91 - Sluggish at WOT - Then sideways when sec pump kicks in

[BigIke]

My fuel pumps came in, fuel pump 1 had been going bad for a very long time. Car is perfect again.
1. I'm guessing in the temp, but it isn't very far off full cold
2. The MPG issue I've thought was due to The Car running poorly on fuel pump 1. We'll see when I get a chance to stretch it out later. 😂
3. Plugs were good. I put NGK 7090's in it but didn't change anything.

4. Not secondaries kicking in, just fuel pump 2 coming online, it doesn't run all the time. And it's not synced directly to the secondary system.

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[XfireZ51]

BigIke,

First of all congrats getting the car running well again.
To clarify, 6E3-A-80 for Code 55 states that "When the ECM turns ON the secondary injectors, it must also turn ON the secondary fuel pump to maintain proper fuel pressure." So the turn on of secondaries IS synched to secondary pump operation. When u disable the SPT, the secondary injectors turn ON Off Idle with the necessary changes made to the calibration.

[BigIke]

I'll look that up, because if read that fuel pump 2 wasn't connected to the secondary function... I can tell you it isn't in my car, fp1 was garbage, when fp2 came online the heavens opened... But I'll read more.

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[XfireZ51]

Consider this. If u have 8 injectors operating at X fuel pressure, and then open an additional 8 imjectors, unless the fuel pump increases its capacity, how do you maintain the same consistent pressure?

[BigIke]

I understand, and thought the same thing, but I read in some old posts that wasn't the case. All 16 inj are not open at the same time, one pump could supply the needs to a certain rpm, then the second pump comes online. I don't know what rpm mine came on, Tach isn't working at all anymore, but it was around 30 mph. And when it did it would knock the 335s out from under the car. Now that fp1 is sat, you power is everywhere... I believe the clogged filter caused the failure, dead dragging at the filter vs the regulator and rails killed it.

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[XfireZ51]

[BigIke]

2 hour road trip just completed (0200...), 22.2 mpg mixed driving!!! That would have been 16 mpg yesterday morning! God damn, my baby is back, better than ever! Those two 340lph pumps hooked her right up!

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[32valvesftw]

Jay, u said your secondaries were wired open?? Did something come loose with that arrangement? it sounds like the engine is taking a few seconds to adjust for the additional fuel or there is a problem that is preventing it from reacting to the additional fuel. Are you sure its not an ignition issue, coils OK, plug wires in place intact, etc..?

[BigIke]

The butterflies are wired open, and are still open. The whole issue was a failing fuel pump. With the performance I have now, I can tell that it's been going out for a long time.

I thought I had to slip the clutch really bad because of the 13lb flywheel, but I was wrong, fp1 couldn't maintain the power near idle to keep the engine running. Now the car is much easier to drive again.

Power is back, fuel mileage went up 6 or more points, it's awesome again. Now I need to find my charging issue.... New alternator isn't maintaining voltage with the AC on... Lol

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