GMC Truck Forum banner

Hard starting when warm

17110 Views 8 Replies 4 Participants Last post by  Hogg
2000 C3500 7.4 vortec, replaced the plug wires with MSD Super Conductor 8.5s, new plugs (factory AC originals), new fuel press regulator, new cap and rotor from DUI, new fuel pump and sending unit and new PCV valve, new K&N cold air kit and new Flowmaster exhaust. First thing in the morn it fires right up, sometimes dies right away, after driving through out the day it takes a lil while to start and not sure if the control mod is goin bad or weak or what the deal is, its got 134,000 miles and everything is factory original untouched except what I have mentioned, any ideas? Thanks
1 - 9 of 9 Posts
Test your fuel pressure. The truck shouldn't be dieing at cold start up either
Do the easy stuff first. Clean the throttle body and MAF sensor. Also seafoam the upper intake.

Had a truck come in one day that was hard to start when cold but not hot. Basically everything fuel related had been replaced. I seafoamed the upper intake and that took care of it. Stuff is magic I tell ya.
I use seafoam in just about everything, but this trucks intake needs it bad but not sure of the best way to do it, cant really take off the intake tube and dump it in the throttle body can I? with the maf seperated from the throttle body, will that affect anything for a short time while I dump seafoam in there? Seafoam is the best, 200% agree, works wonders
I would do it through the brake booster hose. Have a buddy inside the truck to keep it running while you slowely pour it into the hose.
got hydroboost, the only vacume line I have is to the fuel press reg and I have a tee in it to run to my vacume guage that I can reach fairly easy and disconnect and maybe spray carb cleaner in that way, I havnt seen seen seafoam in a spray can yet
Damn. You might try taking the intake off and spraying seafoam deep creep into the intake manifold. Do it with the truck off.
alright thanks, when I had the intake off before to replace the fuel press reg, I noticed alot of oil in there so I knew pcv was bad, shouldve done it then, CRAP. Havnt had the truck too long so just pickin away at it trying to get everything straighened out
When I hear L29 Vortec 454 and difficult hot restarts, I automatically think FPR.

Also check the fuel pressure, the pressure shoudl be lower at idle(when the engine is pulling lotsa vacuum) that when being tested at Key On Engine Off(KOEO). If your fuel system bleeds down once the pump stops running, be sure to test your pressure with the pump actually running. HAve someone cycle the key to engage the pump and read the gauge while the pump is running.

1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.