TOP END REFINISHING

[Schrade]

Where's Cliff here - is there a sequence / write-up for vac test with plenum dry - fit, with all electrical connections? Is it in FSM?

Originally Posted by Franke

Schrade, make sure that new O ring is Viton for ethanol fuel. In the pic it looks like a different color from the others and I was wondering if is was Viton or BUNA.

The one in the snappic ON THE INJ is the original one - sheared off. Looks different because it's dry - reason it sheared off too.

Don't know the make of the LT1 kit from which it came...

Originally Posted by Franke

Schrade, looks about right ... not sure why its being difficult. Perhaps its stuck under the plenum. Check post # 37 to see if any help.

I had it mis-routed - post 37 DOES actually show it between 1' and 2' INJ's...

[Dynomite]

Originally Posted by Schrade

Where's Cliff here - is there a sequence / write-up for vac test with plenum dry - fit, with all electrical connections? Is it in FSM?

Post #267 a bit before you were ready

Before you tighten down the Plenum (with Plenum tipped up in front) and ALL vacuum lines, and DIS module connections in place....check your vacuum systems.

With all vacuum lines connected, turn key on and listen for vacuum pump to shut off. If it does not shut off, start at the closest vacuum line to the vacuum pump disconnecting the line and holding your finger over the end. If the pump shuts off the leak is on other side of that. Go to next fitting and do the same until you are past the leak wherein the vacuum pump will NOT shut off. You have now located the leak.

Also check your HVAC and Cruize Control Vacuum System (check ALL connections). Also check your EVAP Purge system connections (charcoal canister which is under drivers side headlight on your 90'). That single small vacuum port under front of plenum facing rearward (90' only) is for the Evap Purge System. The second larger vacuum port on drivers side lower front of plenum is the main vacuum line for the Charcoal Canister. The second Vacuum port right next to that Charcoal Canister port is your PCV Vacuum port.

With the key on, ground the pink wire in the green connector (third from drivers side) on ECM. Use a small finishing nail stuck in alongside the wire connector with an alligator clip pigtail attached to the end for grounding. This will activate the Secondaries which you can watch with the plenum tipped up in front before you bolt it down. This after you are sure you have NO vacuum leaks in the Secondary System.

I promised GC I would not mention any modifications .....but you should eliminate TB coolant so you do not have to mess with coolant every time you remove the Plenum......DO NOT TELL GC I suggested this

Vacuum Systems 90' and 91' (Secondary and Cruize/HVAC)

[Schrade]

Nano-surgery.

There was a tiny bit of the screw sticking out of the front side, but not enough to get Vise-Grips on it.

So hello Dremel. I got a grinding bit centered in the backside, so I should be able to get enough bored out without touching the threads. Getting the screw remnants out will be tricky, so I can use the screws that BF sent...

Cross yer fingers (and cross yer eyes, teeth, cross yer hair, piggies... )

[Schrade]

3 hours, 5 Dremel bits ground to nubs.

Then I put on the Dremel cutting wheel, and cut a slot in the remnant on the front. Small screwdriver, and had it out in 5 minutes.



Shaft threads are spared. Shaft is still SNUG in the shaft bore (won't suck air).

[Dynomite]

Originally Posted by Schrade

I remember seeing it there Cliff - too lazy to go through all the pages backwards there... (plus it reminds me of some of my ignorance on this mill )

That's gonna' take a while to do right.

I've done backprobes on ECM with paperclips

That was from H41 diagnostic - INCREDIBLE - but a good read-thru'....

I was in the middle of it when I got banned from CF - continued on some other vette boards


Just GOTTA' have pinout ID for all 4 ECM harnesses...

I do not even recognize that ECM...My ECM has the four plugs in line and is black

I grounded the Secondary switch with a finishing nail along side the connector wire going into the plug without unplugging any of the four connectors

It only took me a few seconds to check the secondaries. Actually I had my buddy watch the secondary canisters through a couple runners of the Plenum each side with my remote wireless camera probe as I grounded the pin. He could tell they were not only operating but operating smoothly each time I grounded the pin on the ECM plug. We could also hear the vacuum pump kick on after a cycle to replenish the vacuum lost in the operation of the canisters as I recall

Anyone can do this inspection/test without removing the Plenum. See Verifying Seocndary Operation with Plenum in Place by Marc Haibeck

[WVZR-1]

The PCM in the image is a '94 - '95 MY only reprogrammable original to the LT1

[Schrade]

Just about ready for a vacuum test...

But a question here (imagine that - I have a question ) : instead of putting the plenum down for the vac test, why not remove the [not yet] un-heat sink pasted DIS from underneath the plenum, plug it in alone, withOUT the plenum, and plug in the other peripherals of course, and do vac test withOUT the plenum in place? You DO need to be able to work the vac tubes, if you do have a missed / broken line...

[WVZR-1]

In your last image in post #334 you show a correct ECM but in your post #331 you've got a PCM from an LT1 in the image - care to explain? I didn't duplicate the images because of the size!

*** Never mind it's got an LT1 engine in the image also!!!

[Schrade]

Originally Posted by WVZR-1

The PCM in the image is a '94 - '95 MY only reprogrammable original to the LT1

Correct there Dave - you know your vette mills ; the old snappic was a '94 I did top end housecleaning a few years ago - just posted it to show ECM / PCM backprobe.

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But now on vac test - everything plugged in dry, turned the key on, both fuel pump fuses pulled, and the secondary vacuum pump didn't come on.

With all vacuum lines connected, turn key on and listen for vacuum pump to shut off. If it does not shut off, start at the closest vacuum line to the vacuum pump disconnecting the line and holding your finger over the end. If the pump shuts off the leak is on other side of that. Go to next fitting and do the same until you are past the leak wherein the vacuum pump will NOT shut off. You have now located the leak.

Which connector did I miss here?

I still have some vac lines un-hooked as well - any of them necessary before sec vac pump trips on?

[mike100]

the big tube is for the brake booster line and the small one I think feeds the input to the FPR.