Turns Over But Does Not Start

STANG76

MEMBER
1991 FORD MUSTANG
5.0L
V8
2WD
MANUAL
4,500 MILES

I was driving down the road at 55 mph and it stumbled and shut off. When I crank it starts and immediately dies, but when the key is held in the crank position it starts and stays running fine until the key is released to the run position, then it dies. I have changed the ignition switch, tested volts to coil and from coil to the control module and took control module off distributor and had it tested and it tested good. What else would cause it to start and run while key is held in crank position and die when released to run position?

5 Replies

CJ MEDEVAC

MECHANIC
11,004 POSTS

KEY ON

TEST VOLTAGE AT POSITIVE SIDE OF COIL, ANYTHING?

SAME TEST, THIS TIME WHILE CRANKING, ANYTHING?

IF YOU HAD NOTHING WITH THE KEY ON

CHECK YOUR FUSES, PULL THEM OUT. THEY MAY HAVE MILD CORROSION ON THE LEGS (BUT THE FUSE IS STILL GOOD).

THEN CHECK THE WIRE FROM COIL TO IGNITION SWITCH.

IF YOU GET ALL FLUSTERED WITH THE WIRE TRACING, I MAY BE ABLE TO GET YOU A WIRE DIAGRAM TO FOLLOW

TO HELP YOU UNDERSTAND "RUNS WHILE CRANKING", ON OLDER JEEPS AND FORDS, THE "I" TERMINAL OF THE SOLENOID GIVES THE COIL FULL BATTERY VOLTAGE TO AID IN STARTUP (WHILE THE STARTER IS ROBBING JUICE) THIS HAPPENS WHILE THE STARTER SOLENOID IS ENERGIZED. WHEN YOU RELEASE THE KEY (TO THE RUN POSITION) "I" TERMINAL ON THE SOLENOID STOPS PROVIDING THE "BOOST JUICE". THE COIL NOW RELIES ON THE WIRE FROM THE IGNITION SWITCH FOR IT'S POWER.

CHECK THE FUSES 1st (EASY), THEN THE WIRE (HARDER)

IF YOU DO NOT KNOW HOW TO TEST CONTINUITY THROUGH A WIRE (LOOKING FOR A BROKEN WIRE WITH A VOLTMETER). A DIAGRAM HELPS A LOT. I CAN EXPLAIN THAT TOO.

I'M BETTING ON THE FUSE!

PLEASE LET ME KNOW

THE MEDIC

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Friday, February 26th, 2016 AT 8:39 PM

STANG76

MEMBER
3 POSTS

With the key in run position I am getting 12.09 volts to the coil, while it is being cranked I am getting 14.54 volts. I have checked all the fuses and they are all good.

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Saturday, February 27th, 2016 AT 6:18 AM

CJ MEDEVAC

MECHANIC
11,004 POSTS

ALL SOUNDS RIGHT AT THE COIL THEN MAYBE THE COIL ITSELF IS THE PROBLEM.

TRY PULLING THE DISTRIBUTOR CAP OFF AND "FIRMLY", BE CAREFUL NOT USE TO MUCH FORCE, SEE IF THE ROTOR BUTTON (AND DISTRIBUTOR SHAFT) WILL TURN WITH YOUR FINGER PRESSURE ONLY. IT WILL HAVE PLAY BACK AND FORTH, BUT IT SHOULD NOT TURN.

WHILE YOU ARE IN THERE INSURE THE CAP/ ROTOR/ WIRES/ CONNECTORS LOOK FINE. JIGGLE THE COIL AND DISTRIBUTOR WIRES WHILE SOMEONE ELSE CRANKS IT.

BELOW, I SCREENSHOT THE TEST FOR THE COIL (IF YOU DON'T UNDERSTAND IT LET ME KNOW. I AM ALSO INCLUDING 2 PICTURES OF HOW TO TEST A "REAL COIL", AS I AM A OLDER JEEP KIND OF GUY, I HAVE NOT GOT AROUND TO MAKING A PICTURE FOR THIS NEWER STUFF YET. IT IS THE SAME TEST PROCEDURE, JUST A DIFFERENT LOOKING COIL (MINE HAS DIFFERENT OHM VALUES).

BEFORE YOU GO BUY SOMETHING ELSE, LET ME KNOW WHAT REGION OF THE U.S. YOU ARE IN.

I WILL BE GATHERING JEEP STUFF FOR A WHILE, I WILL MOST LIKELY BE BACK ON HERE THIS EVENING

THE MEDIC

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Saturday, February 27th, 2016 AT 10:42 AM

STANG76

MEMBER
3 POSTS

Thank you medic for the help. While tracing the wires I found the EEC ground wire next to the battery had come unplugged so I plugged it back up and taped it and now it Is running fine again. Thanks again for the help.

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Saturday, February 27th, 2016 AT 11:06 AM

CJ MEDEVAC