Fuel PSI

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ramhunter9

ramhunter9

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Amount of fall ?
 

Mopar1973Man

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Amount of fall ?

Like you seen my fuel pressure I'm only getting 2 PSI of fall... You getting more fall... The amount of fall is the amount demand vs supply. When demand outweighs supply then supply pressure falls.

More here...
http://mopar.mopar1973man.com/cummins/2ndgen24v/fuel-pressure/fuel-pressure.htm

Keep it in the green...

colored-fp-gauge.jpg
 
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ramhunter9

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Got ya ..

We have some CTD guys on here .. this is good info for them also !
 

Mopar1973Man

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Got ya ..

We have some CTD guys on here .. this is good info for them also !

Let me pull a tidbit and explain more...

Operation

Fuel volume from the fuel transfer (lift) pump will always provide more fuel than the fuel injection pump requires. The overflow valve (a check valve) is used to route excess fuel through the fuel return line and back to the fuel tank. Approximately 70% of supplied fuel is returned to the fuel tank. The valve opens at approximately 97 kPa (14 psi). If the check valve within the assembly is sticking open, fuel drainage of the injection pump could cause hard starting. If a Diagnostic Trouble Code (DTC) has been stored for “decreased engine performance due to high injection pump fuel temperature”, the overflow valve may be stuck in closed position.

So looking at the specs of the Overflow valve from the Dodge FSM you'll see that for long life from your VP44 you need to have pressure above 14 PSI and keep it. Now as the pressure falls below 14 PSI the overflow valve start closing.

Part of the testing...
7. Reduce regulated air pressure to 10 psi and observe valve. Valve should stay shut. If not, replace valve.

So by 10 PSI the overflow valve is close and now you lost all your lubing and cooling of the fuel to the VP44 and now failure is knocking...
 
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ramhunter9

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Makes total sense . So it is safe to say if you fall 10psi or lower ... look at the filter first , then kinks or blockage in the lines .
 

Mopar1973Man

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Makes total sense . So it is safe to say if you fall 10psi or lower ... look at the filter first , then kinks or blockage in the lines .

Well the depends on the fuel system and the lift pump...

Stock lift pump is only 35 GPH on a plumbing system only rated for 75 GPH. So the amount of pressure fall is rather large for stock system and very hard to keep above the 10 PSI limit.

But with your 1/2" line its rated for 570 GPH and you got a 150 GPH pump (Raptor) so you pressure fall should be rather small.
 
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ramhunter9

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So I have a 3 psi fall ... how can I tweek it , or is it worth loosing sleep over ?
 

Mopar1973Man

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So I have a 3 psi fall ... how can I tweek it , or is it worth loosing sleep over ?

http://www.ramforum.com/f69/fuel-psi-8259/#post162042

Actually you got a 7 PSI fall... Watch your video again when you got on it it dropped to 11 PSI from your 18-19 PSI idle. When it hit 11 it popped back up to 12 PSI... That what I'm talking about fall.

But your typical cruising speed is 2 PSI fall which is fine but idle to WOT is wide.
 
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ramhunter9

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And that can be corrected how ?
 
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