2003 Fuel Pressures

[RSnaith]

After many moons of procrastinating, I finally got my IssPro 30 PSI mechanical fuel pressure gauge rigged on the 2003 HO. Install was reasonably easy. Just popped out the fuel supply banjo on the fuel injection pump, and threw in a tapped banjo with an elbow, a stainless line and away we went.



First impression is that the noise is considerably higher than a direct connection to a VP44. I may try snubbing it down, but I think I'll move the tapped bolt back to the filter canister next weekend and see how it affects noise and pressures.



And the fuel pressures:

Idle - 9 - 9. 5 PSI

Cruise at 60 mph - 8 PSI

WOT - 5 PSI



And after talking to a few developers who are testing out their prototype fueling boxes, its been discovered the new lift pump is every bit as weak as the old one. Possibly even more so :{ For all you guys installing gauges, make a fuel pressure gauge part of the package...

 

[yogibear]

Mine is hooked up the same as yours, 8--8. 5 idle, 7 at cruise, 6 at wot, empty or pulling a heavy load. I noticed the noise also. Let us know if it changes when you move it, or use a snubber. I have the di pricol guage with antifreeze in the line from banjo to sending unit. I didn't think this would transmit the noise like it does.

 

[Pit Bull]

I guess it is good to know somethings never change

 

[dan.poitras]

Mine is connected the same and I have not noticed any noises.

I have used a stainless steel braided hose from the pump to the isolator about a foot long. (same size as motorcycle brake lines)

#3 I think. Di-pricol guage, A pillar mounted. lucky to get 8 to 10 psi

EZ Edge box on the way. I can see a pusher pump in the near future. Reese fifth wheel front brackets are welded and rear ones are bolted. (oops did I do something wrong?)

 

[$BANKS$rupted]

Is it even a problem with those numbers since there is no vp44 to cool?

 

[dan.poitras]

Probably not as long as it can maintain 5 psi at full torque output.

We'll see once the edge is installed and dyno'd

 

[RSnaith]

Originally posted by $BANKS$rupted

Is it even a problem with those numbers since there is no vp44 to cool?

The common rail pump still uses excess fuel to cool itself, so I'd say that you'll still need decent pressure to keep things held together. 5 PSI would likely be enough, but we aren't really going to know until we get to turning these trucks up. I've talked to two of my suppliers who are currently pulling their pressures down to 2 PSI, which scares me just a hair.

 

[Pit Bull]

Originally posted by RSnaith

The common rail pump still uses excess fuel to cool itself, so I'd say that you'll still need decent pressure to keep things held together. 5 PSI would likely be enough, but we aren't really going to know until we get to turning these trucks up. I've talked to two of my suppliers who are currently pulling their pressures down to 2 PSI, which scares me just a hair.

Sounds like the VP44 type issue all over again. It will be interesting to see what you guys discover as the miles accumulate.

 

[kaffine krazed]

What is the spec for fuel pressure?

 

[dan.poitras]

The DC manual says 9 1/2 psi minimum pressure (transfer pump)

which seems optimistic to me considering my "new" truck gets

max 9 to 10 psi at idle.

No pressure spec from cummins

The cummins manual (transfer pump is mounted behind the ecm on medium duty trucks) states through a . 043 orifice 600ml delivery in 60 seconds. Or 12 ounces in 36 seconds or less.

 

[RSnaith]

Originally posted by dan. poitras

The manual says 11 1/2 psi minimum pressure (transfer pump)

which seems optimistic to me considering my "new" truck gets

max 9 to 10 psi at idle.

I read that number too, however on page 14-60 (of the Canuck manual) it shows a minimum lift pump pressure spec of 9. 5 PSI. I assume this is idle pressure.



I'd say a 2 PSI drop through the fuel filter, the little wee cross drilled holes in the banjos, and that cheap fuel line isn't an unlikely event. So I'm assuming for the time being that 9. 5 at the injection pump is ok, as others have reported similar numbers. I've got a Dakota digital coming in for testing, and I'll be running a dual gauge setup to see what the pressure drop is from the bottom of the fuel filter canister. Then we'll be switching the whole system over to high flow bolts and doing a test. And finally, we'll be putting a 1/2" ID line and our larger banjo fittings on from the Black changeover kit. I'll post the numbers as they become available. Once thats done, I think I'll be looking for a way to adapt a 12 PSI Holley onto the system. With the kind of power these trucks are capable of generating, and the lack of availability from aftermarket sources of the new pumps, we want to make sure we're not going to destroy anything with the new fueling boxes and injectors... .

 

[dan.poitras]

You are right on those numbers. I was in the middle of correcting it when you replied. Sorry

 

[rbattelle]

RSnaith,



After you got the banjo fitting installed at the fuel inlet to the injector pump, did you have to prime the fuel pump or is it primed automatically?

 

[RSnaith]

I didn't have to do any priming other than bumping the key to run the lift pump for 30 seconds to pressure up the system. I'm not sure if it was necessary or not, but I figured it wouldn't hurt.

 

[TDRadmin]

Fuel Pressure Specifications

Hello Members! In the for-what-it-is-worth department, we've noted some fuel pressure specifications that are correct, but they are also incorrect. Here is the story.



In a conversation with some of the tech guys at Cummins, we've verified that the fuel pressure specification that was published in the 2003 Chrysler Service Manual is erroneous. Changes have been made to correct the Chrysler Service Manual to remove all mention of lift pump pressures. Hotline personnel are aware that they should not troubleshoot this system based on lift pump pressure. There is not a fuel pressure specification for the new 2003 lift pump. The only specifications that are critical are flow specifications for this system. The minimum flow from the fuel lift pump is 38 ml per second (using Miller tool #9014) with a max fuel inlet restriction of 6 inhg (using Miller tool #6631 and a vacuum gauge).



I'll continue my discussion as to the "cooling" role that fuel plays in this new high-pressure, common-rail fuel system. I'll advise once I have more information.



Robin

TDR Admin

 

[rbattelle]

Robin,



Thanks for the info! Did you mean 38 ML (milliliters) per second?

 

[RSnaith]

Thanks for the info, Robin. I was wondering how long it would take to get flow numbers coming from Cummins/Bosch. By all rights, the 2nd gen trucks should be tested in a similar fashion, by flow versus pressure. However, having said that, not everyone can afford to have a flow meter in their garage, so pressure is the next best thing. A large reduction in pressure in a fuel system, invariably means a reduction of flow, if all components remain static.

 

[Ramtough]

Braided hose

Originally posted by dan. poitras

Mine is connected the same and I have not noticed any noises.

I have used a stainless steel braided hose from the pump to the isolator about a foot long. (same size as motorcycle brake lines)

#3 I think. Di-pricol guage, A pillar mounted. lucky to get 8 to 10 psi

EZ Edge box on the way. I can see a pusher pump in the near future. Reese fifth wheel front brackets are welded and rear ones are bolted. (oops did I do something wrong?)

Where did you get the stainless braided hose?

 

[dan.poitras]

You can get a hose made up by any custom motorcycle shop.

I make up my own.

 

[docdyno]

In a discussion with some fuel system engineers, it is my understanding that the '03 injection pump requires what we call a "flooded inlet". In other words, it needs fuel to be present at the inlet port and will function properly as long as it does not have to pull a vacuum on the line. There is no inlet pressure specification to my knowledge. The "lift pump" is a completely different design from the '02 and previous units. It should be considerably more robust and dependable. With most of the newer style common rail type pumps & injectors, dirt is a huge issue. Frequent filter changes and water elimination will significantly increase component durability.