Backfired, died

Ok guys. I ran out of gas in the Jeep two days ago in my drive. I bought three gallons and put in it this AM. This PM I was driving to the gas station to fill it up full. On my way out of town the Jeep backfired I've never even heard it backfire under normal circumstances, normally it runs very smooth.

Now it won't even start. So it's 18* out and I thought maybe it was the MSD acting up so I bypassed it. Same thing, no werky. Cranks, backfires once or twice but never sounds like it wants to start.

There's fuel in the filter and three gallons is more than enough for me to go two miles to get gas for it.

I don't understand. Any ideas? I've gotta wait for someone with a truck now to be able to pull me back home.

 

Backfire thru the exhaust? Have you checked for spark yet?

 

I told you everything I did in my post. Yes, through the exhaust.

It's sitting outside of town, I walked home, haven't been able to check anything yet. Wondering where to start.

FWIW, I know nothing about HEI as far as troubleshooting goes, so if it's spark related I'm in new territory.

Dammit, this Jeep has been solid until this.

 

It's probably the module. Check for 12v in to the cap, and check for pulse on the tach feed with a test light.... If you have pulse, the pickup is ok. Autozone has modules for < 20 bucks. You might try that, and if thats not it, you'll have a spare module for backup....HTH

 

I was hoping it was something along those lines. Thanks Patrick. Now I gotta get it home to check that.

 

If it's the module, you'll need a 5.5MM socket. Or a 7/32...

 

Got both. May not have much knowledge of the matter but I have lots of tools to abuse in the process.

 

Then do like me and just throw tools at it...

 

I've got two screws holding my rotor in place, guess it could happen though. Remember it's a :v6: not a :hurrican: . If it were an F-head I know exactly what part you're talking about breaking off.

 

Sparky - HEI Trouble shooting info Below...

HEI Trouble Shooting
Coil:
Clean it up and look at the clear epoxy for signs of arcing to ground.
___________
| | (View of an upside down HEI coil)
| _ |
| /A\ | A - coil secondary output terminal (where the
| \_/ | carbon brush spring makes contact)
| | B - RED wire (BATT terminal connects here)
|_________| C - BLACK ground (held down by a coil mounting screw)
| | | D - YELLOW (or WHITE) wire (TACH terminal)
| | |
B C D

Using this chart, make the following Ohm Meter tests. Any failing test means replacing the coil.
Probe Points Expected Results
B-D about 1.6 ohms
A-C 8.1-8.2 kiloohms
B-C & C-D > 1.2 megaohms, but not infinite
A-B & A-D infinite

Check if the ground strap is in the coil. A broken or loose strap will arc, making a sound like the advance weights clicking against the side of the cap. Some new kits don't come with this strap and many forget to put it on.

GM HEI (internal coil) 1974-1975 6k-30k ohms secondary GM HEI (internal coil) 1976-1979 Infinity GM HEI (internal coil) 1980- (see text)

The resistance between the primary terminals of the coil should be no more than 1.0 ohms. The resistance between the secondary output terminal and the primary should be between 6k and 30k ohms. Integral coils on applications later than 1975 should have infinte ohms between the secondary and the primary. However, 1980 and later applications should be replaced if there is infinte ohms between both the primary and tach lead. This is also true of applications later than 1980 with an externally mounted coil.

Q: My question is why measure for DC resistance between one lead of the secondary and a lead of the primary anyway? Shouldn't this always be infinte?

It would for what you might think of as a regular transformer but the coil is an "autotransformer" -- no pun intended. It's like a transformer with a centertap and no secondary. The "primary" would be from the centertap to one side. The "secondary" across both sides like so:

Secondary -> ----)
| )
| )
| Primary ----)
| | )
| | )
|--> |--> ----)

So the primary and the seconday windings aren't electrically isolated from each other.

Module:
C B G W
__ __ __ __
\_\_ \_\ /_/__/_/
\ \___________/ /
\ /
\ (G) ( ) /
\___________________/

Modules I've seen have the terminals labeled. This may help if yours isn't. The (G) is the ground terminal, and it is one of the holes that the screw runs through to attach the module to the distributor.


Remove the module from the distributor. (watch out for that nasty dielectric grease on the underside, It's relatively hamless, but goopy) Connect a test lamp between the B and C module terminals and jumper +12 volts to the B terminal and then ground the module at the (G) terminal. If the lamp lights then the module is bad.
If the module passes step one, then jumper between the B and G terminals. The lamp will light if the module is ok.
If you suspect the module at this point, you might as well take it with you to the parts store if they'll test it for you, and confirm your diagnosis before you buy a new one.

Pickup Coil:


Remove the pickup coil leads (carefully) from the module. Connect the ohmmeter to the base of the distributor and the pickup coil lead. The book doesn't specify which one, so I assume either one will do. Personally, I checked both. Operate the vacuum advance through it's full range. (I didn't have my vacuum pump with me so I sucked on the vacuum line going to the advance. If you use that method you're likely to spend the rest of the day spitting. I don't reccomend it, but it'll do in a pinch.) The meter should read infinite in all positions.
Connect the ohmmeter between the leads coming from the pickup coil and operate the vacuum advance through it's full range with a vacuum pump. The meter should read 650 to 850 ohms in all advance positions.


--------------------------------------------------------------------------------

 

Sparky, just a shot in the dark, but I've seen it happen, the backfire
might have rotated you distributor. So now it's not timed correctly. See if
the distributor has turned to make it out of time. Again just a shot in the
dark

 

I hope not, I just put new ones on with my Edelbrock timing chain, it's not nylon gears...

But thanks for the help.

Warlock, that's great!!!! Thanks much.

 

I checked to see if it was loose yesterday, it's not but that thought crossed my mind as well John.