'93 5.0 Mustang stopped running-computer??
08-20-2009, 09:22 PM
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Join Date: Aug 2009
Location: Georgia
Posts: 1
'93 5.0 Mustang stopped running-computer??
My '93 5.0 Mustang LX convertible stock engine with 148,000 miles wouldn't start up after sitting for 2 weeks. (about 2 months ago) I had it towed to my local repair shop, and they replaced the ignition coil. It ran fine for about a month.
Then, after not using it for 2 weeks, it did the same thing again. So I called the repair shop and confirmed that they had changed the coil. They said it was a shot in the dark, but it solved the problem??
I checked for fire at the plugs using a timing light. Ignition coil doesn't send fire to distributor when cranking, but fires spark plugs when turning key from "start" to "run" position. (I had noticed a few months ago that the engine wouldn't fire up until I began to release the key from start to run position.) So, I checked the battery and found it fully charged and charged it to make sure I had 12 volts. I checked the ignition switch and thought it wasn't sending correct signal when cranking, so I changed it as well as the key cylinder. Still, no run.
I also noticed that the fuel pump runs constantly when ignition is on instead of stopping after 5 seconds when engine is not running?? Fuel pump pressure 40 psi and flow slightly below spec.
Ignition switch works as indicated in Ford manual.
I'm guessing the computer needs to be replaced.
Closest diagnostic repair shop is 22 miles away, so I'm trying to avoid towing it for diagnostic. Help!
I changed the distributor & Ignition Control Module, but same results.
9.7 volts at coil when cranking, 12.1 volts when not cranking. 9.9 volts at ignition switch when cranking, 12.1 volts when not cranking
10.2 volts at battery cranking, 12.4 volts not cranking
12.1 volts at injectors
Took it to Ford dealer, diagnostic confirmed bad computer (PCM).
I changed the computer and it ran fine for a month. Now it won't run again.
Took it to Ford dealer...
Cajun Stang
Then, after not using it for 2 weeks, it did the same thing again. So I called the repair shop and confirmed that they had changed the coil. They said it was a shot in the dark, but it solved the problem??
I checked for fire at the plugs using a timing light. Ignition coil doesn't send fire to distributor when cranking, but fires spark plugs when turning key from "start" to "run" position. (I had noticed a few months ago that the engine wouldn't fire up until I began to release the key from start to run position.) So, I checked the battery and found it fully charged and charged it to make sure I had 12 volts. I checked the ignition switch and thought it wasn't sending correct signal when cranking, so I changed it as well as the key cylinder. Still, no run.
I also noticed that the fuel pump runs constantly when ignition is on instead of stopping after 5 seconds when engine is not running?? Fuel pump pressure 40 psi and flow slightly below spec.
Ignition switch works as indicated in Ford manual.
I'm guessing the computer needs to be replaced.
Closest diagnostic repair shop is 22 miles away, so I'm trying to avoid towing it for diagnostic. Help!
I changed the distributor & Ignition Control Module, but same results.
9.7 volts at coil when cranking, 12.1 volts when not cranking. 9.9 volts at ignition switch when cranking, 12.1 volts when not cranking
10.2 volts at battery cranking, 12.4 volts not cranking
12.1 volts at injectors
Took it to Ford dealer, diagnostic confirmed bad computer (PCM).
I changed the computer and it ran fine for a month. Now it won't run again.
Took it to Ford dealer...
Cajun Stang
Last edited by Raymond Boudreaux; 10-08-2009 at 04:30 PM. Reason: additional information
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