backfire when grid heater cycles

[CBrahs]

My truck is backfiring when the grid heater cycles. It starts to do it more often after it has been idling for a few minutes. I start the truck, watch oil psi go up and stabilize and then kick on the manual high idle (1100 rpm), watch the truck for a few minutes in the driveway and can hear the grid heater cycle, when it shuts off an the volt meter goes back up, the engine backfires once. sounds like a compressor stahl on a turbine. Any suggestions?

 

[Prairie Dog]

Could it be the a/c compressor kicking in because the defrost is on? Their famous for being loud!

 

[JRD]

mine does the same thing. I cant figure out why... Id describe mine more as a stutter or something, only when its cold, and only at 1100 RPM warming up in the moring. But it doesnt do it everytime. More like 1 maybe 2 times a week.

 

[NUKEMAN]

Could it be the a/c compressor kicking in because the defrost is on? Their famous for being loud!

Unless you hear it at the tailpipe, I would have to go with the compressor kicking over. They are pretty loud and when you describe it as a "sounds like a compressor stahl on a turbine", that's what I'm thinking. Try starting it with all of your HVAC completely off and see if you still hear it. Just a thought.

 

[CBrahs]

it does not matter if a/c is on or off. can hear it at the tail pipe. I was standing right at the pipe the other morning and wanted to hear it from back there and it is Definately from the motor. Mine is doing the same thing as JRD, only happens a few times a week and only when I have it kicked up to 1100RPM.

 

[JHardwick]

it does not matter if a/c is on or off.

Remember that any "defrost" setting will enage the A/C, regardless of the temperature setting.

 

[MCummings]

It's probably not backfiring, but not firing on all the cylinders.



When teh Grids kick back off, the air coming into the cylinders is very cold, and teh fuel cannot competely burn, resulting in a misfire of that cylinder. Should sound like a dull thud from the other cylinders taking up the load, and should sound like a lack of noise for a second, and then a good poof when the next cylinder fires harder than normal.



This should all be compbined with white/gray smoke.





Merrick

 

[Msilbernagel]

I have an 04. 5, and when the grid heaters cycle off, the reduction in load on the alternator causes a brief jump in RPM, followed immediately by a return to standard idle (650RPM?). It sounds like a very short duration poke at the throttle as things adjust. At least, that's my explanation... as there is a lot of current NOT being drawn from the alternator, all of the sudden.



Any chance this is what you're hearing?



Mark

 

[CBrahs]

It's probably not backfiring, but not firing on all the cylinders.



When teh Grids kick back off, the air coming into the cylinders is very cold, and teh fuel cannot competely burn, resulting in a misfire of that cylinder. Should sound like a dull thud from the other cylinders taking up the load, and should sound like a lack of noise for a second, and then a good poof when the next cylinder fires harder than normal.



This should all be compbined with white/gray smoke.





Merrick

Merrick,

I don't get any smoke at all following the pop noise.

 

[foolkiller]

i'm so glad you posted the thread CBrahs. i kept forgetting to. my truck does the same thing. i suspected, as others have already mentioned, the difference in heat and the sudden jolt to the electrical sys... ... . but i don't think it will hurt anything... just drive us mad.



i disconnected the grids on my 99 with zero problems even in COLD weather. i think i might try it again.



easy thing to try and hook back up if you find yourself in north dakota in february.



Msilbernagel's description best fits what i'm seeing... ... no smoke by the way.



jeff

 

[jelag]

Guys... a backfire in a diesel can cause excessive damage..... but its almost impossible because fuel has to be introduced into the combustion chamber before the piston reaches TDC... all diesels fire after TDC and the fuel rushing into the combustions and the ignition of this fuel that usually gives the diesel its noted noise... from piston slap & rod pounding etc... . so the injection we see on our engines is started after TDC and the piston is on the way down... 2 or 3 short pulses of fuel allow for a much quieter engine... .



If your ECM is making a mistake and firing an injector while the piston is moving up... its a very bad shock to the piston and rod... if you have any idea this is happening I'd take it in... I might even tow it in... as I've seen this damage first hand...



In the past we've seen timing devices that advance the timing... . in some cases it 2 or 3 * and I've personally read about these and can only believe that the piston is like 5 or 6 * after TDC and the advance is still firing the injection after TDC... . or what the manufacture is calling advance on a diesel is really retarding the timing in relation to a gas engine... .



If I'm wrong here someone please correct me... after all my fuels and engine class was almost 40 years ago... . but there is a very big difference in fuels and timing... and with gasoline you increase the octane... it burns slower... when you increase the cetane of diesel it burns faster if I remember correctly... so the piston is higher in the stroke and can release more power to the piston and crank... Basic and second year fuels and engines class here...

 

[RMalone]

Jelag is right on, it is a timeing issue, my truck will throw a crank sensor code (0036) everytime if the grid is heating and the truck is on high idle, this only happens when the TST is turned on though. Interestingly I haven't thrown the code with the TST since I installed the Smarty (I still use the TST for timeing).

 

[CBrahs]

It has never thrown a code. It pops once and usually that is it.

 

[foolkiller]

if i remember correctly. you can disconnect just one grid... ... anyone?

 

[cojhl2]

Just to make sure our terminology is correct,, a "backfire" is when the combustion somehow takes place in the input stream.



Impossible with a compression ignition (CI) engine.



What is being described here could well be a problem, but the symptom is not a backfire. .



Just wanna keep our semantics correct.

 

[cojhl2]

Just to make sure our terminology is correct,, a "backfire" is when the combustion somehow takes place in the input stream.



Impossible with a compression ignition (CI) engine.



What is being described here could well be a problem, but the symptom is not a backfire. .



Just wanna keep our semantics correct.

What was I thinkin??? Of course in our vernacular a "backfire" is also the sound caused by the explosion of unburned gases in the exhaust stream.

 

[CBrahs]

What was I thinkin??? Of course in our vernacular a "backfire" is also the sound caused by the explosion of unburned gases in the exhaust stream.

Hence sounding like a compressor stahl on a turbine! It may not be a backfire, but that is what it sounds like. It does not happen all the time, only when it has had a cold soak of several hours, grid heater cycles and when the volt meter climbs back to normal range it makes a "pop"/"backfire" noise simular to a compressor stahl on a turbo-jet engine.

 

[jelag]

A true backfire is when the combustion process happens before the timed event is set to happen... on a car, it could happen with the intake valve still open, and fire and flame would backfire into the intake stream... on a spark ignition engine its possible to fire the combustion chamber with the valve open...



on a mechanical timed diesel, its impossible... on an electrical fired injection system its possible to fire the chamber early... . this is detnation in a diesel (sp) and if it happens before TDC does a lot of damage. . by now all of you have seen the Rod demo at the dodge dealer... . right. . the rod out of a cummins and the rod out of the Duramax and Ford... well the cummins rod is a real diesel engine rod designed to handle some pounding... and the closer to TDC that the injection occurs the more power that is released to the piston and crankshaft as that high compression is contained in a much smaller area...



Hope this helps...



Jim

 

[CBrahs]

maybe I should not have used "backfire" in the title but that is the only way I could get anyone to respond and now I am getting definitions on "backfire" I know what it is and how it happens and the damage it can cause. I posted a thread a few weeks ago about the same thing but used the word "popping" in the title and got NO responses. I guess I should not have even posted it to begin with. I am just trying to see if anyone else is/was having the same "sound" during manual high idle and grid heater cycling on and off.



At this point it would be safe to assume that the definition of backfire has been beat to death. Now, if someone could let me know if you are having or have had and what was done about it please!?!?

 

[DPKetchum]

Been in a friends 03 that when started,dropped in drive and just pulling off from a stop a loud pop/backfire what have you(like a older carbed V8 popping back through the intake) would occur and a quick lag/miss and then ran ok. Did it 6 or so times in the first 5k when new and then never again. Diffiently a fuel explosion. It was not the ac compresser.