-------------- Original message --------------
From: "Dick Benjamin" <dickb@xxxxxxxxx>
Yes, you can check the pressure that way. The pressure there can get up to 80 PSI, so be careful to have a secure connection to your gauge.
The two wire connector on the pump is the one to check. One wire is ground (I think it is black), the other one (I can?t tell you the color because I am colorblind), is the one we care about ? it varies between almost Zero to almost 12 volts, depending on the fuel demand signal put out by the computer, which knows the throttle position, the fuel flow rate, the RPM, and a bunch or other things, like temperature of the air, fuel and coolant, exhaust oxygen, altitude etc..
The power module basically is just a DC coupled power amplifier, which takes the computer output and boosts it up to a strong enough signal to operate the pump motor. One of the failure modes (usually caused by someone shorting the output to ground) is a failed transistor in the final output stage. Depending on which one failed, the power module might be putting out a solid 12 volts all the time; this would also explain your symptom.
The first thing I?d like to have you do is to pull the wire off the FPS as soon as the engine starts ? to see if that reduces the fuel flow to something reasonable and the idle becomes normal. If this works, forget all the other fiddling around ? you?ve found your problem!
Dick Benjamin
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