RE: IML: 81 Imperial changeover

[arbie104@xxxxxxxxxxx]

I just realized that the FPSooks almost identical to the oil pressure sender on my 66 Polara 383!  Does anyone know the limits of the FPS versus the oil pressure sender?
 -------------- Original message ----------------------
From: arbie104@xxxxxxxxxxx
> Will the car start if I just unplug the FPS?  What is the FPS function?  I 
> probably won't have time to try this till Saturday.  Thanks
> 
> -------------- 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

--- Begin Message ---

• From: arbie104@xxxxxxxxxxx
• Date: Fri, 24 Feb 2006 01:30:32 +0000

Will the car start if I just unplug the FPS?  What is the FPS function?  I probably won't have time to try this till Saturday.  Thanks

 

-------------- 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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