Ls swap 2005 4l60e park neutral switch, no fuel.

[wiynwiyn]

Hi all. Can you guys please give me some expertise on this one. Drives me crazy. Search and search, can’t figure out the problem. My ls engine started once before with nothing connected to the park neutral switch as seen below. Now, when I turn the key on and try to start the engine; no fuel, I checked all fuses, fusible link, fuel pump relay seems fine. Could it be that because nothing is connected to the park neutral switch that’s why the engine isn’t starting now. It cranks but no fuel. Please help.

 

[NeverFinis]

As I remember, you shorted your harness. All bets are off once that happens.

What does your GM ECM report via OBDII? If you can't talk to it, you possibly got a dead ECM.

A properly functioning Park/Neutral Safety Switch will prevent a crank, at least in my truck.

You should hear the fuel pump prime when you turn the key to On.

 

[wiynwiyn]

As I remember, you shorted your harness. All bets are off once that happens.

What does your GM ECM report via OBDII? If you can't talk to it, you possibly got a dead ECM.

A properly functioning Park/Neutral Safety Switch will prevent a crank, at least in my truck.

You should hear the fuel pump prime when you turn the key to On.

Thanks for your feedbacks. Yes I shorted the wiring. Accidentally, plug the fusible link into the negative. I ordered a new one will see if the. We one fix the problem. I will check the psi ECU. By the way no prime to fuel pump.

 

[NeverFinis]

No Prime to Fuel Pump is an indication of a bad ECM.

Did you connect the Check Engine light to the GM ECM? If so, does it light up when the key = ON?

 

[wiynwiyn]

No Prime to Fuel Pump is an indication of a bad ECM.

Did you connect the Check Engine light to the GM ECM? If so, does it light up when the key = ON?

Great suggestions. I need to buy a scanner. Need to reprogram the psi ECU since I’m running 35” tires. So will have them check it out too after I scan it. Haven’t run the psi check engine light to the gauge.

 

[wiynwiyn]

Spent all day to diagnose the issue. Computer seems fine. We tested it out with a scanner. Shows signal when you crank such as rpm. There is just no fuel going into the engine. Believe I got the wiring to the fuel pump incorrectly

 

[wiynwiyn]

No Prime to Fuel Pump is an indication of a bad ECM.

Did you connect the Check Engine light to the GM ECM? If so, does it light up when the key = ON?

Thank you very much for your time NeverFinis. I appreciate you. Most probable cause of no fuel is no fuel going into the engine. I’m going to use your method on wiring the fuel pump. Simplifying it. You have wealth of information on the 80s we are fortunate.

 

[NeverFinis]

To be clear..you want a relay to power the R-B wire coming from the Fuel Pump Resistor on the passenger inner fender. It is a straight shot to the fuel pump from there. I mean, as a test you can just add +12V there to see if the fuel pump runs.

Just a note, if you do use the GM to activate the fuel pump, you might need to disable Starter Diagnostics in the ECM (see my post Builds - LX450 "Rex" Build - https://forum.ih8mud.com/threads/lx450-rex-build.1254004/post-15202414)

Fuel Pump Relay:

Relay Pin 87: +12V from Battery, use an appropriate Fuse (GM uses 30 Amp)
Relay Pin 86: +12V from GM Circuit 465 (Fuel Pump Relay Control). This could be different depending on GM ECM
Relay Pin 85: GND
Relay Pin 30: R-B wire found at Toyota Fuel Pump Resistor


I circled it.

 

[wiynwiyn]

To be clear..you want a relay to power the R-B wire coming from the Fuel Pump Resistor on the passenger inner fender. It is a straight shot to the fuel pump from there. I mean, as a test you can just add +12V there to see if the fuel pump runs.

Just a note, if you do use the GM to activate the fuel pump, you might need to disable Starter Diagnostics in the ECM (see my post Builds - LX450 "Rex" Build - https://forum.ih8mud.com/threads/lx450-rex-build.1254004/post-15202414)

Fuel Pump Relay:

Relay Pin 87: +12V from Battery, use an appropriate Fuse (GM uses 30 Amp)
Relay Pin 86: +12V from GM Circuit 465 (Fuel Pump Relay Control). This could be different depending on GM ECM
Relay Pin 85: GND
Relay Pin 30: R-B wire found at Toyota Fuel Pump Resistor


I circled it.
View attachment 3749603

you are brilliant. I got it to start. Thanks so much.!!

 

[wiynwiyn]

I tapped the wires into the psi relay. Stopped working so got a new relay. Neverfinis suggestion, tapping into the LC resistor makes a lot of sense. Won’t have to run a wire directly into the fuel pump, which may cause a bad ground. By the way, psi said you don’t need to connect anything to the ls park/neural switch. Car still start without.