CarlC
05-16-2013, 09:26 AM
Last week James Shipka, Jimi Day, and I participated in the One Lap of America where combined the three of us we put on over 12,000 miles on our cars in one week. On the first long transit stage at about 10:00pm Jimi Day pulled over to the side of the highway with a no fuel pressure condition. James and I turned around to go help Jimi.
As we drove back I thought back to the last gas stop. On the previous stops Jimi and I used almost the same amount of fuel. On the last stop he used almost three gallons more. Figuring it was just a hiccup in something we motored on. Without seeing the car the preliminary diagnosis was fuel leak.
Jimi had "repaired" the leak and the car was running again. However, the reason for the fuel leak was something that sent chills down all of our spines. The high-pressure fuel line connection to the fuel rail had popped off. This connection is right above the valve cover and headers. Jimi just pushed the fitting back on and the car started. There was a gas station a mile up the road so the decision was made to drive the car there and make proper repairs.
The fitting that Jimi had on AMXess is like that on the left below. It uses a plastic clip for fitting retainment. On AMXess the plastic clip stayed on the rail connection but the connector body pulled off, hence leaving an open fuel line in the engine compartment over headers that are wrapped in insulation that can soak up fuel. This fitting and clip were removed and replaced with the type on the right. That is a Russell P/N 644120 and uses a "U" nut instead of the plastic clip to secure the fitting. They are also available in different colors.
https://static1.pt-content.com/images/noimg.gif
Jimi has not done anything abnormal to cause this condition. He does drive the heck out of his car, a testament to the build quality that Randy Johnson put into the car. But Randy did something that saved the car, something that all of us should consider when dealing with high-pressure electric fuel pumps. He followed the suggestions made in the VaporWorx instructions. Let's backtrack just a bit to get a better understanding of the safety concern.
Electric fuel pumps typically need a relay or other device to supply power. Let's consider the VaporWorx PWM control system for now as a relay as well, it's just a device that supplies power to an electric fuel pump. Relays require an electical trigger signal to operate. This trigger often is suppled by the IGN +, hence when the ignition key is on, so is the pump. This also means that the pump runs whenever the key is on even if the engine is not running. So what happens if a fuel line comes off in the engine compartment? Near the exhaust? Heat source? The pump keeps on running and pumping fuel at a furious rate. Pretty scary!
So what is needed is a smart way to control the turn-on function of the relay so that it only provides power to the fuel pump when needed. The GM ECM, as well as many aftermarket ECM's, have a fuel enable function. This FE function is pretty simple, it provides a BAT+ signal to the relay only under certain conditions. The ECM can recognize when there is a relay (VaporWorx PWM as well) attached to the FE connection and will throw an error code if not properly connected. Normally the ECM will provide a two-second prime function when the key is turned on, then shut down the signal. Once engine rotation is sensed the ECM will re-enable the BAT+ signal to the relay and turn on the fuel pump. The ECM is acting as a smart sensor to shut down the high-pressure fuel system when it is not needed. This is where Randy, in my opinion, saved Jimi's car. Randy used the recommended ECM fuel enable signal to turn on the VaporWorx controller instead of opting for the easier IGN+ signal. When the fuel line came off and the engine died, the ECM shut down the fuel system. No more fuel was being pumped over a hot exhaust system.
To boil it all down:
1) Be sure to use secure fittings for all fuel line connections. They should not be able to be pulled off by hand.
2) Use the smart ECM fuel enable signal to control fuel system relays or VaporWorx controller.
As we drove back I thought back to the last gas stop. On the previous stops Jimi and I used almost the same amount of fuel. On the last stop he used almost three gallons more. Figuring it was just a hiccup in something we motored on. Without seeing the car the preliminary diagnosis was fuel leak.
Jimi had "repaired" the leak and the car was running again. However, the reason for the fuel leak was something that sent chills down all of our spines. The high-pressure fuel line connection to the fuel rail had popped off. This connection is right above the valve cover and headers. Jimi just pushed the fitting back on and the car started. There was a gas station a mile up the road so the decision was made to drive the car there and make proper repairs.
The fitting that Jimi had on AMXess is like that on the left below. It uses a plastic clip for fitting retainment. On AMXess the plastic clip stayed on the rail connection but the connector body pulled off, hence leaving an open fuel line in the engine compartment over headers that are wrapped in insulation that can soak up fuel. This fitting and clip were removed and replaced with the type on the right. That is a Russell P/N 644120 and uses a "U" nut instead of the plastic clip to secure the fitting. They are also available in different colors.
https://static1.pt-content.com/images/noimg.gif
Jimi has not done anything abnormal to cause this condition. He does drive the heck out of his car, a testament to the build quality that Randy Johnson put into the car. But Randy did something that saved the car, something that all of us should consider when dealing with high-pressure electric fuel pumps. He followed the suggestions made in the VaporWorx instructions. Let's backtrack just a bit to get a better understanding of the safety concern.
Electric fuel pumps typically need a relay or other device to supply power. Let's consider the VaporWorx PWM control system for now as a relay as well, it's just a device that supplies power to an electric fuel pump. Relays require an electical trigger signal to operate. This trigger often is suppled by the IGN +, hence when the ignition key is on, so is the pump. This also means that the pump runs whenever the key is on even if the engine is not running. So what happens if a fuel line comes off in the engine compartment? Near the exhaust? Heat source? The pump keeps on running and pumping fuel at a furious rate. Pretty scary!
So what is needed is a smart way to control the turn-on function of the relay so that it only provides power to the fuel pump when needed. The GM ECM, as well as many aftermarket ECM's, have a fuel enable function. This FE function is pretty simple, it provides a BAT+ signal to the relay only under certain conditions. The ECM can recognize when there is a relay (VaporWorx PWM as well) attached to the FE connection and will throw an error code if not properly connected. Normally the ECM will provide a two-second prime function when the key is turned on, then shut down the signal. Once engine rotation is sensed the ECM will re-enable the BAT+ signal to the relay and turn on the fuel pump. The ECM is acting as a smart sensor to shut down the high-pressure fuel system when it is not needed. This is where Randy, in my opinion, saved Jimi's car. Randy used the recommended ECM fuel enable signal to turn on the VaporWorx controller instead of opting for the easier IGN+ signal. When the fuel line came off and the engine died, the ECM shut down the fuel system. No more fuel was being pumped over a hot exhaust system.
To boil it all down:
1) Be sure to use secure fittings for all fuel line connections. They should not be able to be pulled off by hand.
2) Use the smart ECM fuel enable signal to control fuel system relays or VaporWorx controller.