Crank, no start, 5 months in, frustrated (1 Viewer)

[jpd motorsports]

the crank sensor has an ohm range for them to be good Mine 1999 would run die run die. found the ohm specs and it was out of range. be something to check easily. also check the wiring to the sensor it could have gotten nicked or rubbed by the serpetine belt, same with cam sensor wires. under the rear vehicle driver back door is a connector for the fuel pump as well.

 

[Cosmo Kramer]

Not sure if you've tried this, but it's something, see below. good luck

Neutral safety switch??

My immobilizer fix

I got the famous crank but not start immobilizer problem. I replaced the 20A EFI fuse with a 30A fuse and it started right away. However, it was a temporary fix. I had the same problem again 4 days later. This is what I did to get the engine started. It has been working with no problem for...

forum.ih8mud.com

EFI Relay Bypass Kit (Immobilizer Fix) for UZJ100/LX470

This bypass kit bypasses the bad EFI relay circuit in the fuse box so that the immobilizer system gets adequate power supply for starting the car. I made this for myself after my new 30A replacement fuse - initial fix for crank but not start problem, failed to start after 4 days. Some members...

forum.ih8mud.com

 

[KFunk740]

Thanks, Did you have a throttle body DTC/OBDII code?

I did, P1128 I think, so its not exact same condition as yours. But seeing as the ECU controls basically everything and is known to get goofy for no reason, I'm always suspicious of it making other similarly bad decisions if everything else checks out.

 

[Brian Burda]

Not sure if you've tried this, but it's something, see below. good luck

Neutral safety switch??

My immobilizer fix

I got the famous crank but not start immobilizer problem. I replaced the 20A EFI fuse with a 30A fuse and it started right away. However, it was a temporary fix. I had the same problem again 4 days later. This is what I did to get the engine started. It has been working with no problem for...

forum.ih8mud.com

EFI Relay Bypass Kit (Immobilizer Fix) for UZJ100/LX470

This bypass kit bypasses the bad EFI relay circuit in the fuse box so that the immobilizer system gets adequate power supply for starting the car. I made this for myself after my new 30A replacement fuse - initial fix for crank but not start problem, failed to start after 4 days. Some members...

forum.ih8mud.com

the bypass kit from medtro/Jackson is the answer... I have a 1998 LX470... would start and run just fine... but then at times would only crank.... and not fire up... at random... it turns out there was/is some sort of short in the fuse box under the hood... that would not allow the security system to pump the fuel... I got the kit from medtro on this site, and have not had the problem since... when it was acting up, I took it to the dealer and they were clueless... here is pic of the thread regarding the kit from

 

[planomateo]

Lolz, a picture vs a link?

 

[bucfl]

Here ya go....found it

EFI Relay Bypass Kit (Immobilizer Fix) for UZJ100/LX470

This bypass kit bypasses the bad EFI relay circuit in the fuse box so that the immobilizer system gets adequate power supply for starting the car. I made this for myself after my new 30A replacement fuse - initial fix for crank but not start problem, failed to start after 4 days. Some members...

forum.ih8mud.com

 

[Mauser]

If you were closer I could loan a used ecu to try. I bet shipping to Canada from New Mexico wouldn't be cheap though.

 

[mixtec]

the bypass kit from medtro/Jackson is the answer... I have a 1998 LX470... would start and run just fine... but then at times would only crank.... and not fire up... at random... it turns out there was/is some sort of short in the fuse box under the hood... that would not allow the security system to pump the fuel... I got the kit from medtro on this site, and have not had the problem since... when it was acting up, I took it to the dealer and they were clueless... here is pic of the thread regarding the kit from View attachment 2661366

Yes, I saw this, but ruled it out with troubleshooting. It is not intermittent, fuse is fine, no deformation, good voltage and the LX does not start with the bypass. I ran a line from battery + to the appropriate relay connections and it still does not start. If the fuse box, relay or fuse was the problem I believe it should start. It does not.

 

[mixtec]

If you were closer I could loan a used ecu to try. I bet shipping to Canada from New Mexico wouldn't be cheap though.

Thanks. My check engine light is on with the key on, so I ruled out the ECU. I understand if the ECU is bad the check engine light is out.

 

[mixtec]

Not sure if you've tried this, but it's something, see below. good luck

Neutral safety switch??

My immobilizer fix

I got the famous crank but not start immobilizer problem. I replaced the 20A EFI fuse with a 30A fuse and it started right away. However, it was a temporary fix. I had the same problem again 4 days later. This is what I did to get the engine started. It has been working with no problem for...

forum.ih8mud.com

EFI Relay Bypass Kit (Immobilizer Fix) for UZJ100/LX470

This bypass kit bypasses the bad EFI relay circuit in the fuse box so that the immobilizer system gets adequate power supply for starting the car. I made this for myself after my new 30A replacement fuse - initial fix for crank but not start problem, failed to start after 4 days. Some members...

forum.ih8mud.com

I tried playing with the shifter, put in Nuetral, moved around. In and out of park. No difference. Would this cause the engine to die while driving? That is what happened, on snowy winter day on the way to the ski hill.

 

[mixtec]

the crank sensor has an ohm range for them to be good Mine 1999 would run die run die. found the ohm specs and it was out of range. be something to check easily. also check the wiring to the sensor it could have gotten nicked or rubbed by the serpetine belt, same with cam sensor wires. under the rear vehicle driver back door is a connector for the fuel pump as well.

So mine just won't start unless the fuel pump is directly wired. It starts and runs for a couple seconds and then dies, even though the pump is running. It won't start at all if the pump is not hot wired.

Any other ideas?

Next is the Fuel ECU and check for continuity between the fuel pump and fuel controller (ECU).

 

[mixtec]

It would seem so, have you chase the wiring from fuel pump to fuse block? A recent thread I saw showing pics of mice damaged wires was horrifying. Was there any work that was done prior to it's no run status?

There is no continuity between the fuse block and fuel pump and not enough power, was at 3 V.

Is the fuse wired to the fuse block or is the Fuel ECU between the fuse block and the fuel pump?

 

[pawwright]

Did you change the crank sensor? I didn't reply as someone replied earlier with that suggestion - Unlike @jpd motorsports my sensor was in spec when tested. For giggles I put in a new one as I had one - and it fired up right away and haven't had an issue since, 7+? months later.

 

[ramangain]

So mine just won't start unless the fuel pump is directly wired. It starts and runs for a couple seconds and then dies, even though the pump is running.

This sounds suspiciously like a mechanical issue with a fuel pump trying to pinch out one last turd before death, not electrical. Does a known working fuel pump do the same thing? Trees from the forest and all of that jazz.

 

[krispykritter]

Just to summarize my understanding:

• Seem obvious that there's an issue with getting power to the fuel pump while cranking/running, but...
• Two different fuel pumps wired directly to the battery will start the 100, but...
• When it starts, it rapidly ends up sputtering and dying, even though the fuel pump is still humming along happily.

Based on these facts, it seems you may have two problems that may or may not be related. First is the issue with power to your fuel pump: as someone else has stated, you need to chase those wires as best you can and figure out where there's a break/corrosion/etc.

I think your second issue may be crank/cam sensor related, and may be tied into your fuel pump problem.

MOST ECUs run the fuel pump for a couple seconds to prime the system when you turn the key (I don't know if the 100 does this). Then, when they detect RPM sync (basically, when they see a signal on both the crank sensor and the cam sensor that makes sense), then the ECU turns on the fuel pump again. No rpm sync, no fuel pump.

However, you could be getting and losing RPM sync because of bad grounding or a bad sensor. When the fuel pump is connected to ECU controlled power, it's not enough signal to switch on the fuel pump. When you hardwire it, there's enough rpm sync to fire the plugs for a bit but then it loses sync again and the engine dies.

I think someone else said it, but I'd be ohming out all your crank and cam sensors, and check their wiring for continuity or damage, and seeing if there's an issue there.

Edit: I'll just add, codes can be incredibly useful for this sort of thing, but a lack of codes doesn't mean much either. Don't take it as truth either way. Good luck!

 

[krispykritter]

I've been informed in another thread that the LC will only supply voltage to the fuel pump while actively cranking. @mixtec did you check voltage while cranking, or only when turning the key to 'on'?

 

[Gatorskin27]

Mixtec, did you ever resolve your issue? Im curious as to I may be experiencing something similar.