backfire when grid heater cycles

[Semicrazy]

Just to give a better idea of the combustion process in a stnadard DI engine under standard timing, taken from Int Comb Fundamentals by J. Heywood.



"Figure 10-4 shows a cumbustion sequence from the DI engine with swirl. The inner circle corresponds to the deep bowl in the piston crown, the outer cicle to the cylinder liner. THe fuel sprays first appear at -13deg (btdc). At -7deg (btdc) they have reached the wall of the bowl; the tips of the sprays have been deflected slightly by the anticlockwise swirl. The frame at -3deg (btdc) shows the first ignition. Bright luminous flame zones are visable , one on each spray. Out by the bowl walls, where fuel vapor has been blown around by the swirl, larger greenish burning regions indicating the presence of premixed flame can be seen. The fuel downstream of each spray is next to ignite, buring yellow-white due to the soot formed by the richer mixture. Flame propagation back to the injector follows extremely rapidly and at tdc the bowl is filled with flame. At 5deg (atdc) the flame spreads out over the piston crown toward the cylinder wall due to combution -produced gas expansion and the reverese squish flow. The brown regions, 13deg (atdc), are soot-laden fuel-rich mixture originating from the fuel which impinges on the wall. The last frame, 30deg (atdc), shows the gradual diminution of the soot-particle-laden regions as they mix with the excess air and burn up. The last dull-red flame visible on the fiulm is at about 75deg (atdc), well into the expansion (power) stroke. "





To me it sounds like the problem is incorrect timing, maybe the timing is slightly delayed, combined with the cold engine engine quencing the heat of the combustion causing incomplete combustion that may or may not cause the cylinder to missfire (thud or knock), and the combustion may still be happening when the exhaust valve opens causing you to hear it out the exhaust.

I do not think it would be advanced timing for this problem, becuase then the cylinder pressures are greatly increased which can help combustion (and power) but can lead to knock (rattle) easily. Most of the older injection pumps have a mechanical timing advance for cold weather.

 

[RMalone]

It is almost certainly a timeing issue, I personally have never seen it without an aftermarket box that advances timeing. But obviously the poster has. To the original poster you have to understand that all threads end up with discussions that veer from the original topic. As to the comment that "I never should have posted in the first place" very untrue!! If you have a question ask, you might not get a good answer but then a again you may, ya gotta try.



I think I know the exact situation you are experiencing, I just haven't had it happen with no box attached so I am not sure how to help, I have had it happen with no codes and with codes, either way I am convinced it has to do with timeing. As long as the thread stays active long enough you should get a satisfactory answer.

 

[CBrahs]

I must appologize for seeming a little frustrated. Have not slept well in over a week and getting online to check emails and such @ 3am and having to work a 10 hour day gets on ones nerves. I think I got my answer and it is a timing issue. It only happens once in a while and only does it once when it does during a grid heater cycle in the mornings or if it has sat all day long in COLD weather. It is going to the shop here in a few days as soon as I can let it go and hitch rides to work. Will have them look at it then. Will post what they say if anything at all. I already told the tech that it needed to stay overnight and I wanted to be there when they started it in the morning so I can show him what i am doing when it happens. He wants the star scan on when we do it so he can capture what is going on. Again, sorry if I was an ***** WHOLEEEEEEEEE.

 

[RMalone]

Perfect, I am glad you will be there when they "try to make it happen" if you weren't I have no doubt that "it didn't happen while we had it" would be your answer. Let us know what happens and for what it's worth I don't think it is hurting the truck one bit, if it happened continuously then perhaps. One thing I never ironed out, are you hearing a loud bang like a true gasser backfire or just the slight stumble/pop? I have been referring to the latter, if it is a big bang then I would be concerned. Hope it works out, and again keep us posted on your findings.

 

[DerekW]

Hey original poster and a few others I am not sure what you mean exaclty is going on but see if my problem matches yours becuase I honestly don't know enough about the heater grid in the a diesel but have other automotive experience in the way of repairs including electrical stuff. On my 04. 5 CR I have a straight pipe so I can tell how the engine is running from inside my house even (and so can the neighbors which has lead to the police coming by a fews time just becuase of the exhaust noise but another story). I only have this problem on very cold mornings. My truck will be running nice and smooth then die like for a second (like crank is just coasting making no power) and spray no fuel. I have personally spent alot of time with this problem. My problem has something to do with the crank sensor. The truck loses signal for a seconds so the computer is blind folded and doesn't know when to fire. So the result is the engine does not fire until it gets the signal back then since the engine is extremely low on engine RPM the engine is under a load to build back the normal Idle rpm. This load makes the truck spray heavy and make a burping (loud echoing in the neighborhood for a short period of time almost like I stabbed the gas for a second while it was dying and let off) sound (remember I am straight pipe). I have installed the banks 6 gun with speedloader option. this kit required the wiring harness to be installed on the vehicle including the crank and cam sensors that affect timing. Before I experienced this for the first time I had power washed the truck after fourwheeling it. I power washed the engine bay from all angles as well. the day after i power washed it I picked up the truck from the dealer and it "burpped" and threw a code. The tech came out and cleared it and said the code mentioned something about the crank sensor. the truck burpped really bad again 2 days later threw the same code and I had it cleared at the dealer and blammed the tech to get it cleared for free. But between the time I took it to the dealer and the time I brought it back the 2nd time the truck did burp alot on cold mornings but didn't throw a code. Also I noticed the truck would do it when I put it in gear (auto) or while in neutral and playyed with throttle (I am the kind of guy who likes throttle repsonse and play like it has good throttle response). Also I would only throw a code when the truck brupped really bad. This all lead me to beleive I had a problem with a wiring harness at the cranksensor. I contacted banks and they told me to try disconnecting the 6 gun wiring harness at the crank sensor (CKS) and plug the factory wiring harness directly to the CKS and run it for a week. if I had no more problem I was to order a new wiring harness for the 6 gun. If I still had the problem, my problem was else where on the crank sensor wiring or the sensor itself. So I wired the truck back up like I was told and I didn't have the problem any more for that week. then I got a new wiring harness for the 6 gun and installed it. right after I installed it the truck Burpped backing down the driveway and needless to say I was ****** cuz the cam sensor is such a ****ing ***** to get to that its not even funny and I wasted my time ****ing with it. I wish it came to my mind though that it wasn't cold the week I tested with the crank hooked up like it came from the factory. It was hot as crap that week like 60 degree so I shouldn't have changed this harness but it did make me more comfortable in the long run while search for the problem



A FEW DAYS LATER I DECIDED TO USE CLOSE TO 30 ZIP TIES (I KNOW THIS CUZ I JUST PICKED THEM UP OUT OF THE SAND IN THE BACKYARD YESTURDAY) AND ZIP TIE THE WIRING HARNESSES ON THE TRUCK SO THEY DIDN'T MOVE WHILE DRIVING. tHIS INCLUDED THE FACTORY WIRING HARNESSES AND THE BANKS WIRING HARNESSES. I WANTED ALL THE WIRING TO BE MOUNTED AS SOLID AS POSSIBLE. OVER THE NEXT WEEK I NOTICED A HUGE GAIN IN COLD WEATHER WHERE I EXPERIENCED A PROBLEM WITH THE CRANKSENSOR IN THE PAST. EVERY CONDITION I HAD A PROBLEM IN WAS ALMOST GONE BUT NOT ALL THE WAY. My next thing to do will be to try to figure out if I can hook up my superchips DPI and use the data logger it comes with to monitor the crank sensor voltage during one of these events. I think what I will find will tell me for sure it is something with the CKS wiring, CKS itself, a problem else where. Mean time my truck still does throw the a code for the CKS immediately after a "Burp" but sometimes it gets by without a burp. Also sometimes when the truck is idling or is in drive no foot on gas going down the driveway and coasting but accellerating to 10 mph topspeed no foot on gas (engine is under small load) the truck will experience a burp instance but without the burp sound cuz the truck will cuz off. I also do get the burps at high idle in neutral. Please tell me if this is the same problem you guy have if it is I will elaborate on more on my testing and things that help me make it better. My neck hurts too bad right now from a trampoline accident where I was stupid enough to be jump on the trampoline using my upper back and landed on my head once.

 

[CBrahs]

Derek,

You wrote a friggen novel!! LOL !! The noise that I am hearing only happens when i have manual high idle turned on (1100 RPM range). It is like when the grid heater shuts off it has a POP noise that can be heard @ the rear of the truck. Kind of loud but one single POP. It usually only does it once during this period but has giving me another POP noise a few cycles later(of the grid heater). It only happens when cold. I don't know, maybe MURPHY and his little brother are messing with me but I tell ya if I ever get ahold of him I am going to castrate both of them!! LOL !!

 

[dieselpwred]

Derek



My Truck Use To Do The Same Thing Pop Noise At Idle. It Did It For A Month Or Two Cold Or Hot And Always Gave Me A Cks Code. After Moving Wires Around The Problem Went Away. Hasn't Come Back In 2 Months. Problem Maybe In The Harness.

 

[RMalone]

Dereks problem sounds like the issues I have had, though mine werent as bad as he describes, I saw it with both 6-gun and TST (not together). CBrahs, sounds like you have a more violent episode happening, I'm interested to know what you come up with.