Question: Noob having problems with 84 Vette.

[wishuwerehere82]

So let me get this straight , the injectors once the car is fired up, they should be spraying the same amount of fuel? Yes, they should alternate, but spray the same amount. and I tried swapping connectors and it did the same. I'm going to try to check the ECM tomorrow, where is it located at?:W

So you swapped the front and rear injector harness connectors to the opposite sides and the problem with the front injector spraying stayed on the front injector? But if you unplug the connector the injector stops spraying? Something doesn't sound right.

 

[boomdriver]

The ECM is behind the drivers seat , right in front of the battery bolted to the bulkhead inside the battery box.

So you swapped the front and rear injector harness connectors to the opposite sides and the problem with the front injector spraying stayed on the front injector? But if you unplug the connector the injector stops spraying? Something doesn't sound right.

The fuel inj should go back & forth spraying. Not both ON at the same time, but alternate off/on so there is always one spraying. This cycle is to service specific cylinders that are assigned to each injector. '

If the inj duty cycle is screwed up,. look at the ECM or PROM. read any/all stored trouble codes that may give a clue about this.

Fuel injection is fairly straight forward. Takes power, fuel & pressure, and an ECM to time when that fuel is moved and how much.
Could also follow the fuel inj wiring back and physically look at each wire for cuts, grounds...anything that could short the system.Remember that ALL control functions are always done thru the ground path. Hot wires are always ON to their servo but its the ground that come from the ECM that do the hard work.

Hope this helps.

 

[bundy26]

Today I checked for codes and nothing came up, so now I'm really confused, I know the ECM is under the dash, if I unplug it and plug it back would it reset it self? I'm running out of options before I die at the shop, help please.:confused

 

[boomdriver]

Today I checked for codes and nothing came up, so now I'm really confused, I know the ECM is under the dash, if I unplug it and plug it back would it reset it self? I'm running out of options before I die at the shop, help please.:confused

To reset all you have to do is d/c the neg battery cable for 10 seconds. That will clear the codes but it does'nt really "reset" anything.

Still when grasping at straws...get a handful ! It may tell you something..

Thing is, the FI system gets its signals from the ECM that makes decisions based on info from sensors. The fuel soaking may just be a symptom, not the problem. Its often difficult to diagnose ECM engines because the codes are not the simple answer, they just tell you what the ECM is looking at. Throttle position comes to mind. If thats failed, the fuel injection would not know how to act. As would other metering devices. It takes them all working together to make fuel injection work,.

 

[bundy26]

Where is the coolant temp sensor located at? if that may be the problem , could it make the front injector dump that much fuel thinking that the car is cold when it's not?

 

[boomdriver]

i think yours is on the front of the intake around the water pump, but in the manifold. If youre lucky you may find a plug thats broken and soplve the problem early..

 

[Buccaneer]

You really DO NEED to buy and GM Service Manual so you know what you’re doing and how to do it. It has just about everything that you will need to diagnose and fix most anything.

Anyway, the ECM on an 84 is NOT behind the drivers seat like an 82, it is located under the dash on the passenger’s side, connectors pointing down. (2)

I wouldn't think that the CTS is the issue since if it was, you would have issues with both injectors, not just one. It doesn't discern between the two injectors which one will get more fuel than the other. Without the proper diagrams which are in the GM book, you are just shooting in the dark and throwing parts at the motor (shotgun method) and hope it gets fixed, not a good idea.

The issue could very well be the ECM and one of the injector drivers, but again, without the book, its hard to trooubleshoot this issue properly. Save yourself the grief and buy a book and find the true root cause. Happy motoring.

 

[boomdriver]

You really DO NEED to buy and GM Service Manual so you know what you’re doing and how to do it. It has just about everything that you will need to diagnose and fix most anything.

Anyway, the ECM on an 84 is NOT behind the drivers seat like an 82, it is located under the dash on the passenger’s side, connectors pointing down. (2)

I wouldn't think that the CTS is the issue since if it was, you would have issues with both injectors, not just one. It doesn't discern between the two injectors which one will get more fuel than the other. Without the proper diagrams which are in the GM book, you are just shooting in the dark and throwing parts at the motor (shotgun method) and hope it gets fixed, not a good idea.

The issue could very well be the ECM and one of the injector drivers, but again, without the book, its hard to trooubleshoot this issue properly. Save yourself the grief and buy a book and find the true root cause. Happy motoring.

Agreed,

A FSM has detailed instruction on how to trouble shoot every part on that car. Where they are, what they look like and how they work.
Feebay has them for $75 used up to $150 new for the 2 book set.

 

[onedef92]

erd:The Factory Service Manual (FSM) is worth its weight in gold. It'll pay for itself in no time. Bargains on Ebay can be found, too. I was able to buy the complete, two-volume set for my '92 in very gently used condition for under $50 (plus shipping).

 

[Buccaneer]

Sorry if I sounded a bit harsh, but when working on a 26 year old car and unless you are the original owner and know everythng about the condition of the car, you have no idea what has been done to it over the years and then you may also have to add in the "Bubba Factor". Not in all cases, but a fair amount anyway. Like mentioned above " The FSM is worth its weight in gold" and is a real MUST have item if you want to work on and maintain an older car...Jus sayin' Good Luck!

 

[bundy26]

Sorry if I sounded a bit harsh, but when working on a 26 year old car and unless you are the original owner and know everythng about the condition of the car, you have no idea what has been done to it over the years and then you may also have to add in the "Bubba Factor". Not in all cases, but a fair amount anyway. Like mentioned above " The FSM is worth its weight in gold" and is a real MUST have item if you want to work on and maintain an older car...Jus sayin' Good Luck!

Don't worry it is completely understandable, I just thought that this was a common problem with Crossfire vettes, I'll be taking it to the shop on friday and let them solve it, thanks anyway for all your responses, this forum is a great help, I'll post pics when I get this bad boy running, thanks again.

 

[Buccaneer]

You may still want to get one of these. 84 CHEVROLET CORVETTE FACTORY SHOP MANUAL & ELEC MANUAL: eBay Motors (item 170528799659 end time Aug-29-10 11:06:51 PDT)

I hope the shop knows how to work on a CF. Good luck.

 

[bundy26]

Resulted that a wire was shorting out the injector , guess I never was going to find that one.
After $300 the car is running like a champ, some you win and some you lose.Now to enjoy it.

 

[Buccaneer]

Glad you got it repaired and running properly.

Resulted that a wire was shorting out the injector

Did they mention which wire it was and where? Jus wondering where in the harness that might be.