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Does not start, there is no fire to the plugs

Tiny
DONN-1
  • MEMBER
  • 1991 DODGE RAM
  • 2.4L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 100 MILES
I have another problem with this little truck. I tried to start the engine and it would not start. I checked for fire at the plugs and wasn't getting any. I checked for fire at the high tension from coil and wasn't getting any, I then checked for voltage to the coil and wasn't reading any. I had my son to turn starter over and checked for voltage, none. This truck listed above is a Power Ram 50, four cylinder 4G64 Mitsubishi engine. I recently rebuilt engine. Can you help with this problem? Thanks, Donn1
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Saturday, December 12th, 2020 AT 5:18 AM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,289 POSTS
Hi,

It's me again. LOL
Take a look at the wiring schematic I attached. I'm seeing a black/white wire going to the coil. That should have power with the key on or in the start position. Is that the one you don't get power from? I also highlighted two fusible links, but don't feel they are an issue if it is cranking.

If you have no power to the black/white wire, you need to check for power out at the switch itself. If there is power, then we have an open circuit between the two. If there is no power, chances are the switch has failed.

Check these things and let me know what you find.

Take care,
Joe
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Saturday, December 12th, 2020 AT 9:38 PM
Tiny
DONN-1
  • MEMBER
  • 24 POSTS
Hi, I tested the black/white wire, it read 12.7 volts, with switch turned on. I then had my son turn over the engine while I held the high tension wire from the coil to close to ground, no fire. What should I try now, thanks, Donn1
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Sunday, December 13th, 2020 AT 5:39 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,289 POSTS
Hi,

If there is power to the coil, we need to check the coil itself.

Here are the directions to test it. The attached pic correlates with the directions.

_______

1991 Dodge or Ram Truck D50/Ram 50 L4-2350cc 2.4L SOHC
Test 8 - Ignition Coil Testing
Vehicle Powertrain Management Computers and Control Systems Testing and Inspection Symptom Related Diagnostic Procedures No Start Test Ignition Tests Test 8 - Ignition Coil Testing
TEST 8 - IGNITION COIL TESTING
Ignition Coil

See pic 1

TESTING OF IGNITION COIL

1. Measure the resistance between the positive terminal and negative terminal of the ignition coil.

Standard value: 0.72 - 0.88 ohm

2. Measure the resistance between the ignition coil's positive terminal and the high-voltage terminal.

Standard value: 10.3 - 13.9 k-ohm

3. If either primary or secondary resistance is out of specification replace coil and retest.
4. If all test are within specifications, check power transistor.

__________________________

Let me know what you find.

Joe
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Sunday, December 13th, 2020 AT 10:35 PM
Tiny
DONN-1
  • MEMBER
  • 24 POSTS
Hello, I'm sorry for not responding sooner. The weather here has not been good. I took the coil off the truck and tried to measure the primary coil resistance, the cheap ohm meter I used wasn't stable. I had better luck measuring the high voltage resistance, it was between 10.3 - 13.9K. But without the former resistance measurement, I don't trust the coil. The power transistor is what triggers the firing of the coil doesn't it? If I unplug the plug from the power transistor and jump 1.5vdc plus to #1 and jump wire #2 and #3 to coil + and negative shouldn't the coil fire? I'm thinking #1 and 2 pins of the transistor activates the transistor switching. Pin #2 and #3 provide the ground to fire the coil. Or hook positive to coil and momentary touch to ground, won't this cause coil to fire? Power transistor un-plugged. What do you think? Thanks, Donn1
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Tuesday, December 15th, 2020 AT 6:07 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,289 POSTS
Make sure the transistor is disconnected and see if it works.

Let me know.

Joe
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Wednesday, December 16th, 2020 AT 1:43 PM
Tiny
DONN-1
  • MEMBER
  • 24 POSTS
Hello, today the weather was better, I checked the power transistor, it checked okay. I then checked the coil by hooking 12vdc to coil, then grounded the other lead, there was a tiny spark from the high tension wire. I attributed it to not having a condenser being used on negative wire. I didn't have a condenser on hand, but I will pick up one and re-check. If I assume the coil is good, what would be the next check for no spark condition? I did check coil with ohm meter, from primary to high tension 11.4k-ohm, on primary to secondary it read zero. This cheap ohm meter probably wont read below 1-ohm.
Thanks, Donn1
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Friday, December 18th, 2020 AT 5:22 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,289 POSTS
Hi,

When you say a tiny spark, that doesn't sound right. A condenser absorbs power when you want to prevent arcing at a different point. Based on what you described, it sounds like the coil is bad. Do you have a different one that could be tried?

Let me know.

Joe
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Friday, December 18th, 2020 AT 10:56 PM
Tiny
DONN-1
  • MEMBER
  • 24 POSTS
Hi from Donn1, I tried the coil with a condenser hooked to it, the spark was improved. However I decided to try a new coil and see what happens. I ordered it Sunday, when it comes in I will try it and let you know. Thanks for your ongoing help. Donn1
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Monday, December 21st, 2020 AT 7:05 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,289 POSTS
Hi,

Sounds like a plan. If you have a chance, let me know the results.

Take care,
Joe
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Monday, December 21st, 2020 AT 7:36 PM
Tiny
DONN-1
  • MEMBER
  • 24 POSTS
Hi, I got the new coil in for the Dodge power ram 50 4.2 truck, it didn't help though. Do you know which wire goes where, in the distribuitor? There are 4 wires, red, black, yellow, white. Thanks
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Tuesday, January 19th, 2021 AT 6:15 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,289 POSTS
Hi,

I attached what I have as far as powertrain management schematics. Take a look and let me know if they help.

Joe
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Wednesday, January 20th, 2021 AT 4:28 PM

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