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High fuel pressure (never saw that before)!!!


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This AM I was fueling up, I had let the coach run since I hadn't been on the road that long and thought getting it to temp was a good idea.
I pumped ~34 gallons of fuel an hit the $100 limit.  Swiped another card and as I was starting to pump diesel the engine started to sputter and stumble and puffed black smoke out the exhaust.  Quickly finished pumping fuel.
No lights came on the dash and I checked the VMSpc diagnostic display.  It showed.
 

ENG PID    94 10 Fuel Delivery Pressure      Abnormal Change   7/24/21  7:58

ENG PID    94  0 Fuel Delivery Pressure         High Reading      7/24/21  7:58
 
Both codes were inactive.  I started driving with my fingers crossed. Drove about 350 miles and the engine didn't act up a signal time. 
 
I do have a FASS transfer pump installed, not sure if it putting ~16psi to the injector pump might have caused the problem.  It never did this before, have ~4500 miles on the rigs since the FASS installed.
 
Any suggestions???
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My FASS fuel polishing system runs between 18-22PSI (depending on engine load) have not had a problem.  Pressure reading "tap" is between FASS system and Secondary fuel filter, where the "primer" "lift" pump used to be (now plumbed out of the fuel system)

Guess I need to learn how to "see" those codes you mentioned.....

could this problem and your generator problem be related to fuel contamination??

Ken

 

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It does seem odd that I had a problem with both.  I did put in some Diesel Kleen and biobor this morning when I filled up.  The Cummins ran fine the rest of the day. 

When I turn the key on and the fuel pressure gauge cycles it stays right at 16 psi.  While I'm running with a heavy load it drop to 13 but recovers as soon as the load drops.

I have a Silverleaf VMSpc and it does have a diagnostic function/tab, the fault codes showed up there right after it was running rough.  I had gotten some fault codes in the past which I suspect were due to the old lift pump. 

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I also used "biobor" (Killem) after I changed the filters (both engines) and suspect dead algae may have been blocking the generator fuel pick up.... the main engine has a "serious" pump sucking on it !.... and I can always see the positive pressure on the inlet to the injector pump so I may never have a problem with it clogging, but I have no idea what those pick up actually look like... are they an open tube or do they have a screen or a "filter" ??...just do not know.

Ken

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I think they are just open tubes. 

I will try and blow the fuel line but with the generator running pretty good right now I still think there is something wrong with my inverter.

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The Inverter could be the problem, causing the generator to "overload" and it auto shuts down to protect itself....  I think that is basically what mine was doing.... the generator was unable to "accelerate" to meet the load (due to fuel starvation) and would auto shutdown and throw the 3-6 code...

Hope you get it figured out.... it's a pain to not have a good reliable generator!

Ken

 

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Yup, this is the first long trip that I've had to depend on the generator.  Installed a Samsung residential so I need to be able to charge the batteries and in the extreme heat out west get the coach cooled down. 

If I figure out what is wrong I'll be sure to post. 

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On 7/24/2021 at 7:54 PM, Cubflyer said:

The Inverter could be the problem, causing the generator to "overload" and it auto shuts down to protect itself....  I think that is basically what mine was doing.... the generator was unable to "accelerate" to meet the load (due to fuel starvation) and would auto shutdown and throw the 3-6 code...

 

My generator had not been run in about 8 weeks until I let someone use my uwave yesterday (I run a gas gen while boondocking unless I need AC).  It started easily, power came up (batts were low + fridge so ~12A load) and ran until (possibly when the uwave came on) it quit suddenly.  3 flashes but didn't see a secondary code.  Tried to restart, wouldn't start.  Then one last attempt maybe a minute later it cranked up and ran the uwave.  On the way home I ran the HW heater + 1 AC and it ran fine. 

I did have an issue with contaminated fuel clogging the primary engine filter.  The gen filter might be next.  

jacwjames, maybe when you blew the gen line back into the main tank you let loose a gaggle of foreign material that the primary engine filter picked up that kicked off your engine while fueling.  I would expect more serious symptoms, but this could be the start of it all. 

- bob

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Bob,

I blew my gen fuel supply line out back into my tank... I do not believe "jacjames" has yet... I suggested he try it...

When I got my coach the fuel in it was black... seems to be cleaned up now after the install and running of the FASS filter/pump system and "bioBore" treatment... and now clearing my gen supply line..

fingers crossed..

Ken

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Haven't blown the line yet.

But yesterday I ran both AC and the water heater, and plugged the refrigerator into the none inverter outlet.  The generator ran fine.  I left both the L1 & L2 breakers off to the generator. 

I would be surprised if I had contamination in the fuel.  The FASS system pumps 100 gpm and only a small portion is used by the engine.  The fuel pressure still reads ~16psi when I start the engine and only drops to ~13psi on a hard pull.  I would have thought if there was contamination the primary filter on the FASS would be showing a restriction. 

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I finally got a chance to look at the service manual to try and determine what may have caused the high fuel pressure fault.  Attached is what I found for the code which indicates there could be a restriction, here is what is in the attached.

Troubleshooting must be focused on inspecting the drain line path of the fuel pressure relief
valve for restrictions/obstructions and checking or replacing the fuel pressure relief valve. A
restriction in the fuel-drain-to-tank return line can prevent unneeded fuel from exiting the fuel
system. Check the fuel drain line restriction from the fuel rail to the tank for damage.
The fuel rail pressure sensor must also be checked. When checking the fuel rail pressure
sensor accuracy, make sure the high pressure fuel rail is not pressurized. The fuel pump, high pressure
fuel lines, and fuel rail contain very high pressure fuel. Do not loosen any fittings
while the engine is running. Wait at least 10 minutes after shutting down the engine before
loosening any fittings in the high-pressure fuel system to allow pressure to decrease to a lower
level. There could be a significant amount of time waiting on the rail to depressurize to 0. It
could be necessary to manually relieve the pressure from the high pressure fuel rail.

So I'm wondering if the amount of flow & pressure the FASS system is pumping is too much for the system.  So far I have not had any other reports of a code like this being thrown.  Although I did bypass the original lift pump on the feed side I did not bypass on the return side. 

Does anyone know of any type of restriction in the old lift pump that would limit high volumes of flow.  None of the drawings or pictures I have of the old lift pump gives a clue on it's internal construction. 

 

SPN 157 - FMI 0 (Fault Code 449) B - Blog.pdf

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1 hour ago, jacwjames said:

So I'm wondering if the amount of flow & pressure the FASS system is pumping is too much for the system.  So far I have not had any other reports of a code like this being thrown.  Although I did bypass the original lift pump on the feed side I did not bypass on the return side. 

James,

(Edited)...So in a word..."NO"

It seems to me you are confusing the high pressure (injector rail) side of the fuel system to the low to no pressure side (the side from the fuel tank to the inlet of the injector pump). I do not believe the original lift pump returned any fuel to the fuel tank, but if it did it was very minor and only for the first 30 seconds while it ran. 

The injector, (or any pump) pressure output is little (if any) affected by inlet pressure, and by design the "rail pressure" is regulated by the rail pressure regulator (by restricting the fuel returned to the tank).  The injector pump could put out 100psi to 10,000psi and as long as the rail pressure regulator and return line is large enough, the rail pressure (theoretically) be maintained at any pressure between 100 and 10,000psi.

Your fault code is more likely a sensor acting up than an actual pressure problem, but if the pressure is fluctuating, it is most likely a regulator problem not a pump putting out too much pressure.  On this type of system (pressure rail), the pump runs wild and the regulator (with a clear return (drain) line) controls the pressure.

Ken

 

Edited by Cubflyer
clarify
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Thanks for the reply.  Just starting to dig into this and the two areas the document I posted says to look at is the return line to tank for any obstructions and/or the relief valve itself, which from the diagram is located at the end of the fuel rail/pump.

This assumes that the fuel delivery system has not been modified.  The original lift pump actually pumps to ~30 psi based on the fuel pressure gauge but only runs ~30 seconds. I would assume some fuel is returned to tank.  Once the original lift pump stops running the injector pump pumps fuel some fuel returns to tank through the old lift pump. 

Now I've installed a ~100 gph FASS pump with a relief valve limiting pressure to ~16 psi.  What happens if the relief valve malfunctions fro some reason.  Just trying to think out of the box as to what would have caused the high pressure fault code. 

As of now 3 potential causes,

  1. relief valve on injector pump
  2. return line restriction
  3. new FASS pump over pressuring system. 

 

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Again, the injector pump input pressure as well as the injector pump output pressure is not what determines rail pressure... that is the rail pressure regulator and it's return lines function. 

Your FASS (like mine) output is regulated by it's return line (that is supposed to be separate from the original line) so your FASS pump is not over pressurizing the injector rail..... if the injector rail regulator is operating correctly and has a clear (drain) return line (it is a separate line from the FASS return line?... if not, all bets are off and disregard everything I said....

Ken

 

 

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On 7/30/2021 at 10:22 AM, jacwjames said:

My FASS return line goes to tank

I am using the original return line, have not modified.  

Just trying to understand the system and potential causes. 

 

Jim, I used the original OEM SUPPLY lines to FEED the FASS pump.  But I installed a separate, additional return line for the FASS pump itself.  I first considered adding a tee and plumbing the FASS RETURN line into the RETURN line leaving the OEM Lift Pump Manifold.  Both the instructions and a call to FASS support confirmed that there is indeed an "over-pressure" sensor somewhere in the ISC return line plumbing, and the extra ouput of the FASS pump, IF CONNECTED TO THE EXISTING RETURN LINE FROM THE LIFT PUMP, would likely trigger that sensor.  Support said it does not ALWAYS trigger the sensor, but that it happened often enough that they recommended the additional FASS-dedicated return line.  I had an unused tapping in my fuel tank, so I ran the FASS-dedicated return to that fitting.  If, anywhere along the line, you joined the FASS return line to the same tapping in your fuel tank, PERHAPS that might be an issue.  IFF that were the case, the sensor would most likely be triggered at IDLE, when the CAPS pump is returning the max amount through the Lift Pump manifold, and the FASS is returning most of what it pumps to the tank at the same time.

I think I understood that you also installed the separate, dedicated return line for the FASS pump.  Is that true? Did it use its own dedicated tapping at the fuel tank?  Interesting problem.  You are a methodical guy.  I'm sure you'll find a reason for the problem.

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Posted (edited)

Van,

I did install a separate return line but didn't have any extra holes and put a Tee in the tank vent line hole and added the FASS return there.   I mounted my FASS pump in the propane tank compartment passenger side.   The return shouldn't be restricting the engine return line.

From now on I'm not going to let the engine idle for an extended time.  Not sure what happens when I get stuck in traffic though.  I was driving through the outskirts of Detroit last week and it was most stop / go traffic for about 1/2 hour. 

Edited by jacwjames
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3 minutes ago, jacwjames said:

Van,

I did install a separate return line but didn't have any extra holes and put a Tee in the original return from the engine and just add the FASS return there.   I mounted my FASS pump in the propane tank compartment passenger side. 

From now on I'm not going to let the engine idle for an extended time.  Not sure what happens when I get stuck in traffic though.  I was driving through the outskirts of Detroit last week and it was most stop / go traffic for about 1/2 hour. 

You probably have your FASS pump energized indirectly by the ignition switch, so there is no EASY way to disable it while running.  If you could disable it at idling (when it is not needed) that might satisfy your curiosity.  If you ever figure it out, please let us know.

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