Intermittent Starting

[Therealtotodile]

Hey everyone.

93 FZJ80, 260k.

This morning, I drove the truck 1 mile to a CVS, walked back out, and couldn't get it to start. CRANK CRANK CRANK but no start. After about an hour of waiting around, it started back up again. Since, it has been fine. Took it to Oreillys to do a load test on the starting system, everything checks out. This makes me think I'm having some sort of fuel delivery issue.

However, I replaced the pump(new denso), filter, and sender(oem) within the last couple months.
Does anyone know what else controls the fuel delivery? I also cannot seem to hear the pump when I turn the key, and am starting to think my relay may be dieing on me.

I know that the relay has two states, high and normal, and goes on high for a second right when the car starts, to push the fuel into the motor. My first guess is that the relay is not sending that high signal.

First thing I'm going to try is swapping the relay. I feel like if it was a pump/filter/sender issue, then it would affect the truck while driving. The relay is 30 years old, and may just have bad contact.

Open to any and all suggestions. Also going to take the truck to a Toyota shop in SD if I cant figure it out, and they can have fun trying to troubleshoot the fuel system. I do not have the banjo bolt to do the pressure test on the rail.

Regards,
Chris

 

[ppc]

The fuel pump relay controls voltage to the pump more than just at engine start. First off you can monitor what the voltage the fuel pump relay is outputting to the fuel pump by attaching a voltmeter to the "FP" pin in the diagnostic connector on the firewall. Drive around and observe the voltage under different conditions. Under higher engine loads and RPM the pump is supplied higher voltage to satisfy fuel requirements. Unless you are having drivability issues under those higher load conditions I doubt that your intermittent starting issues are caused by fuel pump or fuel pump relay issues.

When the starting issue occurs have you verified that the check engine light (CEL) is illuminated with the ignition turned on before starting the motor? That indicates that the ECM is not being powered and the engine will not start. That could be caused by failed fusible links, a problem with the COR - circuit opening relay or some other electrical problem. There are several threads relating to how to diagnose these types of problems you can find by using the search function.

 

[Therealtotodile]

The fuel pump relay controls voltage to the pump more than just at engine start. First off you can monitor what the voltage the fuel pump relay is outputting to the fuel pump by attaching a voltmeter to the "FP" pin in the diagnostic connector on the firewall. Drive around and observe the voltage under different conditions. Under higher engine loads and RPM the pump is supplied higher voltage to satisfy fuel requirements. Unless you are having drivability issues under those higher load conditions I doubt that your intermittent starting issues are caused by fuel pump or fuel pump relay issues.

When the starting issue occurs have you verified that the check engine light (CEL) is illuminated with the ignition turned on before starting the motor? That indicates that the ECM is not being powered and the engine will not start. That could be caused by failed fusible links, a problem with the COR - circuit opening relay or some other electrical problem. There are several threads relating to how to diagnose these types of problems you can find by using the search function.

Thanks for the input sir. Based on my interpretation of above, it sounds like your saying my relay is working, otherwise it wouldn't be able to hold speed because the pump wouldn't be adjusting the amount of fuel sent at higher load.

When you say the diagnostic connector in the fire wall, is that the same connector I jump to get my OBD1 codes? Not sure how I could physically watch my multimeter connected to that port while driving.

There is no CEL and my truck's CEL does work. I think your referring to the relay that goes out and takes the CEL with it, forgot what its called but its silver in the engine bay.

I also wouldn't expect an intermittent issue if a fuse(or fusible links, which are fine) is blown. That's a one way type thing. The ECM works and has been replaced, I had the faulty early 93 one.

My last thought: If the car is cranking, but not firing, it has to be fuel or spark right? And like I said, I had the starter alternator and battery load tested this morning. That's why I am stuck on fuel.

Thanks!

 

[ppc]

You most likely would be able to hold speed or cruise but it would stumble on hard acceleration.
Yes, I'm referring to the connector in which you jump pins to retrieve fault codes. The FP (Fuel Pump) is one of those pins.
Easily monitored if you used extended leads to the voltmeter and place it on the dash. Its not like you have to stare at it continuously.

I'm not asking if the CEL is on during driving. If you place the key in the ignition, turn the key two positions (past accessory) but without turning to "start" is the CEL illuminated with other dashboard warning lights. It the CEL is not on at that point the ECM is not getting power and will not start. The problem with fusible links can be an intermittent problem that will get worse over time. As the engine bay heats up, the fusible links may separate, the COR relay contacts get higher resistance/voltage drop etc. When the engine bay cools off then those things reverse allowing you to start the vehicle again.

The statement you made below is a false assumption. Don't rule even the simplest of things out as the possible cause.
"I also wouldn't expect an intermittent issue if a fuse(or fusible links, which are fine) is blown. That's a one way type thing. The ECM works and has been replaced, I had the faulty early 93 one."

 

[Therealtotodile]

You most likely would be able to hold speed or cruise but it would stumble on hard acceleration.
Yes, I'm referring to the connector in which you jump pins to retrieve fault codes. The FP (Fuel Pump) is one of those pins.
Easily monitored if you used extended leads to the voltmeter and place it on the dash. Its not like you have to stare at it continuously.

I'm not asking if the CEL is on during driving. If you place the key in the ignition, turn the key two positions (past accessory) but without turning to "start" is the CEL illuminated with other dashboard warning lights. It the CEL is not on at that point the ECM is not getting power and will not start. The problem with fusible links can be an intermittent problem that will get worse over time. As the engine bay heats up, the fusible links may separate, the COR relay contacts get higher resistance/voltage drop etc. When the engine bay cools off then those things reverse allowing you to start the vehicle again.

The statement you made below is a false assumption. Don't rule even the simplest of things out as the possible cause.
"I also wouldn't expect an intermittent issue if a fuse(or fusible links, which are fine) is blown. That's a one way type thing. The ECM works and has been replaced, I had the faulty early 93 one."

So the truck is definitely not stumbling, it's good to go once its on. I just tested it on the freeway. It has also been fine for the last 4 hours, as I've been working on it driving around etc. The behavior has not returned.

I knew there is definitely power to the ECM, because all my lights were on with the key in and turned two clicks. That's why I mentioned the EFI relay(couldn't remember the name earlier). Based on the fact my ECM is working when I have the no fire, wouldn't you assume that the COR is good? Otherwise I would have no light right?

I'm also a little confused about the false assumption statement, just not sure how a fuse could "half" blow.

Thanks!

 

[ppc]

A fuse can fail or have an intermittent connection other ways besides blowing as is the case for any wiring or circuit. A fuse needs to be tested with a meter. Visually looking at it is not sufficient.

As far as the ECM being powered, only the CEL being on before starting indicates that. All other dash lights are irrelevant when determining it being powered.

Yes, the problem could be related to the EFI, COR, the contacts and wiring that connects them. That is why you need to debug the issue when it fails and not make any assumptions as you are now doing. @jonheld has posted a document that goes through the debugging steps and should be the first thing to read and follow.

What do I mean by "false assumption"? Every time the word "assume" is used or the phrase like "Based on the fact" .

 

[jonheld]

General Tech - 3FE EFI Diagnostics

3FE EFI Diagnostics updated for 2020

forum.ih8mud.com

Keep in mind that this was written for the 3FE engine, but much of it still applies.

 

[Therealtotodile]

General Tech - 3FE EFI Diagnostics

3FE EFI Diagnostics updated for 2020

forum.ih8mud.com

Keep in mind that this was written for the 3FE engine, but much of it still applies.

Thank you both for suggesting the procedure and posting.

Here is what I found:
1.CEL always illuminated.
2.Fusible Link Diag passed
3.Not sure how to check the AFM -- the write up says that you would check if you have no CEL.
Is there any easy way to check if my flap is stuck open? Not sure where that would be.
4.Coil pack passed diag test
5.Igniter has no test -- I did replace that about a year ago. The truck had some aftermarket or non land cruiser one in from the PO.
Replacing it gave me my tach back.
6.Distributor passed diag test

I also was able to start up the truck fine this morning, and cruise around a bit. I returned home thinking it may have resolved. I then tried to leave again, and the truck died at idle. All lights on, CEL included after I turned the key back. I then fired it again and it started.

I then opened up the bonnet, and swapped out both the EFI relay as well as the fusible link(old one did pass the, "what lights are working" diag). No problems yet, but I have only tested it for around 30 minutes.

I also am thinking I should just order both the COR and FP relays, just to have in case. They both look original, so 30 years old.

Thanks all,
Chris

 

[Bogart]

The fuel pump relay controls voltage to the pump more than just at engine start. First off you can monitor what the voltage the fuel pump relay is outputting to the fuel pump by attaching a voltmeter to the "FP" pin in the diagnostic connector on the firewall. Drive around and observe the voltage under different conditions. Under higher engine loads and RPM the pump is supplied higher voltage to satisfy fuel requirements. Unless you are having drivability issues under those higher load conditions I doubt that your intermittent starting issues are caused by fuel pump or fuel pump relay issues.

When the starting issue occurs have you verified that the check engine light (CEL) is illuminated with the ignition turned on before starting the motor? That indicates that the ECM is not being powered and the engine will not start. That could be caused by failed fusible links, a problem with the COR - circuit opening relay or some other electrical problem. There are several threads relating to how to diagnose these types of problems you can find by using the search function.

He is a 93, may not have a diagnostic port?

 

[jonheld]

He is a 93, may not have a diagnostic port?

Definitely has the diagnostic connector on the firewall.

 

[Malleus]

Unless I'm missing something, this sounds like the starter Bendix to me.

 

[jonheld]

3.Not sure how to check the AFM -- the write up says that you would check if you have no CEL.
Is there any easy way to check if my flap is stuck open? Not sure where that would be.

The switch on the flap of the AFM is the ground path for the fuel pump logic. With the flap closed, the fuel pump shuts down. This ensures the FP is not pumping in the event of an engine stall.
Page 61 of the 1994 EWD gives a brief check of the AFM terminals you can do with a multimeter. You can download the 1994 EWD from the resources section.

 

[jonheld]

You can also bypass all FP logic by shorting pins 1 (FP) and 12 (B+) on the diagnostic connector. This will cause the FP to run continuously with the key in the ON/RUN position.

 

[ColoradoBoy]

OP- your situation sounds somewhat similar to my issues a while back. Thanks to @jonheld and his wealth of knowledge, got it figured out. The main culprit (albiet a 3FE) ended up being the FPR, and was unfortunately the last thing that I checked/tested. Well worth the $30.00 Harbor Freight fuel pressure test kit to rule out lack of pressure in the fuel system. Heed the guidance of Jon, perform the work, and you will get it sorted out.
Cheers!

 

[Therealtotodile]

OP- your situation sounds somewhat similar to my issues a while back. Thanks to @jonheld and his wealth of knowledge, got it figured out. The main culprit (albiet a 3FE) ended up being the FPR, and was unfortunately the last thing that I checked/tested. Well worth the $30.00 Harbor Freight fuel pressure test kit to rule out lack of pressure in the fuel system. Heed the guidance of Jon, perform the work, and you will get it sorted out.
Cheers!

Thank you everyone for your wisdom, I really appreciate the posts. The truck has not had the starting issue since I swapped out the efi relay and the fusible links, and tonight, she would not start after going to the grocery store. Same behavior where it will crank but not turn over.

I tried to jump the FP and B+ slots in my very grimy diagnostic port that has no lid, and wanted to ask about that. I wanted to ask the proper way to jump said ports. And since I don't have a lid, wanted to ask for a diagram. This is what I found and went off of.

And when I say I jumped it, I mean I inserted a u-shaped unbent paper clip in the ports, just like I do to pull codes from the other two ports. Not sure if that makes sense. With the paper clip firmly inserted in both ports, I tried to start the truck. It acted the same. I tried this with the little plug that is needed to see the blinking CEL in and out of the diag port, on a whim.

This time it did not magically restart after about an hour. I have a FPRelay and CORelay comin in the mail. I have not been able to play with he AFM yet. I wanted to ask if you can check it by just removing the large ?intake? tube, or if you need to take it apart. Everyone's description scares the s*** out of me and I will not touch those pins.

I also wanted to mention I can now definately hear the fuel pump, my ear has been trained by listening for it over and over. And it is audible when I turn the key turned to you would need to, to see the CEL.

Thanks all.

 

[Therealtotodile]

Thank you everyone for your wisdom, I really appreciate the posts. The truck has not had the starting issue since I swapped out the efi relay and the fusible links, and tonight, she would not start after going to the grocery store. Same behavior where it will crank but not turn over.

I tried to jump the FP and B+ slots in my very grimy diagnostic port that has no lid, and wanted to ask about that. I wanted to ask the proper way to jump said ports. And since I don't have a lid, wanted to ask for a diagram. This is what I found and went off of. View attachment 2768611 And when I say I jumped it, I mean I inserted a u-shaped unbent paper clip in the ports, just like I do to pull codes from the other two ports. Not sure if that makes sense. With the paper clip firmly inserted in both ports, I tried to start the truck. It acted the same. I tried this with the little plug that is needed to see the blinking CEL in and out of the diag port, on a whim.

This time it did not magically restart after about an hour. I have a FPRelay and CORelay comin in the mail. I have not been able to play with he AFM yet. I wanted to ask if you can check it by just removing the large ?intake? tube, or if you need to take it apart. Everyone's description scares the s*** out of me and I will not touch those pins.

I also wanted to mention I can now definately hear the fuel pump, my ear has been trained by listening for it over and over. And it is audible when I turn the key turned to you would need to, to see the CEL. And that is with it not jumped or jumped.

Thanks all.

 

[ColoradoBoy]

Hard to start when weather and vehicle are hot- SOLVED

forum.ih8mud.com

For what it may be worth, read through this. (3FE motor on mine)
The FSM is your best friend; if you don't have one, get one. DON'T MESS WITH THE AFM- very unlikely the issue.
Keep digging- you'll get it!
Cheers!

 

[Therealtotodile]

Hard to start when weather and vehicle are hot- SOLVED

forum.ih8mud.com

For what it may be worth, read through this. (3FE motor on mine)
The FSM is your best friend; if you don't have one, get one. DON'T MESS WITH THE AFM- very unlikely the issue.
Keep digging- you'll get it!
Cheers!

I will definitely be running through the FSM. I was able to start the truck this morning, after playing with the AFM flap(which seems to work, goes back to position with an audible !dink! each time I move it with my finger. It started, and I was able to drive it home with no issue. Now that it is home, I cannot get it to start again.

I also just received he CORelay and the FPRelay and installed the new ones. No affect here either.

Like I said, the car drives fine, doesn't stumble or idle, once its starts.

Chris

 

[Therealtotodile]

Also just confirmed spark per the FSM. removed the plug, reconnected to the wire, ground and saw spark coming out during the key turn.

 

[Therealtotodile]

Hey everybody.
Truck sat at a shop for a week, so they could tell me that they think I should start by fixing the 15A fuel pump fuse. The fuse box spot(7) for that pin had melted, and I pulled the wires, and worked in an inline fuse. I started the truck a few times, and noticed that it was stumbling. About he 5th start, it just cranked cranked cranked. I went to see if I could hear the fuel pump, and I could not. I then pulled the fuel sender/pump combo, and nada. No gas squirting out. No noise. And that was with the key on a click before ignition(where you can see the CEL lit because my EFI fuse works) as well as cranking. I then pulled out my multi meter, switched it to amps, and checked a couple of the pins from the fuel sender connector while holding it to the ground wire. There are a blue and a red wire, blue was .26 A steady and red was .11 A steady when key was turned in the ignition to the CEL is visible position.

Hoping someone could let me know if those numbers check out, because if they do, I think I need a new pump. Brand new sender and pump like 6 months ago. I basically just want to do a pump diagnostic, before I order a new one. The one that's in there giving me trouble is denso PN 9500109 (950-0109), purchased about 6 months ago.

Is it possible I could have gotten a s*** one? My tank is pretty gross(rusty inside) but the sock filter is good.

I'm super happy I was at least able to show that during the no start, it does have to do with the fuel pump. Now I just need to figure out if its the pump, or the wiring going to the pump.

Thanks all that helped me out!
Chris