My First Plenum Pull

[98indypacer]

Symptom: I don’t notice much difference with key in the full power mode and also have a vacuum leak. The vacuum pump runs 1 second on and 1 second off.

What I checked so far: I grounded terminal 12 of the DLC and get a code of C12, “no stored DTC’s” reported by the CCM. I removed the vacuum hose at pump and plugged pump inlet. Pump shuts off and stays off. I disconnected the vacuum line at connection on passenger’s side of plenum, the pump holds vacuum there. I used a MityVac hand pump to check vacuum line going under the plenum to the reservoir. I was not able to hold vacuum with hand pump. Pulled the vacuum line in the center of plenum on the driver’s side to test the check valve. Holding my finger over the vacuum line did not make a difference, so I don’t think it is the check valve.

Next steps: So it looks like I will be doing my first plenum pull. I purchased the Under Plenum Service DVD from Marc. It doesn’t look too difficult but a lot of things to watch out for like bent pins or vacuum lines that became disconnected upon reassembly. I ordered a few plenum gasket sets from Jerry since I know this will not be the only time to pull the plenum.

Question: I plan to replace whatever I find wrong with the vacuum system and hope replacement parts are not too hard to find. While I have the plenum off I should I replace vacuum system components that still function as a preventive measure? Should I replace the spark plug wires and coil packs as a preventive measure? If so what brand and part number of coil packs? What brand of plug wires? Any other suggestions?

Thanks, Ed

[Schrade]

Originally Posted by 98indypacer

Symptom: I don’t notice much difference with key in the full power mode and also have a vacuum leak. The vacuum pump runs 1 second on and 1 second off.

What I checked so far: I grounded terminal 12 of the DLC and get a code of C12, “no stored DTC’s” reported by the CCM. I removed the vacuum hose at pump and plugged pump inlet. Pump shuts off and stays off. I disconnected the vacuum line at connection on passenger’s side of plenum, the pump holds vacuum there. I used a MityVac hand pump to check vacuum line going under the plenum to the reservoir. I was not able to hold vacuum with hand pump. Pulled the vacuum line in the center of plenum on the driver’s side to test the check valve. Holding my finger over the vacuum line did not make a difference, so I don’t think it is the check valve.

Next steps: So it looks like I will be doing my first plenum pull. I purchased the Under Plenum Service DVD from Marc. It doesn’t look too difficult but a lot of things to watch out for like bent pins or vacuum lines that became disconnected upon reassembly. I ordered a few plenum gasket sets from Jerry since I know this will not be the only time to pull the plenum.

Question: I plan to replace whatever I find wrong with the vacuum system and hope replacement parts are not too hard to find. While I have the plenum off I should I replace vacuum system components that still function as a preventive measure? Should I replace the spark plug wires and coil packs as a preventive measure? If so what brand and part number of coil packs? What brand of plug wires? Any other suggestions?

Thanks, Ed

I say 'No'.

But that's just me, and sometimes it's easier to get responses going, by being wrong...

[Dynomite]

Originally Posted by 98indypacer

Question: I plan to replace whatever I find wrong with the vacuum system and hope replacement parts are not too hard to find. While I have the plenum off I should I replace vacuum system components that still function as a preventive measure? Should I replace the spark plug wires and coil packs as a preventive measure? If so what brand and part number of coil packs? What brand of plug wires? Any other suggestions?

Thanks, Ed

I concur with Schrade......You do not have to replace parts that are still functioning in perfect order.

But that is not to say you might want to replace with NEW as I did for a complete restoration of the TOP END

It is a personal preference exactly as Schrade suggests

Let us know where that Vacuum leak was

An example is Plug Wire Replacement...if you decide you need new Plug Wires....you can get the cheaper non original plug wires for $70 or the LT5 Plug Wires for $300......it is all Personal Preference.

Same goes with Injectors......the prices and quality vary but all will function perfectly for a long time. It is a concensus however as I understand it to not try and rebuild Injectors but rather buy NEW Injectors if you suspect Injector issues (Ohm them).

And take a look at Schrade's New Thread on Top End Reconditioning Schrade's Top End Refinishing

See also Removing Plenum (including the 10 minute Plenum Removal)

[98indypacer]

Originally Posted by Dynomite

I concur with Schrade......You do not have to replace parts that are still functioning in perfect order.

But that is not to say you might want to replace with NEW as I did for a complete restoration of the TOP END

It is a personal preference exactly as Schrade suggests

Let us know where that Vacuum leak was

An example is Plug Wire Replacement...if you decide you need new Plug Wires....you can get the cheaper non original plug wires for $70 or the LT5 Plug Wires for $300......it is all Personal Preference.

Same goes with Injectors......the prices and quality vary but all will function perfectly for a long time. It is a concensus however as I understand it to not try and rebuild Injectors but rather buy NEW Injectors if you suspect Injector issues (Ohm them).

And take a look at Schrade's New Thread on Top End Reconditioning Schrade's Top End Refinishing

See also Removing Plenum (including the 10 minute Plenum Removal)

Thanks to Schrade and Dynomite for your suggestions. Going to take the plunge this weekend. I'm going to do a complete top end restoration with some help!

[Franke]

Just an additional note to Dyno's response. If you ohm the injectors cold there is a good chance they might read good as mine did. About 12-13 ohms. However, when mine got hot 4 of them dropped in resistance by a third to a half the cold value so be aware. They were the original injectors.

[98indypacer]

Originally Posted by Franke

Just an additional note to Dyno's response. If you ohm the injectors cold there is a good chance they might read good as mine did. About 12-13 ohms. However, when mine got hot 4 of them dropped in resistance by a third to a half the cold value so be aware. They were the original injectors.

Franke - Thanks I'm to replace them all with "new" FIC injectors.

[Paul Workman]

Originally Posted by 98indypacer

Franke - Thanks I'm to replace them all with "new" FIC injectors.

Hello!

If you're going to replace injectors, I would not risk fussing with "rebuilt/conditioned" injectors (or you might end up using another one of those plenum gaskets in short order**...Just sayin.). A while back, it was not uncommon to read where refurbished injectors later developed problems. No amount of customer service makes up for the hassle of "new" parts suffering "infant mortality", resulting in having to troubleshoot and yank the plenum and replace the gaskets - even one time. Instead, go with a new stainless set from FIC. Feedback on the new SS ones from FIC has been...well...I don't recall a single person having an issue with them in some years now.

Just a thought. Good luck!

Paul.

**PS: I've had good luck reusing plenum gaskets by laying the gasket on a hard surface and spraying what will be the top side of the gasket with silocone lube spray as a future release agent.

To save the gasket, I've had good luck with the silicone. After removing the bolts and gently prying on one corner of the plenum, I slip s thin putty knife between the gasket and the plenum and slide the putty knife the length of the gasket - separating it from the plenum. With the silicone spray having been applied on the last installation, I've been able to reuse the plenum gasket a couple more times w/o leaks.

Far as coils go, I went with AC Delco, but others have used MDS and others with success.

One other gasket worth considering is the breather box under the plenum. It is usually the culprit that results in the valley getting covered with oil.

I might suggest you pull the starter off and inspect/clean up the copper contact ring in the solenoid: one of the prime culprits for "dreaded no-start". I used some emery paper and was able to remove all the pits and carbon tracing: hasn't failed in 4+years!

on my 3rd plenum pull, running down a vacuum problem, I "ripped**" out the secondaries (as Scottfab would say) and installed a chip from Marc Haibeck. No more secondary issues, and a nice performance perk to boot. I couldn't be happier with the way it runs now (but "**certain purists", who will remain nameless (!), are quick to at the idea.)

[mike100]

Unless your car has a higher mileage, I would spend the money on the injectors and fixing your actual vacuum secondary problem. The ignition stuff is optional, depending on your budget etc. Taking off the plenum isn't too difficult, but original injectors are 100% likely to give you grief so plan on doing something about those for sure.

[98indypacer]

Paul - I agree. I am replacing all of the injectors with new FIC injectors not rebuilt. I put new in quotes to refer to not rebuilt.

Mike - I figured while I had the plenum off I might as well renew as much as possible so will replace the coil packs and the wires. I going with ACDelco coils and original wire$$.

Thanks, Ed