tried to start 5.3 definetly no spark at plugs.

[Dustytrix]

Well I finally got to turn my engine over today but it will not start. I have 12v at the injectors and coils but cannot get spark at the plugs. It has 12v while cranking, I have checked all the grounds they are hooked up. Crank and cam sensors are plugged in. I checked fuel pressure and have only 40lbs but it has the new delphi pump intank. Could clogged injectors stop the spark? Any ideas?

[BR3W CITY]

ignition fuse/relay, I've heard of coolant temp sensors causing no spark if not plugged in (cannot verify), cam sensor may be bad

[Dustytrix]

I checked the relay and I am getting 11.9 volts while cranking could that be to little? Also is there anyway to check the cam sensor?

[vannatta20]

Grounds usually get me. One missed ground and it will not start. I assume VATS security is removed?

[Dustytrix]

No the vats has not been removed, I have read and heard that the engine will crank with vats still enabled, I am tired of fooling with it. I will be sending the computer to someone next week to get the vats and other crap removed.

[BR3W CITY]

engine will crank and COULD even start with VATS on, but it will die almost immediatly. In a new install, it could prevent it from starting.

[Dustytrix]

I had read that also, the guy that is supposed to remove the vats and reprogram the computer wanted to do it with the engine running. I pulled the harness back off yesterday to triple checked the connections and ohmed each wire out they all tested good. I guess I will have to send it off since I can't get it to crank, no spark.

[Dustytrix]

OK I pulled my harness and went back thru each sensor wire, I got to the coils main connector and found the external ground only runs from one main connector to the other, it does not ground to the engine, so I hope I can ground this external coil ground wire to the engine and solve this no spark problem. What do yall think could that be the culprit?

[BR3W CITY]

There should be at least one external ground (to head) off the coil connector on the harness.

[clinebarger]

Originally Posted by Dustytrix

OK I pulled my harness and went back thru each sensor wire, I got to the coils main connector and found the external ground only runs from one main connector to the other, it does not ground to the engine, so I hope I can ground this external coil ground wire to the engine and solve this no spark problem. What do yall think could that be the culprit?

The ignition coils are grounded at G-102, G-102 is on the drivers side of the block & easily missed.....

[Dustytrix]

Thanks guys, I will be putting the harness back in tomorrow I hope I can tell yall it cranked

[Dustytrix]

Yes it cranks....... but only stays running for about 2 seconds. We are making progress, the external coil wire kept it from firing. Now I have to figure out why it won't stay running.

[mooseknuckles]

...is the VATS removed from the pcm?

[BR3W CITY]

^Ya Dusty, we mentioned VATS earlier, and it can still be an issue. IIRC you hadn't had it removed yet, so that will need to happen.

[vannatta20]

Sweet sounds like you got it figured out. Soon as you get Vats removed it will run. With Vats enabled to will run for @ 2 sec then die.

[Dustytrix]

Yea thanks again for the helpful info, I got a guy that is supposed to remove the vats Friday.

[Dustytrix]

Well I got the vats removed today and she cranked up immediately. Damn it sounds good even with all the exhaust leaks. I am having trouble with my stock tach not moving, has anyone used the oem tach in a 92 silverado?

[OKGMC4]

Does it not move at all or only a little? If it moves a little I need to deal with this in my 56 with a 5.3 but luckily my brother in law already figured it out in his LS7 swappped vette. It seems that the tach wire from the LSx ecm only supplies like 5 volts and it's not enough signal for most tachs. Most people seem to counteract it with a resistor. There are a couple ways to do it. One is inline and one requires a 12v reference wire. Just google "LS1 tachometer resistor" and you'll see how others have done it.

[Dustytrix]

Thanks OKGMC4 I will check into that. My tach doesn't move at all.

[ls1nova71]

Newer PCM's, generally '03 and up are notorious for having a weak tach signal. Go to Radio Shack and get a 680ohm 1/4 watt resistor (they come in a pack of 5 for around a buck) and put one between the power wire and the signal wire to the tach. This will make the signal stronger, but if you haven't already changed it in the tune, you need to change the tach resolution from 6 to 3. Since LS PCM's put out a 4 cylinder tach signal, your tach will only read half of what it should, changing the resolution doubles it.

[Dustytrix]

I put the resistor in and it works like you said, I will have to get my tuner to fix the read out. But at least I know its double the figure now. Thanks

[Shon]

set tach setting to 3 from 6 and it should work in PCM.

[Dustytrix]

My tach is oem 92 silverado I don't think you can change the setting can you?

[ls1nova71]

Originally Posted by Dustytrix

My tach is oem 92 silverado I don't think you can change the setting can you?

No, you can't change the tach, you have to change the tach resolution in the tune.
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