1998 silverado start and die

[CL-1969c10]

Hello, I have never posted on this site before, so forgive me if I am in the wrong section here. I recently picked up a 1998 extended cab chevy with a 305 and spider injection. Previous owner said that it is on a 95 4wd chassis, and has a 305 with spider injection out of another truck. He claimed that the original engine to this cab/electrical system was also a 305 with spider injection. when I attempted to start it it would fire for a second or 2 and immediately die. it had a security light that would come on for a second or 2 and turn off. I stated by inspecting the Passlock module under the radio, and there were no burnt circuits. from there I tried to bypass it with a resister between the yellow wire and the orange/black wire in the ignition cylinder. that did nothing, so I soldered the wires back up and tried a different way. Another video showed to strip the purple wire going into the passlock module and use a jumper wire from it to a ground and release it when the engine was running. that didn't work either. So I went and picked up another passlock module from a junkyard and put it in as another video had instructed. After that I noticed that the security light had disappeared, but still no change in stating. I have since checked fuel pressure at the rail and have 60. I figured since I couldn't see if it would maintain pressure while running I would replace the fuel pump and filter and figures, that didn't help either. I checked a different thread that said I could check the voltage at the ignition cylinder. It said I needed 12 volt at the white wire, and with the wires un plugged it should have 5 volts at the yellow wire, and the voltage on it should drop while cranking. It had around 2.5 volts to the red/white wire, and the correct 5 volts at the yellow; however the voltage wouldn't drop when cranking. The truck runs fantastic if I pour fuel down the throttle body. And for some reason when I plug a diagnostic reader into the OBD 2 port it doesn't recognize the truck.
This is WAY more complicated then my C10... I don't know where to begin Haha.
Any help appreciated, Thank you.

[speedygonzales]

So you are either loosing fuel or ignition. The easiest way to see which is by spraying fuel or ether into the intake while cranking and see if keeping the "fuel" going, keeps it running. If it does not, then you have to see if ignition is dropping out.

For ignition a timing light can do it. There are also inline spark testers.

As far as Vortec's go. The cap and rotor are critical. I once parked mine after driving fine and the next morning would not start. Turns out the cap and rotor were bad. Changed them out and took off for the 600 mile Xmas trip.

There are 2 vents in the distributor that for Vortec's are critical. If they clog up, your cap and rotor is toast in 300 miles.

That will keep you busy for a while.

[CL-1969c10]

Ok, that makes sense. but if ignition were the issue, wouldn't it not run by pouring fuel down the intake? I checked each wire for spark and they had it with a in-line spark tester. I was able to rev it up while someone put fuel down the intake and it would run until you ran out of fuel.

[Mr_Rich]

You would be chasing your tail if you continued with PassLock. The engine would not even click when you turned the key. Something else has to be going on there; an intermittent open on a switch of some kind. I replaced a fuel pump and did a tune-up on a '99 Tahoe and that's about the limit of my experience with that version of fuel injection.

[Just call me Sean]

Originally Posted by Mr_Rich

You would be chasing your tail if you continued with PassLock. The engine would not even click when you turned the key. Something else has to be going on there; an intermittent open on a switch of some kind. I replaced a fuel pump and did a tune-up on a '99 Tahoe and that's about the limit of my experience with that version of fuel injection.

No, that's exactly what it does when the Passlock is malfunctioning. It will start then die, my 99 did it. I rewired mine to use a 96 computer, but one can have the Passlock removed from the computer by having it reburned which would be the easier way to go.

[CL-1969c10]

How does that work?

[Just call me Sean]

It's like getting a tune, they reflash the computer with a different tune. One without Passlock. The Passlock shuts down the firing of the injectors but not the ignition system which is why it will run briefly, it uses the little fuel in it before the injectors are shut down.

[CL-1969c10]

Ahhh, ok. so all I would have to do is take my computer out and bring it to one of those tuner shops and they can delete the passlock system entirely?

[Just call me Sean]

According to my research yes, but I didn't do mine that way. You could even have them do a mild tune while they're at it.

[CL-1969c10]

Sweet, thank you very much. If that's not it, and ignition is not the issue, what else could it be? Just to have a plan B I guess

[Mr_Rich]

PassLock started malfunctioning in my H3T at over 100K. Turn the key and not even a click. Lights, radio, etc., all worked but no start. I turned the key to ON for exactly ten minutes while the system reset. There was a small unit the size of a throttle position sensor on the end of the ignition key switch on the column. Of course, GM would sell the entire unit instead of just the switch, but that was all that was needed. My truck was a 5M and I don't know if it made a difference or not but I tried replacing that switch and never could get it to reset properly. My next course of action was possibly cutting a pink striped wire to disable the PassLock but I didn't. I sold the truck at the start of Covid as a means of economic survival. I lived with the intermittent problem until it was sold.

[Mr_Rich]

Originally Posted by Just call me Sean

No, that's exactly what it does when the Passlock is malfunctioning. It will start then die, my 99 did it. I rewired mine to use a 96 computer, but one can have the Passlock removed from the computer by having it reburned which would be the easier way to go.

Something did not sound right to me about this and I did further checking. I had a '98 Firebird that had the VATS/ Theftlock systems in the car. During that time PassKeyI,II, &III followed preceding the PassLock system. Your calling it PassLock but it was actually the PassKey system that behaved like that and later on PassLock was the term that came to be used on all these systems. PassLock behaved in the manner I described with my H3T and other GM cars and trucks.

[Just call me Sean]

It doesn't really matter to me what it's called because I know what he's talking about, the security system on his 98 truck which is the same as my 99. I don't know of any of these systems that can be bypassed by cutting a wire, that defeats the whole purpose of a security system. Cutting any wire to the security system will stop the truck from starting. You can bypass the system once the truck has been started, but once the battery is disconnected or dies the bypass doesn't work anymore and you have to bypass it again. I had a 92 Firebird with VATS, I bypassed that with a bypass module. The module created the signal needed to allow the car to start, but I didn't find any such module for these trucks.

[CL-1969c10]

Hey, saying thanks for all the input. I took the advice and sent my PCU out to get the passlock system removed. I received the PCU yesterday, put it in the truck, and now it starts and runs great! Thanks again.

[b454rat]

if you have a scanner you can clear the code. I had a 99 CC that battery kept going dead, and whenever jumped it, (sometimes) it would not start cause of the security BS. I got rid of it couple years ago, so don't remember exactly what scanner said..