normannova64

iTrader: (1)

I've been working on a 2005 4.8 3500 express van. It'll start and run sometimes and just won't start at all later. Good fuel pressure. Got spark. No codes. I can see tps working in scanner and unplugged it once just for a shot, nothing. New fuel pump regulator sending unit assembly. Turned off vats via hptuners just to be sure. Cleaned all my grounds and applied electric die grease. Check pcm connectors for corrosion, no dice. I'm running out of ideals. Can a shorted injector kill a whole bank? Also when you crank it, it will almost start occasionally when you let off of the ignition. IE as you return to key on engine on not crank. Any help, or suggestions would be appreciated. Thanks.

lt1pwr1

iTrader: (1)

Sounds like your ignition switch may be going if it tries to start when the key returns...although if you are getting spark and fuel then maybe not.

These motors are notorious for building carbon around the throttle body blade and throttle body (where the edge of the blade rests at idle). This causes the problem where air can't get into the engine and I've seen them where usually they will barely idle and then die.

If this is the issue with yours then you have an extreme case but it is an easy and cheap try. Just clean the blade and throttle body really good with carb cleaner and a rag.

On a side note..a 4.8L in the 3500? Maybe someone swapped engines and that is your issue? I don't think they make the 4.8L in any 1 ton vehicle.

normannova64

iTrader: (1)

Hey, thanks for the reply. Yeah I thought for sure that it would have 6.0 in it but it's a work van and hasn't been altered. I was thinking about the ignition lock cylinder today and how maybe the contacts could be worn. Or should i be looking at the actual switch on the column? I'm going to try that for sure. I hear what you're say about the carbon and will check it out but i don't believe thats it. I had the intake duct off shooting a little fuel in it to see if would hit and opened the throttle blade and it looked very shinny and clean. I wonder if I was seeing the firing at the end of the cranking cycle when my buddy let off the key. We'll see. Thanks again and I'll report back for others that might be having the same issue that I'm encountering.

lt1pwr1

iTrader: (1)

Yeah the key is try things that don't cost anything or that are very cheap first.

Not sure I would just replace the ignition but to answer your question, I'm sure the issue is with the ignition switch itself (if that is the problem). Not the cylinder.

Try unplugging your MAF and see if it starts. Seen those so far off the charts that a car will start and stall until replaced.

normannova64

iTrader: (1)

Thanks Lt1pwr1. Ignition switch seems to have done the trick. Once I got it all apart and clocked the new switch it fired right up like a champ. Man i feel like a jack wagon for not catching this. Thanks again.