Sound like valve rattle when hot?

[BDaugherty]

OK. I just had my injectors tested and put new stock nozzles on them. I had very high return flow and couldn't start below 50 degrees before. With the new nozzles on my old bodies, I can start cold soaked down to 30 degrees (hasn't been cold enough to test any further). My rail pressure when cold is around 6,000 at idle. When the truck reaches operating temperature, rail pressure is only about 4500 psi at idle. Also, when the truck warms up a little, I get a sound like the valves rattling under light load. Under heavy load, it either goes away or can't be heard. The engine runs smooth, but you can hear the "valve clatter" noise mostly under light load and a little at idle or just off idle. I have checked the valves and they are all well within specs. Could this all be injector related? Or should I be looking at the FCA or some other component? The only other test that I have done is the verify that the rail relief valve is not leaking. I also pulled the valve cover and double checked all the injector hold down bolts. They were all tight after a week of driving.

 

[JJPage]

Curious as to who tested your injector bodies, and how? If the injector(s) body's integrity was sound, then the high return flow had to be caused by loose cross tubes (bad tip(s) would not cause high return), therefore the hard start.



As far as the rattle, it sounds like my 03 has always behaved, and is more pronounced without fuel additive, especially lack of 2 stroke oil. I am not trying to discount your concern, but it kind of sounds normal.



Glad it is starting good for you.



Jess

 

[cerberusiam]

Rail pressure on mine as measured by an ISSPRO gauge hangs right at 6300-6500 warm or cold at an idle. Wonder if the 1500 psi drop when warm is further leaking in the cross over tubes, normal, or just the way your gauge reads?



I am thinking like Jess that the tips were not the high return problem, rather, the cross over tubes are the prime suspect. Might try retorquing them again. Did you use any loctite on them when installing?



Do you work the truck hard? Mine always quiets down after several hundred miles of a good heavy pull and some extended EGT's. The rattle has gotten progressively louder as the miles rolled up. I figure it is just a combo on injector wear and tip wear on mine.



Have you re-phased the CP-3 to see if that makes a difference? Did somewhat on mine.

 

[AH64ID]

Rail pressure on mine as measured by an ISSPRO gauge hangs right at 6300-6500 warm or cold at an idle. Wonder if the 1500 psi drop when warm is further leaking in the cross over tubes, normal, or just the way your gauge reads?

03-04's idle lower when warm, sounds normal.



I agree, tips don't seem like they were the issue based on the reported issue.

 

[JJPage]

Rail pressure on mine as measured by an ISSPRO gauge hangs right at 6300-6500 warm or cold at an idle. Wonder if the 1500 psi drop when warm is further leaking in the cross over tubes, normal, or just the way your gauge reads?

My Dipricol RP reads about 6k when cold, after the engine is warm it will drop to just under 5k. Prior to re-torquing the cross tubes, it would drop to -3k.



I checked the torque on the tubes again late last fall, they were still right on. I guess they could have some corrosion from leaking, causing a "not so good" seal, but my return was less than 100 ml after the initial re-torque.

 

[LNaugle]

I would check the fuel supply tubes... the ends where they contact the injector can become " chromed" there and will cause psi problems. does it have a long hot start? if yes then i would check the supply tubes while engine hot first... then check the releif valve... remove banjo bolt and pull line off to the side then start engine and see iff any bubbles coming from inside have someone rev it up and observe... . watch out! the line will have fuel running out so do it fast or find somethin to put over it and direct it into a bucket. to check the fca simply rev motor to 1500 rpm or so and unplug it... this should make your rattle much louder... if so shows it is working. would be great if u could get a hold of a scanner to watch rail pressure. if can then start truck hot watching fuel psi then shut off and quickly turn key back on so u can observe psi. . if dropping to 0 immediately then u still have a fuel leak internally. hope this helps, i have to go back to work!

 

[TSPowell]

Have you re-phased the CP-3 to see if that makes a difference? Did somewhat on mine.

What does this mean? First time I've heard of this.

 

[JJPage]

What does this mean? First time I've heard of this.

Remove/disengage the CP3, turn the shaft 90/180*, put back in service. It just changes the rotation/pulsing of the pistons in the pump. Not real sure on the * as I have not done this, but not sure that's real important as long as it is in a different position. Maybe Cerb will chime in and tell us the correct *.

 

[cerberusiam]

Pull the gear loose on the CP-3 and turn the engine 20 degrees, tighten nut and test. Basically do it 3 times and if it doesn't change the sound thats not the problem



If the CP-s compression stroke is out of phase with the compression stroke on the engine the gear train cna have a rattle form the pressure waves. Just another noise a gear drive high pressure pump can generate.

 

[JJPage]

Thanks Cerb!



Here's a link to help you remove the CP3 access cover from the front of timing cover to get gear off the shaft.

Replacing your CP3 - DIY - Dodge Cummins Diesel Forum

 

[BDaugherty]

The reason I suspect injector problems causing the noise is that it started when I changed part of the injector. I'm reading rail psi with my TST R49 gauge. Before the nozzle swap, rail psi at idle was always below 5000. Now it's higher and drops off as the engine warms. Also, the noise is not normal fuel knock. It's more of a rattle like a gas engine would do under detonation conditions. The jumper tubes are original, but have no damage and have been rechecked for torque. That's a good tip about seeing how fast rail psi drops to zero after stopping the engine. How long should it take?

 

[JJPage]

03-04's idle lower when warm, sounds normal

Exactly, that why rp is lower when warm.

 

[Prairie Dog]

Exactly, that why rp is lower when warm.

My 03 idles at 750 hot or cold and never strays from it

 

[JJPage]

My 03 idles at 750 hot or cold and never strays from it

Could depend which flash is in the ECM?

 

[LNaugle]

rail psi shouldnt drop to 0. if it does then u will get longer than normal crank time because u have to build psi each time. my scanner always shows 25-50 psi after shutting truck off.

 

[LNaugle]

o... . and the cp3 pump feeds the rail and one would think that the pulses would be absorbed there since they are coming both directions into it. I dont under stand the phasing but if you are going to try that i recommend a new 18mm lock washer on final time. also you should check fuel psi at filter and then check psi with scanner at wide open throttle top gear loaded as much as possible... . psi should be up in 20,000 - 24,000 range.

 

[AH64ID]

My 03 idles at 750 hot or cold and never strays from it

Seems high, what do you read it with?

Could depend which flash is in the ECM?

Possible I suppose, but I all the 03-04 stuff I have seen shows them lower. The Smarty UDC demo SW is a 03-04 (not sure if its HO or SO), but you can see the low pressure on that demo.

rail psi shouldnt drop to 0. if it does then u will get longer than normal crank time because u have to build psi each time. my scanner always shows 25-50 psi after shutting truck off.

That's essentially 0, and is nothing more than a 26K psi gauge reading close to 0 psi. The gauges work from 0. 5-4. 5V, so 1V is 6500 psi, and 50 psi is 0. 0077V. You can see how it would be easy to have 25-50 psi showing. My truck shows about 20 psi when shut-off, but there isn't any pressure in the system. The trucks also need about 3K psi to fire, so the time required to go from 50 to 3000 is really no more than from 0 to 3000.

 

[cerberusiam]

rail psi shouldnt drop to 0. if it does then u will get longer than normal crank time because u have to build psi each time. my scanner always shows 25-50 psi after shutting truck off.

Rail pressure will always be at zero at start of cranking. Turn the key on and listen under the hood. That clicking is an injector in each bank cycling to bleed off pressure and any air in the system. The bleed off will continue until the starter is engaged then quit to build rail pressure.



The CP-3 bleeds any air and dead spots thru the lube circuit on crank start also. Should not have any residual pressure in the system nor should air be a problem. The system is solid at getting that done correctly.



The caveat is the ECU will NOT fire the injectors until pressure passes a certain point, generally believed to be about 3000 psi in the rail. If the CP-3 is weak, the PRV is weal, the injector sbypassing too much fuel, the cross over tubes leaking, rail pressure either will not build fast enough or enough and you get long crank start or no start.



Idle pressure seem to vary from 5k psi to 7k psi depending on the year of truck with the earlier models being on the low end of the scale. Normally 5k psi is the bottom end BUT gauges read differently, flashes are different, rail pressure sensors are different. The real test is look at it with a scanner to compare actual to demanded (IF you can rely on the RP sensor being correct). If it is demanding 5500 psi and all it is reading is 4500 psi there is a problem somewhere.



Rattle could very well be the lack of pressure causing the ECU to compensate with timing and duration throwing the spray pattern off. It could be the injector solenoids simply being worn and not reacting like the ECU expects. It could be excessive bypass in the injectors that is NOT out of spec.



The ECU will attempt to compensate quite a bit for lack rail pressure using readings from the RP sensor, MAP, rpms, ambient temp\pressure. However, the compensation almost always seems to introduce the potential for ignition rattle or other symptoms.



The comes a point at which turning UP the radio so you can't hear the noises while driving it is the only way to maintain your sanity. Otherwise, you will chase noises until you believe it is on the verge of sudden death. :-laf



If it idles decent, gets decent mileage, has good power, and does not make oil, drive it and worry about the other idiots on the road instead of your truck.

 

[LNaugle]

I understand and all i meant was trucks with a leak go to 0 immediatly. wasnt trying to mislead... just help out.

 

[AH64ID]

I understand and all i meant was trucks with a leak go to 0 immediatly. wasnt trying to mislead... just help out.

Even a truck without a leak will be at or near 0 within seconds of shutdown. My pressure goes from idle pressure to 24K-25K to near zero within 3-4 seconds of shutdown.