Low pressure on rail

vilonek · 09-30-2024, 09:01 AM

Hello, I am solving a problem with BMW F15 30d where the car does not want to start due to low pressure in the rail.
The high pressure pump went out in the vehicle. After replacing the pump, injectors and cleaning the fuel system, the vehicle ran for a few seconds and then won't start.
The new pump and injectors were put to the test and the vehicle was tested with parts from another car that work, but the vehicle still behaves the same. The test of the new pump and injectors was in order.
The low-pressure pump supplies diesel at approx. 4.2 bar, but at start-up there is approx. 80 bar in the rail. A new pressure regulator on the rail was also given. Tried another rail from a working vehicle.
I don't know what could be wrong.
Thank you very much for any help.

m4forum · 09-30-2024, 02:12 PM

did you check pressure on low pressure side to make sure there is no restriction there? I suggest check the whole system starting from fuel tank. See if ISTA has some ABL that can be used.

vilonek · 10-03-2024, 02:18 AM

Hi I did check it only by ISTA and it looks good. When I disconnected return line of fuel, pressure was more than 6 bar.
There is what ISTA show me during start.

Name: IMG_8781.jpg
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Name: IMG_8781.jpg
Views: 46
Size: 279.6 KB

m4forum · 10-03-2024, 06:57 AM

sorry but cannot see the color on graph.

why did you disconnect return line?

vilonek · 10-03-2024, 09:22 AM

I disconnected return line only to check that low pressure rise up.
I try to make better picture later.

vilonek · 10-04-2024, 11:29 AM

On this graph is only
rail pressure - black
Low fuel pressure- light blue
Fuel injection volume released by DDE dark green

m4forum · 10-05-2024, 05:44 AM

was the new pump tested. does the new pump was a pressure regulator that could be not working?

vilonek · 10-05-2024, 01:05 PM

Yes, the new pump was tested at Bosch with regulator and no problem was found

vilonek · 11-08-2024, 09:36 AM

Update: when I Connect rail regulator and quantity regulator on HPFP to external power supply and close them the car start. But to pressure is so high that it shut down.
That’s mean DDE is opening regulators.
Does some one know why? I want to try dde-EWS adjustment in insta (that’s work on older models) but it’s not supported.

09-30-2024, 09:01 AM	#1
vilonek New Member 0 Rep 6 Posts Drives: BMW X5 40d E70 Join Date: Sep 2024 Location: Czechia iTrader: (0)	Low pressure on rail Hello, I am solving a problem with BMW F15 30d where the car does not want to start due to low pressure in the rail. The high pressure pump went out in the vehicle. After replacing the pump, injectors and cleaning the fuel system, the vehicle ran for a few seconds and then won't start. The new pump and injectors were put to the test and the vehicle was tested with parts from another car that work, but the vehicle still behaves the same. The test of the new pump and injectors was in order. The low-pressure pump supplies diesel at approx. 4.2 bar, but at start-up there is approx. 80 bar in the rail. A new pressure regulator on the rail was also given. Tried another rail from a working vehicle. I don't know what could be wrong. Thank you very much for any help. Last edited by vilonek; 09-30-2024 at 10:51 AM.. Reason: Adding model of car
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09-30-2024, 02:12 PM	#2
m4forum Lieutenant 150 Rep 528 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	did you check pressure on low pressure side to make sure there is no restriction there? I suggest check the whole system starting from fuel tank. See if ISTA has some ABL that can be used.
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10-03-2024, 02:18 AM	#3
vilonek New Member 0 Rep 6 Posts Drives: BMW X5 40d E70 Join Date: Sep 2024 Location: Czechia iTrader: (0)	Hi I did check it only by ISTA and it looks good. When I disconnected return line of fuel, pressure was more than 6 bar. There is what ISTA show me during start. Last edited by vilonek; 10-03-2024 at 02:45 AM..
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10-03-2024, 06:57 AM	#4
m4forum Lieutenant 150 Rep 528 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	sorry but cannot see the color on graph. why did you disconnect return line?
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10-03-2024, 09:22 AM	#5
vilonek New Member 0 Rep 6 Posts Drives: BMW X5 40d E70 Join Date: Sep 2024 Location: Czechia iTrader: (0)	I disconnected return line only to check that low pressure rise up. I try to make better picture later. Attached Images
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Low pressure on rail

10-04-2024, 11:29 AM	#6
vilonek New Member 0 Rep 6 Posts Drives: BMW X5 40d E70 Join Date: Sep 2024 Location: Czechia iTrader: (0)	ISTA rail pressure test On this graph is only rail pressure - black Low fuel pressure- light blue Fuel injection volume released by DDE dark green Attached Images
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10-05-2024, 05:44 AM	#7
m4forum Lieutenant 150 Rep 528 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	was the new pump tested. does the new pump was a pressure regulator that could be not working?
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10-05-2024, 01:05 PM	#8
vilonek New Member 0 Rep 6 Posts Drives: BMW X5 40d E70 Join Date: Sep 2024 Location: Czechia iTrader: (0)	Yes, the new pump was tested at Bosch with regulator and no problem was found
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11-08-2024, 09:36 AM	#9
vilonek New Member 0 Rep 6 Posts Drives: BMW X5 40d E70 Join Date: Sep 2024 Location: Czechia iTrader: (0)	Update: when I Connect rail regulator and quantity regulator on HPFP to external power supply and close them the car start. But to pressure is so high that it shut down. That’s mean DDE is opening regulators. Does some one know why? I want to try dde-EWS adjustment in insta (that’s work on older models) but it’s not supported.
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