1998 Chevy Cheyenne no spark, engine turns over, truck died

RUPE1123

MEMBER
1998 CHEVROLET CHEYENNE
V8
4WD
AUTOMATIC
115,000 MILES

I found the negative battery cable insulation was melted, core corroded and the positive cable had a bad connection. Replaced both, still no spark, replaced cap and rotor (was replaced 2 months ago, ignition module replaced 8,000 miles ago, battery replaced 2 months ago). No codes come up with autoscanner. 12 volts going to distributor with ignition on. Truck turns over strong, resistance of coil is 5500 ohms(new one bought and returned 6000). Getting a low voltage pulse from the cam or crank positioin sensor to coil. What do I do now? It is a 2500 5.7L with the 140 amp alternator. My multimeter only goes up to 20K and don't want to see if it will blow up checking for 40,000V leaving the coil. Is is my ECM or Ignition module and how would I know? On hah, unrelated, Fuel pressure is good.

Wednesday, April 1st, 2009 AT 2:54 PM

7 Replies

JDL

MECHANIC
16,098 POSTS

The white wire/ black tracer at the coil driver module, is there a tach signal on that wire, engine cranking?

The pink wire at the driver module, is ignition feed, goes hot when you turn on the key.

The solid white wire is pcm coil control, should be a tach signal with the engine cranking.

My first thought is always about the rpm signal. Can you tell if the injectors are pulsing? Because of the o/p switch in the fuel pump circuit, the pump will run even without an rpm signal.

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Wednesday, April 1st, 2009 AT 3:46 PM

RUPE1123

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6 POSTS

I used a multi meter on the pink and white wires. Pink is solid 12 volts with ignition on and I am not sure if I check both but one of the white wires would drop when the engine was turned over. I assume this satisfied my concern about a low voltage pulse to the coil. Am I wrong? My multi meter is digital of course and does not show it dropping to zero, it just averages out. Would a test light do me better at checking for a constant pulse?

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Wednesday, April 1st, 2009 AT 4:44 PM

RUPE1123

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6 POSTS

How would I be able to tell if the injectors were pulsing? I only checked for fuel pressure (no gage) at the test port. If I used a gage and it changed while cranking over would this tell me that the injectors were pulsing or were you speaking electrically?

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Wednesday, April 1st, 2009 AT 5:09 PM

JDL

MECHANIC
16,098 POSTS

Hello, the white wire with the black tracer, is primary ground for the coil. You should be able to use a testlite, to check for pulse. The lite may brighten and dim, when you crank the engine. You can use the same teslite on the injector plug, two wire connector, B+ and ground, use led testlite, the lite should pulse with the engine cranking. If your digital multimeter has a tach--dwell--duty cycle setting, any of these settings will react to a pulse.

The problem may lead back to a crank sensor or circuit. I try to be sure.

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Thursday, April 2nd, 2009 AT 6:23 AM

RUPE1123

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6 POSTS

I stopped by the auto parts store to get a test light and followed my gut feeling about the ignition module. Hooked it up and she fired right off. Thanks anyhow. Do you think it was the bad cables that burnt the module out twice or should I keep looking?

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Thursday, April 2nd, 2009 AT 9:38 AM

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