?

2. if you pull 4x fuses for headlight and 1 for tailight, do they still work?


Horn functionality may be horn itself, horn-button on steering wheel, or wiring in between.
Good thought, will pull those fuses and check. Far as how I'm checking the voltages....using test light to ground and probing both sides of the fuse. Also of course ohmed out all fuses. Seems odd to me that all those fuses don't have power, even with the key on.

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For headlights/taillights, fuses are in-line with bulbs after headlight & taillight relays. So fuses won't pass power until you turn headlight switch ON and relays are activated.

Those circuits are powered directly from battery through fusible-link, so will operate independently from ignition switch.
 

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Discussion Starter · #33 ·
That makes sense dannoxyz. I kinda suspected it was like that, just never checked the voltages with headlights or such on. Guessing the "CHARGE" fuse is same way, maybe only energized when engine running and alternator producing power.
Thanks again for all the help!

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I had a problem with my supra about 20 years ago where it slowly was loosing power, then eventually would only run for a second. The engine turned over, I had spark, and I had fuel at the fuel rail, I was stumped. It turned out that the fuel pump would run, but wouldn't make the required pressure to operate the injectors. The fuel pump was replaced and problem solved. The fuel pressure should be 36 - 38 psi on 1984 Supra.
 

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Discussion Starter · #35 ·
I had a problem with my supra about 20 years ago where it slowly was loosing power, then eventually would only run for a second. The engine turned over, I had spark, and I had fuel at the fuel rail, I was stumped. It turned out that the fuel pump would run, but wouldn't make the required pressure to operate the injectors. The fuel pump was replaced and problem solved. The fuel pressure should be 36 - 38 psi on 1984 Supra.
Yep! I'm strongly leaning towards a fuel problem of some kind. Just ordered a test gauge kit from Amazon. Should be here on Sat. Gonna start getting some dang answers!!

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I would also second the advice to check the fuel filter. After being taking out of Winter storage a few years ago, my '84 was stumbling, running rough, and quitting. After changing the plugs to no avail, adding several bottles of fuel system cleaner helped somewhat, and I was about to pull all the injectors and send them out for overhaul. For some reason I thought about the filter. Book says to change it every 12,000 miles. Hmm, I have put about 150,000 miles on this car, and I can't remember EVER changing the fuel filter. So a new filter was installed, and it runs perfectly. Unless you have maintenance records for your car, you really have no idea as to what has been done or not done, so certain things should be done just so you know what you have and can go from there.

Good luck and welcome to the community.

Bob
 

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Discussion Starter · #37 ·
I would also second the advice to check the fuel filter. After being taking out of Winter storage a few years ago, my '84 was stumbling, running rough, and quitting. After changing the plugs to no avail, adding several bottles of fuel system cleaner helped somewhat, and I was about to pull all the injectors and send them out for overhaul. For some reason I thought about the filter. Book says to change it every 12,000 miles. Hmm, I have put about 150,000 miles on this car, and I can't remember EVER changing the fuel filter. So a new filter was installed, and it runs perfectly. Unless you have maintenance records for your car, you really have no idea as to what has been done or not done, so certain things should be done just so you know what you have and can go from there.

Good luck and welcome to the community.

Bob
Thanks, Bob!
I will definitely look at the fuel filter. I bought this car (pretty cheap) as a project, and I'm realizing quickly it's gonna be a big one! But, like many I'm seeing a vision of what it could be with some blood, sweat and beers!


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Hi all,
I know it's not easy (or impossible) to accurately diagnose problems without being there in person....just hoping someone can point me in the right direction.
So.....my '83 Supra will turn over, has good spark (now) but will only "run" for a few seconds if I spray starter fluid into the air intake. The fuel pump is running, (I can hear and feel it). No idea if it's producing enough pressure (is there a Schrader valve somewhere to be able to connect a pressure guage to test that?). I have siphoned out about a gallon of fuel into a clean white bucket. The fuel doesn't look or smell old or bad. No "trash" or water droplets noted in it.
This is basically where I'm at so far. If I let the fuel pump run for a few minutes, the engine will shudder and kinda attempt to start on the first crank. Then just spins over. With the starting fluid, it will run (very rough) for a few precious seconds. Basically, it appears to be starved for fuel to me......
Any help would be greatly appreciated!!


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Here is the Toyota 5M Troubleshooting Guide, I hope it is helpful to some:
Troubleshooting 5M-GE 6M-GE Repair Manual
 

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I would also second the advice to check the fuel filter. After being taking out of Winter storage a few years ago, my '84 was stumbling, running rough, and quitting. After changing the plugs to no avail, adding several bottles of fuel system cleaner helped somewhat, and I was about to pull all the injectors and send them out for overhaul. For some reason I thought about the filter. Book says to change it every 12,000 miles. Hmm, I have put about 150,000 miles on this car, and I can't remember EVER changing the fuel filter. So a new filter was installed, and it runs perfectly. Unless you have maintenance records for your car, you really have no idea as to what has been done or not done, so certain things should be done just so you know what you have and can go from there.

Good luck and welcome to the community.

Bob
What book says to change it every 12,000 miles? I have a hard time swallowing that if we are talking about the oversized fuel filter these cars come with. There is a lot of historical information on the forum that disputes that, if we are talking about the same filter.
 
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