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

[BigIke]

Hey Y'all,

I had alternator issues, the car made it back home 8hrs with some tricky driving to keep RPMs up, worst drive of my life, no AC in the rain and traffic, LOL. Installed new alternator in 1 hour, at night and that is good now!

Problem at hand... Been having issues when the car is hot, sometimes it will load up and die, then when i floor it, there is no power, then BOOM, car goes sideways. My secondaries are wired open with the supporting Haibeck tune, and i've got 106,000 miles on The Juan.

So i'm thinking that i might have a clogged fuel filter, and when the second pump comes online, the fuel demand is satisfied and i get a shot of nitrous feel when full power comes online. Seriously, the car will try to swap ends if the AC is off; before that, it won't get out of its own way...

I've also purchased two new fuel pumps, and when the hurricane passes, i've got a fuel filter on hand. Thinking that the filter might be clogged enough to where the single pump isn't enough.

What do y'all think?

[BigIke]

Replaced fuel filter - it was clogged, but my main problem is still present.

When I go WOT, there is black smoke and no power, when the rpms get up, something happens, maybe the second pump coming online... But full power comes online hard... It black smokes during this time to, but I've got a great time, without headers so it's a little fat.

No replies, so my effort to be precise, could have been to wordy or incoherent... Any help poor fa-voor? Lol

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[XfireZ51]

If u have deleted the secondaries, and a Haibeck calibration for that, the secondaries are ON beginning at Off Idle. So the secondary fuel pump is running from Off Idle.

[BigIke]

If u have deleted the secondaries, and a Haibeck calibration for that, the secondaries are ON beginning at Off Idle. So the secondary fuel pump is running from Off Idle.
O okay, I thought I'd read that the secondary pump didn't come online immediately...

I know that even The Car is cold both are online, during that time The Car runs great.

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[QB93Z]

You can get a fuel pressure gauge and tape it to the windshield and go for a test drive. It will answer your question about fuel pumps.


I suggest investigating the black smoke. That is not normal for a ZR-1. Check your spark plugs to see if one cylinder is ingesting oil.


I am not sure what you mean by "goes sideways". If you mean that the rear end tends to move to the right, you should investigate the drive train support called the C-Beam. Make sure the bolts at the transmission and at the differential are properly torqued. If the problem continues, you may want to install C-Beam plates.


Good luck,


Jim

[DRM500RUBYZR-1]

I know that even The Car is cold both are online, during that time The Car runs great


Just to confirm.
The car runs fine with no problem, even at WOT, until it "warms-up"?
Then the problem ALWAYS happens, once warm?
Also, please define warm, i.e. what coolant temp?
Black smoke when cold also, or just when hot?
Those answers might help narrow it down a bit.
Marty

[XfireZ51]

BigIke,

I have recently investigated a condition of black smoke when I would go deep into the accelerator also. Pulled my spark plugs and #7 was very "sooty".
Motor idled fine, seemed to accelerate ok, etc. Compression was good. 220psi.
Turns out I had a cracked top compression ring. In 4 places.
Not wanting to panic u but if u keep getting black smoke it may not be just the motor clearing itself out. As Jim notes, it isn't normal operation.

[BigIke]

Thanks for the replies guys!

1. When cold out runs perfect, from initial start-up, tell warm.
2. Somewhere around 140-160, it behind to act up.
3. When the second pump comes on, the tires break loss like I've spayed a 300hp shot of nitrous. Lol
4. The tune is super fat, it's a header tune with stock manifolds.
5. I'll replace the plugs.
6. The fuel mileage was really bad, got 17mpg on my last trip, I'm use to 23 on my trips to Louisiana for work. I go 7mph over the speed limit, everywhere on cruise control.
8. I'll buy plugs today and set the TPS at .54vdc with a true RMS VOM also.

Thanks again y'all! Jay

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[secondchance]

Just in case, check fuel pressure regulator hose for fuel. When my regulator failed, I was getting additional fuel sucked into the plenum especially in high vacuum condition.

[XfireZ51]

Thanks for the replies guys!

1. When cold out runs perfect, from initial start-up, tell warm.
2. Somewhere around 140-160, it behind to act up.
3. When the second pump comes on, the tires break loss like I've spayed a 300hp shot of nitrous. Lol
4. The tune is super fat, it's a header tune with stock manifolds.
5. I'll replace the plugs.
6. The fuel mileage was really bad, got 17mpg on my last trip, I'm use to 23 on my trips to Louisiana for work. I go 7mph over the speed limit, everywhere on cruise control.
8. I'll buy plugs today and set the TPS at .54vdc with a true RMS VOM also.

Thanks again y'all! Jay

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1. 140-160F is where the engine management goes into closed loop.
2. The tune is probably NOT super fat. It may be richer although probably not at part throttle. Certainly not to the tune of 6mpg.
3. Let's see what the plugs look like.
4. And again, w secondary delete, ur second pump comes on at Off Idle, so ur sideways excursions shouldn't be due to the secondaries kicking 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]

:cheers::handshak:

[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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