In Limp Mode constantly

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In Limp Mode constantly

Postby Tritonx2 on Sun Jun 05, 2022 8:13 am

Hi,
Great forum!,
Ive got a ML 3.2 diesel 2007, that went into Limp Mode after towing a 1ton trailer, Check Engine light came on and wouldn't rev over 2k rpm. after a mechanic put a scan tool on it, it came up as faulty (or stuck) SCV.
Next day it was ok at first, check engine light not on, but CEL and Limp mode happened again while towing, after researching this forum and on the net, I sourced a new OEM SCV from Repco and fitted it, still had the problem.
After an auto sparky put the scan tool on again it was still showing Stuck SCV, he did a fuel pressure test and said it was about a third of what it should be from memory it was reading 11,000PSI. He suggested changing the fuel filter first which i did, it was filthy inside the white sensor on the bottom of the filter, (might have been 25k or more since filter changed :oops: ).
Still got the Limp mode problem, what would my next step be?, take it to a dealer for this MUTT3 recalibration thing of the ECU/SCV I read about?
Put 300ml of Castrol Activ FC rated 2T in a full tank?, but cant really drive it properly in Limp Mode?
Cheers
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Re: In Limp Mode constantly

Postby RHKTriton on Sun Jun 05, 2022 10:44 am

If your fuel filter was that contaminated it may be possible that the strainer on the fuel pump inlet may be clogged.

With the age of the vehicle it may be worth checking the EGR valve, MAP and other sensors.
Don't let the b'strds get you down!!
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Re: In Limp Mode constantly

Postby Tritonx2 on Tue Jun 07, 2022 2:15 pm

Thanks RHK,
I took it to Diesel specialist, they scanned it and it still shows Stuck Suction Control Valve, as I knew it still would, its still in Limp Mode, they think the SCV could be installed incorrectly, maybe a pinched O-ring, I'm sure I didnt pinch it, as I was particularly careful about that.
However the new o-ring looked a little too big, straight out of the sealed packet, so im going to remove the new SCV and re-install, put 300ml of 2T in a full tank, and see what happens.
Mechanic said if not the SCV, could be faulty Fuel Rail Pressure Sensor, which im thinking is more likely, but ruling out SCV first.
cheers
Tritonx2
 
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Re: In Limp Mode constantly

Postby Tritonx2 on Tue Jun 07, 2022 5:18 pm

For anyone else replacing these SCV's make sure you oil both o-rings, I only oiled the larger one first time.
When I pulled the SCV out the smaller o-ring had shredded a bit all-around, I put the old-o-ring on, as it looked fine, put it back together, but doing that didn't fix the limp mode.
Back to the mechanic.
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Re: In Limp Mode constantly

Postby RHKTriton on Mon Jun 13, 2022 10:38 am

When you say the small O ring was shredded, did you make sure no bits were left in the pump.

As I've probably stated before somewhere, with the extra fine tolerances involved, you gotta treat the job like brain surgery when working around the Diesel injection system, ie. super clean.
Don't let the b'strds get you down!!
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Re: In Limp Mode constantly

Postby WUNSIE on Mon Jun 13, 2022 6:41 pm

RHKTriton wrote:When you say the small O ring was shredded, did you make sure no bits were left in the pump.

As I've probably stated before somewhere, with the extra fine tolerances involved, you gotta treat the job like brain surgery when working around the Diesel injection system, ie. super clean.


Bloody oath mate got it in one ;) , even a human hair under 20,000 psi will score a precision bore,
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Re: In Limp Mode constantly

Postby Tritonx2 on Sat Jul 02, 2022 2:44 pm

A follow up on the problem,
after taking it to the mechanic, still in limp mode and throwing the SCV code, they took out the new SCV, and put in another one they had lying around, it run ok for a few minutes then started running really rough, but it did throw up a ECU not reading SCV code correctly, needs to re-learn the new SCV.
So they put the new SCV back in, and got the ECU to re-learn it, and its running fine now, fixed for $360.
But it is missing a bit around 2000rpm, they suspect a dodgy injector.
Also had them do a rego check, needs a new Tail-shaft centre bearing and uni-joint, so thats next on the list to learn about and fix myself.
cheers.
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Re: In Limp Mode constantly

Postby RHKTriton on Sun Jul 03, 2022 9:20 am

Good to see things are pointing in the right direction.

Vehicles love eating your money. Lol
Don't let the b'strds get you down!!
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