98' cranks but wont start, fuel pump not recieving power.

[McStudRunner]

This has started to become quite the frustrating issue and im looking for some refreshing input since my own research has left me with no solution.

Here's a little background on the issue:

1998 Limited 4runner 3.4 V6 4WD Rear Locker

It happened to me three seperate times before, progressivly getting harder to start (More Cranks) each time but would eventually start up and run perfectly like normal, and now finally it just cranks and wont turn over at all.

Intial thought was fuel pump and or relay was going bad, so replaced those with a new denso pump and relay and nothing still the same problem. I hooked up 12V directly to the pump and cranked the engine over and it started right up with no hesitation. Leads me to think somewhere i have a bad ground to the fuel pump or something?

Appreciate any help, this is my first post on here.

Happy Veterans Day! :usa2: :gun6:

 

[LookAtThatDog]

Your battery is good, right?

 

[McStudRunner]

Yeah, battery is good and terminals are clean and tight.

 

[JayRolla]

How much volts are you getting to the pump when cranking?

As a side note if there is an issue with the wiring you can directly wire the pump with larger gauge power line with a good relay. I have done in on cars in the past and used the fog light relay to turn the pump on and off.

 

[jeremyc74]

Are you getting any codes at all? A crank position sensor could cause it not to start (the ECU fires the pump once it sees the crank turning) but if that were the problem I'm don't think it would run after you jumped the pump out.

I'm not sure though, because these engines also have a cam position sensor that comes into play for ignition timing.

Any chance you have a scanner you can plug in?

Also, verify the fuse is good with a meter. You can't always tell visually if it's bad. If you don't have a meter just replace it for good measure.


Edit: There are also two relays involved in firing the fuel pump. The EFI relay, and the circuit opening relay. The theft deterrent system can also come into play if you have one.

Wiring diagrams for a 2002 are here. They may not be exact for your truck, but they'll be pretty close for most stuff.

http://web.archive.org/web/20100531053202/http://www.ncttora.com/fsm/1996/SIL/fsm/wiring.html

 

[TheDurk]

A few points:

1) The ECM calls the fuel pump when it sees voltage to the starter, among other things. It KEEPS it running when the crank and cam sensors tell it the crank is turning after the starter is no longer engaged. So those sensors are not your problem.

2) The EFI relay is not your problem because that also feeds power to the fuel injection control, and the motor could not run at all without those.

3) '98 and 2002 differ in some important respects. One is that the 7.5A STA fuse keeps a 2002 from cranking but not a '98, it just cuts the fuel pump. So definitely check that fuse.

4) Problem can't be fuel pump ground because pump ran with the direct 12V+ feed. Issue is not on ground side.

5) Confirm all this by pulling the COR. Confirm 12V+ with key on at Pins 1 and 5. See if you have ground at Pin 2 with key in START position. If you do, replace COR. If you don't, that means the ECU is not calling the fuel pump, either because it is not receiving an input it requires or there is a wiring defect. To nail that down, go through the tests in the Service Hints in the bottom of the '98 5VZ-FE Engine Control Wiring Chapter, attached.

If you need help with that, post back and we can do it step-by-step.

 

[McStudRunner]

How much volts are you getting to the pump when cranking?

As a side note if there is an issue with the wiring you can directly wire the pump with larger gauge power line with a good relay. I have done in on cars in the past and used the fog light relay to turn the pump on and off.

Not sure the exact volts while cranking, i can check tomorrow morning though.

Yeah i'll be putting in a fuel pump kill switch, so the thought crossed my mind as well but id prefer to fix whatever this issue is.

 

[McStudRunner]

Are you getting any codes at all? A crank position sensor could cause it not to start (the ECU fires the pump once it sees the crank turning) but if that were the problem I'm don't think it would run after you jumped the pump out.

I'm not sure though, because these engines also have a cam position sensor that comes into play for ignition timing.

Any chance you have a scanner you can plug in?

Also, verify the fuse is good with a meter. You can't always tell visually if it's bad. If you don't have a meter just replace it for good measure.


Edit: There are also two relays involved in firing the fuel pump. The EFI relay, and the circuit opening relay. The theft deterrent system can also come into play if you have one.

Wiring diagrams for a 2002 are here. They may not be exact for your truck, but they'll be pretty close for most stuff.

http://web.archive.org/web/20100531053202/http://www.ncttora.com/fsm/1996/SIL/fsm/wiring.html

It could have something to do with the crank or cam position sensor but i would think it wouldn't start up even if i jumped the pump with power, but what do i know haha

I don't have a scanner but my buddy does and ill have him bring it over tomorrow and hook it up and report back.

which fuse are you referring to? I'll check the engine fuse block and driver's side one under the dash and see if see anything out of the ordinary.

Also i did replace the EFI relay with another denso relay. Ive had trouble determining which one is the COR but I'm 99% sure its the relay under the driver's side fuse block and i replaced that one as well.

Thanks for the wiring diagrams, I'll give em a look through.

 

[McStudRunner]

A few points:

1) The ECM calls the fuel pump when it sees voltage to the starter, among other things. It KEEPS it running when the crank and cam sensors tell it the crank is turning after the starter is no longer engaged. So those sensors are not your problem.

2) The EFI relay is not your problem because that also feeds power to the fuel injection control, and the motor could not run at all without those.

3) '98 and 2002 differ in some important respects. One is that the 7.5A STA fuse keeps a 2002 from cranking but not a '98, it just cuts the fuel pump. So definitely check that fuse.

4) Problem can't be fuel pump ground because pump ran with the direct 12V+ feed. Issue is not on ground side.

5) Confirm all this by pulling the COR. Confirm 12V+ with key on at Pins 1 and 5. See if you have ground at Pin 2 with key in START position. If you do, replace COR. If you don't, that means the ECU is not calling the fuel pump, either because it is not receiving an input it requires or there is a wiring defect. To nail that down, go through the tests in the Service Hints in the bottom of the '98 5VZ-FE Engine Control Wiring Chapter, attached.

If you need help with that, post back and we can do it step-by-step.

So its not the sensors, fuel relays and pump ground, check.

I did get to my ECM and unscrew it and check the board itself but that looked perfectly fine to me, maybe it was a loose or dirty connection but when i hooked it back up, still the same problem. I have read that the ECM can go bad but I seriously doubt thats the case here, plus I don't want to hunt one down in the yards here in San Diego haha

I'll go and check the 7.5A STA Fuse, I hope its just that.

Really appreciate the meat and potatoes in this reply i'll go through your COR testing tomorrow with my meter and report back.

 

[jeremyc74]

A few points:


2) The EFI relay is not your problem because that also feeds power to the fuel injection control, and the motor could not run at all without those.

.

I wouldn't completely rule out the EFI relay based on this. It depends on how he installed the jumper, but if the COR relay is working, and you jumper power straight to the pump with the harness intact it could backfeed through the COR and power the rest of the circuit.

EFI relay isn't a likely culprit, but it's still a possibility.

 

[TheDurk]

I wouldn't completely rule out the EFI relay based on this. It depends on how he installed the jumper, but if the COR relay is working, and you jumper power straight to the pump with the harness intact it could backfeed through the COR and power the rest of the circuit.

EFI relay isn't a likely culprit, but it's still a possibility.

Please explain to me HOW the COR relay could possibly close when the EFI does not, since that is what energizes the COR coil? And if the COR is open, there is no feedback from the pump to the rest of the circuit.

I assume by direct he meant at the fuel tank. To energize the COR and the pump, he would have to jump upstream of the COR coil and and downstream of the EFI load contact and that can only be done under the hood INSIDE the engine room relay box. I don't think that is what he described.

 

[jeremyc74]

Please explain to me HOW the COR relay could possibly close when the EFI does not, since that is what energizes the COR coil? And if the COR is open, there is no feedback from the pump to the rest of the circuit.

I assume by direct he meant at the fuel tank. To energize the COR and the pump, he would have to jump upstream of the COR coil and and downstream of the EFI load contact and that can only be done under the hood INSIDE the engine room relay box. I don't think that is what he described.

The EFI relay doesn't energize the COR it just feeds power to the contacts. Its coil is controlled by the ECM via the G-Y wire.

If you inject power directly to the pump with the harness still hooked up (and as I said, I don't know if that's what he did) and the COR is energized by the ECU it will backfeed power to the whole circuit, even if the EFI relay isn't energized.

 

[TheDurk]

The EFI relay doesn't energize the COR it just feeds power to the contacts. Its coil is controlled by the ECM via the G-Y wire.

If you inject power directly to the pump with the harness still hooked up (and as I said, I don't know if that's what he did) and the COR is energized by the ECU it will backfeed power to the whole circuit, even if the EFI relay isn't energized.

We disagree on how the ECM works. It controls the COR coil on the ground side, through the green-yellow wire, as confirmed by the transistor drawing inside the ECM box. The hot side wire, designated +B when it hits the ECM, is an ignition-on power signal wire TO the ECM as is clearly explained in Sub-Item 7 under Item 1- Input Signal on the first page of the EWD I posted.

What you are saying is the ECM is liable to backfeed power upstream to an input wire from its full-time 12V+ and energize the COR relay coil on the one hand but not provide power sufficient to run the pump on the other. One purpose of the COR is to cut power to fuel delivery when the ECM detects an abnormal situation, hence its name. Such a backfeed from the ECM would be a major prejudice to this mission. Do you think the people who design these things are idiots? I just don't buy your scenario.

Of course, you are also looking at the WRONG EWD. The COR is wired differently on the '98, as you can see in my post.

 

[jeremyc74]

We disagree on how the ECM works. It controls the COR coil on the ground side, through the green-yellow wire, as confirmed by the transistor drawing inside the ECM box. The hot side wire, designated +B when it hits the ECM, is an ignition-on power signal wire TO the ECM as is clearly explained in Sub-Item 7 under Item 1- Input Signal on the first page of the EWD I posted.

What you are saying is the ECM is liable to backfeed power upstream to an input wire from its full-time 12V+ and energize the COR relay coil on the one hand but not provide power sufficient to run the pump on the other. One purpose of the COR is to cut power to fuel delivery when the ECM detects an abnormal situation, hence its name. Such a backfeed from the ECM would be a major prejudice to this mission. Do you think the people who design these things are idiots? I just don't buy your scenario.

The hot side of the COR relay is connected directly to the IGN fuse. It's hot anytime the Ignition switch is on. The manual states the ECM closes the COR when the ignition is on or when the starter is running. It doesn't say anything about B+ being on as a condition for that to happen. So I wouldn't make that assumption.

From the diagrams and the description in the manual the EFI relay doesn't have any bearing on the contact closure of the COR, it only supplies power to the contacts, therefore I would not make the assumption that the EFI relay is good if you have injected 12V into the circuit downstream of it.

 

[TheDurk]

The hot side of the COR relay is connected directly to the IGN fuse. It's hot anytime the Ignition switch is on. The manual states the ECM closes the COR when the ignition is on or when the starter is running. It doesn't say anything about B+ being on as a condition for that to happen. So I wouldn't make that assumption.

From the diagrams and the description in the manual the EFI relay doesn't have any bearing on the contact closure of the COR, it only supplies power to the contacts, therefore I would not make the assumption that the EFI relay is good if you have injected 12V into the circuit downstream of it.

How do you think the ECM KNOWS if the ignition is on? Power to the +B is the only way. So yes, THAT is the condition. And again, in '98, the COR is NOT "connected directly to the IGN fuse". Both coil and contacts get their power from the contact side of the EFI relay. It would be nice if you looked at the right diagram. If what you are saying is true, the ECM would never power down the fuel injection circuit, even when the key is off.

 

[jeremyc74]

How do you think the ECM KNOWS if the ignition is on? Power to the +B is the only way. So yes, THAT is the condition. And again, in '98, the COR is NOT "connected directly to the IGN fuse". Both coil and contacts get their power from the contact side of the EFI relay. It would be nice if you looked at the right diagram. If what you are saying is true, the ECM would never power down the fuel injection circuit, even when the key is off.

The only diagram I have access to is that one. If you realized they were different why not just post the other one instead of being argumentative?

In the diagram I was looking at what I'm saying would be the case. It powers the COR if the ignition is on, OR the starter is running. If you have 12V hooked to the pump, and hit the key it will close the OCR, which is then going to feed power to the rest of the circuit downstream of the EFI relay, whether it's pulled in or not.

In any case, it has taken longer to debate the whole thing than it would have taken to just check downstream of the EFI relay to be sure it was closing, so it's not worth wasting any more time on.

 

[IBallEngineer]

A few points:

1) The ECM calls the fuel pump when it sees voltage to the starter, among other things. It KEEPS it running when the crank and cam sensors tell it the crank is turning after the starter is no longer engaged. So those sensors are not your problem.

2) The EFI relay is not your problem because that also feeds power to the fuel injection control, and the motor could not run at all without those.

3) '98 and 2002 differ in some important respects. One is that the 7.5A STA fuse keeps a 2002 from cranking but not a '98, it just cuts the fuel pump. So definitely check that fuse.

4) Problem can't be fuel pump ground because pump ran with the direct 12V+ feed. Issue is not on ground side.

5) Confirm all this by pulling the COR. Confirm 12V+ with key on at Pins 1 and 5. See if you have ground at Pin 2 with key in START position. If you do, replace COR. If you don't, that means the ECU is not calling the fuel pump, either because it is not receiving an input it requires or there is a wiring defect. To nail that down, go through the tests in the Service Hints in the bottom of the '98 5VZ-FE Engine Control Wiring Chapter, attached.

If you need help with that, post back and we can do it step-by-step.

Wascally Wabbitt!

:hunter:

 

[TheDurk]

The only diagram I have access to is that one. If you realized they were different why not just post the other one instead of being argumentative?

In the diagram I was looking at what I'm saying would be the case. It powers the COR if the ignition is on, OR the starter is running. If you have 12V hooked to the pump, and hit the key it will close the OCR, which is then going to feed power to the rest of the circuit downstream of the EFI relay, whether it's pulled in or not.

In any case, it has taken longer to debate the whole thing than it would have taken to just check downstream of the EFI relay to be sure it was closing, so it's not worth wasting any more time on.

You're kidding, right? I noted there were important differences and posted the correct diagram in the very post you have been arguing with since the beginning of the dialogue. Here's the link if you are too lazy to scroll back:

http://www.toyota-4runner.org/3rd-gen-t4rs/209633-98-cranks-but-wont-start-fuel-pump-not-recieving-power.html#post2180604

I told the OP to confirm 12v+ from the EFI relay in Point 5 of that same post, giving location and pin numbers from the correct year EWD. Even though it's just not possible, I'm a belt and suspenders guy. Still, YOU decided to argue with it. So don't complain about that now.

 

[TheDurk]

Wascally Wabbitt!

:hunter:

Truth is, I was just being lazy. At that point, there are a number of reasons the ECM could be unhappy and not call the COR, and I didn't feel like figuring them all out and then listing them if it was not to be needed. I was going to ask you to do that if we got that far.

 

[McStudRunner]

Just to update everyone on this thread and give a solution to my headache of a problem:

Turns out it was my fuel pump ground all along. I found I had 12v while cranking at the fuel pump, so i decided to cut the ground wire of the fuel pump and temporarily ground it to the bottom seat bolt nearby and she fired right up :dancin:

Guess I have a bad ground somewhere, but weirdly I don't have any other electrical issues. I check the ground for the fuel/injector rail on the plenum with my impact (yes, I know I shouldn't have but I did) and the bolt broke so i grounded it to the diagnostic port bolt and I imagine that would all well and good.

I'll keep the fuel pump ground to rear seat bottom bolt until I get back there again and do my fuel pump kill switch.

Thanks for all the quick feedback on here guys, really appreciate it.