russellaporter3

I would greatly appreciate some insight into this problem with this truck. I have a 1994 Chevy S-10 with a z code 4.3L TBI on an auto. This truck was runnning fine, I parked it and shut it off and 3 hours later it would not start.
It does turn, the starter is strong.
It is getting power (+12v on the plugs) to the injectors, as well the resistance on the injectors themselves are fine. There is fuel line pressure to the throttle body. There is voltage going to the coil, but no spark coming out.


#10 Fuse labled ECM/IGN is good, has +12v as checked from the hot side of the fuse socket to ground.

Replaced:
Coil
Fuel Filter
Ignition Control Module
Fuel Pump

Any Ideas?

mack1

Hi russellaporter3 and welcome to TSF,

How did you test for spark? Extra plug laying on the metal block with a plug wire connected to it is a good way. Look for a good blue spark across the gap.

Try spray starter fluid straight into the intake to check for fuel problems, but it's probably a spark problem.

Check the pickup sensor located down at the front of the engine near the harmonic balance. Using a voltmeter on AC, you should get some indication of signal when the engine is turning over.

Let us know what you find and post back. I'll be out of pocket for an hour or so, but will check back then.

Very best regards,
Mack1

russellaporter3

Same method for spark check, but grounded to exhaust.

I have tried to ether it, nothing.

I cannot locate the pickup sensor, I am a pc tech, not a mechanic, so I apologize if im a little dumb when it comes to these things. Can you better explain to me where that sensor may be and what it may look like? The same for the harmonic balancer...lol

wrench97

The balancer is the round part behind the lower (crankshaft) belt pulley, not sure which side of the engine it is but I think the left side. It's just a magnetic pick up the should generate a low voltage pulses when the crankshaft turns.

mack1

Hi russellaporter3,

According to my maintenance book, your ignition system is HEI (high energy ignition). I've attached a pictorial diagram out of the Haynes Repair Manual.
It shows that the pickup sensor goes dirrectly to the ignition control module.
You should be able to take the signal measurements there. It also shows the connections to the PCM (powertrain control module, or just the computer).
You should also be able to measure signals from it to the ignition control module. It will also be a low level signal.

To take the measurements while the connectors are connected, you will need to back probe the connectors. Use straight pins from a sewing kit pushed beside the wire into the connector until it makes contact. Unplug the connector and use the ohm meter to be sure you have contact with the pin.
For the pickup sensor, use a pin on each of the two wires and measure the AC voltage between them. For the other measurements, measure form the pin to ground ( a bare place on the block or the negative battery terminal).

Hope this helps.

Best regards,
Mack1

04s10ign 001.jpg

russellaporter3

cant find it
is it missing from pic? There is some kind of mount pointed at the harmonic balancer???

Attached Images

sensor.jpg (27.7 KB, 10 views)

wrench97

look up from under the motor.

mack1

Wrench is right, if you want to find the sensor, go under the front of the truck. If you want to measure the voltage that it puts out, take a look at the picture I posted. Sorry the pic don't call out the wire color codes, but there is normally only one sensor at the lower front of the engine and that would be it. You can measure sensor voltage at the top of the engine at the ignition module. The print calls it a pick-up coil.

russellaporter3

I have been looking from underneath the truck... Isnt the pickup coil inside the distributor? When I installed the ignition module, the side of it with just the male two pronged connector hooked to a plug under the distributor cap.
there is nothing with wires on it on the front bottom of the engine, nothing on the lower 2/3 of the front.

wrench97

If that does not have coil packs, but rather a distributor with the module and pickup then no there is not a CRK sensor, Check the pick up coil with a ohm meter if it's not shorted or open then it's probably a bad module.

Raylo

That year S10 has the single coil and HEI distributor.... at least mine with the CPI W code motor did. I think the Zs are the same.

mack1

With egg on my face, I went back to the repair manual and found that the pickup coil is in the distributor. The ohms value of the coil is 500 to 1500 ohms. It suggests that you should flex the wires while measuring to look for intermittent opens.

russellaporter3

i just checked the coil with an multimeter set to ohms, and got nothing, and i checked continuity and got nothing....is the pickup coil bad?

mack1

I'm assuming you meant that it measured infinity. Yes, that would indicate that the coil is open and bad.