1FZ-FE Cranks but won’t turn over without starter fluid, then drives fine.

[Tools R Us]

If jumping the pin at the FPR with 12v runs the fuel pump at full steam the issue likely isn't between the FPR connector and the fuel pump.
...

The FPR is powered by the same wire that powers the pump. To switch to full pump pressure, the coil is grounded by the ECU. The relay is normally to the low pressure side of the switch, ground signal from the ECU closes the full pressure side of the switch.

 

[SmokingRocks]

Thanks thats what I was thinking after halfway into typing my last post

 

[jonheld]

I can't remember if the ECU provides 12v or a ground to terminal 1 to trigger the FPR.

I gave bad info in my last post.
The ECU should GROUND the FC terminal (E4-14) that feeds the coil on the COR. The COR then feeds +12 to the coil of the FPR. The ECU will then GROUND the FPR terminal (E7-13) activating the FPR.

 

[Tools R Us]

1) (Blue) I know the low-speed circuit is working completely as it should because the car runs fine after it gets started.

Good.

2) (Purple) I know the high-speed circuit wiring between pin 3 on the FPR plug, through the fuel pump, to the battery is good because I hooked up a jumper to bypass the relay

Good

3) I know the relay is working because the relay has to be energized in order for the low-speed circuit to run (which it does because I can idle and drive normally after car is started.) Which means that the wiring from the COR to Tr2 on the board is good because the relay would be in high-speed mode all the time otherwise.

The FPR is normally to the low speed side, no relay action is needed.

4) So, the only thing I can think of is that something failed in the ECU which is causing the Tr2 to send power to the relay AT ALL TIMES, thus not allowing the FPR to disconnect from the low-speed circuit and the low speed circuit can't send enough fuel to handle start-up or full-throttle?

Or there is a poor/dead connection on the high speed side. When the FPR is in high speed, the pump isn't getting power, doesn't run. If the FPR didn't switch, the motor should start/run on the low speed setting, maybe not the best, but still.

Orrrrrr, is it possible that my fuel-pump just stops whenever it tries to run at high-speed, but it runs fine at low-speed?

This is likely, it fails when switched to high speed.

 

[Chachi254]

Hi, Are you sure those fuseable links are sound ? If they are not codes will throw up and the car will run poorly, not start, or randomly die. Don't keep throwing parts at it. In all the cruisers I've had Ive never replaced the computer,they are almost bullet proof. Almost always a wiring issue. Even on the Efi once you replace the wires going in under the panel to 12 gauge the problem goes away. Mike

I needed to get myself a backup FPR anyway, and the original TPS was out of range and could not be adjusted any further so fortunately I didn't throw any unnecessary parts at it. I'll see what I can do with the wiring and finding broken wires.

Thank you.

 

[Chachi254]

Good.


This is likely, it fails when switched to high speed.

Thanks for helping confirm those statements and offering your thoughts. I'm gonna do some more digging tonight and will let you know what's going on.

Thank you so much for your help and input!

 

[SmokingRocks]

I don't think the fuel pump is failing at high speed since you said you hotwired the pin at the FPR connector while flooring it and it ran fine with no stumble.

Lets not jump ahead, do the test on the FPR connector to see if you are getting continuity with ground at the FPR's trigger terminal as I said earlier.

 

[dugsgms]

Sounds like either 1. open circuit between terminal 3 on the fuel pump relay and splice I14 in the harness(red/blk wire), 2. open circuit between terminal 1 on the fuel pump relay and the ECM (white/red wire) or 3. bad Tr2 driver in ECM. A test light and little bit of time will verify.

Edit- The first suggestion seems the most likely as in the 2 others would still allow starting and WOT operation even if not ideal.

 

[Chachi254]

Edit- The first suggestion seems the most likely as in the 2 others would still allow starting and WOT operation even if not ideal.

I don't think that's possible since I have a jumper between Terminal 3 and the battery, which runs the fuel pump at high speed. Which would mean that everything between Terminal 3, through I14 --> all the way back to the battery would be good, right?

It's almost like I'm not getting power to terminal 1 to power the relay, or power is never shutting off. Unfortunately, the diagrams I posted show two different relay operation styles.

See that in the first photo, the switch is normally high-speed, and the activated relay would change the switch to low-speed. Whereas in the second photo, the relay is normally low-speed, and the activated relay would change the switch to high-speed. Is one or the other just a wiring diagram typo or are these diagrams for two totally different relays?



1) Normally high-speed

2) Normally low-speed

I haven't been able to test the wires yet because of other obligations. This thread has been immensely helpful, but I'm almost to the point where I'm more confused now than I was at the beginning haha. I'm not sure I'm fully understanding the "grounding" part or how to test that.

 

[SmokingRocks]

The fpr defaults to low speed. Not sure where that first wiring diagram came from but I’d stop lookin at it and solely use the factory manual (colored wiring diagram).

Port 1 is not going to show voltage when the ECU is trying to trigger the FPR. It’s providing a ground to port 1, so if you test with a multi-meter port 1 should show continuity with ground (-). That’s what triggers the relay.

Look at the power flow, you have 12v coming into port 5 of the relay which flows through the FPR to the resistor but also has a path through the relay trigger. The reason it’s not triggered right away is because there is no ground at port 1 until the ecu calls for high flow, at which time the ecu internally switches on the ground for port 1 on. That allows current to flow through the relay trigger which should switch the FPR to high flow.

So let’s just keep this simple, you need to put a probe in port 1 and a clip the other probe on the negative battery post. Set the multI meter to test continuity then start up the car, if the ecu is working you should see continuity.

I can make some diagrams in my circuit simulator tonight and screen shot them to help illustrate what I'm trying to explain. Don't know about you but I'm a visual guy.

 

[Chachi254]

The fpr defaults to low speed. Not sure where that first wiring diagram came from but I’d stop lookin at it and solely use the factory manual (colored wiring diagram).

Port 1 is not going to show voltage when the ECU is trying to trigger the FPR. It’s providing a ground to port 1, so if you test with a multi-meter port 1 should show continuity with ground (-). That’s what triggers the relay.

Look at the power flow, you have 12v coming into port 5 of the relay which flows through the FPR to the resistor but also has a path through the relay trigger. The reason it’s not triggered right away is because there is no ground at port 1 until the ecu calls for high flow, at which time the ecu internally switches on the ground for port 1 on. That allows current to flow through the relay trigger which should switch the FPR to high flow.

So let’s just keep this simple, you need to put a probe in port 1 and a clip the other probe on the negative battery post. Set the multI meter to test continuity then start up the car, if the ecu is working you should see continuity.

I can make some diagrams in my circuit simulator tonight and screen shot them to help illustrate what I'm trying to explain. Don't know about you but I'm a visual guy.

Thank you! You are a lifesaver.

I am definitely a visual guy so that will be immensely helpful. I have a second vehicle now so there's no pressure on time.

I can't thank you enough!

 

[SmokingRocks]

Almost all of the circuits in our land cruisers are ground switched, including those controlled by the ECU. So the ECU is switching the ground leg of circuits on or off.

Toyota used ground switching to reduce the amount of 'hot' or 12v + wires in the harnesses. Multiple circuits that are in the same general location in the car have their ground legs (after the switch) combined and grounded to the body.

There are many combined ground locations in our rigs; each driver side footwell, the base of the shifter, rear quarter panels etc. etc. etc.

Additionly ground switching helps with diagnosis because you could easily see that the load was getting power (or not)...and you just had to give it a ground (jumper).

You CAN test the Fuel Pump Relay IN CAR. You just need to trace back the wire going to port 1 to a point where you can cut it and tie in an in cab switch to ground. Then you can test it as I outline below. You will need to reconnect the wire back to the ECU when you are finished with this test.

 

[SmokingRocks]

You can also bench test the new Fuel Pump Relay by hooking 12v up to the lug that goes in port 5 and ground port 1. Then with a multi-meter in the voltage setting, touch the lug that goes into port 3 with one probe while the other probe is attached to ground.

If you don't have 12v at that port when you have port 1 grounded and port 5 fed with 12v the relay is faulty.

This is not the same as the in car test. The in car test is a stress test.

Similar to this test:

 

[dugsgms]

Here's a quick test. During cranking, you should have battery voltage at terminals 3 and 5 but essentially no voltage at terminal 1 of the fuel pump relay. During idle you should have battery voltage at terminals 1,2 and 5. If all of that holds true the you can eliminate everything electrically upstream of the fuel pump relay.

 

[SmokingRocks]

Here's a quick test. During cranking, you should have battery voltage at terminals 3 and 5 but essentially no voltage at terminal 1 of the fuel pump relay. During idle you should have battery voltage at terminals 1,2 and 5. If all of that holds true the you can eliminate everything electrically upstream of the fuel pump relay.

We've determined that terminal 5 is receiving voltage, and that the engine runs after an assisted start up, and that the engine will run WOT if terminal 3 is jumped with 12v. So this eliminates these components: Fuel Pump resistor, fuel pump. And confirms that the electrical pathway from the FPR to the fuel pump is intact and functioning.

We need to determine if the ECU is triggering the relay and/or if the relay is defective. @dugsgms your method would do this as will the test I've outlined. In an effort to not overload @Chachi254 lets have him work one test at a time.

There are three possibilities that we are closing in on:

1. ECU is not triggering the FPR
2. FPR is malfunctioning and not switching when triggered
3. ECU & FPR are functioning correctly but power is being shunted upstream of the FPR

Out of these options #2 is the most likely, then #1, #3 is highly unlikely.

@Chachi254 put the FPR back in, use a razor to strip back the wire insulation on the wire going into port 1. Clip one of the multi-meter probes to that and the other to the negative terminal, set meter to continuity and check for continuity between ground and port 1 as shown below during WOT or start up. This will allow us to eliminate option 1 or 2 depending on the outcome.

 

[dugsgms]

You're right, probably shouldn't overwhelm. I would still be curious at how much voltage was at each terminal of the relay during both conditions, would say alot about whats going on electrically before and after the FPR.

 

[SmokingRocks]

@Chachi254 did you ever figure this out?

 

[Chachi254]

@Chachi254 did you ever figure this out?

I haven’t yet

Just been using my hardwired home light switch to manually activate the high-pressure fuel pump circuit. Tried unplugging and re-plugging in all of the plugs to the ECU but no dice. Idk where the heck the grounds are located. I have this, but I don’t really understand where the ground points are 1996 electrical circuits guide.

 

[SmokingRocks]

Page 30, 32 and 34 show ground point locations (they are the upside-down triangle) List of circuits tied to each ground point ID is listed on page 9. If the engine runs good when you jump the circuit that indicates the grounds are fine, don't dick with them.

If the truck runs fine when you jump the high-pressure fuel pump circuit at the fuel pump relay location that means either the fuel pump relay is bad or the circuit open relay is bad. Since you've replaced the Fuel pressure relay you should Replace the circuit open relay. It's located to the left of the dead pedal behind the plastic trim and wiring harnesses (you'll see a relay block back in there).

Ignore the arrow, this is the relay block as if your looking at it from the brake pedal straight left. (You need to remove the dead pedal and the plastic door sill trim piece to find this.

THis image is taken from the angle further back, like if your eyes were near the front of the driver seat and you are looking to the front left of the foot well.

 

[Chachi254]

Page 30, 32 and 34 show ground point locations (they are the upside-down triangle) List of circuits tied to each ground point ID is listed on page 9. If the engine runs good when you jump the circuit that indicates the grounds are fine, don't dick with them.

Thanks so much for taking the time to help me through this, @SmokingRocks! I am happy to report that after over a year of chasing this pest of a issue, I have finally fixed it!

I did what you said and checked the relay again and tested the COR. I replaced both of them with new parts again and had no luck. Since all the grounds were checking out OK, I decided to start back at the fuel pump relay and cleaned the female connector plug from the wiring harness again. After doing that, I noticed that the catch pins on the inside of the female plug looked to be stretched out a bit. So I decided to take the connector plug apart and pinched the connector catch pins together to make a tighter connection between the male pins on the relay and the female pins inside of the connector. After doing that, it started right up and I have been able to slam on the gas and the engine doesn’t cut out anymore. Now, it is very possible that I just jostled something Enough to fix whatever else was causing the issue, but I am going to stick with making myself feel accomplished by telling myself it was the stretched wiring harness pins were causing my issue haha.

With that said, I cannot thank you enough for the time and effort you put into helping me fix this issue. You saved me a lot of time and frustration from not breaking something while falsely chasing some other diagnosis step. You saved me a lot of time and frustration from not breaking something while falsely chasing some other diagnosis step.

1FZ-FE Cranks but won’t turn over without starter fluid, then drives fine.