no spark!

Hi, I have a 78 caprice with hei, some days ago I found it does not start, How do I check for spark? I have a clear dist cap and see sparks inside, but when I check the sparkplugs nothing happen and car does not start. I have checked gas pump and filters and injection on carb is OK, so I think problem is spark.
Can anyone help me?
Thanks.

to check for spark you can either puul out the plug and hold it against the cylinder head of the engine with the spark plug wire attached and turn the car over and check for spark, or an easier way is to puul off the plug wir, take a long scredriver insert one end in the boot of the spark plug wire and hold the screwdriver near the cylinder head and turn the car over to check the spark

Thanks for support, In case of no spark on both tests, is there any easy way to know if is the coil or anything else easy to change or test?
Thanks again.

hve somebody hols the plug while you turn it over...lol. they sell testers for them.

There's a few things that can cause this with HEI. One being a lack of power, another the magnet reluctor/pickup assembly, the next being the modue and the final being the coil. If you have access to a multimeter, check the voltage at the BAT terminal with the ignition in the on/run position. You want to see a full 12 volts here - HEI does not use a ballast resistor. If you have full volts, using the multimeter you can check both the primary on the coil and the pickup. To check the primary on the coil, remove the BAT wire, and the distributor to coil wire assembly (the three wire plug closer to the cap). With those wires removed, place one probe of a multimeter set to read in ohms (1K is ok) on the BAT terminal, and the other on the GROUND terminal. You should see little DC resistance on this wire. If the meter reads infinite, the coil is definitely a cause of your problem. You can check the secondary by placing one probe on the center button in the distributor and the other to the ground terminal. Once again, you are looking for anything other than infinite resistance, which would signify an open winding. Some coils might have DC continuity between the BAT terminal and the center button - so while you can check to see if there's continuity here, the presence of continuity does not always mean the two windings are shorted together (as they may be by design, google "autotransformer").

Next we can check the pickup. Inside the distributor, you will see the module. One side of the module is connected with the wiring harness that goes up to the cap for the coil. The other side of the module has (for 1978) two leads that come from the thing in the center - this is the pickup. You will need to remove the module - two screws hold it down and it's easier removed with the rotor off - and disconnect the wires coming from the pickup. Check these leads for continuity - same 1k ohm setting on the multimeter - you again do not want to see infinity on the reading as this will show the pickup coil is open. If you get a good DC reading (should be some ohms, less than 1k but probably in the tens if that) then you can take one probe and touch it to the distributor casing while leaving the other on the other wire of the pickup. Here is the One place where you DO want to see infinity - if you see any DC reading at all, the pickup coil is shorted to the distributor. In that case, or if you have infinite ohms across the two leads, you have a bad pickup and will need to replace it - this involves removing the distributor, using a punch to knock out the roll pin holding the drive gear to the shaft, then pulling the shaft up through the top of the distributor. You can now replace the pickup - these are pretty cheap. I think I paid $10 for the last one I got. Make sure that if you do this, you put the vacuum advance arm back on it.

Anyways, if both of these parts check out OK, then suspect a bad module. These cost about $15 or so for your car.

im thinking the module inside the ditributer, but first check the cap and rotor and your coil, also check the wire going to the magnetic pickup to see if the any good, just give them a gentle tug

Thanks silicon and blownbyalcohol, I have checked my dist cap and see that is a little melted in the middle and the small carbon looks very used and short, I will buy today a new cap and replace it, maybe this is the problem. I will let you know.

that sounds like the problem

Did u fix it? I had a no spark on my 85, and it turned out to be the ignition module in the distributor.

Rage

Finally I fixed it, the problem was that the small contact metal leaf at the rotor melt with together with it, also the cap bushing moved, I think it was the cause, anyway I changed the rotor and runs excellent again!
Thanks.

glad to help