Engine Weird Start problem 89 GT

[Aoneill5.0]

Hey,

Just bought my GT a free days ago

155k
Edelbrock Intake
KN Cold air are the only mods I can tell

Anyway
I’ll get right to it

Shut it off yesterday,
Wouldn’t start but cranked fine.

I learned I had good fuel at the rail and spark was decent

Plugs were dry bigtime..injectors not opening obviously

After many thoughts and wire wiggling

I disconnect the BAT +/-
Let sit 10min.

She fired right up
Ran ok to get me home

Now it will only start after a full disconnect

The IGN Module is my only suspect as it has a small crack on the plug area but I’m not sure if that is in line with telling the injectors to open at startup ceanking

Any advice or similar issues are appreciated

Must be a relay or something associated with the EFI

Thanks Folks!

Reliving my youth,
Love the car!

 

[Mustang5L5]

Next time it won’t start, depress the gas pedal to the floor fully and try cranking. See if it fires up.

 

[Aoneill5.0]

I actually did that during the initial diagnosis
As I thought I may of flooded ot

That’s the clearing procedure as I recall from school..

Thanks tho for the reply

The fact that I can get it started reliably unhooking the bat tells me something to do with fuel/ecu is being held open/closed with Voltage…

I’m that guy who loves learning from this stuff..

 

[General karthief]

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

www.stangnet.com

Thanks ti jrichker and others for putting together this, read and follow the instructions.

 

[Aoneill5.0]

Well.. car is running,

Removed Battery
Cleaned as many engine grounds as I could find.

Reinstalled battery
Charged it up as it showed 12.45V but was only 20% on charger

Car fired right up and I could not replicated the earlier problem/scenario

We will see I guess.

Still plan on going through wiring with a good clean and replace a few sensors..

 

[Mustang5L5]

I would pull the ECU and inspect the capacitors.

Given that you said it would not start until a full disconnect, i wonder if some/all are bad as caps tend to go through a charge/discharge state depending on power being applied. Could be the reason why it didn't run again until a full disconnect.