fuel knock?

[lb7lbz]

driving the other day pulling my trailer when the truck(01 dmax) made a clattering noise then went away. it did this several times throughout the day. went to work today same thing. checked balance rates with the predator had 2 injectors way off +5and+6 . put the lucas fuel treatment to it which brought numbers back in check +1to+4. however the clatter still comes and goes however only under load will not do it just revving it up. checked oil and its not making oil. is this what u guys refer to as fuel knock? if so guess its time for injectors anyone know where to get some for a good price?

[lb7lbz]

thought i would post an update to help u guys diagnose this one. just took truck for a ride un loaded. clattering came and went mostly getting up to speed. got to where i was going (6 miles) and shut it off. came out 5 min. later and started it up no prob. but it idled erratically, like a big surge. drove home same clattering on and off.checked balance rates +1 to +4 in park dosnt appear to be making oil. i also noticed when it makes the clattering sound the temp gauge goes down. what do u think?

[DmaxMaverick]

Is the SES lamp on? If so, what's the DTC? If not.......

You have: (pick one)

1. Fuel system air leak (usually fuel filter)
2. Tank of bad fuel
3. Water in fuel
4. Gasoline in fuel

[lb7lbz]

yes the ses is on but not related to that its for a tcm code and it was already on way before this started no other codes are present i check everyday. weird that the fuel filter would start leaking now i changed it 2 months ago. my fuel always comes from the same place well 90% of the time anyway, so safe to say thats not the problem.hhmmmm i"ll keep looking thanx

[Mark Rinker]

Which truck? How many miles on this set of injectors?

[lb7lbz]

its the 01 mark approx 150k. miles on this set of injectors. the erratic idle seems like the same symtom it had at 85k when they replaced the fpr.can anyone explain why the temp gauge would go down when it makes the clatter.also fueled up today at a different place and the clatter still comes and goes. the 06 is doing just fine made a trip to labrador last month with it haulin a 10k snowmobile trailer. cold up there 35 below

[Mark Rinker]

Temp gauge fluctuations usually indicate a head gasket leak. So does the fact that its a 2001 - first year production flaw.

Most pressurize the cooling system - you can see the bubbles in the overflow tank when idling. My '01 that did this would run fine, but puke coolant any time both thermostats were closed - i.e. when in cold weather towing into the wind.

My guess is somehow yours is getting coolant into a cylinder and that is the clatter. Do you see any white smoke at that time? Are you losing any coolant?

If not coolant loss, then probably a bad injector. Don't let it knock for very long, or under towing loads...or you'll risk burning a piston.

[lb7lbz]

so i drove the truck tonight unloaded 40 mile roundtrip.if i can keep my foot out of it and i mean way out(very slow acceleration from a stoplight) it dosnt clatter. any hill will almost certainly make it do it and temp. gauge drops sharply.dosnt seem to be down on power at all. coolant light would come on if it was down and i havnt seen any leakage anywhere its been parked.got to tow 150 miles tom. with the trailer on so we'll see how it goes. any suggestions on how to test this to see if coolant is getting in the cylinders?

[Mark Rinker]

It may simply be fuel related...one or more sprays no longer spraying.

I wouldn't tow anything until its fixed...unless you want a new engine.

[lb7lbz]

yet another update in the saga. drove it 150 miles today towing my trailer. clattering came and went as usual, however as day went on it seemed to do it less often. in fact i couldnt even make it do it. fueled up 5 miles from home at a different station which uses a 5% bio-blend. by the time i got home truck was idleing errattic again and clattering almost all the time even at idle. it even tripped the ses light for high voltage for the temp. cicuit.I know its not the fuel at that station because its also in my 06 with no problems. it seems to me the truck runs better with less fuel in the tank. does this make any sense? i wish i didnt have to drive it but my wife is carting around a newborn so i cant stick her in something i dont trust. what the f***** is going on with this truck?:confused: is there any way my predator can tell me by having it plugged in while driving? this is driving me nuts,:mad: it sounds like a dodge(gross):(

[DmaxMaverick]

Do you have a tune installed? If so, use your Predator to restore the factory tune. If not, do it anyway.

With the Predator, you can monitor several things relative to your issues. FRP regulator, fuel rail pressure, and the DTC's, of course. Watch for desired/actual figures. If the fuel pressure can't stabilize (the desired will be very close to the actual), it can cause several issues.

Also, try driving with the fuel cap loose. If the vent has failed closed, it can cause fuel starvation and outgassing, as well as exploit any potential fuel system leak. Either can cause noisy combustion events.

I think you can rule out the injectors (for now). It must be a fuel supply issue, or you'd have a bunch of specific DTC's hounding you. Injector problems are usually much less sporadic.

[lb7lbz]

removed tow tune and ran it stock and it still did it. also kept close eye on actual and commanded pressure and they were always very close to each other. set the cruise going up a hill with the trailer and it would clatter on and off but only for a split second and the funny thing was the truck lurched forward like it had more power. still idled erratic frp was howering around 35% most of the time but would change as u gave it throttle. could this be a frp problem? mine was replaced at 85k now the truck has 250k. i remember the truck surging before they replaced it but dont remember any noise. short run tom. 60 miles or so i'll run it with the fuel cap loose, however i dont think i'm that lucky lol:(

[lb7lbz]

drove it today with the predator out of it and the fuel cap loosened up and the noise is still there comes and goes. anyone want to buy a duramax?

[Mark Rinker]

More or less 'diesel clatter' is usually a function of timing advance.

Run the same tests, but watch main injection timing. Maybe a pump issue...especially considering the miles.

[lb7lbz]

will do what should main injection timing be?

[Mark Rinker]

Not sure on LB7 - maybe JK can chime in here...

[lb7lbz]

congrats to mark rinker i think u answered the million dollar question. as i drove today i watched main injection timing and sure enough it jumped up when thr truck got to clattering. the pilot injection numbers did as well. what exactly does this mean, i'm assuming the injection pump is on the way out?

[Mark Rinker]

Glad I can help.

It would be interesting to swap in another ECM, before assuming/tearing into the IP...maybe its a 10 cent resistor on a circuit board that's on its way out!!!

Sounds to me like the IP is doing what its being commanded to do...

[DmaxMaverick]

Glad I can help.

It would be interesting to swap in another ECM, before assuming/tearing into the IP...maybe its a 10 cent resistor on a circuit board that's on its way out!!!

Sounds to me like the IP is doing what its being commanded to do...

I agree with Mark. If the pump is able to develop and sustain pressure as commanded, it's doing its job. It sounds more like a regulation problem, either the regulator, an issue of communication, or something interfering with fuel flow.

It still sounds to me like an issue of air in the system. The timing will jump around, as you have seen on your Predator, as a cause OR effect. Air in the system will play havoc with fuel timing, and the fluctuations you are seeing are likely the result of the PCM attempting to compensate. From your description of the symptoms, the pump is not suspect. While it is, admittedly, possible the pump has failed, we've seen too often dealers throwing the wrong parts at a problem. It is more likely they'll fix an unknown problem accidentally while replacing the wrong part.

[lb7lbz]

ok sounds logical to me and the pump cant be gone as i'm still driving/towing with it every day. so where would you guys start? i have a friend with an 02 other than that same truck can i swap in his ecm? where would i look for air getting in the system? (already changed the filter). also just how bad is it to drive this truck it dosnt seem to bother it but i know it cant be good for it either.

[Mark Rinker]

IIRC, you should be able to swap 2002 LB7 ECMs between the trucks and see if the symptoms move to his truck. I would also check to make sure the new fuel filter is seated properly...

[lb7lbz]

his truck is an 02 mine is an 01. i changed the filter after the prob. started happening with the same results. will try ecm swap tom. if i can track him down. i'll let you know the results.

[lb7lbz]

is the ecm under the little cover on the rad. shroud?

[Mark Rinker]

Nope, the LB7 is under driver's side battery area, IIRC.

Find and trace two huge (~1" diameter) wiring harnesses from top/drivers side area headed down in that direction - you can't miss it. The ECM simply clips into place. After releasing it and pulling it upward into view, you can release the small modular connector first by rotating the rachet-style rack-in-pinion lock, then gently rock and pull the connector loose. Repeat same process for the large modular connector. The first time can be a bit awkward, but you'll do it in 60 seconds or less, once you've done it a few times.

Be careful with the connectors, until you see how they work. If they are gritty - try blowing them clean with compressed air before actuating. You want to keep the pins and sockets clean...

Reverse the process for reinstalling, i.e. big connector first, small connector second, snap back into holder.

[jbplock]

Mdrag's Fast Idle Install instructions (http://www.kennedydiesel.com/docs/HIGH%20IDLE%20INSTALL%20FINAL.htm) listed in the Kennedy Diesel (http://www.kennedydiesel.com/) Tech Tips section has some good pics of the ECM location.

[Mark Rinker]

Thanks for the link - I couldn't remember exactly where the LB7 ECM was. LB7LBZ, it appears you were looking at the TCM location, not ECM.

Good luck - looking forward to the results of your tests!

[lb7lbz]

havnt got to smap ecms yet but truck got worse today after i hammered on it with the predator on setting five. immediatly after it was clattering all the time. drove it straight home and parked it. idle is high and fluctuates truck shifts funny as well. when i pump up the pump on top of the fuel filter(w truck off) then start it she runs ok for a few seconds then goes back to clattering.I'll prob. be working on this in my driveway, any suggestions?

[Mark Rinker]

Remember to remove the Predator, before swapping ECMs...

[lb7lbz]

the knock went away for several thousand miles after i replaced the cp3 pump and the fpr as well as several dry rotted or heat cracked fuel hoses. well now its back on and off errattic idle to go w it. i feel there is air getting in the fuel system somewhere but am not sure where. checked balance rates with the predator and all but one injector in spec. one is running around a -5 reading. could this clattering b from the injector? could rotted metal fuel lines be drawing air? please help this is driving me nuts i just had the tranny rebuilt and am putting in a suncoast valvebody on wed. now i have this to deal with as well. any ideas or someone out there who has been through this?

[Mark Rinker]

Clatter could be from that injector - any white smoke when clattering?

[lb7lbz]

hey mark and anyone else who chimed in to try to help me i figured it out today and it was the stupidest thing.i was watching my predator while driving particually the engine coolant temp. when the truck was making the noise it would read-30 or something crazy up until now i had only watched the stock temp. gauge drop.long story short bad connection on the ect temp. sensor. unplug it sometime on a running truck and shazaaam u got a cummins under the hood. fuel timing goes crazy it really makes a racket. all is good now i have a quiet duramax again. hope this helps anyone who has an intermittent clatter noise.

[Mark Rinker]

Where is this temp sensor located?

[lb7lbz]

found the answer today. while watching real time data on the predator noticed when the truck made the clatter ect(engine coolant temp.) went from 160 degrees to -30. as i had said on previos posts i watched temp gauge in the truck go down but had just never monitored it with the predator. bad connection on the connector at the switch. pull the plug on a running dmax and shazaam you will have a clattery cummins under the hood. it alters injection timing and also appears to somehow get air in the fuel system as i had to reprime after i figured it out. all better now. thanks for the help.