tcorn

Howdy, ive got a 98 k1500 5.7 a family friend brought me to replace the rear end in, it came to my shop about 3 months ago (ran when it was parked), and due to parts not be available, and my work schedule it took me about 3 months to get to the rear end replaced. I went to start it and nothing but crank, I placed the spark plugs on the exhaust manifold while cranking and can see spark, and it does not respond to starting fluid, i dont have fuel pressures yet, troubleshooting that today. also replaced the ICM with no changes. (I'm an industrial diesel mech) but if i have spark fuel and air i dont understand why its not even trying. I have the security light so the passkey is good. thank you all in advance.

oldchevy

Welcome from Florida. This might not be your problem, but I have seen in several occasions that you have spark but it is not hot enough. Check the coil!!

Gumby22

oldchevy is on to something here.

Spark can jump a gap much easier outside the cylinder than inside of it due to the compressed air in the cylinder. It takes significantly less energy to jump a gap at atmospheric pressure, so it’s possible the in-cylinder spark isn’t adequate.

But there are several known issues with these trucks, so let’s start with the easiest checks.

1) Make sure the battery gets a proper charge.

2) If it’s a side post battery, disconnect both terminals and make sure they’re clean. If needed, remove the insulator sleeves; also, the battery bolts can be replaced with 3/8x16x1” hex bolts.

3) Monitor Voltage on the pink wire at the coil while cranking to see if voltage is being pulled low. If yes, check for excessive amperage draw from starter.

4) Check the distributor rotor and cap contacts for corrosion. Anything more than some carbon tracking on the contacts is reason for replacement. You can try cleaning them but IMO it’s not worth the time.

If none of this results in it starting, and you have adequate fuel supply/pressure, crank the engine for up to 30 seconds, then pull the plugs to check if they’re wet or dry. If dry, the injectors may not be pulsing.

One last thing - at key on, engine off, does the security light turn off after 2-3 seconds or does it blink/stay on? What about after cranking?

Typically these trucks will start and stall after 2 seconds with a flashing or steady security light if the fault is related to the PassLock/PassKey system, but that’s not always the case. If the security indicator isn’t turning off, it could be the system is active for another reason.

Luckylove

thank God I found your post. here is out problem. we replaced the ignition and the cluster to the ignition, twice now. the security light comes on solid then goes off after a couple of seconds, it will crank but cuts right off. we were having a problem with the dash lights having no power, the radio and headlights came on, but the trunk would not crank. we read that the problem might be in the wiring under the in hood fuse box. do you have any other suggestions? please help

Gumby22

Please clarify the following so I can better understand the problem and what parts have been replaced.

1) Is this a 98 K2500 as well (per OP’s original post) or do you have a different model year and engine /chassis combination?

2) Ignition coil? Ignition switch? Ignition key cylinder and/or housing(Passlock sensor)?

3) Wire cluster? Instrument cluster?

4) What cuts right off? Is the starter cutting off while you’re still holding the key in the crank position?

Or does the engine start, then stall after a couple of seconds?

If the latter, watch the passlock/security indicator light in the instrument cluster before turning the key to the off position after attempting to start. If it’s on steadily or blinking after an attempted start, it is a security related issue and will require a bidirectional scan tool in order to properly diagnose it.

5) There are SEVERAL possible reasons for a crank/no start problem. A methodical approach is necessary to accurately solve the problem. I can only help you in as much as you allow me to.

Luckylove

Ok sorry I didn’t include more details. No, this is a 1998 c2500hd Cheyenne with the 5.7l v8. We replaced the ignition cylinder a while back and that’s when the problems started. Sometimes when you would turn the key to the start the truck, there would be no lights on the dash. The radio would have power and the headlights worked, but no dash lights, no fuel pump engaging, truck would not do anything. So, he was told it was the security system. He was told to put a resistor on these wires by the ignition switch to bypass the security system. That didn’t help. Sometimes it worked fine, but sometimes you would be stuck with no dash lights so no start. With it only happening sometimes, it was almost impossible to diagnose. No check engine light, but I decided to scan it anyway and I got a code about the passlock system. Anyway, long story short, he was told that it was a wiring problem. So he bought a new ignition switch wiring harness that came with a new ignition cylinder. However, on this wiring harness there was a small clip with three wires that plugged up in a place where the wire colors were different. He just spliced them in where he thought they went, but this really has nothing to do with it sorry. Anyway, after the new wiring and new cylinder we got constant power to the dash lights, the security light came on solid but only like it does when you turn the key to on right before you crank it, then it went off and the truck cranked. But it immediately cut off. No security light, just went dead. He back probed all the wires because he was told it may be the wires that are under the fuse box under the hood causing the problem but they were fine. And I don’t know if this matters but a few days ago before installing the new wiring, I was driving the truck down the road about 55pmh it made this slight reving noise and just cut off. I stopped the truck, tried to crank it, but of course no dash lights so I was just sitting there for several minutes. So he installed the new wiring and cylinder yesterday when the latest problem of cutting right off started. I tried every relearn procedure I found online and none of them worked. FINALLY today he put the last cylinder back in. we tried a relearn procedure again and finally it is working. I am just so afraid of this happening again. It has been fine before and it a day or two here we go again. I just don’t have the energy to do this again. Any idea what the problem was/is/could be? Thank you for taking the time to respond.

Gumby22

No problem - I just need to be able to look up accurate information for your vehicle.

To be clear - the passlock system will not cause a complete loss of power in the cabin (no lights/radio/etc). It will only interrupt the engine fuel supply, resulting in a start/stall condition. The reason is because at key on, the ECM primes the fuel line by turning on the pump for a couple of seconds. This provides enough fuel to start but not enough to stay running.

The pass lock system first verifies the correct key has been used, and if so, communicates a “fuel enable password” to the ECM to allow the engine to run after startup (keep in mind that under normal conditions, this is all happening almost instantly once the key is turned on).

There are ways to bypass the security but it depends on the generation of the system (pass lock 1, 2, or 3) and the functionality of the pass lock module.

For now, don’t overlook the simple things - make sure the battery is good and the connections are clean and tight (if side post, remove the terminals for inspection - corrosion builds up between the terminals and battery). Make sure the power cable from the battery to the fuse block is in good condition and both ends are clean and tight. Make sure the alternator is working correctly,

If the basics all check out, Remove the under hood fuse block & inspect the wiring/connections underneath it - inspect all the fuse terminals for corrosion. Inspect the wiring that passes thru the firewall into the cab for exposed wires.

I’ll post more specific information when I have it.