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1979 cj7 304 v8 no spark solved

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HawkEyeEarl

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Discussion starter · #1 ·
1979 cj7 304 v8 no spark solved. I pulled the jeep in the barn one day and the jeep kept running when I turned it off. Sometimes the starter kept turning over. I started it a time or 2 and same thing. I replaced the ignition switch. Now it would not start all. No spark.

It took me a few hours reading on the internet and in jeep manuals and several hours looking and testing on the jeep.

I had battery voltage at the + coil terminal and no spark at the coil.

I tried to follow the trouble shooting in the jeep manual and the internet.

I replaced the solenoid and still had no spark and still had battery voltage at the + coil terminal.

I tested the coil + to - terminals and got a good resistance value. I tested the coil + to the coil center contact and could not get a good resistance reading that was steady. So I replaced the coil and still had no spark and still had battery voltage at the + coil terminal. But the new coil had good resistance readings. The old coil was very old and rusty. I do not for sure it was really bad.

I then replaced the ignition module. I turned the key and it start right up, running great.

I just thought I would post and return the favor for what some you have given me here.

Thanks for the help.
 
#2 ·
One reason I went to a HEI distibutor. Way less electrical components to trouble shoot. At least you got her running tho
 
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#3 ·
jeep_boy02 said:
One reason I went to a HEI distibutor. Way less electrical components to trouble shoot. At least you got her running tho
Click to expand...
Typical HEI Clone fan response...

Here goes,
Same components in an HEI as any other factory electronic ignition of the period.

Ignition switch,
Ignition Fuse,
Ignition Module,
Starter Relay Connection,
Distributor Body,
Shaft & Drive Gear,
Centrifugal Advance,
Vacuum Advance,
Rotor,
Distributor Cap,
Plug Wires & Plugs for each cylinder,
Ignition Coil,

HEI/Clones don't have a coil wire, maybe that is the ...way less electrical components... you are talking about?

Since you HEI fan boys didn't know about taking the factory resistor wire out until I started telling you about it...
And most of you still don't do it, that doesn't count.

-----------

To the OP,
If you were getting the starter running on, it was more than an ignition module issue.

There is no possible way for a module to keep the starter cranking when you let off the key switch.

The two most likely candidates for the issues you describe are a sticking ignition switch (NOT key switch, but the ignition switch down on the column under the dash), which will keep the starter cranking, will keep the engine running on after key switch is turned off, and will supply power to ignition circuit with key turned off.

The second possibility would be a sticking starter relay ('Solenoid').

A third, but less likely probability would be some melted together wires in the harness.
 
Discussion starter · #4 ·
no spark

When I replaced the ignition switch down on the column it fixed the starter continuing to turn. Somewhere during that continuing to run or turn over the ignition modules must have went out. It looked melted on the back.

But next after replacing the ignition switch, I replaced the solenoid and then the coil and finally the ignition module fixed it. Probably the solenoid and the coil were ok, but I did not know that. I was fishing and learning, just a little. I looked at some diagrams on this forum and followed some discussions.

I had been out on the road but the jeep quit nicely in the barn that evening but did not want to stop. :)

Thanks
 
#5 ·
I have no spark on my 1979 CJ7, started and ran fine then just quit. I tightened the starter solenoid and it caught of fire, and I mean a bid flame. Lucky I just bought a new fire extinguisher that morning. Today I replace the solenoid with a new one and all new starter and battery cables. Still no spark at the plugs. Engine turns as if it wants to run, however same result no spark with a spark plug light. I believe it is in the big distributor unit? Any suggestions?
 
#6 ·
I went to HEI because good Ignitions Boxes are a Thing of the Past, and I don't like Parts that Piss all over my Jeep when they go Bad. I don't know, 1 wire Hookup and can get Parts in any Parts Store in America, Can throw a Spare plug and play in the Box and go any were and Forget about it, yea thats a real Stupid Reason to go HEI.:wink2: And I almost forgot, the 55 gallon drum of wiring you get to Eliminate is really Stupid also because you don't get to Trouble shoot all that wiring.
 
#7 ·
Charliemack said:
I have no spark on my 1979 CJ7, started and ran fine then just quit. I tightened the starter solenoid and it caught of fire, and I mean a bid flame. Lucky I just bought a new fire extinguisher that morning. Today I replace the solenoid with a new one and all new starter and battery cables. Still no spark at the plugs. Engine turns as if it wants to run, however same result no spark with a spark plug light. I believe it is in the big distributor unit? Any suggestions?
Click to expand...
So, what engine is in the jeep?
 
#8 ·
hello

motorcraft still makes the blue grommet ignition box. i have one with no problems. it doesnt matter who made the ignition box they all have the same problem. HEAT. if power is left going to it and not running they will make alot of heat and burn up the circuit. even the almighty HEI. if you dont put enough of the thermo grease under it when installing you will be redoing it in a year. if it was so good, companies would have never made a killing on replacement ones in the 70's and 80's. im not saying one is better then the other but they all have there fault. even the might mopar unit.

when you say big distributor unit are you talking hei or a large ford cap?

oldschool
 
#10 ·
Not So FAST, 1978 CJ 5 with 304 V8- frame off resto- was running great until ran out of gas, had to use starter- in 2nd gear to get it of the road- put gas in it, finished drive home, noticed it was mis firing at lower speed- next day no start, no spark. I have pulled steering, replaced keyed ignition as well as ignition switch on steering column, replaced 7 yr old Optima Battery with same-new, Replaced Starter Solenoid, replaced ignition resistor (on fire wall), replaced Coil and replaced (blue grommet) ignition module- no spark from coil to distributor- I've had mutilple buddies with their testers leave stumped and me sad. Wiring harness is new from resto- PLEASE HELP A BROTHER OUT
 
#11 ·
hey Bro,

You are piggy backing on a 8 year old thread. Starting a new one on such a common subject usually gets a better response. :)

You have a Duraspark style ignition system so here are the basics (Duraspark II with the large dizzie cap):

Image



Your main observation is no spark at the coil.

A great test tool here is a 12 Volt test bulb with some long leads. You can see k out voltage and check grounds quickly and confidently. Digital Voltmeters measure potential difference, which can be misleading as it reports voltage where no current can be drawn. Never mind, you need something to check the voltage and grounds.

There are a few things to look at:

1. Take off the positive lead. Measure the voltage, it should be around 7 Volts in Run, and battery voltage (about 13V) in Start. If not, no way it is going to start. This may be due to a broken wire, broken ballast etc.
2. Take off the negative lead (was light green). Connect your test device between this and battery positive. When you try Start it should either flash the test bulb or the readings should go up and down. (This is where a test bulb is so much easier). The module grounds the coil every time it wants a spark, that is what you are checking. No flashing means module is not operating.

If it all tests OK but no spark, the coil is not operating.

If the negative is not flashing that bulb, it is the module.

Take off the 2 pin plug. test inside for voltage.

1. Red with tracer, live in Run and Start.
2. White, live in Start only

Take off the 4 pin plug

1. Black, is there a ground present? This wire passes to the distributor and grounds there. it is unreliable.
2. Light green. This is the wire to the coil. You may want to check its continuity.
3. Last 2 wires, orange and purple. There are the sensor wires from the distributor. The sensor is a coil of fine wire. Check you have a resistance on this wire.

report back.
 
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#12 ·
Then there's a nuther way!

I keep a Fuel Pump, a coil, and a ignition module always on board.

Lot's of other stuff too! Tire plugs, different hoses, chow, water, tools, fuel, oil. etc and another 100 or so pounds of other good stuff!

My Pics below reflect about 1/2 or so of my On board Jeep Hoard!

Over the years, those 1st three items have had me dead in the water at one time or another

------Not to mention also done the same to a few other CJs I've run into.

Those 3 items are pretty EZ fixes----IF ONLY I HAD HAD THEM IN THE PAST, I coulda been moving in 10 minutes or less!

Since they are now part of my spare stuff, I haven't needed them yet---however, I've aided 2 other CJs with the fuel pump and module.

Many folks, including myself, do not agree with "Throwing Parts" in an attempt to fix an issue. However, those 3 parts on standby

keep you from having to wait for one, for how long? And within a few minutes or so, you can "rule out" the coil, or module as the problem,

when you quickly swap one in as a test.

------JEEPFELLER


Image


Image


Image
 
#16 ·
Same issue I am having on my FSJ, and when I get back to it, distributor pick up is next and last to trouble shoot.
 
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#17 ·
QCBigDog said:
Not So FAST, 1978 CJ 5 with 304 V8- frame off resto- was running great until ran out of gas, had to use starter- in 2nd gear to get it of the road- put gas in it, finished drive home, noticed it was mis firing at lower speed- next day no start, no spark. I have pulled steering, replaced keyed ignition as well as ignition switch on steering column, replaced 7 yr old Optima Battery with same-new, Replaced Starter Solenoid, replaced ignition resistor (on fire wall), replaced Coil and replaced (blue grommet) ignition module- no spark from coil to distributor- I've had mutilple buddies with their testers leave stumped and me sad. Wiring harness is new from resto- PLEASE HELP A BROTHER OUT
Click to expand...
BagusJeep said:
hey Bro,

You are piggy backing on a 8 year old thread. Starting a new one on such a common subject usually gets a better response. :)

You have a Duraspark style ignition system so here are the basics (Duraspark II with the large dizzie cap):

View attachment 4149838


Your main observation is no spark at the coil.

A great test tool here is a 12 Volt test bulb with some long leads. You can see k out voltage and check grounds quickly and confidently. Digital Voltmeters measure potential difference, which can be misleading as it reports voltage where no current can be drawn. Never mind, you need something to check the voltage and grounds.

There are a few things to look at:

1. Take off the positive lead. Measure the voltage, it should be around 7 Volts in Run, and battery voltage (about 13V) in Start. If not, no way it is going to start. This may be due to a broken wire, broken ballast etc.
2. Take off the negative lead (was light green). Connect your test device between this and battery positive. When you try Start it should either flash the test bulb or the readings should go up and down. (This is where a test bulb is so much easier). The module grounds the coil every time it wants a spark, that is what you are checking. No flashing means module is not operating.

If it all tests OK but no spark, the coil is not operating.

If the negative is not flashing that bulb, it is the module.

Take off the 2 pin plug. test inside for voltage.

1. Red with tracer, live in Run and Start.
2. White, live in Start only

Take off the 4 pin plug

1. Black, is there a ground present? This wire passes to the distributor and grounds there. it is unreliable.
2. Light green. This is the wire to the coil. You may want to check its continuity.
3. Last 2 wires, orange and purple. There are the sensor wires from the distributor. The sensor is a coil of fine wire. Check you have a resistance on this wire.

report back.
Click to expand...
thanks for this, I did start a new thread- please take a look- everything you shared here, I did successfull. I even replaced the Coil twice, everything is there voltage wise but it’s like the coil isn’t
John Strenk said:
#3 on BagusJeep post:

Don't forget to test the pickup inside the distributor. 790 to 850 ohms is good.

Image
Click to expand...
replaced it as well
 
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