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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 08-07-2014, 07:35 PM   #1
1990 7-UP
 
Join Date: Jul 2014
Vehicle: 1990 7-UP Convert
Location: Louisiana
Posts: 2
Angry Runs 3 mins--dies--hard to start

1990 5.0 7UP, been sitting over a year. Replaced fuel pump and fresh fuel, fires up when cold, runs 3-5 mins, starts stumbling and dies,fuel pump reland and WOT relays clicking, rapidly, NEW TFI, then found dead EEC relay...replaced. Same Problem. WON'T pull codes. Is the STO supposed to have batt voltage when key is off?? Goes off when turn on Key. Ran wiring harness, found no problems, have voltages at EEC per info I can find. Even opened up EEC looking for bad capacitors. Didn't look like any leakage, although board looks like overheated on section where you would add a piggyback. Have spark at plugs and 35psi when problem happens. Seems to be all electrical problem..........anyone have any ideas?? Been running on this for over a month!!!
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Old 08-08-2014, 08:55 AM   #2
88 orangepeel notch
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That sounds Ilike the same symptoms my car had a couple years ago. It turned out to be a bad ECM. Bought a reman. from AutoZone for $99, ran perfect after that. Just for giggles, make sure your grounds are good and clean.
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Old 08-12-2014, 07:41 PM   #3
1990 7-UP
 
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Vehicle: 1990 7-UP Convert
Location: Louisiana
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Orange Peel-- major problem was INDEED the eec. A bad eec relay going bad had fried the eec. Ran quite well considering it's been sitting so long, even with a new fuel pump and fresh fuel. At least now the MIL comes on, pulled a code 54 on it. Gotta' do a little more work.
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Old 08-12-2014, 07:41 PM
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