Coil Sparks, but no spark at the plugs
#17
Jim, it looks like you have an interesting setup on your 86. Mine has 134,000 miles and is still a very good truck. I really hated to see this truck just sitting; I like bringing things back to life that other people have given up on.
#18
Check some voltages please...
Key ON truck not running. Volt meter negative lead on battery negative post.
Coil positive
Coil negative
Remove small red wire on starter solenoid (so it doesn't turn over), then check coil positive voltage with key held in the START position.
Do you have a 12 volt test light?
Jim
Key ON truck not running. Volt meter negative lead on battery negative post.
Coil positive
Coil negative
Remove small red wire on starter solenoid (so it doesn't turn over), then check coil positive voltage with key held in the START position.
Do you have a 12 volt test light?
Jim
#20
Key on coil positive has 7.14 volts
I just ordered a set of Motorcraft plug wires; (I live 50 miles from town) hopefully they will be here in a day or two.
#21
Plug Wires do seem like the next likely choice
Jim
#22
#24
So I replaced plug wires, coil & coil connector... no change. Further testing with a straight pin on the ICM & the ignition in the run position shows 5.8 volts,according to the manual it should be 90% of the battery. It says to check to ignition switch and the wiring between it & the ICM. Do they mean the switch on the column or the key switch could cause this low voltage?
#25
So I replaced plug wires, coil & coil connector... no change. Further testing with a straight pin on the ICM & the ignition in the run position shows 5.8 volts,according to the manual it should be 90% of the battery. It says to check to ignition switch and the wiring between it & the ICM. Do they mean the switch on the column or the key switch could cause this low voltage?
If you suspect this is not the case just unplug the 2 wire connector and add a jumper wire from the battery positive to feed the red wire / DS2 IGN module.
Let just focus on getting it running, then back track to fix the wiring issues.
Jim
#26
The red wire that goes to the DS2 IGN module, as seen next to the blue plastic relief / wire holder as it enters the box, should have full voltage any time the key is ON.
If you suspect this is not the case just unplug the 2 wire connector and add a jumper wire from the battery positive to feed the red wire / DS2 IGN module.
Let just focus on getting it running, then back track to fix the wiring issues.
Jim
If you suspect this is not the case just unplug the 2 wire connector and add a jumper wire from the battery positive to feed the red wire / DS2 IGN module.
Let just focus on getting it running, then back track to fix the wiring issues.
Jim
#27
Okay, I hooked up a jumper wire from the battery to module red wire, it shows 11.84 volts in the run position of a possible 12.11 volts at the battery.
The plug wire will still not spark the HEI spark tester. However, just out of curiosity, I hooked up the timing light to various plug wires and it will light up occasionally; apparently not a strong spark though.
So, backtracking on some of my testing & replacing items, I decided to hook the old Ballast Resistor back up just to double-check things; it shows 2.5- 5 ohms, (too high), however with it hooked up, I get 11.84 volts at the module red wire. I cranked it from the cab & it did not try to fire, I did not check to see if it sparked as the direct wire from the battery had the same voltage with no difference.
I'm not an expert mechanic or electrician, but this seems odd to me; that the good Ballast Resistor checks out at 1.1 ohms but only shows 5.83 volts at the module... I'm still at loss as to what it may be.
The plug wire will still not spark the HEI spark tester. However, just out of curiosity, I hooked up the timing light to various plug wires and it will light up occasionally; apparently not a strong spark though.
So, backtracking on some of my testing & replacing items, I decided to hook the old Ballast Resistor back up just to double-check things; it shows 2.5- 5 ohms, (too high), however with it hooked up, I get 11.84 volts at the module red wire. I cranked it from the cab & it did not try to fire, I did not check to see if it sparked as the direct wire from the battery had the same voltage with no difference.
I'm not an expert mechanic or electrician, but this seems odd to me; that the good Ballast Resistor checks out at 1.1 ohms but only shows 5.83 volts at the module... I'm still at loss as to what it may be.
#28
The next step will be to run 12 volts directly from the battery to BOTH the coil positive and the red wire on the DS2 IGN module.
This will eliminate all truck wiring. It will / should start with your remote starter.
Full voltage at the coil will help deliver a hotter spark. Check this at the coil wire, spark tester to ground.
Jim
This will eliminate all truck wiring. It will / should start with your remote starter.
Full voltage at the coil will help deliver a hotter spark. Check this at the coil wire, spark tester to ground.
Jim
#29
The next step will be to run 12 volts directly from the battery to BOTH the coil positive and the red wire on the DS2 IGN module.
This will eliminate all truck wiring. It will / should start with your remote starter.
Full voltage at the coil will help deliver a hotter spark. Check this at the coil wire, spark tester to ground.
Jim
This will eliminate all truck wiring. It will / should start with your remote starter.
Full voltage at the coil will help deliver a hotter spark. Check this at the coil wire, spark tester to ground.
Jim
It seems as the spark is just not strong enough to spark the fuel.
Are these HEI spark testers supposed to get a spark from a plug wire on a DS2?
#30
I hooked it up like that & still it will not spark the HEI tester on a plug wire. I did try some ether & it will fire the ether but does not take off on gas. It will do this with or without the direct hot to the coil hooked up.
It seems as the spark is just not strong enough to spark the fuel.
Are these HEI spark testers supposed to get a spark from a plug wire on a DS2?
It seems as the spark is just not strong enough to spark the fuel.
Are these HEI spark testers supposed to get a spark from a plug wire on a DS2?
It cant start on ether if there is not a spark jumping the gap on the plugs.
I would gap the plugs at .030, OK I do know that is a small gap , like what is used on a old point set up, but I am running out of ideas here.
If it make you feel better my airplane engine has the plugs gaped at .015-.019 .. and it wont start much past that gap.
All that is left is dwell issues which should be taken care of buy the DS2 IGN module.
In proper dwell causes a weak spark.
How to Make Sparks
Coil Dwell, I don't think its right causing weak spark. - evolutionm.net
Jim