undulating sound under acceleration when cold, gauges steady

barley00 · **Posted:** Mon Oct 05, 2015 12:20 pm

Adding to the list of recent 05 CRD issues, This might have something to do with rough start issue but it's shown up since. When accelerating out of my road in the mornings when engine still cold there is an undulating sound coming from under the hood, meanwhile, rpms, boost and fuel rail readings on Torque Pro are steady. After warm up the undulating sound goes away. Any ideas? Thanks a lot.

Yeti · **Posted:** Tue Oct 06, 2015 5:57 pm

I have had an issue like this with a defective mprop , right pressure , but not right quantity

barley00 · **Posted:** Tue Oct 06, 2015 7:10 pm

Sorry you lost me on mprop...?

Yeti · **Posted:** Wed Oct 07, 2015 4:17 am

it's the fuel qunatity solenoid , attached in the back of the High pressure pump , my start to do it only when cold , and after some time when is warm too , you can hear near the 2000 rpm with static foot on the gas , low load

barley00 · **Posted:** Tue Oct 13, 2015 5:33 pm

Problem solved with new fuel filter. Filter was not overdue and it looked clean but with running homemade b.d. one never knows...

jrsavoie · **Posted:** Tue Oct 13, 2015 8:59 pm

barley00 wrote:

Problem solved with new fuel filter. Filter was not overdue and it looked clean but with running homemade b.d. one never knows...

Are you processing bio-diesel or just filtering the oil?

barley00 · **Posted:** Tue Oct 13, 2015 9:46 pm

processing

barley00 · **Posted:** Wed Nov 18, 2015 11:40 am

I take that back, problem is not solved, it's back, might have to look into mprop.

flash7210 · **Posted:** Thu Nov 19, 2015 2:14 pm

I'm not sure that your problem is the MPROP but its really hard to tell based on you description.
Usually, a problem with the MPROP will throw a code.

Here are some tests you can try:
1. unplug the MPROP and take it for a drive. It will drive but will be in limp mode with limited power. If the problem seems to go away then it might actually be the MPROP.
2. plug it back in, clear the code, and start the engine. Wiggle the connector going into the MPROP. If the engine stumbles and sputters while you are wiggling it then the problem is the wiring harness connector.
3. Do voltage and resistance checks of the MPROP. With key-on engine-off the MPROP connector should have 12v at one wire and ~3v at the other. And if you can, test the resistance through the MPROP solenoid. Should be about 30-80 ohms or so, but its kinda hard to do without some jumper wires that will connect into the solenoid.

When using TorquePro, the fuel rail pressure display is not a direct reading of the fuel rail pressure sensor. It more directly correlates to the fuel pressure solenoid valve at the end of the fuel rail.
If you want to see for yourself, with TorquePro running and engine at idle, disconnect the fuel rail pressure sensor and see what pressure TorquePro displays.
I installed a AutoMeter fuel rail pressure gauge so I could get a direct read of the fuel rail pressure sensor.

barley00 · **Posted:** Fri Nov 20, 2015 2:09 pm

Hmmm, yeah not getting any codes. It's a very subtle undulating sound (wahwahwahwahwah) with no other side effects like bucking. Only happens when the engine is cold. I'll try your suggestions asap. Thanks.

Yeti · **Posted:** Fri Nov 20, 2015 6:11 pm

mmmmm this do not seem fuel , you hear at every range or in partcular rpm range ?

mass-hole · **Posted:** Fri Nov 20, 2015 10:09 pm

Is it speed or rpm related? Does the undulating speed up or slow down with either engine or driveline speed?

barley00 · **Posted:** Sun Nov 22, 2015 10:59 am

I only hear it when accelerating, at any rpm, when the engine is cold. once the engine warms up I can't hear it anymore. Going to play around with mprop today.

Yeti · **Posted:** Sun Nov 22, 2015 11:28 am

have you worked with the air box in this days ? if yes check the grommet where they attach , if it's not well fixed can produce a resonance in cold condition , but when is warm the air inlet hose become soft and allow the airbox to sit in right position .

if you never touch it do not consider this

WWDiesel · **Posted:** Sun Nov 22, 2015 11:31 am

Just a thought, have you checked your fan clutch?? :idea:

barley00 · **Posted:** Sun Nov 22, 2015 11:35 am

Just went through flash7210's tests suggested above. Mprop tests out ok, here are the details: 1' the sound did not go away with the mprop unplugged and driving although it was more difficult to tell because it was more difficult to get the rpm's up, therefore engine noise, without turbo. 2' wiggling the connector didn't make a difference. 3' voltage tested out, didn't test resistance though.

I will check the airbox as I have been messing around with it recently...

Fan clutch should be good, recently replaced.

rankom · **Posted:** Sun Nov 22, 2015 12:51 pm

i say , remove serpentine belt and see if nose goes away

barley00 · **Posted:** Tue Dec 01, 2015 7:35 pm

finding it hard to believe noone else has had this problem, bumping to the top in hopes to get some more wisdom...

undulating sound under acceleration when cold, gauges steady

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