Question for Innovative

[DavidPhillips]

The programmer does not change the physical dynamics of the system but it does use more fuel. If you going to 500+ RWHP then your approaching an 80% increase in power which demands a lot more fuel.

It comes down to the amount of fuel that's available. Volume is the issue. If more fuel is used than what is supplied there will be a pressure drop at the high pressure pump intake. Starving this pump is going to damage it. I understand your theory that the pump will not be damaged but I must disagree there. Many a good pump has been damaged by lift pump failure. I see no reason to believe this pump is any different.

By installing a gauge there these problems can be ignored completely.

When I put a fuel pressure gauge on the intake to the injection pump on my other truck I found that the pressure drops to 0 psi. That pump needs 3 psi to function properly. It will run without any lift pressure but will be damaged.

The fact that it can handle 24 psi means nothing other than you need to make sure any lift pump mod does not exceed that pressure at 0 volume. The pressure at 0 volume is the greatest on a lift pump that is independant of the engine. As the volume increases the pressure will normally drop because the pump can't keep up 100%. The volume of fuel supplied is inadequate whenever the pressure drops below the minimum specified limit.

Hopefully there is no problem but I would still like to see someone put a gauge on it to prove that it does not starve the pump.

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Last edited by DavidPhillips : 05-18-2008 at 09:44 AM.

[737tdi]

David: Don't misunderstand what I'm saying. I totally agree that starving the pump of fuel will cause a failure, i.e. by using a higher volume then is able to be supplied. I also agree that we should determine if the HFCM can provide the volume and pressure (3psi) downstream of the engine mounted filter. My main problem with the poster on the "other" website is that he threw this failure/problem out without any background or explanation, just that if you tune you're going to blow your pump up and take out the injectors and O.M.G.. I just do not believe this is the case. If you learn and understand the system (be it fuel, electrical or mechanical) you can avoid failure "due to a tune". I believe with posts like this and intelligent input we can all benefit. Thanks.

737tdi

[DavidPhillips]

I agree the quoted post seems to be lacking any kind of proof and makes some pretty wild statement without offering any explanation.

I just hope somebody will put a pressure gauge on soon and prove it one way or the other.

Short term failure seems unlikely but I would like to know for sure. I will eventually put one on as I did with my other truck. The injection pumps are too expensive to take a chance. I know a guy who lost one on his 5.9 due to a lift pump failure.

As complicated as this system is there may be an error code in the event of lift pump failure, anybody know if there is?

[SANDDEMON08]

From what i understand the PCM has a built in safety that shuts the engine down in the event fuel lift pressure is low which prevents the High pressure fuel pump from damage if the truck was run out of fuel by accident, would'nt this protect the engine from the event being discussed?

[Jcard]

I had an injector fail last week, running liquid diesel out the taipipe. apparently not enough to hydrolock a cylinder though. Mid December build bone stock truck. Glad I hadent deleted yet.

[DavidPhillips]

There is a code P117F.
----------------------------------------------
This error occurs when any of the fuel pressure
corrections either become less than a minimum
threshold or more than a maximum threshold.
----------------------------------------------
Maybe that's what you would get. Not sure about shutdown but a light should come on at least.

Another good reason to not run with your MIL on for some other problem.

[737tdi]

SandDemon: From what I can determine the only sensor in the HFCM (lift pump) is a water in fuel sensor, so this wouldn't do it. There are no sensors on the secondary filter (engine mounted filter) and nothing in the lines from the HFCM to the High pressure pump. So, as far as a failure in this portion of the fuel system, I see nothing that would shut down the engine. Maybe the Fuel pressure control valve or Fuel volume control valve could do something but at that point I would think it would be too late. This info. is just me studying the wiring diagrams and the Powertrain Control/Emissions Diagnosis book. It's very possible I missed something.

737tdi

[sheepman]

I found this interesting that the lift pump pressure should be 4-7 psi. So if the lift pump is pumping 4-7 psi and the check valve is set a 3 psi, it seems to me that there should be enough fuel supply.

Click here

[DavidPhillips]

That's when there is no fuel or less fuel being used. Sort of like a garden hose with a nozzle on it gets hard. The same hose with no nozzle on it stays limp.

Pressure is only a resistance to flow. As fuel flows the pressure may drop if the volume of fuel supplied is less than what's needed. How far it drops depends entirely on how much volume the fuel system can provide vs how much the engine needs.

By the way thanks for the Manual. Seems like were getting a pretty good collection of documents going here.

One thing I noticed in the Manual is the test procedure for checking the fuel pressure. It requires a gauge. That would seem to indicate we do need one. Or maybe this is to check for air holes or something of that nature. They are checking at the cooler which is in the return line. We need to know what the rated volume of the pump in the HFCM is.

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Last edited by DavidPhillips : 05-19-2008 at 06:30 AM.

[George C]

You guys are the best.
I am sure we can either be warned or totally rule out any pump pressure changes caused by a tuner very soon.
Thanks again.