2005 Dodge Low Rail Pressure

[Mopar1973Man]

I've got a 2005 Dodge Ram 3500. There is no error codes presently and rail pressure is a max of roughly 5,000 psi and at idle its start to surge dropping as low as 1,900 PSI on the rail. I know this is not enough rail pressure at all for normal operation. I've changed the FCA without any change in pressure or operation.

Where to go next?

[dorkweed]

RPRV, CCOV come to mind real quick.  Rail pressure should be around 6500psi at idle.

Do you have enough fuel to the CP3??

 

[Mopar1973Man]

Just ordered a test cap for the rail and a fuel pressure test gauge (low pressure side). I've got my OBDLink for the high pressure side.

So as soon those tools come I can continue testing.

[Mopar1973Man]

Well after getting the Vulcan Performance test gauge and hooking it up we found this truck only has a mere 5 PSI at idle. Now rev the engint to 2k and you can pull it down to zero without even putting it into gear.

New in-tank fuel pump will be hear in the morning.

All I can say is these thing are a PITA to deal with. We did the bed lift idea and man that's a PITA too. All the rusted bolts in the bed. All the stuck and hung up connectors on the tail lights. As for installing it does make it easy being the tank it full of fuel better than pumping the tank out.

[AH64ID]

What are you using to read pressure? If it's the OBDLink I am VERY surprised it hasn't thrown a code.

It will not run at 1,900 psi so I am going to guess that it is an indication issue.

The specs for the CP3 inlet pressure are -5 to + 15 psi. So what you are seeing is within spec and most likely not the cause of the rail pressure. The idle pressure is a little low but I only idle at 8-9 psi normally. These aren't VP44's and they don't need pressure to preform. The duramax version doesn't even have a lift pump.

What are the symptoms that brought the truck to you?

[Mopar1973Man]

Drove only 3 miles and power drops off to about to 40 MPH WOT. Rail drops to 3,000 PSI roughly at WOT.

Like today we installed a brand new fuel pump (Stock In Tank - NAPA) tested the pressure at the CP3 inlet port seeing 11-13 idle to holding 2,000 RPM free rev. Left the shop. Good rail pressure getting 11,000 to 13,000 PSI driving nicely to allow the truck to warm up. Drove up canyon made it 3 miles and the rail drop out to nearly 2,800-3,000 PSI at WOT. Come back test the lift pump and can pull it down to 3-5 just free revving at 2,000 RPM. I'm really sure the lift pump is dropping to ZERO on a load. I check the fuse, relay, and made sure 12V was getting to the pump. Just not keeping fuel pressure. So I've got another pump coming on warranty tomorrow in McCall. This time I'm going to leave my test gauge on the fuel system when test drive this next go around. Once the fuel pressure drops out its barely 3-5 at idle and rail is at 1,900 PSI and loping/surging at idle. Stalls really easy.

Previous initial problem was a error code for the FCA. So I did replace it and no change in performance same issue no error codes. That what lead me to the lift pump. Now we are trying to just keep fuel pressure up so it will keep going. I'm using a Vulcan Performance test gauge 0-30 PSI. Brand New....

As for changing these pump its for the birds...

[AH64ID]

What is he running for filtration and tuning?

IIRC the injectors need at least 3,500 psi to fire. The spring that seats the pintle is what requires the pressure. If it's running on less than 3,500 I still say indication issues.

What was the specific code?

Edited November 13, 2015 by AH64ID

[Mopar1973Man]

Stock everything. No tune. Stock fuel system. Fresh filter. When it drops below 3,000 PSI it becomes lopey and you can see the rail pressure bouncing. As it quits firing and the rail builds it pops again with a surge and rail drops again.

Cold it just fine runs good. But the fuel pressure is also good too.

[BBHD]

I had very similar symptoms on my old d-max. it was a failed fuel pressure relief valve that would bleed all pressure to return to the tank. I replaced it with a plug and solved my issue. 

[AH64ID]

There is a big difference in power dropping off and quits firing. You have used both to describe the issue, so which is it? The difference is what could be causing the issues  

 

On on stock tuning there are very very few places that cruise at 11-13K psi so that is another issue. Pressure should be higher than that while cruising with stock pressure. 

 

Does your scan tool also show desired rail pressure? Of not what about engine load? If you give me load and rpm I can tell you about what pressure you should see. But in short above 1800rpms and 6% load the pressure should be over 13K.

 

What at was the FCA code? 

 

I really don't think it's the lift pump and I look at a few others things before doing that again. It's not acting like a lift pump, even the initial symptoms don't really say lift pump. 

 

Dont  to get too hung up on lift pump pressure, this isn't a VP44. 

Edited November 13, 2015 by AH64ID

[Mopar1973Man]

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There is a big difference in power dropping off and quits firing. You have used both to describe the issue, so which is it? The difference is what could be causing the issues  

Its both...

Going down the road WOT it maxed out about 40 MPH. Power dropping out.

Come back home sitting in the driveway it quits firing in burst. Surge and lopey idle which you can see rolling up and down in rail pressure.

Quote

On on stock tuning there are very very few places that cruise at 11-13K psi so that is another issue. Pressure should be higher than that while cruising with stock pressure. 

I'm starting to think the rail pressure regulator is purging pressure off. I don't have a test plug yet.

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What at was the FCA code? 

Can't remember that was a week ago. All I remember was it was the FCA. I check codes and basic stats before touching anything on the engine. First day I see the truck it had the code and rail pressure was low (4,000 to 6,000 PSI) barely do 60 MPH then.

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I really don't think it's the lift pump and I look at a few others things before doing that again. It's not acting like a lift pump, even the initial symptoms don't really say lift pump. 

After laying in bed think about it last night and the fact if you disconnect the FCA there is no change in rail pressure tells me the FCA has been wide open all the time and the rail is purging out through the regulator. So if the flow rate is high then the lift pump most likely can't keep up. So I'm going to try and create a test plug or something for the regulator temporarily to see if the rail pressure pops up.

[AH64ID]

Ahhh... more symptoms. Those would be helpful in internet support. 

 

Like I mentioned the HPCR needs approx 3500+ to fire so if you are running at 1,900 psi it's generally a good indication of an indication issue which is why that was my first thought. But now that you say its sputtering and not running that's a different approach to a different issue.

Yes, if you unplug the FCA and rail pressure doesn't peg then you likely have a HPRV issue; however, I would NOT just make your own test plug. The pressure will spike above 26K psi on shutdown and I wouldn't want to find out it wasn't a good temporary plug.

IIRC you cannot buy just the HPRV from Dodge/Cummins/NAPA/etc but Todd at T&C Diesel sells them. Since a few parts have already been thrown at the issue what is one more :-) I am not sure he needs a higher than stock HPRV, but they are an option from Todd too.

Be sure to keep notes of codes when troubleshooting a HPCR they can be helpful even if they don't throw again. I am willing to be the reason you don't have any codes is because the engine hasn't gotten to operating temperature with all the issue. I bet a 15-20 mile drive would produce a code or two, if you could make it that far.

[Mopar1973Man]

Ok.

What I've done was borrowed a known good FPRV and installed it. The original lift pump would only produce 5 PSI with just the key on. The new pump would produce 12 PSI on key on. So we kept the new pump.  Start cold and had good rail pressure 6,000-7,000 PSI idling. Now unplug the FCA the pressure jumps up to 17,000 PSI little more rev and easy 20,000 could be reached. So we left the truck to idle and warm up. As it warmed up the rail pressure faded out rapidly as the coolant temperature rose to 160*F by the time it hit 180*F is was back down to 2,000 PSI and starting to lope again.

So we ended the day by pulling the new FCA, left the new lift pump in, and removed the borrowed the FPRV. I'm going to assume at this point there is a cracked injector body. It the only thing that makes any sense at this point. There is no oil growing and no outward leakage of fuel. So the loss of rail is going into the return to the tank.

What's your thoughts John?

[dorkweed]

I'd almost have to say injectors are shot...........

[Mopar1973Man]

Some info I didn't add... Didn't figure it was important till find more odd stuff.

I was going to attempt to remove number 3 injector. I everything dealt with right down to exhaust rocker removed and loosen the 8mm bolts. But the injector lines wasn't wanting to come loose. I could move it a little but didn't want to damage the injection line which was turning with the  compression nut. So I just reassembled it gave up for the day. It started and roll outside and died. Figured just air bubble. The owner and I just pushed it back and gave up.

Tired and didn't really give a darn at that point.

This morning I wanted to move the truck. Didn't want to start. Purged the low pressure system. Cycled the key a few times. Presto it started. I figure I let it run a bit. Talking to my neighbor that pulled up. It only ran for a minute of so and started loping. Then died. I'm assuming now that #3 injector might have or be the issue since I disturbed the #3 injector now its not running long.

Edited November 14, 2015 by Mopar1973Man

[AH64ID]

Unplugging and going to only 17K tells me that you may still have a leak somewhere. You should have zero issues going above 23K-26K psi with the FCA unplugged at idle. 

A cracked injector can go into the return or into the block so that is a possibility, or just a failing injector(s) with a VERY high return flow. 

How old is the software in the ECM? There is a update from a few years ago that helps detect too much return flow. 

They should be able to run on 5 cylinders so unsure what the issue is there. 

You could pull all 6 injectors and have them tested. There is a shop in Boise that will test them with the Bosch machine. There is also a shop in Boise that can get you NEW, not reman or even OEM reman, injectors if needed. 

What is he using for a fuel filter?

[Mopar1973Man]

Problem solved. Well kind of...

#3 injector line and crossover tube is rusted together and the crossover tube nut is loose. I managed to tighten the cross over tube nut and problem is gone. So to resolve this permanently would require cutting the high pressure tube near the nut and removing the entire unit. Then replacing the crossover tube, nuts and high pressure line for #3. I would like to suggest to the owner that all the injectors still get tested and at that time we can deal with all the rusted lines and tubes (if any more exist).

I got to admit it runs very well for stock 05 Dodge.

 

Edited November 16, 2015 by Mopar1973Man

[AH64ID]

Glad to hear it!!

 

Why wouldn't a stock 05 run well? 325/610 isn't a shabby motor. 

[Mopar1973Man]

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Why wouldn't a stock 05 run well? 325/610 isn't a shabby motor. 

I'm just use to the power my 02 makes. Feels a bit slow comparing. Truly not a shabby engine at all just needs a Smarty for some pick me up power.

Oh the owner was super pleased his comment is its got way more power than it did the day he bought it. (It should now the rail pressure is holding up!)

Edited November 17, 2015 by Mopar1973Man

[AH64ID]

I'll bet most of that is the torque management difference as I doubt you have much more sustainable power with a stock turbo and 3" exhaust. You have the fuel thou.