2003 GX470 crank but no start (1 Viewer)

[AKcruiserfreak]

Hi all,
I’ve been having an intermittent issue with my GX470. It will crank and crank without starting. It will start and run with starting fluid. Obviously it’s not getting fuel. Let me list what all I’ve done to try to eliminate issues.

- new fuel pump
-cleaned throttle body
-new spark plugs
-cleaned battery terminals
-checked the EFI fuse and switched with new
-checked EFI relay and switched with new

When I replaced the fuel pump it started perfect for several months. When I cleaned the throttle body it started great for a few weeks and now it’s acting up again.

A few questions I have are: is the fuel pump supposed to prime when the key is in the “on” position? Also, does anybody have a wiring diagram of the fuel pump system? I’m trying to see if I should be getting 12 volts at the EFI fuse or relay.
I’m stumped here.

Thanks

 

[z00t3ch]

Fuel filter? Fuel pressure regulator?

 

[AKcruiserfreak]

Fuel filter? Fuel pressure regulator?

I’ll be checking both tomorrow. I just Hate pulling the interior to get to everything. Lol

 

[lndshark]

The fuel pump does not prime with the key on, engine off (KOEO).

The basics should be to check for fuel pump output, and adequate pressure. From there you can see if the fuel pump circuit is getting power, or is shorted to ground.

Did you replace the fuel pump with a new OEM unit? I’ve seen a lot of these fail from poor quality, internal leaks/bypassing within the fuel tank (or the supply line fitting broken on the pump inside the tank).

 

[AKcruiserfreak]

The fuel pump does not prime with the key on, engine off (KOEO).

The basics should be to check for fuel pump output, and adequate pressure. From there you can see if the fuel pump circuit is getting power, or is shorted to ground.

Did you replace the fuel pump with a new OEM unit? I’ve seen a lot of these fail from poor quality, internal leaks/bypassing within the fuel tank (or the supply line fitting broken on the pump inside the tank).

Thanks for the response! I figured out the fuel pump only comes on when the key is cranking/ motor is running the hard way. The pump is running perfectly when I jump the relay contacts. I did replace with OEM Denso unit with the filters. I'll start a new post on my findings last night...

 

[AKcruiserfreak]

So after some troubleshooting I have narrowed down my problem. Air is being introduced into the system somehow. I was able to get it runing and stay running after shooting a bit of fuel directly into the intake. This truck has ALWAYS had slightly longer than normal crank times. The crank/ no start issue began last Summer and has become increasingly frequent.
I believe that one of more of the injectors may be leaking and causing the system to de-prime. Will a advanced diagnostic computer be able to tell if the injectors are the culprit? My little $100 unit will not.

Thanks again!

 

[lndshark]

So after some troubleshooting I have narrowed down my problem. Air is being introduced into the system somehow. I was able to get it runing and stay running after shooting a bit of fuel directly into the intake. This truck has ALWAYS had slightly longer than normal crank times. The crank/ no start issue began last Summer and has become increasingly frequent.
I believe that one of more of the injectors may be leaking and causing the system to de-prime. Will a advanced diagnostic computer be able to tell if the injectors are the culprit? My little $100 unit will not.

Thanks again!

Nice find! A handheld tester isn’t going to diagnose this. You’ll need to get fancy with the diagnostic tools and run an injector drop test. Or, do it the old fashioned way and physically check the spray pattern of each injector.

Basically you’ll want to monitor fuel pressure at the fuel rail as you trigger (and close) each injector. The fuel pressure will drop or bleed off as you open/close it. Or, as I said before, find a way to flow (and safely!) flow fuel from each injector to check the spray pattern and see if fuel drips when the injector is commanded to close.

Good luck!

 

[AKcruiserfreak]

Nice find! A handheld tester isn’t going to diagnose this. You’ll need to get fancy with the diagnostic tools and run an injector drop test. Or, do it the old fashioned way and physically check the spray pattern of each injector.

Basically you’ll want to monitor fuel pressure at the fuel rail as you trigger (and close) each injector. The fuel pressure will drop or bleed off as you open/close it. Or, as I said before, find a way to flow (and safely!) flow fuel from each injector to check the spray pattern and see if fuel drips when the injector is commanded to close.

Good luck!

Thanks, that's kinda what I was thinking. I'll drop her off at a shop with a little more advanced diagnostic capability that I have.

Out of curiouslity, is there a "how to" video or set of instructions floating around the interwebs? I'm having a hard time finding a specific set of instructions for a 4.7.

Thanks!

 

[lndshark]

Thanks, that's kinda what I was thinking. I'll drop her off at a shop with a little more advanced diagnostic capability that I have.

Out of curiouslity, is there a "how to" video or set of instructions floating around the interwebs? I'm having a hard time finding a specific set of instructions for a 4.7.

Thanks!

I’m sure if you Google “injector drop” or “fuel pressure leak down” you’ll find something close. Maybe not 100% 2UZ specific but you’ll get the general idea

 

[CarolinaGX]

If you are getting air into the system, that would be the O-rings on the injectors, right?. I don't know if the "carb cleaner trick", often used to find vacuum leaks, will help find a leaky injector seal.

 

[lndshark]

Air around the injectors would create a vacuum leak and a poor idle condition. Yes, the carb cleaner/brake cleaner trick would work for diagnosing THAT issue. But injector o-rings are outside of the pressurized fuel system and wouldn’t have an effect on fuel delivery and pressure.

 

[AKcruiserfreak]

I've got to admit that I am tempted to replace the injectors and o-rings no matter what as they are 17 years old with 120,000 miles on them.

I think I'll download a FSM and work through the injector removal procedure to see how easy/ quick it is. If I have to remove more than the rails and misc. hoses, it may not be worth it for me to do unless necessary as this is a daily driver. There are not very many writeups on 4.7 injector removal out there.

Thanks!

 

[lndshark]

Unless someone else has been in there, the o-rings should be fine, even at that age. If it makes you feel better though, it’s easy-peasey. Once you get the intake hose out of the way, it’s two bolts at each end of the fuel rail, the fuel inlet quick connect, passenger side) and some vacuum hoses. You can do it!