Carbed 85 / What does the ecm control?
Thread Starter
Instructor
Joined: May 2008
Posts: 120
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From: Missouri
Carbed 85 / What does the ecm control?
I'm looking for some help on what to look for when removing the ecm and what all it controls in an 85.
Fuel Pump,,,,,no problem
Fan,,,,,,,,,,no problem
Guages,,,,,,,no problem
What else should I be looking out for? Thanks in advance guys.
Fuel Pump,,,,,no problem
Fan,,,,,,,,,,no problem
Guages,,,,,,,no problem
What else should I be looking out for? Thanks in advance guys.
Pro
Joined: Feb 2005
Posts: 560
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From: Hamilton New Jersey
That's an interesting question, I'm really not sure myself. I know this may sound stupid but what is there to gain by removing the ecm? I simply left mine in. It doesn't weigh that much and nobody will ever know it's there except you.. I'm kind of curious to know the answer too though.
Melting Slicks
Joined: Nov 2004
Posts: 2,799
Likes: 2
From: Cape Coral FL
I left mine in as well
For the fans, I cut the feed wire to the relay (low-current switch side), and ran it to a switched power source. I replaced the OEM fan switch with a "low temp" switch kit (it controls the ground on the low current side of the fan relay), and ran another relay for the A/C compressor to turn on the fan relay (using it to control the ground side of the fan relay low current circuit) - too simple!
Fuel pump, I cut and reconfigured the feed for the relay exactly like the fan relay (taking the ECM out of the loop)
Overdrive relay was stupidly easy.. I cut the wires to the ECM and spliced them together (ECM controls the ground to the relay). I now have a "4+4" trans (OD works in First gear)
I left the speedo circuit alone - no need to monkey with the ECM
ECM does NOT control the gauge display, btw... (well, the mileage computations for the instant/avg fuel economy it does, but that's a nitpick).
Not hard to do with a little common sense..
For the fans, I cut the feed wire to the relay (low-current switch side), and ran it to a switched power source. I replaced the OEM fan switch with a "low temp" switch kit (it controls the ground on the low current side of the fan relay), and ran another relay for the A/C compressor to turn on the fan relay (using it to control the ground side of the fan relay low current circuit) - too simple!
Fuel pump, I cut and reconfigured the feed for the relay exactly like the fan relay (taking the ECM out of the loop)
Overdrive relay was stupidly easy.. I cut the wires to the ECM and spliced them together (ECM controls the ground to the relay). I now have a "4+4" trans (OD works in First gear)
I left the speedo circuit alone - no need to monkey with the ECM
ECM does NOT control the gauge display, btw... (well, the mileage computations for the instant/avg fuel economy it does, but that's a nitpick).
Not hard to do with a little common sense..
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Iroc57
I left mine in
I see no reason to remove it and I still get the 2 sec prime at ignition.
I see no reason to remove it and I still get the 2 sec prime at ignition.
RACE ON!!!
Thread Starter
Instructor
Joined: May 2008
Posts: 120
Likes: 0
From: Missouri
It's not out of the car yet, was headed that way real quick though.
The shop guys said the fuel pump can just be wired to a key-on positive and will still give me the 2 second prime,,,,,,,is that correct?
I am replacing the elec dash with AutoMeter Cobalt's so no worrys there.
Does the ECM have anything to do with the A/C ? I am wanting to keep it.
As far as the fan, the shop guys also said that was no big deal, just make it completely independent.
I don't care if the ECM is there or not really. Just trying to simplify the wiring in the car as much as possible and not have a bunch of stubby wires tucked in somewhere.
My set up is a simple torker II intake and a edelbrock 1405 card with a MSD distrib.
Any further comments, ideas or thoughts would be greatly appreciated.
The shop guys said the fuel pump can just be wired to a key-on positive and will still give me the 2 second prime,,,,,,,is that correct?
I am replacing the elec dash with AutoMeter Cobalt's so no worrys there.
Does the ECM have anything to do with the A/C ? I am wanting to keep it.
As far as the fan, the shop guys also said that was no big deal, just make it completely independent.
I don't care if the ECM is there or not really. Just trying to simplify the wiring in the car as much as possible and not have a bunch of stubby wires tucked in somewhere.
My set up is a simple torker II intake and a edelbrock 1405 card with a MSD distrib.
Any further comments, ideas or thoughts would be greatly appreciated.
Pro
Joined: Feb 2005
Posts: 560
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From: Hamilton New Jersey
It works perfect like that for me, starts just like a car with a carb and a mechanical pump. A mechanical pump doesn't pump until you crank the engine, if you think about it the oil pressure switch is almost the same in the sense that it doesn't power the pump until the engine cranks, the 2 sec prime is more than enough to get ya goin while you wait the split second for oil pressure to build up. My car with the carb setup starts within what sounds like maybe 1/8th revolution of the engine, even faster than my tpi car starts.
Drifting
Joined: May 2005
Posts: 1,302
Likes: 1
From: Tomahawk WI
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Drifting
Joined: May 2005
Posts: 1,302
Likes: 1
From: Tomahawk WI
The shop guys said the fuel pump can just be wired to a key-on positive and will still give me the 2 second prime,,,,,,,is that correct?
I am replacing the elec dash with AutoMeter Cobalt's so no worrys there.
Does the ECM have anything to do with the A/C ? I am wanting to keep it.
I am replacing the elec dash with AutoMeter Cobalt's so no worrys there.
Does the ECM have anything to do with the A/C ? I am wanting to keep it.
Make sure you get a short distributor... clearance issues.
Also, the throttle cable bracket assembly you see in the below picture works great.
Last edited by AZC4Guy; May 22, 2008 at 12:33 AM.
Pro
Joined: Feb 2005
Posts: 560
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From: Hamilton New Jersey
never tried starting it in cold weather yet.. but it starts like any car with a well tuned carb, much faster than an injected car. I may have exagerated a tad but it never takes more than maybe half a second unless you forget to pump the pedal first. It's probably more like half a revolution if you really wanna get technical.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Pony Eater
The shop guys said the fuel pump can just be wired to a key-on positive and will still give me the 2 second prime,,,,,,,is that correct?
Originally Posted by Pony Eater
I am replacing the elec dash with AutoMeter Cobalt's so no worrys there.
Originally Posted by Pony Eater
Does the ECM have anything to do with the A/C ? I am wanting to keep it.
RACE ON!!!
Pro
Joined: Feb 2005
Posts: 560
Likes: 0
From: Hamilton New Jersey
Wiring the pump to run with the key in the on position isn't very safe for the reason CFI mentioned above. Also it's not cool to have fuel pumping into a stalled engine. IMHO it doesn't make sense to do it any other way than using the factory oil pressure switch, that way you won't have fuel pumping if your engine isn't running, plus from a pratical standpoint it's already there for you to use with no modifications nessicary. I'm sure others have found other ways to tackle the issue so that it doesn't pump without the engine running, I just couldn't think of a simpler way.
Last edited by 86GoldProject; May 22, 2008 at 11:35 PM.
Drifting
Joined: May 2005
Posts: 1,302
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From: Tomahawk WI
Drifting
Joined: Nov 2005
Posts: 1,361
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From: Downriver Mi.
No. At least not easily. If the pump is wired to an ignition on hot point, the pump will just start to run when you turn the ignition to "On". It won't shut off after 2 seconds. Also, it won't shut off when the car is upside down with a blown engine and it is pumping a steady stream of gasoline on to you.
The ECM only controls the fuel mileage read out, so there is no big loss there. All the other factory gauges would continue to work.
No.
RACE ON!!!
The ECM only controls the fuel mileage read out, so there is no big loss there. All the other factory gauges would continue to work.
No.
RACE ON!!!
Very true,I know a person that flipped an 84,the pump kept running?Lost both legs almost his life.
