biggiefl

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

biggiefl

Nobody?

Dominic Sorresso

Have u checked Dynomite’s stickies and over at the Registry?

biggiefl

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.

Rkreigh

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

biggiefl

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.

biggiefl

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.

biggiefl

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.

ccmano

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

biggiefl

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.

ccmano

Yup, just remove the accordion piece and drive with out it. You'll know pretty quick.
H

biggiefl

No luck!


Next is fuel filter and vac test secondaries, etc with a vac tester, don't know what else it can be.

Dynomite

Do a Secondary Functional Test with Key On by grounding the pink wire with black strip on ECM and observing Secondaries function between the Plenum Runners

Secondary Functional Test and Reconditioning the Secondary Actuators

And I assume your vacuum pump turns on with key on and then turns off for several seconds or minutes? The amount of time the pump is off indicates the severity of vacuum leaks. The longer the vacuum pump is off between cycles indicates good vacuum.

biggiefl

That is the funny part. Sometimes it turns off and does not cycle then the next start up it will cycle every 10 seconds or so. I have an intermittent vac leak which leads me to believe the secondary pump(s) or a check valve is leaking/sticking, etc.

Dynomite

That is peculiar......could be electrical connection to vacuum pump. Cycling every 10 seconds should be enough vacuum for full secondary operation. However, if the vacuum pump turns off it could mean there is zero vacuum in the secondary system which would normally trigger the vacuum pump which is now electrically incompacitated. The vacuum pump may have lost its capacity to sense secondary vacuum.

There is a check valve within the secondary system under the plenum that may be a factor.
Secondary Port Check Valve

Page 9 and page 10 (count the pages) Marc Haibeck Finding and Fixing Vacuum Leaks Explains the location and test for this Secondary Port Check Valve.

Also see item #3 Finding A Vacuum Leak

Keep in mind Plenum vacuum provides the required secondary vacuum most of the time but is supplemented by the vacuum pump under FULL Throttle Positions for example when plenum vacuum is LOW.

In your case you may have zero supplemental vacuum normally provided by the vacuum pump when Plenum vacuum is low under acceleration for example. (This is simplified discussion but in general applies).

biggiefl

Yeah it is peculiar. Haibeck said my vac(12-13) is fine for stock cams. It is steady as a rock which leads me to believe the vac is OK. I just need to spend some time Thursday(day off) trying to see if butterflies are opening.


Can you explain the vac pump losing its capacity to sense secondary vac a bit more?

Dynomite

Check the Diagnostic Vacuum Sensor under the ECM.
This is shown without the Vacuum line attached on the left.

biggiefl

Is that vac line supposed to be hooked up to anything? If I unplug that grey plug she won't go over 2500rpm and SES light comes on so I think that connector to the ECM is working. I will double check that vac line however.

Dynomite

Is this what your ZR-1 does? We know what you did but what were the issues again?

feels like rev limiter at 5,000 rpm in 3rd gear

biggiefl

No sir...I wish I had WFO in 1st & 2nd but that is not the case.

When I got the car it had a dead battery. I charged it and went for a ride. She pulled like a train in 1st and I quickly hit the rev limiter at 7k +. I replaced battery next day or so and it did not run correctly. I pulled that grey plug off under ecm and she would only run 2500 before bucking & puking and setting off SES. Somebody mentioned the vac line under ECM but I could not locate it. I did find a lose vac line on plenum drivers near front that was off. Car then idled down and started missing and I realized an injector was bad on #3. So I have replaced air filter, plugs, injectors, fuel pumps, socks, etc. Car runs fabulous but does not make much of a difference between full power on or off. I will look for that vac line now that I know where it is.