So currently a new problem has came up after replacing volt reg and alternator also had a shop tune my carb for emissions which I’m still trying to get through and now when the trucks hot and been driving and I park and turn the ignition off it will rumble I can start it again by turning the key not even turning it over kinda confused and need help thanks

 

Sounds like you are having a "dieseling" issue. A couple of things cause dieseling. 1) Badly worn out piston rings that are allowing oil to enter the combustion chamber, this condition usually takes decades of poor maintenance and hard engine revs. 2) Your timing is not set right. Since you have recently had a "tune", this might be your actual problem. Look up the factory timing and grab a timing light to fix this issue. If that's not it, then 3) your carb is not properly adjusted. Depending on what carb you have, adjustment recommendations will vary. Posting the engine size, any performance mods, type and brand of carb, etc. will help us all out.

 

Lower octane in a higher compression engine will also cause it.

If you have a 4spd just turn the key off and kill it with the clutch. if you have an auto just ignore it if you can.

the only think it will hurt is your smog pump if you have one . the factory put a solenoid on the throttle linkage to prevent this.

 

That carb tune may have also left you with a vacuum leak which will lean you out and contribute. Check your hoses.

 

sorry I totally didn’t give enough detail i have a 74 f-250 engine is a 360 5.9 2wd auto(supercab) and I have a Eldrock 4 barrel carb

I’m still learning I inherited the truck anyways when it came time to go to emissions the truck failed on idle hydrocarbons and loaded hydrocarbons didn’t know where to start so I took it in and they said I had an air leak and they said it was running rich also I had a parasitic draw and my alternator wasn’t working correctly I replaced those and the voltage reg they did the work on the carb after I got the truck back noticed the whole not wanting to die never had the issue before recently took it back explained to them this issue came up they said it’s unburnt fuel leaking in on the compressions stroke they tuned the carb again and retarded the ignition timing and still can’t get through emissions just on the idle I’m barely failing by 40 units on idle but I was reading the brochure and hydrocarbons failing is linked to failure in the ignition system and just kinda need a pointer of how I should tackle the situation i don’t currently know where to start and how everything should be done and set to what

 

young and learning how would I go about doing that and what hoses? I can send pictures tomorrow

 

Speaking from experience with an edelbrock on a older ford motor. You really need to get your initial timing set and get a vacuum gauge to tune your idle mixture screws and get the idle speed screw as far out as you can. Let me explain.


If the engines running poorly, it’ll take a lot of throttle position to keep it going. If it’s running very efficiently it won’t take near as much throttlle at the top of the engine to keep it running. It will running smoother and easier thus meaning it’s taking less fuel and air to do it. It’s not “fighting” itself.


All carbs flow fuel at idle, more so as the throttle blade opens. Even if you aren’t pushing the throttle and pumping the accelerator pump.

So if something in your engine isn’t tuned correctly and is causing the truck to run rough you probably also have the idle speed screw turned to far in to keep the truck running. So then even at idle the truck is spraying an unnecessary amount of fuel into itself. Then add on your combustion chambers are all dirty, soot filled and covered in hot spots, your timing is probably a little off, and your fuel air mixture is a little off, and your fuel pump will continue to pump fuel when the engine is running.


So after all that, you turn the key off and it wants to continue to pop that extra fuel your sending into that extra hot and dirty chamber and it lights a little. Just enough to keep turning the fuel pump thus pumping the carb spraying fuel igniting it blah blah. I’ve found my edelbrocks would do this easily on our old trucks. Maybe because your probably putting twice the carb on as came from the factory, who knows how much fuel at idle an edelbrock is capable of flowing compared to a factory 300 cfm 2 barrel. It’s all in the tuning. Get a vacuum gauge and learn how to use it. That solved my dieseling problems after I chased the timing for awhile.