Tuesday, March 24, 2009

Fuel Blues

We worked on the wiring last night, hooking up the kill switches and start buttons for both the Civic and CB750 motors. The reward at the end should have been the thunderous roar of both motors. The actual result was fuel everywhere.
The Civic motor started up fine. The fan motor at first was not getting spark. After some wiring troubleshooting we got the plugs sparking and moved on to the next problem: no fuel.
Our plan to get fuel to the fan motor was to tee into the high pressure fuel line and run it to a regulator so that the carbs wouldn't get flooded with fuel. With no gas coming we took another look at our setup and realized we had plumbed into the low pressure return line. Another tee into the correct line and we tried again. The result: fuel everywhere. It was leaking from the carbs and from the regulator.
Turns out the cheap Holley regulator we bought is only intended for use with a low pressure fuel pump and can only handle a few psi of input pressure. The fuel injection on the Civic runs closer to 50psi and was overpowering the regulator which in turn overfilled the carbs.
So now we need to find a new regulator that can handle the high input pressure but still deliver only a couple of psi to the carbs.
Update 5 hours later: the tech guy at Aeromotive pointed out that we don't understand how fuel regulators work and put us on the right track. The key is that the bypass type regulators allow fuel to pass until the UPSTREAM pressure has dropped to the set point. Thus, even if we had a regulator that could handle the input pressure, it would have short-circuited all the fuel headed for the Civic motor. He suggested putting a bypass regulator on the return side of the Civic regulator, forcing all of the return fuel through it and raising the return fuel pressure to the 4psi setpoint to feed to the carbs. This will probably boost the Civic FI pressure a bit as a side effect. Either way, the Holley non-bypass regulator was not the one for the job.

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