Fuel pressure at idle

[JCasper]

I just hooked up my new FP gauge tonight.



I used a banjo bolt on the front of the CP3 and ran that to my isolator. From the isolator to the gauge I left the line dry. I was told that if it was shorter then 6 feet it didn't need anything in it.



Anyways, I have 6-7psi at idle. I can draw it to 3 at about 2/3 throttle in 3rd and 4th gear. That seems low to me.





TIA, Joe

 

[oneshotkyle]

you have a HVLP lift pump. just be thankfull it only goes as low as 3lbs. mine would go to to zero... .....

 

[JCasper]

you have a HVLP lift pump. just be thankfull it only goes as low as 3lbs. mine would go to to zero... .....

It may go that low, I haven't tried very hard yet.

 

[ENafziger]

That sounds right. Get you a GDP kit, and it you'll run a solid 20 psi, maybe dropping to 17 at WOT. --Eric

 

[DerekW]

you have a HVLP lift pump. just be thankfull it only goes as low as 3lbs. mine would go to to zero... .....

yal are scaring me!!!

 

[JCasper]

yal are scaring me!!!

Why, my truck has probably been doing that since it was new and it now has 63K on it. I just now hooked up a FP gauge.

 

[231jasonS]

Mine is only at about 6-8 range at idle, but will actually go up to a steady 9-10 under a load.



all stock fuel system

 

[Johnstra]

Mine's about 6, maybe a shade under, at idle.

-john

 

[R_Painter]

sound right put a chip on it at watch it go to and stay at zero at wot

 

[WStephens]

I have a 3/8" fuel line from the stock fuel filter and a 2 micron fuel filter down stream from the stock and the gauge is picking up the pressuer after the second filter and is 9. 5 psi at idle and 7. 5-8. 5 crusing and have pulled it down to 5 psi.

 

[gtobey]

I just hooked up my new FP gauge tonight.



I used a banjo bolt on the front of the CP3 and ran that to my isolator. From the isolator to the gauge I left the line dry. I was told that if it was shorter then 6 feet it didn't need anything in it.



Anyways, I have 6-7psi at idle. I can draw it to 3 at about 2/3 throttle in 3rd and 4th gear. That seems low to me.





TIA, Joe

Do you still have the original pump in back of the fuel filter, or did Dodge put that thing in the tank? Seems pretty close to right for the stock pump behind the fuel filter. With the stock common rail fuel system, you don't need the super high pressures and volume that some have on the "chipped" VP44s & high horsepower common rail engines.



If you need one of the stock pumps behind the fuel filter, I have a few coming in about a couple of weeks. Daimler and Cummins discontinued the one on the engine and went to the "in-tank" unit.

 

[JCasper]

Do you still have the original pump in back of the fuel filter, or did Dodge put that thing in the tank? Seems pretty close to right for the stock pump behind the fuel filter. With the stock common rail fuel system, you don't need the super high pressures and volume that some have on the "chipped" VP44s & high horsepower common rail engines.



If you need one of the stock pumps behind the fuel filter, I have a few coming in about a couple of weeks. Daimler and Cummins discontinued the one on the engine and went to the "in-tank" unit.

It is still up by the fuel filter.



Until this one fails I don't need another.



How long is it covered for under warranty? Are they expensive?

 

[Badunit]

I have a gauge and the stock lift pump on the side of the filter housing. Until alst weekend (75K miles or so), it's held around 7. 5psi. Last weekend I noticed my gauge (which is hooked up with a banjo bolt on the injector pump) reading 3psi while I was cruising down the highway. I replaced the filter but no change to the pressure. If I bump the starter, the pump runs but the pressure never gets above 3psi. Does the lift pump have an internal relief valve or would something else be keeping the pressure low? I'm going to check the pressure with another gauge but, assuming I really only have 3psi, is this a lift pump failure?

 

[gtobey]

Fuel Pressure

I have a gauge and the stock lift pump on the side of the filter housing. Until alst weekend (75K miles or so), it's held around 7. 5psi. Last weekend I noticed my gauge (which is hooked up with a banjo bolt on the injector pump) reading 3psi while I was cruising down the highway. I replaced the filter but no change to the pressure. If I bump the starter, the pump runs but the pressure never gets above 3psi. Does the lift pump have an internal relief valve or would something else be keeping the pressure low? I'm going to check the pressure with another gauge but, assuming I really only have 3psi, is this a lift pump failure?

As has been told to us for a good while, and what we have experienced here, the supply pumps on the Common Rail Engines are to provide a sufficient volume of fuel to the high pressure pump so that you will not “starve” it for fuel when you call for power, (are you running any power enhancing products, chips, programmers, etc. ?). It is not as critical to the high pressure pump as it is on the 98. 5-02 engines with the VP44s. However, in this instance, I would seriously look for what is causing the supply pump pressure problem because if the pressure dropped in half, the pump may decide to quit altogether. I have not cut one of these pumps apart to see what is inside of it. It does sound like something has happened to it though, unless you find an external cause. You can take the time if you have it and connect a separate line to the supply pump and bypass your fuel tank, run the engine, and see if the pressure is different because there is some sort of restriction in the tank. If the pressure comes back up, then something is awry in the tank. If not, you might try another supply pump.



Are you experiencing any loss of power?

 

[Badunit]

Test gauge showed fine pressure. Whew. It was a problem with my fuel gauge isolator. I removed the line to the gauge and reattached it and it is back to normal (for the time being at least). I didn't find any actual problem to "fix" so I suspect it will happen again.

 

[MChildress]

You guys hooking up at the CP3. I had harmonic vibration coming off the isolator that bugged the hell out of me at low RPMS. I read on here about using the same banjo bolt and placing the fuel pick up on the other end of the supply line at the bottom of the filter canister and presto no more noise. It was easy to get to through the drivers side wheel well. Just for info if someone runs into the noise issue.

 

[gtobey]

Test gauge showed fine pressure. Whew. It was a problem with my fuel gauge isolator. I removed the line to the gauge and reattached it and it is back to normal (for the time being at least). I didn't find any actual problem to "fix" so I suspect it will happen again.

Glad you found your problem (gauge). It's always good when a problem turns out to be really no problem. Doesn't always happen that way to me. Good to hear someone is lucky.