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Need some final tuning help(full power)

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Old 11-12-2017, 10:35 PM   #1
biggiefl
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Default Need some final tuning help(full power)

OK....1990 stock ZR1 #451 Just put in 16 new injectors a few weeks ago(Bosch). Went through all the vac. lines and all seemed good. Runs and idles great now. So......:

1) at idle I have 42psi pressure on fuel rail. With engine off it drops to like 39 and stays. Will hit under throttle like 48psi but at around 4800-5k rpm it drops sharply to around 30psi.

2) Vacuum gauge run off the drivers side center vac line going into the plenum. Read 12nm or whatever at idle. Would drop close to 0 when throttle blipped and up close to 25 and settle down to 12 again, no 17-22 normal. Brand new gauge and might not be accurate(will test on another car)but steady at 12. I think I might need to use a manifold vac line, not plenum?

3) I have used cold and warm engine temp. and sprayed ether around the entire engine, no pick up in idle.....nuttin unless sprayed in the air filter. Sprayed around every line and pump....nuttin.

I'm thinking fuel pump(s) or filters or both......thoughts?

I'm getting tired(literally my back) with messing with this and would appreciate any and all ideas.

I know the info. is here but if you can supply part/pump info. #,s from rock auto or just the car/model(97 suburban?) would be mucho helpful

Thanks, Nick
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Old 11-13-2017, 10:57 AM   #2
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Nobody?
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Old 11-13-2017, 01:01 PM   #3
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Have u checked Dynomite’s stickies and over at the Registry?
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Old 11-13-2017, 01:23 PM   #4
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I have checked most of his stickies and they are very helpful. Was hoping somebody would post "Whoa....30psi at WOT is way to low, secondary pump is bad." etc. One said 47psi cold and dropping slightly to 45 at 3k is fine. I'm getting the 47 but it drops to 30 @ around 5k and not sure if that is OK.


I will try a couple of his techniques for looking for vac leaks as I might have a clogged check valve or the ether does not find a leak on certain lines at idle, especially the SPT solenoids, etc.


I have not tried the registry yet as it is blocked at work for some reason and wanted to be able to view a few times today.
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Old 11-14-2017, 07:01 AM   #5
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Quote:
Originally Posted by biggiefl View Post
I have checked most of his stickies and they are very helpful. Was hoping somebody would post "Whoa....30psi at WOT is way to low, secondary pump is bad." etc. One said 47psi cold and dropping slightly to 45 at 3k is fine. I'm getting the 47 but it drops to 30 @ around 5k and not sure if that is OK.


I will try a couple of his techniques for looking for vac leaks as I might have a clogged check valve or the ether does not find a leak on certain lines at idle, especially the SPT solenoids, etc.


I have not tried the registry yet as it is blocked at work for some reason and wanted to be able to view a few times today.
no bueno

you have likely a bad pump seek ye out the old suburban pumps that gm sells and a pair of new filter socks, and a filter

check the silly stuff like fuses and wiring

relatively ez fix but gee that's not tuning? you had me all worked up
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Old 11-14-2017, 11:28 AM   #6
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Just ordered 2 Airtex E3240 with socks, strainers and filters from Rock Auto. For $76 delivered I'll just replace the stuff and have peace of mind. Will check fuses again for S&G's. Does my vacuum look ok or too low? Everything says for normal cars it should read 17-22, mine is at 12 but steady.
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Old 11-15-2017, 01:53 PM   #7
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Mark Haibeck chimed in on my ZR1.net post and stated that 12in of vac at idle is normal for stock cams...good to know. He agrees with secondary pump and filters and I should be 100%. Thanks everyone for your help and after 2 months of diagnostics and work on this 24k mile beauty...I think I got this. New wiper blades, fresh tank of ethanol free gas, 2 coats of wax and a fresh tummy full of Mobil 1 oil, she is gonna be happy....me too.
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Old Yesterday, 11:07 AM   #8
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Well.....pumps were working but I am glad I changed them. Both are AC/Delco so might be original but socks were shot, etc. Dropped in 2 new pumps and she runs great but falls on her face still. I was UNABLE to change the filter due to not having lift access. Darn good chance filter is clogged enough to restrict it when secondary kicks in. Will update after filter change.
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Old Yesterday, 06:09 PM   #9
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Check the plastic intake accordion connector to the filter housing. They have a tendency to collapse on full throttle with age. Had that on mine, felt like no secondaries. A very common issue. Haibeck makes support rings that can be installed or you can make them yourself from 1/8 brass rod like I did.
Here’s the Haibeck link...
H


http://www.zr1specialist.com/HAT%20W...ucts/hoops.htm
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Old Yesterday, 06:17 PM   #10
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I was going to try that but I figured since I have the filters and the socks were that shitty, might as well change it.


Actually I am going to try that tomorrow. Main reason is that when I bought the car it ran with secondaries, spinned through most of 1st gear. I bought a new air cleaner and noticed the accordion was lose on both ends and tightened it up along with putting the filter in correctly. Might be that friggin simple.

Last edited by biggiefl; Yesterday at 06:43 PM.
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Old Yesterday, 07:40 PM   #11
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Quote:
Originally Posted by biggiefl View Post
I was going to try that but I figured since I have the filters and the socks were that shitty, might as well change it.


Actually I am going to try that tomorrow. Main reason is that when I bought the car it ran with secondaries, spinned through most of 1st gear. I bought a new air cleaner and noticed the accordion was lose on both ends and tightened it up along with putting the filter in correctly. Might be that friggin simple.
Yup, just remove the accordion piece and drive with out it. You'll know pretty quick.
H
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