Help! Supra doesn't run right

[suprarx7nut]

Could be true but would think this is a reman starter that I bought three months ago and it started the day I bought it. Wouldn't the company that reman'd it do that? With it having a warranty I think it be better to get an exchange on it.

Also still cold here in houston so will probably check out things this weekend when it warms up.

FWIW, I had a Denso reman starter that would not engage the flywheel fresh out of the box. I couldn't figure it out, ended up returning it. I never would have expected that from Denso, but it was a good lesson in "just because it's new, doesn't mean it works."

I'm not saying yours is similarly non-functional, but just thought it was a relevant tidbit of info.

 

[Piratetip]

Ah, yeah. I thought it was the old OEM one. If it's a reman just exchange it out for one that works properly.

 

[Abe's 1987]

Will do

 

[simond355]

edit

 

[Abe's 1987]

Ok reran a bunch of test.

Fuel pressure
+B and Fp 38 psi
Idle no fpr 38 psi
Idle with fpr 38 psi
Snap throttle drops from 38 to 30 psi
Full rev drops to 10 psi

Volts to fuel pump
Idle at 8.78 volts
Full rev 11.50 volts

Battery
12.6 volts car off
14.5 volts engine running

Car idle at 900 rpm cold start then dropped down to 750 after 15 mins

Throwing code 12 still

Timing in test mode 10 BTDC, out of test mode jumps to 15 BTDC

Afm at idle 0.02 kHz at 750 rpm and 0.40 kHz at 4000 rpm

Check engine light is still off. Antilock light is on. Battery light comes on with key in on position then goes off with engine is running. Have a burning smell coming from the exhaust.

 

[Abe's 1987]

Seems like not enough power is getting to the fuel pump. And seems like fpr vsv is not letting vac to the fpr.

Also when I shut off the engine fuel pressure dropped to 10 psi fast then held at 10 psi for a good 10 minutes.

Am I really facing blockage problems or maybe fuel pump isn't giving enough fuel to compensate the usage due to lack of power to the pump? Let me know what you guys think!

 

[suprarx7nut]

I forget what all you've done, so sorry for the repeat questions.

1. Have you tried a new CPS to try to fix code 12?
1a. alternatively, have you back-probed the ECU to troubleshoot everything?
2. Have you dropped the fuel tank to clean it and inspect the pump?

 

[Abe's 1987]

I forget what all you've done, so sorry for the repeat questions.

1. Have you tried a new CPS to try to fix code 12?
1a. alternatively, have you back-probed the ECU to troubleshoot everything?
2. Have you dropped the fuel tank to clean it and inspect the pump?

No haven't tried another cps

I've been backprobeing a few things on the ecu

I haven't dropped the fuel tank but I did put my inspection camera in the sender unit hole to see the condition of the pump and tank. All looks clean.

I just figured something else out hopefully. Jumped +B to Fp on the check connector and checked volts to the pump. It's only getting 9.60 volts at the fuel pump. Shouldn't it be getting the same number of volts as the battery output when the +B and Fp are jumped together?

Also what volts should I be getting to the fpr vsv at idle?

 

[suprarx7nut]

I would test every single line on this page and the page after it. If any one thing is out of spec, chase down the cause.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=50

 

[3p141592654]

Don't worry about code 12. Its probably the STA signal to the ecu is bad. Its a non-issue for now.

The fuel pressure is the key issue you have. Based on your test results, especially 10 psi at full rev and 8 psi drop on snap test says you have a fuel system that cannot supply enough fuel. This is hardly a surprise, since you have ruled out most of the other possibilities.

The stock system has two fuel pump speeds, set by a relay on the passenger side engine bay near the shock tower. Normally, at low load the relay switches in a resistor that drops the voltage to 10V. At high load the ecu commands the relay to supply full battery voltage to the fuel pump. Your idle voltage of 8.78V seems low, the voltage drop across quite a long piece of wire between the FP speed relay and the fuel pump in the back should be about 0.25-0.5V. The high speed voltage of 11.5 V also seems low for a battery voltage of 14.5V.

Possible causes are a restriction in the fuel line or rail that is loading the pump hard, a pump that is drawing too much current because its bad, or bad connectors somewhere in the fuel pump wiring.

Since the pump sucks about 8 amps at 14V (5.7 amps at 10V), when you jumper FP and B+ at the diag box, you need to use a thick copper jumper. I use some 14 AWG house wire that I hammer flat so it fits into the diag connectors. If you are using a thin jumper or paper clip that could explain your low voltage you see when jumped.

To start, you should try to measure the current through the FP B+ jumper. For 14V, it draws about 8A. If you see larger number than that, then you know the pump is loaded from a restriction, or is bad itself.

 

[Abe's 1987]

Don't worry about code 12. Its probably the STA signal to the ecu is bad. Its a non-issue for now.

The fuel pressure is the key issue you have. Based on your test results, especially 10 psi at full rev and 8 psi drop on snap test says you have a fuel system that cannot supply enough fuel. This is hardly a surprise, since you have ruled out most of the other possibilities.

The stock system has two fuel pump speeds, set by a relay on the passenger side engine bay near the shock tower. Normally, at low load the relay switches in a resistor that drops the voltage to 10V. At high load the ecu commands the relay to supply full battery voltage to the fuel pump. Your idle voltage of 8.78V seems low, the voltage drop across quite a long piece of wire between the FP speed relay and the fuel pump in the back should be about 0.25-0.5V. The high speed voltage of 11.5 V also seems low for a battery voltage of 14.5V.

Possible causes are a restriction in the fuel line or rail that is loading the pump hard, a pump that is drawing too much current because its bad, or bad connectors somewhere in the fuel pump wiring.

Since the pump sucks about 8 amps at 14V (5.7 amps at 10V), when you jumper FP and B+ at the diag box, you need to use a thick copper jumper. I use some 14 AWG house wire that I hammer flat so it fits into the diag connectors. If you are using a thin jumper or paper clip that could explain your low voltage you see when jumped.

To start, you should try to measure the current through the FP B+ jumper. For 14V, it draws about 8A. If you see larger number than that, then you know the pump is loaded from a restriction, or is bad itself.

Ok so I retested with a 14 awg copper wire. Fuel pump backprobed and +B jumped to Fp still reads at 9.61 volts. I unplugged the fuel pump and tested the connector of power supply to fuel pump with +B jumped to Fp and it reads at 12.17 volts. Reconnected the fuel pump and tested the amps of +B jumped to Fp. At 9.61 volts it is getting 4.60 amps.

 

[3p141592654]

Current draw of pump seems good. Is that 12.17 volts with the engine off? If so, seems about right.

There is no fuel flow spec that I know of for the 7MGTE. But this seems so severe that it should be obvious I hope. Disconnect the return line from the FPR and attach a short hose to a container. You should see at least a quart per minute with B+ FP jumpered. Have an extinguisher handy. Keep any sparking from the jumper away from the open fuel. If flow is weak, you are going to have to move up stream until you find the restriction.

I think you said the fuel filter was replaced. I would check that the hard line to the filter is not kinked. It can be hard to remove those fittings and the line can be twisted in the process.

Also check that the fuel rail mounting bolts have the correct factory spacers. If spacers are deleted, then the injectors will push further into the rail and block the internal passage. Especially near the fuel dampener.

Given that its not holding pressure after removing power it could also be that the pump check valve is bad.

 

[Abe's 1987]

Current draw of pump seems good. Is that 12.17 volts with the engine off? If so, seems about right.

There is no fuel flow spec that I know of for the 7MGTE. But this seems so severe that it should be obvious I hope. Disconnect the return line from the FPR and attach a short hose to a container. You should see at least a quart per minute with B+ FP jumpered. Have an extinguisher handy. Keep any sparking from the jumper away from the open fuel. If flow is weak, you are going to have to move up stream until you find the restriction.

I think you said the fuel filter was replaced. I would check that the hard line to the filter is not kinked. It can be hard to remove those fittings and the line can be twisted in the process.

Also check that the fuel rail mounting bolts have the correct factory spacers. If spacers are deleted, then the injectors will push further into the rail and block the internal passage. Especially near the fuel dampener.

Given that its not holding pressure after removing power it could also be that the pump check valve is bad.

Yes 12.17 volts engine off and fuel pump unplugged
9.61 volts with engine off and fuel pump plugged in. I guess as you said the relay is reducing the amount of volts getting to the pump due to the restriction.

Yes I did put a new fuel filter on and don't remember seeing any kinks in the lines. Will crawl under the car and double check it.

I will start checking where the blockage is this weekend.

So based on the numbers my fuel pump is most likely good?

 

[Piratetip]

12.17 volt measurement is really meaningless.
That is just telling you the wiring is capable of a voltage sense to the battery, NOT under any load.

The 9.61 volt reading is the clue telling you something is wrong.
Also, where are you taking the pump voltage reading from exactly?
At the pump? Edit: Nevermind, I see you were backprobing the pump connector.
As Pi mentioned before, you should only see a MAX of ~0.200 Voltage Drop across all the wiring back to the pump. (Assuming the resistor pack is out of the equation)
You are measuring a drop of 2.50 V, which is way too high.

You really need to find where the voltage drop is occurring in the wiring.
Somewhere there is a high resistance in the wiring, or the relay controlling the resistor pack switching is not working.
Could be the positive side of the wiring or the ground side at the pump could be badly corroded.

Another check you can perform:
Unplug the connector at the pump and measure the resistance in the wiring all the way back to the check connector. - Record it
Then take a resistance measurement from the check connector to the passenger side connector where the fuel pump relay. -Record it
Also take the resistance of the pump ground pin to a known good chassis ground. - Record it
Should clue you in to where any wiring issues may be.

Wiring diagram.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=70

 

[Abe's 1987]

Would these be the proper spacers for the fuel rail?

 

[Piratetip]

Yes.
The 3 spacers should have the black ring on the rail side.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=89

 

[Abe's 1987]

Yes.
The 3 spacers should have the black ring on the rail side.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=89

Yup they all three have the black ring on the rail side.

Will start testing wiring and for restrictions within the fuel lines this weekend.

 

[Abe's 1987]

Ok so with +B and Fp jumped I'm reading a 2.60 volt drop through all the wiring even at the jumper. Without the jumper +B is getting the 12.6 volts.

As Pi said the pump is more likely going into overload mode due to a restriction which most likely is causing the volt drop.

I will start looking for the clogged part now!!!

 

[3p141592654]

For reference, this is my car

Engine at idle, battery 14.31V:
at pump: 9.89V, at FP terminal diag box: 10.03V (this is the pump in low speed mode, with dropping resistor in place).
wiring drop is 0.14V

Engine at idle, battery 14.31V: Jumpered B+ to FP
at pump 12.77V 4.9A
diag box FP: 13.85V
wiring drop is 1.08V from FP to pump, and 0.46V from B+ to battery.

Are your numbers above with engine on or off? Your B+=12.6V if engine is on seems low.


Based on that, it does seem your wiring has more drop than expected. Since you measured about 5A draw that seems normal for the pump, suggesting the wiring is the issue.

 

[Abe's 1987]

Ok here are my numbers

At idle of 1000 rpms
Batt ~ 14.57 volts
+B ~ 13.67 volts
Fp ~ 9.48 volts
Pump ~ 9.03 volts

Idle jumpers at 1000 rpms
Batt ~ 14.53 volts
Fp/+B ~ 12.99 volts
Pump ~ 11.51 volts
Draw of 4.30 amps