donald.emmack

OK,
I've heard all over town and the net about how biofuels and veg oil "coke" the injectors and internal components of the high pressure pump, fuel rails etc.

My first gripe - I can't find any good photos of injectors which are "coked" and the same age/mileage injectors which are not "coked". What the heck do you look for anyway - seems like age makes its mark no matter what.???

2nd - What are the objective symptoms of "coked" injectors? I mean, before they are toes up...does the engine run rough, does the ECM spit out a certain code, white billowy clouds streaming out the pipes...?

3rd - Specifically, does "coking" happen due to heat, pressure or what combo? What prevents normal diesel from "coking". Is there a certain temperature factor?

4th - Is "coking" actually a build up of contaminants in the biofuel or veg oil? Or a result of the oil drying out at high temperature?

5th - If you CAN tell your injectors are getting messed up, is there a chemical way to fix the problem? Seafoam, powerserve etc.

6th - If you need to replace the injectors which are "coked" etc., can it be done by a shadetree mechanic...Like me! during an afternoon or are there special procedures necessary to make the electronic firing work with new injectors?

Finally - $300 per Bosch injector seems ridiculous! Not to mention the pump! Where can you order aftermarket injectors or similar at a better price!

Thanks for reading!!

Spooler

If you can get a Bosch injector for 300 dollars, I say good luck. You get what you pay for. I keep hearing around 600 dollars per injector. Never heard of biofuel coking an injector. I wonder if you are talking about caboning up an injector. Biofuel by nature is a solvent and lubricant keeping things clean and lubed. 3rd Gen trucks are notorious for carboning up injectors on trucks that are not worked on a regular basis. No codes will be found, just a louder running engine with poorer fuel economy.

donald.emmack

Wow $600! That's a drag.

I've been told by local diesel mechanics to stay away from bio's and veg oil because of damage to the injectors by "coking". I'm a pessimist with advice so I'm looking around for other data.

thanks

N.Johnson

I have seen coked injectors off a VW TDI that ran straight used veg oil . Also the valves and exhaust system were almost closed off. Black goo sticking to all the parts. Bio diesel made to spec won't coke the fuel system. What happens with the common rail system, is the high rail pressure, can change the bio at a molecular level and cause it to polymerize. Form stringy deposits that clog the fuel filters. But many guys are running up 100% with no problems. Actually proper made bio is a excellent solvent, cleaning the fuel system of petro residue. Another term is CARBON FOULING. Continued low cylinder temps operation, below 600F will leave deposits on the tips,combustion camber and valves. Because the tip holes are so tiny any carbon build up disrupts the spray pattern/angle and will cause a cold start rough idle. I know it happened to me. Pulling or hauling above 900F will burn these off, CURED! The cummins is a medium duty industrial engine not designed for commuter grocery getting. But it will live a long and trouble free life if worked occasionally with regular pm. Think of it as the difference between a cold smoky fire or a hot clean burning fire. Good topic, thanks

AJenson

So basically what your saying is to get out and burn the carbon every once in a while????

Spooler

Yeap, go out and work the dog out of it from time to time. The Cummins is like Mikey, it likes it, it like it.......