Diagnostic please- dead on the highway...

[ugly]

Thanks 4x4high, it's running now!

So, I'm driving on the highway, the blazer begins to back fire and sputter. No power when you hit the gas but will keep moving slowly at idle.

I pulled over and the engine shut off. I can't get it started since.

Fuel pump is running and getting gas to the fuel filter; 4.5 psi fuel pressure. Checking the wires, I get a spark with a tester set on a tight gap but not a larger gap. Compression shows 150 on the 4 cylinder I tested.

I replaced the plugs and wires; some of the wire boots were melted to the headers and the plugs looked normal.

For some reason, the battery ground wire is hot. What could cause that?

Any idea what I should test next?

Timing- any chance the timing chain can jump?
Compression- check all cylinders?
Electronics- hei coil, cap or rotor? How can I test this further
Carb- qjet seems like it squirts gas when you open the throttle?

 

[4X4HIGH]

The cable could be hot from trying to crank the engine.

My first diagnosis is going to be a bad ignition module. Wait for a while until the engine has some time to cool down and then see if it will fire back up. If it does and will drive fine for a while that is a good indication of a bad ignition module (GM are famous for them going bad and i keep a spare in the tool box because of it). Could also be the ignition coil but i've rarely seen a coil go bad (doesn't mean that they don't or won't).

 

[ugly]

It's been sitting for almost a month and still will not start.

Ignition module is inside the distributor (hei)? Coil is part of the cap?

Thanks for the help, additional ideas?

 

[4X4HIGH]

yes, pull the cap and the ignition module is held down with 2 small screws and will have 2 separate wire harnesses attached to it, one on each end. That module commonly fails and is only about 30-40.00 for a new one. Very easy to swap out just make certain to clean all the old "grease" off the distributor housing and make 200% sure you apply the new grease that comes with the module to the backside of the module before placing it back into the distributor. If all else and this isn't the problem throw your old one in the glovebox or tool box as a spare.

 

[Russell]

That HEI should be able to throw a hot blue spark a good 1/4", if it is a fuzzy reddish spark, your coil may be getting weak. I've had one or two of them fail on me in the past, usually caused by the grounding strap being MIA.

 

[ugly]

Grounding strap from the motor to the frame? That is missing...is there another inside the distributor?

Thanks

 

[4X4HIGH]

Yes, there is either a ground strap or a grounding wire inside the cap where the coil is. It's the ground for the coil.

 

[uglytruk]

I had a coil fry in a Pontiac a few years ago. No reason, was a mild day, just toodling around... It smelled burned. I would change the whole distributor. Just read about how to index the oil pump drive , and proper orientation. a long screwdriver is mandatory

 

[ugly]

Not sure I understand why you would scrap the distributor for a new one. That thing will be a bitch to get out without removing the motor too; it's a 454 with a clearanced firewall.

If I change the ignition module, cap, coil and wires what else is left? Weights and vacuum advance?

Thanks again....

 

[4X4HIGH]

There is also a pick-up coil located within the distributor and to replace that the distributor would have to come out and completely apart. Those don't fail nearly as often as the modules though. My first piece to replace would be that module since it's a known problem, and like i said earlier if it still isn't the problem throw the old one in the glovebox or toolbox as a spare.

 

[ugly]

New cap, rotor and ignition module and the ugly beast is running again!

Thanks for the help.