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84 w/CF won't start

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
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88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Well as a last ditch effort

Try pulling the battery and reseat the ECM connectors......

MAKE SURE YOU HAVE GOOD POWER & GROUND.....I'll have to look up the pins tomorrow ( or someone else will chip in here.......)

DOUBLE CHECK YOUR FUSE PANEL WITH A TEST LIGHT....Maybe you lost a MAIN fuse or link.

Vig!
 
Joined
Dec 27, 2001
Messages
160
Location
Matthews, NC USA
Corvette
1984 Coupe
Fuses are OK

Went throught the injector diagnostics step by step and every symptom leads to ECM problems.

Checked all the fuses, all working.


It's not a big deal to replace the ECM is it?

Ken
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
No, pretty easy

1/2 hr MAX
Remove pass side hush panel
Disconnect batt
Using 10mm socket remove 2 bolts holding ECM in.. it sits up behind LOAF twds firewall.
ECM drops down ( you will have to move some of the harness around to get access)
Drop ECM down... remove connectors
remove prom chip....re insert chip in NEW ECM
Reverse order... now you can start the car WITHOUT re installing the ECM in it's cradle.


Vig!
 

Twin_Turbo

Well-known member
Joined
Jan 11, 2001
Messages
618
Location
Enschede, The Netherlands
Corvette
1982 Twin Turbocharged Red/Black
Try Howell EFI, don't buy this stuff from Ecklers or Mid America.

Replaceing it is easy, just plug & play.

I'd make sure I knew WHY this one fried before I risked frying another one!

Some on the CFI Forum have lots of spare ECM's.

Marck
 
Joined
Dec 27, 2001
Messages
160
Location
Matthews, NC USA
Corvette
1984 Coupe
Too Late!

Read the email too late to consider Howell EFI. I've already ordered from Ecklers.

Anyway, Howell didn't have anything listed for an 84. Only 87 and up.

Ecklers ECM should be here tomorrow. That's one of the reasons I ordered from the.

I believe I must have had the ingition on when disconnecting/reconnecting the battery. Car started and was pumping fuel before disconnecting the battery and didn't afterwards.

Well, this was only a $200 mistake this time.

Ken
 

Twin_Turbo

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Messages
618
Location
Enschede, The Netherlands
Corvette
1982 Twin Turbocharged Red/Black
It really should not fry w/ the ignition on. Either it's a case of really bad luck or something else. Le't's hope it's the 1st. :)

Marck
 

Twin_Turbo

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Messages
618
Location
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1982 Twin Turbocharged Red/Black
Oh, and for future reference. Maybe they're cheaper straght from Delphi (they refurbish the old ECM's, it's what used to be Delco)

Marck
 
Joined
Dec 27, 2001
Messages
160
Location
Matthews, NC USA
Corvette
1984 Coupe
How screwed am I?

Got distracted and hooked my new ecm up without disconnecting the battery.

I must be loosing it.

Scanner reads no troulbe codes
Shorting A&B on the ALDL displays repeating 12s.

Other wise, everything looks normal.

Checked all the fuses and they are all good.

I'm hoping I didn't burn anything up.

Fuel pressure greater than 15psi.

Back to the drawing board.

Ken
 

vigman

Motor head!!!!
Joined
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Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Dude....

You SHOULD be fine..If she's flashing 12's

Start her UP!



Vig!
 

Twin_Turbo

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Messages
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Location
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1982 Twin Turbocharged Red/Black
12 is tripped by having the igniton on and engie nut running. The ECM won't get an rpm signal and therefore will think something's wrong. Since this is the design of the system code 12 is used to diagnose if the thing is working or not. One nasty side effect is that IF there really is something wrong w/ the rpm signal you won't know.

Start it up!

Marck
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
So Lets review

New ECM is in.....

Injectors STILL not pulsing.

But you NOW have the ability to read codes!

So the OLD ECM ( I think did cook ).

But the only way the ECM knows the engine is rotating is the HEI spark trigger.

So 1 of 2 things.

1) Fire the engine pouring some gas down the TBI holes and see if it will light off for a breif moment... this exercise will tell you if you have spark and it's being properly distributed.
AND IF YOU HAVE SPARK>>> THAT DOESN'T MEAN THE HEI PULSE IS GETTING TO THE ECM!

2) EITHER the HEI trigger module ( under the cap ) is loose/ shorted/open or the EST module

( that black box on the side of the AC blower by wiper washer resivoir... Pass side ) is faulty or has become unplugged or corroded!

I believe the path is Distrib/ EST module/ ECM.

No HEI pulse.. ECM will not Squirt the injectors.. since the ECM THINK'S the engine is NOT rotating!


Pin 19 on the ECM HAS to see the HEI pulses.... those pulses come from the distrib.

Since all your wiring has been "disturbed" from the previous owner.... I would trust NOTHING... take the time to inspect EVERYTHING! AGAIN! Remove connectors... check for fit.. corrosion...condition! AND LOOK FOR FUNKY SPLICES & MYSTERY WIRES


Start @ the Distrib... and work you way back to the EST & ECM. When you use the ohm meter to buzz particular circuts... make sure the Batt's disconnected and the devices on both sides of the wire path are removed.


I am unsure IF the distrib is the correct one for you..... but if you DO NOT have mechanical & Vac advance it's a good bet that it's OK... the weak spot of those HEI distribs are the connection points to the IGN trigger ( the black box on the base of the distrib) the plastic connectors... going out to the real world break and the rubber boot going thru the distrib explodes.... leaving the wires to chafe against the pot metal base.

As you buzz a line out take a yellow hi lighter and mark a copy of your schematic.


DONT GIVE UP........ Buck up laddie!


Vig!
 

Twin_Turbo

Well-known member
Joined
Jan 11, 2001
Messages
618
Location
Enschede, The Netherlands
Corvette
1982 Twin Turbocharged Red/Black
Does the pump run?

The oil press sender next to distr, it acts as a switch for th FP relay (in case oil press is too low the thing won't start) maybe it's not working properly or the connector is not making good contact.

Crank input (or crank discrete) is a purple wire from the ECM. It's pinout #1 (906) on connector C425

It's a blue wire from the distrubutor (connector 455 blue -> purple)

Marck
 
Joined
Dec 27, 2001
Messages
160
Location
Matthews, NC USA
Corvette
1984 Coupe
#$%&*(!!#$%^&****

Vigman- ( EITHER the HEI trigger module ( under the cap ) is loose/ shorted/open or the EST module)

Twinnie - (It really should not fry w/ the ignition on. Either it's a case of really bad luck or something else. Le't's hope it's the 1st. )

I could kick myself.

After talking to Vigman last night about the ingnition/fuel injection circuitry and how the ECM wouldn't ground the injectors unless it detected a trigger from the Dist., I went back through all the wiring around the dist. this evening.

Found that the plug coming from the distributor to the distributor cap was loose just enough so it wasn't making contact. Couldn't tell it by looking.

Seated the plug and it started right up. Yeah, the vette is running again, but not very well.

Damn, now I have two extra ECMs. Oh well, there is always ebay.

Thanks again guys.

Ken
 

Twin_Turbo

Well-known member
Joined
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Messages
618
Location
Enschede, The Netherlands
Corvette
1982 Twin Turbocharged Red/Black
Great :)

So why is it not running very well? Crappy idle?

Marck
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Ta-Da

Ok... now what boss!?

Which ECM do you have in?

Did you get a NEW 02 sensor YET?


Round 9 DING!

Vig!
 
Joined
Dec 27, 2001
Messages
160
Location
Matthews, NC USA
Corvette
1984 Coupe
Not running well

Idle seems fine.

When I depress the throttle quickly, the engine bogs. If I slowly increase the throttle it reacts ok.

When the tranny shifts from 1st to second, it also bogs. (automatic)

I set the timing several weeks ago, but it needs to be checked again.


Ken
 

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