Help please????
Thread Starter
Cruising
Joined: Nov 2011
Posts: 11
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Help please????
I have recently purchased a 1985 corvette and the car had a carb on it when I bought it. I've had my mechanic reinstall the factory f.i. system. Everything works on the car except there is no ground to the injectors. All other systems seem to be fine. Can anyone please help me with this?? Thanks.
Last edited by jls85vette; Nov 20, 2011 at 01:56 PM.
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
The injectors are grounded by the ECM.
The ECM needs to see that the inputs and outputs are connected. If everything is not as it should be the ECM will not function. It does have a limited ability to work without everything being correct (limp mode), but you still need to have almost everything connected for that to work.
The ECM needs to see that the inputs and outputs are connected. If everything is not as it should be the ECM will not function. It does have a limited ability to work without everything being correct (limp mode), but you still need to have almost everything connected for that to work.
Thread Starter
Cruising
Joined: Nov 2011
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Thanks for that info, but. We're still where we were on this. Everything is hooked up and all systems are good. Still no ground to the injectors. We have checked all the straps,wires,connectors. Almost to point of giving up and selling it. Any more suggestions would be greatly appreciated. Thanks again!!
Le Mans Master
Joined: Jul 2007
Posts: 5,043
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From: Tampa Florida
This is kind of a loaded thread/question.
You need to mention that you pretty much just got this car and that it had a carb installed on it when you got it...and for whatever reason you've swapped it back to the stock FI setup.
I'm sure there is a lot of stuff that more than likely got "messed" with by the previous owner (P.O.) during the swap....perhaps a question to ask yourself or better yet the P.O. is why did the P.O. go to a carb in the first place.
I recommend you get ahold of a year specifc factory service manual (1985 FSM) and dig in.
You need to mention that you pretty much just got this car and that it had a carb installed on it when you got it...and for whatever reason you've swapped it back to the stock FI setup.
I'm sure there is a lot of stuff that more than likely got "messed" with by the previous owner (P.O.) during the swap....perhaps a question to ask yourself or better yet the P.O. is why did the P.O. go to a carb in the first place.
I recommend you get ahold of a year specifc factory service manual (1985 FSM) and dig in.
Le Mans Master
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From: Australia
Thread Starter
Cruising
Joined: Nov 2011
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While engine is turning over, taking a test light and probing the wires. they both show to be positive. Yes, it did have a carb on it when I got it. When I asked the previous owner why, He responded with he has his reasons. So, we're going in blind and trying to get it all back original. All pieces are here and on the car. Just no fuel getting to the injectors. You can spray fuel into it and it will run until it burns what little fuel is there gets gone. I'm at my wits end almost.
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
I certainly am no expert, but are you sure the ECM is good?
That is what controls the injectors, also (I'm sure you have) make sure you have fuel pressure at the rail on the intake.
There are lots of experts, so here's a bump!!
Oh, and we all get discouraged and want to junk the car on a regular basis. Then something goes right, and we re-group our efforts.
Good luck!
That is what controls the injectors, also (I'm sure you have) make sure you have fuel pressure at the rail on the intake.
There are lots of experts, so here's a bump!!
Oh, and we all get discouraged and want to junk the car on a regular basis. Then something goes right, and we re-group our efforts.
Good luck!
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Thread Starter
Cruising
Joined: Nov 2011
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Well, I bought a new/rebuilt ecu from Advance. So, this could be an issue. Everything else works though. That's what's got me scratching my head and ready to scream and take a sledge hammer to it.
Yes, fuel pressure is at rails and pump and relays all seem to be fine. New pump and filters along with lines too. Thanks!!
Yes, fuel pressure is at rails and pump and relays all seem to be fine. New pump and filters along with lines too. Thanks!!
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Should be using a noid light to test for inj pulse
http://forums.corvetteforum.com/c4-t...tor-pulse.html
http://forums.corvetteforum.com/c4-t...tor-pulse.html
http://forums.corvetteforum.com/c4-t...tor-pulse.html
http://forums.corvetteforum.com/c4-t...tor-pulse.html
Last edited by rodj; Jan 3, 2012 at 05:48 PM.
Le Mans Master
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From: Australia
Le Mans Master
Joined: Aug 2010
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this is going to sound symplistic, but, jumper the ground wire on the individual injectors to ground, actually might get away with grounding one on each bank, in other words, provide the injectors with a ground. if that gets it to burp on its own, take all related grounds loose and wire brush them.....
Le Mans Master
Joined: Oct 2006
Posts: 6,842
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From: Palmdale CA
Thanks for that info, but. We're still where we were on this. Everything is hooked up and all systems are good. Still no ground to the injectors. We have checked all the straps,wires,connectors. Almost to point of giving up and selling it. Any more suggestions would be greatly appreciated. Thanks again!!
Gotta ask. Do you and your mechanic have the Factory Service manual? Cliff has a good point about the ECM. Sure all the systems may be good, but are all the conditions met? There's a sequence of events that the ECM needs to fulfill and see before putting the ground to the injectors. Also, are there any codes being thrown?
None of this is easy, but keep plugging away here and the forum will help out.
Le Mans Master
Joined: Aug 2010
Posts: 9,272
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another place to check, up by the thermostat housing there's a wire or group of wires with an eyelet big enough for a bolt to go thru, thats usually the ground for most of the things that need ground on the top of the engine, make sure it has a bolt thru it and is making clean contact. also at the back of the engine block. If you still have trouble, msmoore is better than most folks who claim to be mechanics at trouble shooting . hope this helps
Last edited by oldalaskaman; Jan 3, 2012 at 07:39 PM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
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From: Australia
http://forums.corvetteforum.com/c4-t...lp-please.html
Five min after answering here you asked exactly the same question again ( but left out the important info about repairing a carb car !)
Just confuses everyone as to what else is being said elsewhere.
If you are not happy with the answers 1st time around just bump question back to the top
There are commercial online sites that will give you instant answers ( for $$$ );
free advice takes a little longer
Last edited by rodj; Jan 3, 2012 at 08:01 PM.
Instructor
Joined: Apr 2011
Posts: 218
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From: Littleton CO
I have recently purchased a 1985 corvette and the car had a carb on it when I bought it. I've had my mechanic reinstall the factory f.i. system. Everything works on the car except there is no ground to the injectors. All other systems seem to be fine. Can anyone please help me with this?? Thanks.
--Calvin
Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
Ummm....at the risk of sounding stupid and pointing out the obvious, if you are just using a DVM to check for ground at the injectors when the car is not running you should see a high impedance path. Remember, 12V is constantly fed to one end of the injector, so if ground were there all the time then the injector would be constantly on whenever the car was in the "on" position. The low side is switched. You need to check the waveform at the injector with an o-scope or if you have a more advanced DVM there are some of them that can check it.
--Calvin
--Calvin