hotgrips
07-13-2012, 08:11 AM
I have a Supra Mariah with the 351 Ford Windsor that is going thru restoration and have replaced distributor cap, points and condensor, ignition coil, spark plugs and their wires, starter relay, and my engine cranks over fine, but no spark.
I understand the neutral safety switch is not the problem or it wouldn't even crank over the starter.
1. I have set the points gap at .018" by eye with fiber block ont he cam hi point,
2. checked the resistance of the coil to confirm 8060 and 1.8 ohms for primary and secondary,
3. confirmed voltage 12.6 vdc at positive terminal on the coil,
4. confirmed voltage at ballast resistor,
5. confirmed the test spark plug is to a good ground with a clamp to metal (not to paint)
6. confirmed voltage coil is grounded.
7. have disconnected the positive red wire to coil and replaced it with direct wire to battery positive.
8. get no spark when holding spark plug wire 1/8" from ground, or coil wire 1/8" from ground and turning over starter.
But note digital voltage reading is identical on positive and negative terminals on the coil and understand that is wrong.
Note that digital voltage reading on both sides of ballast resistor is 12.6vdc yet ballast disconnected from wires correctly is 2 ohms
Note that using ignition key, I CAN crank over the starter motor regardless of gear I am in: forward, neutral, or reverse and know that is wrong.
Have confirmed that the engine block is negative ground.
All dash switches such as horn, blowers, lights function fine.
There is a black wire and a grey wire on the ignition coil small negative terminal, and a red wire on the positive terminal. What is the grey wire for on a 1998 Mariah?
If I run 12vdc direct to ignition coil positive why doesn't that successfully eliminate any dash wiring issues and allow a spark when engine is turning over?
Other unrelated restoration notes: I thought I would be clever with replacement of wood that was found rotten so as a machinist and woodworker I did the following at the bottom rear of the engine cover: I used a piece of 1" x 3" box profile aluminum, press fit a piece of pressure treated to completely fill the interior of the aluminum, used "Liquid Nails" and rivets to secure a piece of 1/2" thick pressure treated on top of the aluminum for something to staple to, and used "Liquid Nails" and 8 pop rivets to hold the piece to the engine cover. Changed to 4 hinges rather than 2...figure it should last for a long time now.
Given my "No Spark" condition, can someone advise me how to get back to basics and just get my 351 to give a spark as if it was sitting on an engine stand, independent of the wiring possible problems? I tried removing the red positive wire to the coil replaced it with direct to battery positive, have tried removing the grey wire to coil negative terminal, confused by why both small terminals on coil are reading 12v positive.
Are there any other tests I haven't covered? Is there any test I can do to the distributor with the distributor cap off?
Does anyone have the wiring diagram of the electrics for the 351 Ford engine? I did fine a general boat wiring diagram for a 1987 SUPRA but has all wiring except engine wires (gauges, switches, lights, blowers, bilge pump, Nav, radio, etc.)
Thanks for helping me to solve this mystery.
Jim in NH
I understand the neutral safety switch is not the problem or it wouldn't even crank over the starter.
1. I have set the points gap at .018" by eye with fiber block ont he cam hi point,
2. checked the resistance of the coil to confirm 8060 and 1.8 ohms for primary and secondary,
3. confirmed voltage 12.6 vdc at positive terminal on the coil,
4. confirmed voltage at ballast resistor,
5. confirmed the test spark plug is to a good ground with a clamp to metal (not to paint)
6. confirmed voltage coil is grounded.
7. have disconnected the positive red wire to coil and replaced it with direct wire to battery positive.
8. get no spark when holding spark plug wire 1/8" from ground, or coil wire 1/8" from ground and turning over starter.
But note digital voltage reading is identical on positive and negative terminals on the coil and understand that is wrong.
Note that digital voltage reading on both sides of ballast resistor is 12.6vdc yet ballast disconnected from wires correctly is 2 ohms
Note that using ignition key, I CAN crank over the starter motor regardless of gear I am in: forward, neutral, or reverse and know that is wrong.
Have confirmed that the engine block is negative ground.
All dash switches such as horn, blowers, lights function fine.
There is a black wire and a grey wire on the ignition coil small negative terminal, and a red wire on the positive terminal. What is the grey wire for on a 1998 Mariah?
If I run 12vdc direct to ignition coil positive why doesn't that successfully eliminate any dash wiring issues and allow a spark when engine is turning over?
Other unrelated restoration notes: I thought I would be clever with replacement of wood that was found rotten so as a machinist and woodworker I did the following at the bottom rear of the engine cover: I used a piece of 1" x 3" box profile aluminum, press fit a piece of pressure treated to completely fill the interior of the aluminum, used "Liquid Nails" and rivets to secure a piece of 1/2" thick pressure treated on top of the aluminum for something to staple to, and used "Liquid Nails" and 8 pop rivets to hold the piece to the engine cover. Changed to 4 hinges rather than 2...figure it should last for a long time now.
Given my "No Spark" condition, can someone advise me how to get back to basics and just get my 351 to give a spark as if it was sitting on an engine stand, independent of the wiring possible problems? I tried removing the red positive wire to the coil replaced it with direct to battery positive, have tried removing the grey wire to coil negative terminal, confused by why both small terminals on coil are reading 12v positive.
Are there any other tests I haven't covered? Is there any test I can do to the distributor with the distributor cap off?
Does anyone have the wiring diagram of the electrics for the 351 Ford engine? I did fine a general boat wiring diagram for a 1987 SUPRA but has all wiring except engine wires (gauges, switches, lights, blowers, bilge pump, Nav, radio, etc.)
Thanks for helping me to solve this mystery.
Jim in NH