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Hi Guys,
If anybody could help with my issue I would be so grateful. I have a 1980 monte carlo that has a no spark condition I have verified battery, crank, fuel is all ok. I have installed a new coil, cap,rotor, module and new distributor(hei)
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I’ve seen this many times. I used to work in a shop back in the 80s and 90s, and we would get HEI systems in all the time with no spark after someone replaced the cap and left out the coil secondary ground. Sometimes the new cap didn’t come with it and the person changing the cap either forgot it or didn’t know to move it over to the new cap.
It looks like this:
and goes here:
Make sure you have one, and make sure the hook end is touching metal on the coil. That is the first thing I would look for.
Hi cap269,
Thanks for you’re reply. Yeah I know the part is in there I even tested it after. check for shorted to ground connections, by probing the “BAT” connection and the center terminal with your DVOM leads. There should be infinity resistance or OL on your meter<it passed. This no start issue happened with my car all of a sudden before this it was running fine. I turned it on and moved it out of my garage to let my wife out when I went back to start it it wouldn't start. Since then i verified that it is cranking, the battery is 12.6volts, fuel is going to carburetor. All the hei parts have been replaced even the distributor and tested i.e coil and pickup coil. I have checked the fuse box all fuses are fine. So thats why I am focusing on power to batt terminal on distributor why would it drop to 7 volts at crank? Is there anything I could be missing?
The pink wire is a resistance wire. It will drop voltage. If you look carefully at the printing on the insulation of that wire it should be marked as “resistance wire-do not cut” or something like that. Also, the starter will drop the voltage while cranking. Normally it shouldn’t drop it that far, but it could if the starter motor is drawing excessive current or there is an electrical issue such as high resistance in the battery cable to the starter or resistance in the ground cable going to the engine block, a loose connection on a starter terminal, or a failing ignition switch.
You want to also make sure that the tach signal is not being shorted to ground. You can test that by checking continuity between the tach terminal and ground. If there is continuity it is shorting the ignition to ground and the coil won’t fire. Also, if it did ground, it probably fried the ignition module.
Also, don’t rule out the basics. Just because a part is new and ‘was working 10 minutes ago’ doesn’t mean it can’t quit. To avoid spending unnecessary money and time, re-test all the parts.
Check your main grounds that they are clean and tight. There are three to check. One is the main battery negative cable from battery to block, one is the braided strap from the back of the engine to the firewall, and the third is the small wire from the battery cable to the fender. Check also that the ignition switch wires haven’t gotten loose at the starter solenoid.
Re-test the secondary resistance on the coil (between rotor button and ground = 6k-30k ohms). Re-test the primary resistance on the coil (between tach and bat terminals = 0.5 ohms). Re-test the resistance on the pickup coil (between both wires of the pickup coil = 800-1500 ohms). Just because it was good before doesn’t mean it still is. If you didn’t put dielectric grease under the ignition module then it could have overheated and fried. As I posted in the previous reply if the tach terminal shorted to ground, even for an instant, it could have toasted the ignition module.
I am sure that once everything is tested out you will find the problem.
Hi Cap269,
Thanks for your help. I found this trouble shooting guide but i don’t know what they are referring to when they say distributor terminal C/+, + and C terminals I have listed the 3 steps they say below.
1. disconnect Distributor terminal “C/+”
2. ignition on , engine not running
3. check voltage at “+” and “C” terminals of the distributor harness connectorHi cap269,
The trouble shooting guide says to check for spark at coil. How to I check for spark at the coil?
Hi cap269,
I tested the tach terminal contnuity to the ground with my multi meter. I am kinda novice at using the multi meter. So I turned the dial to the ohms range. I received a 1 at 200ohm,2000ohm,20k,200k but a 12.25 at 2000k. does this mean I have continuity in the tach terminal or not?
Continuity tests, where the multimeter doesn’t have a specific mode for continuity, should always be done on the highest range of the ohmmeter. You have to be careful not to touch the probes while testing as your skin resistance can also be measured and corrupt the test. When checking for resistance against a known specified value, such as for the coil resistance where you know what it is supposed to be, select the ohmmeter range closest to that value without going below. For example, if your coil secondary is 6 to 30k, you would want the 200k range, because the 20k range is below the maximum expected value.
Here is the wiring diagram for your ignition system. As you can see, the tach terminal is a signal, not a ground, so there should not be continuity to ground.
You asked how to check for spark at the coil earlier. It is difficult on HEI, but not impossible. Here is a pic from one of my manuals that shows how. Once the test is set up, have a helper crank the engine for a few seconds. The spark from the coil is produced during cranking. This test is dangerous, btw, so if you choose to do it, be careful. I don’t recommend this test, because the tests I posted before are just as good, and spark can be tested at the cyl #1 tower after the system is put together and is much safer to do that way.
hi how to I check resistance on grounds with a multi meter? Keep in mind I have no access to the starter and my car is not running
One more thing I wanted to add to this forum @cap 269. When my car is in battery on position the volt meter in dash only shows 7 to 8 volts but when I put leads on battery(multi meter) the battery is 12.55v. What does this mean?[quote=”jessedukhia” post=138412]When my car is in battery on position the volt meter in dash only shows 7 to 8 volts but when I put leads on battery(multi meter) the battery is 12.55v. What does this mean?[/quote]
That means the voltmeter is not reading the correct battery voltage, most likely due to a poor ground. It could also be a faulty voltmeter. The in-dash voltmeters are never very accurate, but even still, it should be reading closer to the correct battery voltage than that. There could also be an electrical fault. There may be high resistance in one of the circuits on the vehicle causing a voltage drop so that even though the voltage at the battery reads good, by the time it gets to the voltmeter it has dropped. The way to test this is with a voltage drop test. The first thing to do is to test the battery voltage with the key on and then with the key off. If the voltage drop only happens with the key on, then the fault is in a circuit that is only on when the key is on. You can find what circuits those are by examining the wiring diagram for your vehicle. If the voltage drop stays the same regardless whether the key is on or off, then the voltage drop is occurring at the battery, in one or both of the battery cables, at the points where the cables connect, or in one or more of the main grounds.If you take some time to think about how things work on your car, you may be able to reason your way through narrowing down the possibilities. I usually start at the battery posts themselves using the voltage drop method (after checking all fuses) and then work out from there. Here is a short video describing this.
You can do the same test at the other connection points of the battery cable. Keep one probe on the battery terminal and touch the other probe to the connection point. When you are testing voltage drops on the same side of the circuit, the meter should always read zero, or close to it. It doesn’t matter if the voltage displays as negative or positive, it is the number you are interested in. If there is a voltage between the points, then whatever wiring between them is causing the drop.
how to I check resistance on grounds with a multi meter?
Similar to the voltage drop test above, except with the meter on resistance (ohms) scale, you place one probe at one end of the connection and the other probe at the other. Again, you want the meter to read as close to zero as possible if you are testing regular wiring. Spark plug wires are supposed to have high resistance, so there is a different testing method for them. If the connection you are testing has one end that is too far for your probe lead to reach, you may need to purchase extra long probes or try a different test, such as a voltage drop test with voltage or ground access closer to the terminals you want to test.
Here are some more good resource videos for you on electrical troubleshooting.
Your information is great thx. I hope not a stupid question but how do a voltage test on a no post battery? also can i do the resistance testing at the fuse box if the issue is with the on circuits if so how?
No, dropping from 12.55 to 12.35 between key off and key on sounds normal to me, because you are measuring the complete electrical loop and anything within that circuit is consuming power and dropping the voltage a little bit. So, what would be a fault? If you saw a LARGE drop. For example, the starter motor usually makes the voltage drop to about 10-10.5 volts during cranking, that is normal. What is NOT normal is to see a drop to 10-10.5v when the starter is NOT cranking. So, if you are NOT cranking and see an unusually high voltage drop, there is excessive current going somewhere, usually a short circuit to ground or a bad connection. When you mentioned before 12.5v to 8v, that is a huge drop, and if it cannot be explained through normal operation of that circuit then it would be a fault. To clarify, Just because you see a drop doesn’t automatically mean it is a fault. A large unexpected drop could mean a fault. You have to understand the circuit, what the circuit powers and how it works (when working properly) and what drops you might ordinarily expect in order to be able to accurately diagnose an electrical fault.
Testing voltage drops across a connector (or a wire) is a good test, because there is not supposed to be anything (except wire or metal) between the points you are testing. No components, no bulbs, no sensors, no modules, etc. Therefore the voltage drop should always be zero, because there should be nothing between the test points that will consume power. Therefore if there IS a voltage drop, that piece of wire, that rusty connector or corroded terminal is causing the drop. Whatever voltage is being consumed by that electrical fault is power that is not available to the vehicle. If the drop is large enough it can keep the vehicle from operating at all.
[quote=”jessedukhia” post=138419]Your information is great thx. I hope not a stupid question but how do a voltage test on a no post battery? also can i do the resistance testing at the fuse box if the issue is with the on circuits if so how?[/quote]
There is no such thing as a no-post battery. But, I know what you mean, you are referring to the side post batteries common in GM vehicles. They still have posts, they are just different. Anyway, you test them in a similar way. Do the voltage drop test from the center of the terminal screw to edge of the terminal where you can see the contact ring under the boot. Is there a drop? Probably. So, examine the terminal screw. Remove it. Pop it out of the rubber terminal boot. Is it rusty? Corroded? Discolored? If so, replace it with a new one. Now look at the contact plates where you took out the screw. Rusty? Corroded? Discolored? See if you can clean it up with baking soda/water and a wire brush or old toothbrush. If it is so far gone that you can’t clean it up, replace the cable.The best way to test circuits at the fuse box is simply to measure voltage on both sides of the fuse. In other words, put the black lead on a known good grounding point (some exposed metal part or screw on the body) and the red lead on each side of the fuse. You should get the same reading. If you only get voltage on one side and not the other, the fuse is bad. If you get no voltage on either side of the fuse, there is a power problem feeding that circuit (or the circuit hasn’t been switched on, like, if it is only on when the key is on).
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