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What is FUEL DRAIN MANIFOLD return line?

scubieman
scubieman
in 4th Generation Ram

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Posted

I have no clue what this is? I am trying to learn the truck and everything about it. It appears the fuel system has 3 return lines.One from the CP3, One from Rail, and one from Fuel Drain manifold which all combine into one.

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  • Author

So each injector has a feed line and return line? I assume the excess fuel lubricates before being returned?

  • Owner

Your injector are very simular to mine except mine don't have the solenoid to control firing.

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You can see the extra hole at the top of the injector that is the bled hole that the excess fuel is return to the return rail. So yes the injector is lubed and cooled by the fuel and then return to the tank.

As the CR engines they are a bit different on the top half of the injector but basically work the same.

  • Author

Does it go to the fuel rail after lubing or different system to return to tank? Better question how does the excess fuel exit engine?

  • Owner

There is a hollow rail through the head that exits at the back of the head... On the 24V it tees into the VP44 return line and return to the fuel tank.

  • Author

Do you have pictures of this inside the engine?Also when it exits the engine is that low pressure then?

  • Owner

Here is the best I can do...

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Its a bit more to the right center of the head will be a banjo bolt...

As for pressure there really isn't much...

http-~~-//www.youtube.com/watch?v=YREpPrMxkHU

Remember this is all 24V information its pretty close the same but little differences...

  • Author

Thank you!What pressure does your dummy light come on. My fuel pressure is 10.5 max. What is a dangerous psi?Also how does someone know they are gelled vs other possible issue?

  • Owner

What funny about fuel pressure the early years of CR engine specified 9.5 PSI for MIN PSI then the whole pressure tables where remove later on. :shrug: As for my low pressure light is a Cummins Switch which is set at 3.5 PSI way too low for my truck being MIN pressure is 10 PSI and I typically keep it above 14 PSI. http://mopar.mopar1973man.com/cummins/3rdgen/fuel-system/fuel-system.htm But after reading about the CP3 pump a bit I found its also got a overflow valve just like the VP44 got. But the problem is I can't find any specs on this overflow valve and when it opens. Like I'm learning your fuel pressure should be just high enough all the time to keep the overflow open. This would keep the CP3 happy with extra fuel flow lubing and cooling as well as the VP44 style pumps do. But I know on Chevy Duramax truck there have no lift pump before the CP3 so :shrug: Fuel gelling will show up as a fuel pressure drop of about 2-3 PSI lower than typical and may or may not improve...

  • Author

I have my fel pressure gauge after fuel filter right before cp3. So if i see 7 psi then im gelled. I though like 5 and under would be gelled.Thanks again.

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