Archived Low Fuel Rail Pressure

[LewisD]

Been chasing a Low Fuel Rail Pressure issue but first let me tell you how we got there.

I have a 2011 RAM 3500 with about 64k on it. The truck has a FASS Titanium 95GPH unit on it from a fuel issue that I had more than 1 year ago.

Almost 2 Months ago I started having issues, truck running rough multiple codes. I took the truck into the ******* and they diagnosed the issue as 1 possibly 2 bad injectors. OK Get er done. Not covered under warranty because of the aftermarket fuel system (I guess I can't argue with that) After the replacement they ran the truck and another injector threw a code so they replaced that injector. Ran the truck again and 2 additional injectors. They tell me that they are going to replace those 2 injectors and the very last injector. At this point the dealer has had my truck for 40 days and they feel that they can't keep doing this to me so they will cover the last 3 injectors under warranty.

They also did a fuel test and said that there was sediment/contaminated fuel coming off the fass pump. They did a bottle test on the line leading to the injector pump. The fuel flow rate was more than adequate however there was contaminated fuel. The fass system, with original filters has been on the truck almost a year at this point and the filters have about 6500 miles on them so I couldn't believe that they would be passing bad fuel. I tell the deaier that I will be bringing new filters and they order the last 3 injectors. They also decide that it would be best if we pulled the tank and cleaned the lines. When I arrived they showed me my fass filters, and it appears the particulate filter had a failure and there was excessive corrosion present on both filters.

Here are the filters ~1 year old at this point with 6500 miles on them

I know right!

I can't explain why/how they look like that other than the fact that I always get fuel from the same Meijer store with exception of a trip I took down to the Florida keys towing a boat. I'd say that I've probably gotten some real bad stuff. The one filter is caved in and probably failed allowing that particulate to flow through the system.

On day 53 all injectors have been replaced, tank and lines purged and fresh diesel in tank. fresh filters in place, flow rate fine. Dealer takes truck out for a run and we get the low fuel rail pressure. They attempted to clean the sensor without any luck. They tell me that it's probably either the sensor or the injection pump. It will be $600 for sensor and 3-6K for the injection pump replacement plus labor. They want me to do the sensor first since it is cheaper and if that doesn't fix it then the injection pump.

I tell them not to do anything until I call them back... I go and get my truck.

Ordered and replaced the fuel rail sensor ($148) on ebay No fix
Ordered and replaced the injection pump, with the help of one of my friends really not that bad a job (ebay $575) No Fix
Ordered a race plug to swap out the fuel rail relief valve No fix

So this is where I am at now. If the truck is cold, and the DTC is cleared I can run down the road a few miles until the code pops up. It seems to run great until I get the code and then protection mode kicks in.

I bought a tuner so I could watch the fuel rail pressure and reset codes, I'm not a specialist but it seems like pressure is fine and dandy until the code pops. I have 6 new injectors, I put a gauge on the low pressure pump right before the injection pump and I have 16lbs (I think it's 16, the gauge only goes to 15 so it's pegged). I have a new fuel rail pressure sensor, I have a plug in for the pressure relief valve and I have a new injection pump.

Where do I go from here?

 

[Bob4x4]

When you get a contaminated system the cheapest in the long run is to replace everything at once.The contaminates will get trapped then free up and recontaminate something else.Every part That has any risk of holding any tiny bit Needs to be cleaned or replaced.Every time the dealer started the truck after the first injector replacement they sent more particles through the system

 

[LewisD]

When you get a contaminated system the cheapest in the long run is to replace everything at once.The contaminates will get trapped then free up and recontaminate something else.Every part That has any risk of holding any tiny bit Needs to be cleaned or replaced.Every time the dealer started the truck after the first injector replacement they sent more particles through the system

I agree 100%, the dealer was a parts swapper just like me. The only code I have now is the low fuel rail pressure. Truck seems to be running great. I didn't verify that the dealer did a proper job on the injectors (not sure I know how) and if I've replaced the injection pump, PRV and Fuel Rail Sensor, what should I be looking at? I will NOT take it back to the dealer!

 

[LewisD]

I found a post on another forum where someone was having the same issue and it ended up being the injector tubes were not tightened properly. Since the dealer replaced all my injectors and tubes, I will start looking into that.

 

[cerberusiam]

Look into what injectors the dealer used for replacements, that is the usual problem. The dealer system is notorious for using some of the crappiest remans available as replacements, unless you dropped them NEW injectors or specifically requested NEW and verified they are likely you got junk.

You need to replace the rail, it still has rust and garbage in it from the bad fuel that was ingested. There is also a good possibility the rail lines have FOD in them.

 

[sag2]

I have to admit the dealer went about it backward. There are specific instructions in the service info that tells them how to check and properly clean (or replace) the fuel system parts. After that if the dealer was using reman Mopar injectors they might get one that runs bad, but not likely one that will not allow the truck to maintain rail pressure. The first thing I would do is a fuel return test. It can be done without the special tool by disconnecting the pump return line from the filter housing at the front of the filter, and measuring the injector return off the quick disconnect below and to the rear of the filter. Cap off the male end of number 3 on the diagram so fuel does not dribble out from the injector return.
The proper way to run the test is hot engine and use the fuel pressure override test in the scan tool. You don't have the tool so you will need to disconnect the FCA to raise the fuel pressure instead. It will set a code and will rattle pretty good but don't be concerned.
If you have over 210ml or close to it, tighten the connector tubes and run the test again.

View attachment 6.7 Fuel Return.pdf

 

[LewisD]

Thanks for the info! I'll keep you posted on my results, I've got a loaner for now but I hope to get back at it this week and get this figured out.

 

[LewisD]

I was able to get back to this last week. I pulled off the fuel rail and and re torqued all of the injector tubes. all were loose except number 6. Number 4 almost went an entire revolution. Cleaned up the fuel rail and put everything back together. Low Fuel Rail Pressure is Gone!!!

I will be visiting the dealer for a discussion.

Thank you for all the help!

Happy Truck!

-Dave