Lean at high rpm

[ALLTHECAMS]

Dynoed my car today after top end porting. Did 3 pulls and it made 383, 384 and 389 on the last pull. The graphs also dipped between 6k and 7k rpm. Before porting it made 374. Also leans out above 5k rpm so I think it's pulling timing. We checked fuel pressure and at WOT it was 40psi. Are my pumps dying?95039504

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[Ccmano]

Yes, should be ~48-55 psi at WOT... At the risk of stating the obvious this assumes the fuel filter is good.

With the car cold, hook up a pressure gauge then simply turn on the ignition, don’t start the car. You should see 48-55 psi that way too. Another good way to test is to check the amp draw of the pumps. Good pumps draw 4-5 amps each, 8-10 amps when both pumps run. Less and your pumps are going bad. It’s nicely written up by Paul here...at post #7.

http://www.zr1.net/forum/showthread.php?p=136108

H
:cheers:

[ALLTHECAMS]

Ok thanks

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[Ccmano]

Based on the HP your car is modded. Curious what mods your running?
H
:cheers:

[ALLTHECAMS]

Based on the HP your car is modded. Curious what mods your running?
H
:cheers:OBX headers, Borla Challenge exhaust, top end porting, lightweight flywheel, Haibeck chip.

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[Ccmano]

Almost identical to mine, you should pick up some hp at the top end with the lean condition resolved.
H
:cheers:

[Hib Halverson]

It's a little difficult to diagnose this problem from those phone images.

Did the dyno facility give you print outs of the power and torque as well as the AFR chart? If so, can you scan them and post?

Better yet, did the shop give you the DynoJet run file? If you have the run file, please post it.

The blue and green runs demonstrate what you see when the ECM is commanding a lot of knock retard

In the other image, my comments are based on the assumption that the dotted red line is 12.5:1. If that's correct, the engine is clearly lean.

Given proper calibration and injectors, the problem could be pumps, pump pickups, fuel line restriction, fuel filter or regulator.

Has the fuel filter been changed?
Have you run all of the fuel system tests in the FSM?

[ALLTHECAMS]

It's a little difficult to diagnose this problem from those phone images.

Did the dyno facility give you print outs of the power and torque as well as the AFR chart? If so, can you scan them and post?

Better yet, did the shop give you the DynoJet run file? If you have the run file, please post it.

The blue and green runs demonstrate what you see when the ECM is commanding a lot of knock retard

In the other image, my comments are based on the assumption that the dotted red line is 12.5:1. If that's correct, the engine is clearly lean.

Given proper calibration and injectors, the problem could be pumps, pump pickups, fuel line restriction, fuel filter or regulator.

Has the fuel filter been changed?
Have you run all of the fuel system tests in the FSM?I have the printouts but not the files themselves. I will scan them later tonight. The first thing I do will be change the fuel filter. I do not have a FSM.

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[Ccmano]

The fact remains, 40psi fuel pressure at WOT doesn’t cut it. As noted it could be the fuel filter, the pumps or a restriction. Generally if the pressure regulator gives up the pressure goes to the high end. More testing is needed.
H
:cheers:

[ALLTHECAMS]

Didn't have much time but did some testing tonight. fuel pressure with key on engine off was barely above 10 psi :0. started the car and it was 38-40 at idle. I am going to change the filter because i am embarrassed to say I haven't done that on this car. Just one of those things I never thought of. After that Ill check pressure again.


Here are scans of my dyno sheets:

[XfireZ51]

I would agree w Hans. Dyno ing the car makes no sense until u have the fuel issue resolved. The shop should be able to email u the run file.

[ALLTHECAMS]

I would agree w Hans. Dyno ing the car makes no sense until u have the fuel issue resolved. The shop should be able to email u the run file.Dynoing the car is how I found out it was lean.

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[XfireZ51]

Dynoing the car is how I found out it was lean.

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Yes I understand that altho checking FP ahead of the dyno would have also made u aware of it. What I meant is that going forward dyno would not make sense.

[ALLTHECAMS]

Yes I understand that altho checking FP ahead of the dyno would have also made u aware of it. What I meant is that going forward dyno would not make sense.Yes you are right.

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[ALLTHECAMS]

Tested the pumps at the test plug by the ECM. Read 7 amps.9512

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[Ccmano]

Tested the pumps at the test plug by the ECM. Read 7 amps.9512

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That’s too low. 8amps is minimum for both pumps. Now pull the FP1 fuse (in the fuel box) and test it again. It will give you the draw on the secondary pump, FP2. Subtract that from the 7.1 you just got and you have the reading for the primary pump FP1. I would replace both pumps.
H
:cheers:

[ALLTHECAMS]

That’s too low. 8amps is minimum for both pumps. Now pull the FP1 fuse (in the fuel box) and test it again. It will give you the draw on the secondary pump, FP2. Subtract that from the 7.1 you just got and you have the reading for the primary pump FP1. I would replace both pumps.
H
:cheers:Did that test and got 3.8 on the secondary and 3.3 on primary. Given that I have a few mods, should I get high flow pumps?

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[Ccmano]

Did that test and got 3.8 on the secondary and 3.3 on primary. Given that I have a few mods, should I get high flow pumps?

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Thought so... for the mods you have standard pumps are more than enough. You have to go to a larger cubic inch engine before you need high capacity pumps. Don’t waste your money. Glad you found your issue.
H
:cheers:

[ALLTHECAMS]

Thought so... for the mods you have standard pumps are more than enough. You have to go to a larger cubic inch engine before you need high capacity pumps. Don’t waste your money. Glad you found your issue.
H
:cheers:Thank you for the help!
Matt

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[Paul Workman]

After blowing up the AF graph, I noticed it looks a little like my initial dyno pulls, i.e., trends up with RPM, and looks like the operator cut it off just shy of 7000 rpm - prolly cuz AF was going lean?

Here are the graphs of my stock 90 Z, taken back in 2007. The leaning you see was due to deteriorating OEM injectors in the presence of alcohol doped fuel; a fact born out by reading the resistance across each injector, AFTER the motor was fully warmed up.

(I'll post the procedure for measuring the injectors w/ o removing the plenum...if/when I can find the diagram I made!)

My 1990 LT5 base case with defective OEM injectors

[ALLTHECAMS]

So I ordered Airtex e3240 pumps. Do they have the same connector as the stock pumps?

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[Ccmano]

Yup, your good.


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[Reichert]

So I ordered Airtex e3240 pumps. Do they have the same connector as the stock pumps?

Sent from my XT1710-02 using TapatalkYes. I installed these same pumps recently. Pretty straightforward. Replace those plastic hose clamps too! You'll need both 5/16 and 3/8 inch.

-Stephen 1990 #2288

[ALLTHECAMS]

Yes. I installed these same pumps recently. Pretty straightforward. Replace those plastic hose clamps too! You'll need both 5/16 and 3/8 inch.

-Stephen 1990 #2288Gotcha. Thanks

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[ALLTHECAMS]

One more question. Are the o-rings for the fuel filter the same size as the ones for the rail?

[ALLTHECAMS]

Installed the new pumps last night. Tested amp draw after and it was 9.5x. Took the car for a test drive and it lost power on the highway while testing WOT. Got a tow back home (luckily I was only a mile away). Tested amp draw again and it was 4.3. Primary pump isn't running. :(

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[Reichert]

Blown fuse?

[ALLTHECAMS]

Blown fuse?I checked the fuse and swapped it with another one. It's fine.

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[Ccmano]

Bummer... when you pull the assembly again, check the connectors especially the one at the top of the of the entire assembly where the wiring exits through the top. Also apply 12v directly to the pump and confirm it is really dead. No need to replace the pump if it’s really something else. Most likely it’s just a bad new pump. It happens.
H
:cheers:

[ALLTHECAMS]

Thanks. Maybe a dumb question but which one is the primary? The lower one?

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[Ccmano]

Thanks. Maybe a dumb question but which one is the primary? The lower one?

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The upper one is primary...
H
:cheers:

[ALLTHECAMS]

The upper one is primary...
H
:cheers:Thanks. Glad I asked.

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[ALLTHECAMS]

Took it apart and primary pump hose had slipped off. Amp draw was low because pump(s) were freewheeling. I tightened them as tight as I dare but I wish Airtex pumps had nipples on them.

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[Paul Workman]

Took it apart and primary pump hose had slipped off. Amp draw was low because pump(s) were freewheeling. I tightened them as tight as I dare but I wish Airtex pumps had nipples on them.

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Daryl (aka "GOLD CYLON") had some jumpers (links) made up for emergencies that when inserted would swap the pumps electrically. That way you wouldn't be stranded somewhere if the primary pump failed...and there have been a few instances where that DID happen.

With a couple connectors and some 'hook-up' wire you could make your own, if you're handy with tools and a soldering gun. Just swap the wires (on you DIY jumper) so that the secondary pump is powered by the primary wire coming from the stock wire harness. (I keep my jumper in the glove box for emergencies.)