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Discussion Starter · #1 · (Edited)
Hi,

i have an outstanding issue with my nitro's fuel pressure.

The engine does not rev more than 3.000/min and we assume fuel pressure. As the genuine lift pump is no more available and if, then it's used garbage.

So i decided to order a Carter fuel pump from the Dodge Ram. I am not sure if this was a good decision,because the Carter has a pressure relief valve which limits pressure to 350 kPa equal 50 psi.

But the nitro OEM Diesel pump powers up to 4 bars equal 58 psi. My idea is to remove the pressure relief valve which directs exceeding pressure to the return line (see picture below) , but i am not sure how the nitro controls lift tank pump activity.

Arm Yellow Font Engineering Wrist


On MAR the pump is active some 10 seconds and then returns to sleep mode. I do not know if the engine is running ift the pump is controlled by the pressure valve of the rail or any other signal.

Some people say, the lift pump is continously operated and never in on-off-on-off mode. Might be possible, because 9 of ten failed lift pumps are diesel lift pumps.

My Question is ...

Does anbody know more details how the pump is controlled? By Interval? Or continous mode?

Thank You

Fritz
 
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I'm 99,9% sure the pump works all the time, just like almost any other diesel/petrol car.
Also, your pump has 4 wire connector: 2 grounds, level sensor output and only 1 "+". If it is on on/off mode the level sensor would go nuts.
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Discussion Starter · #3 ·
Interesting thread here ...



Being a constant displacement pump means that it you can't hook just any supply pump up to it. Whereas an injection pump like a P7100 can tolerate a large difference in flow rates to/through it with relatively little pressure change, the CP3 cannot. If you try to push too much fuel to the CP3, the pressure will skyrocket. There are no internal relief valves in the CP3, only a direct feed to the supply pump. Conversely, if there isn't enough flow to it, the pressure will drop and the supply pump may actually start developing a vacuum in an attempt to get enough fuel.
 

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Discussion Starter · #4 ·
I better will keep the relief valve of the Carter pump.

I am not sure what is the best stragedy . Removing the relief bypass or not ..
 
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Conversely, if there isn't enough flow to it, the pressure will drop and the supply pump may actually start developing a vacuum in an attempt to get enough fuel.
But there isn't mechanical supply pump

I'm not even sure you electrical pump is faulty- if the supply is too low you should have "rail pressure too low" fault codes.
 

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Discussion Starter · #6 ·
I'm not even sure you electrical pump is faulty- if the supply is too low you should have "rail pressure too low" fault codes.
Hi Jan, yes You are right ... if we believe in fault codes then the lift pump is not the problem. But I do not only believe in fault codes, because you measurements give a significant hint to not sufficient pressure by the lift pump.

I will change when the china pump insert is delivered.
 
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Discussion Starter · #8 ·
When was your timing belt changed? Maybe it skipped a tooth and thats why you're having rpm issues.
Cool idea ...

But there would be a fault code by the camshaft position sensor ... you agree?

Oh man, i can put this whole rig apart as the issue spreads to every topic. I know, my avatar is perfect for me. it is about 40 years old, i sketched it because i had trouble with an Yamaha TX 750 twin.
 

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I don't know about diesels, but european petrols usually don't notice, if only one tooth is wrong. They just adjust ignition according to sensors and try to work on.
 

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Discussion Starter · #10 ·
Yes, petrols do this way. Any ECU controlled engine has to have a sensor to find the suitable timing.

Sensoring on a diesel engine is also necessary to be very precise, especially on the CP3 pump of the nitro. Because pressure peaks can overlap or reduce each other.
 

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Discussion Starter · #12 ·
Hi Jan,
This is very helpful for me to countercheck. Feedback will take some time. The Diesel Particle Filter is out and i have to do some other work to prepare water lines for our horses to prevent the lines from freezing in winter. The colder days are, so much more ideas and wishes come from my beloved wife.
 

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Discussion Starter · #14 ·
Just an idea thinking about your AlfaOBD skills ...

When I checked the IMA codes of my nitro, alfaOBD shows empty, blank tables.

Very confusing what this program really does and what is the real quality of code inside .. See your last screenshot.

Your speed was 1741 km/h ... You are the first Owner of an Ultrasonic Dodge Nitro.
 

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Discussion Starter · #16 · (Edited)
By IMA codes you mean injector quantity codes?
I can't find this check in alfaobd. I do have other programs for it though....
Hi Jan,

AlfaOBD shows no IMA Codes in these tables ..

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(I tried several times with 2 seperate Bluetooth adapters, but no success. The screenshot was taken in Not connected mode) Good news ->Today i received the identical Gerotor pump unit from China. I will insert this part into the lift pump unit because it is identical to the OEM part (same part number): It will take me some time to get this in, because everywhere round me is trouble on all fields.

And it's cold ,,,

Cu,. Fritz
 

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Discussion Starter · #18 · (Edited)
I think this test is only for adding new codes, not checking present ones.
Yes! That's my interpretation too. But, this is a real sample of bad programming. AlfaOBD is, to some extend, a hidden bomb.

If you have a type mismatch, You will fall into trouble with this way of data input.
 

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Discussion Starter · #19 ·
Hi Jan,

some news, although i got stuck in motivation to work on the floor in the dirt. The car lift is for next year, but these tasks have to be done in carpet crawling mode.

I received the Carter pump and i am not happy with this pump regarding its bypass between the in and out.



I found a spec from Dodge which says Nitro lift pump diesel pressure has to be 400 kPa +/- 34 kPa (58 psi +/- 5 psi).

Carter specifies its pump with Peak pressure of this unit is = 200 ~ 350 KPa
Unit will flow = 140 lph @ 100 KPa.

These values / Informations are with such a huge tolerance that i wonder if the tech support did guess or play with dice,

I asssume the low pressure is of the Carter pump is caused by the bypass (pic above).

A a very disappointing lack of information is what type of pump sits inside the lift pump unit. The nitro pump is gerotor, most common for high pressure lift pumps.

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But what type of pump is inside the Carter Pump? Looking inside is a risk, the danger that the plastic of the Carter pump breaks down during disassembly the samme way as my nitro pump is very high ...

this plastic notches are prone to break while trying to disassemble the pump.

Should i remove the bypass and play the game with the Carter Pump? I think i won't do this in a first step and reassamble the old nitro lift unit with a new identical chinese gerotor copy spare part.
 

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