My friend bought a 96 cummins 4x4, ever since he got it, it pops at high rpm. We are not sure what has all been done to the truck, we know it has a intake, the truck smokes real good, makes ok power, but it sounds like a machine gun at about 2400/2500 rpms! anyone have any sugestions on what it could be or what/where to look for.

 

When i encountered this problem it was happening because i wasnt getting enough fuel to my injectors. I had this problem on my 01 24valve and on my 03 Common Rail. I only had the problem after upgrading to a larger injector that my stock injection pump could not fuel hard enough in the higher RPMs. My sugestion is to check this problem and see if it helps. In both situations I found myself upgrading to at least a FASS 150gpm pump and a "Hot Rod" injection pump. After doing this I never had the problem again.

 

No need for a fass on a 12 valve unless your over 6 or 700 hp, the popping could be bad timing, not enough fuel or to much fuel need to check and see what all has been done to the truck, what position the fuel plate and afc, starwheel are. Any boost leaks? When was the last time the fuel filter was changed?

 

i would change the fuel filter before I did anything else. If that didnt fix it, I would check the pressure, and put on a new lift pump if you need it. Then I would go to timing if it still isnt fixed.

Eric

 

fuel filter, pre-filter screen, overflow valve, fuel pressure, timing!! IN THAT ORDER!!

Thats what i would do. Start with the easiest and keep going till its fixed.

Lance

 

does it make the poping noise when you take it to 2400-2500 slowly or when you go WOT and get to 2400-2500? Any odd colored smoke?

 

well today it blew a lower rad hose, while repairing that i found that a boost tube from the turbo outlet was ripped. i repaired that and the popping went away and a ton of power was found. now to say that, soon after getting back on the road, another water leak! After a short ride back home on a tow truck, i tore into the motor and found that a freeze plug had blown out(the one behind the fan housing). well to say the least it is a dealer item. wont be in till tuesday. i will see yall soon

 

If I rev mine from idle quickly,just stomp on the throttle, it will pop blue smoke at about 2500 rpm, but if I rev it slowly it runs up fine. Is that normal?

 

yeah, add a little bit of tioming aropund 15.5 or 16 it will go away and run nicley, also get urself a gsk and youll be grinning from ear to ear

 

mine pops and alternates white and black smoke when it hits the governor. I know it's the gov b/c it used to do it around 2500RPM until i was able to get back in there and tighten down the springs a lil more. now it rev's to 3000 before it does it.

 

mine does it at 1500-1700 rpm and whe i gte into the 21-2500 rpm range its so loud i cant hear anything any more... i have had people ask me if i had a problem with the motor before...

 

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