Help me please
Thread Starter
|
Junior User
Joined: Apr 2015
Posts: 80
Likes: 0
Help me please
84 f250 351w just made me walk 3mi. While driving it started missing on the hiway so I pulled over and it idled good but moving it had a hard time and the tach was erratic and then it quit. No start, lots of gas and it squirts in carb. I have no emissions and use a blue tab ignition module the coil is 1 year old as is the dist. I do not have a resistor on the coil. Any ideas of what to check and how to check it.
Laughing Gas
Joined: Nov 2011
Posts: 1,033
Likes: 11
From: Wausau, WI
Are you saying the ignition system was switched over to the blue tab from a different one?
You need the resister on the "RUN" power wire to the module. Without it, it will run for a while, but you will burn them out in time. You should not see the full 12V on the RUN wire. The "START" power wire does not need a resister, full 12V power. The only other thing on the coil (besides the wire from the module and a tach wire) would be a noise filter that's screwed right to the coil bracket.
Have you tested for spark?
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
You *will* see 12V on a meter at the coil unless the engine is running.
A voltmeter does not pass enough electricity to ground for the resistor to drop the voltage that you are reading.
Think if you had a garden hose with a tiny pinhole in it.
If you had the nozzle closed and just cracked the spigot open, the pinhole would build quickly to line pressure.
But if you were to open the nozzle water would only trickle out of it after the first gush.
Did you not use a DSII donor harness?
Why do you not have a resistor in the run circuit?
A voltmeter does not pass enough electricity to ground for the resistor to drop the voltage that you are reading.
Think if you had a garden hose with a tiny pinhole in it.
If you had the nozzle closed and just cracked the spigot open, the pinhole would build quickly to line pressure.
But if you were to open the nozzle water would only trickle out of it after the first gush.
Did you not use a DSII donor harness?
Why do you not have a resistor in the run circuit?
Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
You haven't stated which coil you did actually use, but I am pretty sure it wasn't the one off the 82 Bronco.
The resistor reduces the current flow to the DS2 ignition module also, as this is a series circuit. While it might be true that the coil you used could indeed survive without a resistor the DS2 module which is next in line won't.
With the DS2 ignition system it is very importance to use all the correct original parts, don't mix and match parts or you will be walking home often.
Jim
Thread Starter
|
Junior User
Joined: Apr 2015
Posts: 80
Likes: 0
Coil is aftermarket but not one of the super ones, it has horseshoe connector. Here are some readings. 12v to ignition module--everywhere I measured without engine running was 12v (except for coil when dist was unplugged then it was 1.88v)---Dist wires unplugged (orange and purple) limit is 400-700 ohms mine reads 708--positive coil to nipple 785 ohms. I do not know what coil should read. But it looks like the pick-up coil in the dist is bad.
Trending Topics
Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
708 is close enough, I don't think the pick-up in the dist is bad..
I would have your DS2 IGN module tested at the auto part store.
Do you have the specs on the coil you used? What is the primary resistance?
A stock coil would be about 1.3 ohms, after market stuff is usually about .7 ohms.
So... skipping the resistor wire and using a .7 ohm coil will result in 4 times the normal current flow and thus most likely a failure of the DS2 IGN module.
You are not the first to test this concept.
Jim
I would have your DS2 IGN module tested at the auto part store.
Do you have the specs on the coil you used? What is the primary resistance?
A stock coil would be about 1.3 ohms, after market stuff is usually about .7 ohms.
So... skipping the resistor wire and using a .7 ohm coil will result in 4 times the normal current flow and thus most likely a failure of the DS2 IGN module.
You are not the first to test this concept.
Jim
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
I've always read 450-950 ohms is good.
Certainly my dizzy never gave me trouble at 700.
Fordification used to have the complete factory DSII troubleshooting manual online, until Fomoco went crazy a few years back issuing takedowns for all its IP.
Certainly my dizzy never gave me trouble at 700.
Fordification used to have the complete factory DSII troubleshooting manual online, until Fomoco went crazy a few years back issuing takedowns for all its IP.
Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
Can you look up the coil specs on the web site of where you bought it, or was it a used junk yard thing.
http://www.autozone.com/ignition-tun...?checkfit=true
http://www.autozone.com/ignition-tun...?checkfit=true