Well guys, I need some help. Yesterday my '88 ran fine, and this morning it won't start. Cranks normally, but doesnt catch at all. I pulled a plug wire, put a bolt in the end of it and put it up to the engine in several places and got no spark whatsoever. How would a layman like me begin to figure out what the problem is? It's my daily driver, so I need to get this solved ASAP. I've tried the search function here with no luck.
Any guidance would be greatly appreciated.

Update: I replaced the condenser, rotor and cap. Autozone checked the ICM with their analyzer and said it is fine. Still no spark. This really has me baffled.

 

I have a client appointment on Monday, so I am desperate to get this fixed. Any ideas.....anyone?

 

Yes,

Was waiting for others to answer your question but no one else did so today.

Obtain a simple 12 volt automotive test light & a bare steel wire paper clip.
Unwind the paper clip( must not be 1 of those plastic colored pink, blue, red, ect.) Into a straight wire.
Then bend the paper clip into a "L" fashion about 1-1/2" inches from the end.

Next open the hood on Your C4 & leave it open.

Next take the paper clip backprobe lead you made prior & insert it into the backside of the HEI distributor Power lead connector.
Its a heavy thick wire Orange- pinkish in color,
10 gauge wire.
Roughly 3/16" diameter thick.
Will also be marked on the end of the distributor cap +12V Battery.
Leave the connectors plugged in as normal.
Just take the paper clip & jam it up firm with your fingers till you feel something solid like metal.
Then you made positive contact with that copper terminal.
What You want.

Connect the loose test light lead to that paper clip.
The other probed end of the test lead tape down to the top of the TPI upper plenum - intake.

Turn the Ignition Key on.
It should light up.
Then crank the engine over,
Test light should continue light up & likely will dim down in intensity some, thats OK, because the starter motor is drawing the available battery voltage & current down while cranking.

If engine did not fire & start which it likely did not........

Remove the paper clip & insert it into the other terminal(back probing style) next to the + 12 v battery terminal on the HEI distributor cap..........
Will be marked TACH, stands for tachometer.

Again connect the loose lead of the test light to the paper clip,
& leave the other probe end of the test light connected to the intake.

Crank the engine over for at least 10 to 15 seconds.......
carefully watch the test light.
If it does not light up & flicker at a rapid & synchronized pace.....

something is A- miss with the HEI internal ignition module.
Or the HEI Pickup coil is at fault.
The HEI pickup coils fail very rarely on these C4 generation Corvettes.
99 out 100 times the HEI module is at fault.

A new HEI module from NAPA, Carquest, Autozone, O'reiley's, Murry's, local GM dealership, ect should get you & your C4 going down the road once again.

We can get more scientific about trouble shooting with scanners, DVM's, & Snap On Diagnostic equipment or similar.
Not necessary in your situation I believe right now.

Had the HEI module fail on my 87 in the past away from home.
All I had with was my 12 volt test light, screwdrivers, 1/4" inch nut driver, needle nose pliers, Cellphone.

Diagnosed & repaired my 87 on the spot 20 miles from home.
A friend drove out & brought me the correct 7- pin style HEI ignition module to get the car going again.

Let me know what you see with the test light.
Must have Ignition pulse present output from the HEI ignition module.
Its what saurates the Ignition coil ON & OFF on the primary winding side with 12 vdc current & creates high voltage DC on the ignition coil winding secondary side to jump across the spark plug gaps each to ignite gasoline fuel & air- oxygen.

VVVROOM or no VVVROOM.

Takes a hot bright blue ignition spark to start the engine & keep it running on all C4's.

Brian R.

 

Excellent information. My sincere thanks for your thoughtful and generous response.

 

http://members.shaw.ca/corvette86/Ig...System-EST.pdf

 

Could be your ignition control module, your coil or your pick-up coil. Us the attached write-up to test each. I any one of these are defective, replace them. You should be able to get any of these parts at your local NAPA or other national parts store (even on Sunday).

Check it out and let us know what you find out.

 

Check the plug that goes in the side of your HEI cap.
Red wire especially, should be nice and secure. Hopefully its something simple.

 

Geez, this is getting frustrating.
OK, here's what's going on. Because I'm running out of time, I took the "throw parts at the problem" approach. I have replaced the cap, rotor, control module (the one inside the distributor) and even the ignition coil. Still no spark.
The only reason that I didn't replace the pick up coil as well is that nobody that is open on the weekend has one in stock. But something has occurred to me that I should have thought of before. Just because I have no spark, doesn't mean that I do have fuel going to the injectors. I opened the schrader valve in the fuel rail. Got no gas spurting out. I then turned on the ignition key, but heard no fuel pump pressuring the fuel rails. Does this tell me anything?
Is there any switch or system that would prevent both spark and fuel, but still allow it to crank? Could it be the ecm? I checked for error codes, it is showing none. I've checked fuses.
I may have been chasing my tail here and looking in the wrong direction.
Please help if you have any ideas. I'm really under the gun to solve this.
Life with a twenty three year old 'Vette as my daily driver can be a challenge, but I'll still never sell it. Never.
I'm very grateful for your help here, guys.

 

The ECM turns on the fuel pump for 2 seconds when you turn on the ignition to prime the fuel rails.

After that the ECM turns on the fuel pump when it sees pulses coming from the distributor (which don't seem to be happening in your case).

The fuel pump is also turned on by the oil pressure switch when the pressure reaches 4 PSI.

It sounds like the distributor and ECM are not seeing the voltage from the ignition switch. The ECM will turn on the Service Engine Soon light if you turn on the ignition without starting the car. I suggest checking the fuses.

 

My first thought is a faulty fuel pump relay switch.

 

Many thanks to all of you who took the time to help me.
It was the pick up coil.
Jeff

 

So are you back up and running now ?

 

I am, indeed, thank you; and delighted to be so.

 

I have a similar problem only I have fuel pressure. I checked the HEI coil and replaced the Ignition control module. I have 12 volts from the battery wire to the distributor, but no spark to the plugs. Is there an easy way to check the pickup coil and will one injector with only 11 ohms cause the same problem?
Thanks for any advise.
Bob

 

You can measure the resistance of the pickup coil. It should be around 800 ohms. That would be .800 on the 2K range.

Measure all the injectors and compare the readings. If one or more are very low (like more than 2 ohms lower) compared to the rest then you have a problem. Measure them hot (if you can). They are more likely to show a problem when hot. I'm not giving exact numbers because they changed over the years. That's why you compare all of them to each other.

 

Thanks for the info. I checked the resistance and all but one was 17 ohms and there is one that is 11 ohms. I will change that one and see if that cures my problem.

 

Usually if one is bad the others are sure to follow...

 

It has been a couple of months since I have been able to get back to troubleshooting my no spark problem, but since then I have replaced all injectors with new ones and have replaced the distributor as well. On a fully charged 12 volt battery, I am getting 9.5 volts to the coil when turning over the motor, but still no spark to the spark plugs.
Any help would be great.
Thanks

 

9.5 volts sounds low, but you said "while turning over the motor", so it might be OK. When you're cranking the engine the starter puts a heavy load on the battery and can drag down the voltage. The ignition module should still work at 9.5 volts.

The voltage on the distributor comes from the ignition switch, so it should be the same as the battery voltage. What voltage do you measure with the ignition on, not cranking? Measure the battery voltage with the ignition on also to see how much it's loaded down by the various accessories.

You might have a problem with the pickup coil or the high voltage coil.

 

I need to make a correction..The voltage with the ignition turned on but NOT cranking is 9.5 volts. This is at both the battery side and tach side of the coil.
Thanks in advance any further recommendations.

Bob