ECM questions

[tomtom72]

Jeff thank you again for helping me out! Now I realize what I saw in pictures of injector housings, it was the primary O-ring in the bore, not on the injector. The secondaries have the O-ring on the injector. I'm sorry I'm so dense but I've never actually seen an LT5 until I bought one.

wdo-mkr, I would not even know where to begin to do any modding to an injector. I guess if RC has direct bolt on replacements I'll be okay. If not I'll just get OE primaries from GM. I don't have any knowledge or experience with FI systems so I'm not qualified to mess with the parts. I guess if I can't figure this out I'll ask more Q's.

Thanks guys for the help!
Tom

[wdo-mkr]

Originally Posted by tomtom72

wdo-mkr, I would not even know where to begin to do any modding to an injector. I guess if RC has direct bolt on replacements I'll be okay. If not I'll just get OE primaries from GM. I don't have any knowledge or experience with FI systems so I'm not qualified to mess with the parts. I guess if I can't figure this out I'll ask more Q's.

Thanks guys for the help!
Tom

Tom, I just wanted to make you aware of the issues that need to be considered if you decide to move something from the primary to secondary position on a 90-92 style lt5. Its not a big deal and one could remove the locators on the connector side in a couple minutes per injector. I am a bit puzzled though. Why not just order the entire set of 16 from RC and be done with the project? I personally like driving the car more than I like working on it and pulling the plenum is not hard but still a pain if you have to. With the RC injectors being all SS, why not put this part of the maintenance behind you and go from there? Just a thought. Ask all the questions you like. That's how we all learn. Having pulled my plenum and couple others several times, its now not all that exciting for me anymore.

[tomtom72]

wdo-mkr, I e-mailed RC with my request for injectors, all 16, and they said that they were out of stock on "OE primary injectors" till end of Sept.
Not being up on all this stuff I took them for telling me the only injectors that they sell were the secondaries. They thru me for a loss when they said "OE primary injectors". Of course I figure now that they meant "OE style replacement Primary injectors". They kind of confused me with the e-mail response.

I'm gonna get 16 of some one's injectors and change all in one sitting. I know it's kind of a waste if you only have two or three bad ones. I have a vacuum leak that is slowly gett'in worse and I figure to get all the stuff under there so I make this a one time restoration, instead of a repair type operation.

This may make me sound very ignorant of an LT5, well I am, but I completely missed the point you were making. The thought never crossed my mind that it would be possible to switch electrical connections from a primary to a secondary. My lack of experience & knowledge shows! I think when I do this I'm gonna do one side of the motor at a time. This sure ain't nothing like my 72 sb C3!

Thank you for sharing your knowledge
Tom

[wdo-mkr]

Originally Posted by tomtom72

wdo-mkr, I e-mailed RC with my request for injectors, all 16, and they said that they were out of stock on "OE primary injectors" till end of Sept.
Not being up on all this stuff I took them for telling me the only injectors that they sell were the secondaries. They thru me for a loss when they said "OE primary injectors". Of course I figure now that they meant "OE style replacement Primary injectors". They kind of confused me with the e-mail response.

Ah, now I see your issue. I thought you were just going to do the change the secondaries thing and then go back under there again later and deal with the primaries later. Personally I think its a small pain the you know what which is why I was recommending that if you can afford to, go ahead and change them all while you have the fuel rails out. Don't bother trying to clean the old ones. I had a set done and then when I put them back in, they just stuck and or leaked immediately. Not worth the time, loss of weekends, etc IMHO.

Originally Posted by tomtom72

I'm gonna get 16 of some one's injectors and change all in one sitting. I know it's kind of a waste if you only have two or three bad ones. I have a vacuum leak that is slowly gett'in worse and I figure to get all the stuff under there so I make this a one time restoration, instead of a repair type operation.

Ah not exactly. Its not a waste at all. As others here have mentioned. Often times if you have one injector thats either shorted out, stuck, leaking, failed, then the others are not far behind. Its just sound preventative maintenance IMHO.

Originally Posted by tomtom72

This may make me sound very ignorant of an LT5, well I am, but I completely missed the point you were making. The thought never crossed my mind that it would be possible to switch electrical connections from a primary to a secondary. My lack of experience & knowledge shows! I think when I do this I'm gonna do one side of the motor at a time. This sure ain't nothing like my 72 sb C3!

Not at all. Look at the photos again. On the secondaries for both models you will notice a small tag on the connector where the harness connects to the injector. If you look at the 90-92 injectors, the main differences between the primary and secondaries are two items.

On the 90-92primaries, the bellows around the bottom has been shaved off and the bottom of the injector has a taper on the seat of the part that fits in the housing.

Next if you look at the photo of the 90-92 secondary photo below, you will notice a little locating tang on the bottom side of the connector that the harness plugs into. Its centered in the middle of the connector on the injector. If you try and plug the secondary into your injector harness (at least on both of my 91s it was this way) the edge connector will not allow you to plug the harness into the injector if a secondary injector is in a primary position with the tang still in place. The tang will need to be ground off first.



The same thing applies if we look at the 93-95 injectors for the primary and secondary. The primary injector for the 93-95's now has the locating tang on it. Its also offset from the factory secondary injector. Why they did this, I have no idea, since the primaries and secondary injectors are supposed to be the same here.

One could again, just as easily grind the locating tab off the connector and you would be set and the primary and secondaries could be interchanged at that point.

Not owning a 93-95 car, I have not seen a an injector harness up close from this model year to see if they have both of the slots in the injector harness connectors to allow for this, but as I mentioned, one could just grind this tab off and you will be able to connect the harness to either injector and move them around. Something to think about if one is trying to flow balance a set of injectors. Perhaps someone with more knowledge than I could comment on the 93-95 injector harness.


Glad to hear you are doing the lines, secondary actuators, cleaning up the valley area under the starter and coils, and swapping the injectors at once. Its best if you can do it all at once. I would also purchase a set of injector housing to head gaskets, and a center crankcase gasket as well just to be safe. Most times the cover that the two hoses that come from the block to the injector housings are loose and the oil blows back and fills the area in the block under the starter with lots of nice oil, dirt and what ever else the local rodent population can store underneath there. My white car with 65k miles on it at the time had a couple half eaten pecans under the starter and about 1/4 inch of oil,dirt slime mixture in it. All of the bolts on the crankcase cover were loose as well. Its a great way to get a peek inside your lower end of the motor with this cover off as well. (item 2 in the photo below) credits to the corvette action center for this great photo.

[tomtom72]

wdo-mkr, I have said this before but it bears repeating. Yes these cars are special but it's not just the car. The people that own them are what makes owning a ZR-1 special! The willingness to educate the rookies so that they can carry on and hand down the info to the next rookie. That's what makes owning a Z the real deal! It's the people. Thank you & all the members!!

Yea the pics are of Rob's 90. It's so clean it hurts to look at it!

You see it the same way I do, why not just do it all if the plenum has to be pulled. I mean my car is going on 16 yrs old and things don't last forever. I figure to get all the injectors, 4 coils, both ignition modules, rebuild parts for the alternator & starter. The Actuators, vacuum line assembly, solenoid & filter, tank, breather hoses, magnecor 8.5 wire set and a "top end" gasket kit I found on the net are inbound. I'll wait a bit for the finances to recover & start collecting the rest of the parts so I will have all of it before I take the plenum off. It's extreeme but it would be like a new car to me and then I could drive the new off of the parts.

Thank you again for being generous with your knowledge!
Tom