[67_LS1]

I’m currently using the fuel pump relay driver output from my ECM to power a fuel pump relay coil to turn on my fuel pump. The pump is not PWM And does have a bypass/return line.
Can I change this to used switched B+ from the ignition switch to drive the coil instead?

 

[B52bombardier1]

You can but I think this could be unsafe after a car accident. The PCM stops the fuel pump when it detects no RPM. Your method eliminates that feature.

Rick

 

[rpol78]

Just out of curiosity does the fuel pump you're using have a regulator to turn it on and off based on pressure since you're not running PWM or a bypass/return?

 

[67_LS1]

You can but I think this could be unsafe after a car accident. The PCM stops the fuel pump when it detects no RPM. Your method eliminates that feature.

Rick

Interesting. I hadn’t thought about that. I wonder if I could use a roll over or crash relay from a later model car??

Just out of curiosity does the fuel pump you're using have a regulator to turn it on and off based on pressure since you're not running PWM or a bypass/return?

I am running a bypass filter and a return line to the tank.
But that makes me wonder…The pump primes for approx 2 seconds and then stops when I turn the key to the on position. It runs full time when the engine is running. what stops the pump after two seconds? Probably the ECM. Crap.

 

[123pugsy]

What's the problem with it being run thru the ECM?

If the power goes thru a relay, doesn't that mean it's not PWM?

 

[marcrose]

you can get an oil pressure sensor with a safety fuel shut off wired in. I use them on the 502 with no mech fuel pump boss.Basically an in tank sump with a 12 volt relayed voltage thru the oil pressure sensor.return line with pressure regulator at rail.No oil pressure no fuel pump.,car rolls over no oil pressre.(UNLESS ITS A DRY SUMP) pulse width modulated is the way to go but as long as the motors getting fuel safely alls good..(your ecm 12 volts will suffice.)

 

[67_LS1]

I’m suspecting that something is amiss with the signal from the ECM. I’m only getting 2.54 volts at the relay. So I’m wondering if I can use an ignition source to turn the fuel pump relay on rather than getting a new ECM and sending it out to have it reprogrammed for my swap application. ($$$$)
My pump is not PWM but the original donor car pump was. it also had a relay in the circuit but the relay turned on the fuel pump control module which then controlled the pump.

 

[pannetron]

The GM ECUs usually sink current, not source it. That means you connect one end of a relay to (switched) +12 and the other side of the relay to the ECU. The ECU triggers the relay by connecting the other end of the relay coil to ground, completing the circuit. I HIGHLY recommend checking out the VaporWorx PWM control system. It's easily retrofitted into an EFI fuel system and reduces wear and current draw on the pump. My boost referenced setup controlling a GM CTS-V2 pump has been working flawlessly for six years.

 

[123pugsy]

I’m suspecting that something is amiss with the signal from the ECM. I’m only getting 2.54 volts at the relay. So I’m wondering if I can use an ignition source to turn the fuel pump relay on rather than getting a new ECM and sending it out to have it reprogrammed for my swap application. ($$$$)
My pump is not PWM but the original donor car pump was. it also had a relay in the circuit but the relay turned on the fuel pump control module which then controlled the pump.

Control module. No point in checking voltage.

I found this after reading this thread:
Other Control

 

[67_LS1]

The GM ECUs usually sink current, not source it. That means you connect one end of a relay to (switched) +12 and the other side of the relay to the ECU. The ECU triggers the relay by connecting the other end of the relay coil to ground, completing the circuit. I HIGHLY recommend checking out the VaporWorx PWM control system. It's easily retrofitted into an EFI fuel system and reduces wear and current draw on the pump. My boost referenced setup controlling a GM CTS-V2 pump has been working flawlessly for six years.

Mine has been running flawlessly for years too. It makes much more sense that the signal would be a ground but if so, why am I getting 2.54v there?

 

[pannetron]

An open collector output can "float" up toward +12 but will only source a few microamps. Some may have pull-up resistors to ensure that the controlled output pulls up far enough above ground to avoid triggering the output. Do you measure that 2.54V with the load connected? If so, then that is a puzzle!

 

[67_LS1]

An open collector output can "float" up toward +12 but will only source a few microamps. Some may have pull-up resistors to ensure that the controlled output pulls up far enough above ground to avoid triggering the output. Do you measure that 2.54V with the load connected? If so, then that is a puzzle!

No, I measure 2.54v at the relay socket with the relay removed, so no load.

 

[123pugsy]

What year and car is the PCM from?

 

[67_LS1]

2013 Camaro with the LFX V6 and 6L50e 6 speed auto.
Engine, transmission, harness and ECM all came from the same donor. The stock harness was modified and the stock ECM was reprogrammed to eliminate all of the items not applicable to my installation, ie, vats, tank pressure sensor, etc.
It has been running fine for approx 6 years.

 

[marcrose]

Some of the high speed gm lan systems run on 5v and toggle aroung 2.5. your ecm could be shorted to a 5v ref subsystem.Not sure what you have eliminated or kept.fuel pressure runs on 5v to.You have the 120 resisters eliminated.

 

[Bronco3738]

Interesting. I hadn’t thought about that. I wonder if I could use a roll over or crash relay from a later model car??




I am running a bypass filter and a return line to the tank.
But that makes me wonder…The pump primes for approx 2 seconds and then stops when I turn the key to the on position. It runs full time when the engine is running. what stops the pump after two seconds? Probably the ECM. Crap.

What’s the problem? That’s exactly what It’s supposed to do. Initial key on, the pump primes for 2 seconds. Then it shuts off if you don’t crank the engine. Pump will cycle 2 seconds each time you cycle the key. Pump runs full time when the e I fr is running.