Engine/Transmission (1998.5 - 2002) Lift Pump

[Mak]

I just had a lift pump failure, or so I was told. The only indication I had was a engine check light. All other functions were good..... power, etc. I have a low fuel pressure idiot light(5psi) that did not indicate low pressure. The dealer R and R'er both the lift pump and the injection pump. I took the truck out for a run and while climbing a "not so steep hill "( I am in Precott,Az) my low pressure light came on. I took it back to the dealer and told him what happened. I couldn't explain to him why this happened. I suggested that maybe the transducer for the light was dropped or mishandled in some way but was told no. I then suggested that maybe the pump they installed was faulty..... Ha they said and proceeded to spend the next eight hours trouble shooting. So they ended up putting another pump in and declared it good. I read the report and it said that the light will come on a around 2300 rpm but they called it good because the way they check the pump is by volumn only, no pressure check. I've read on this site many times over that the minimun the injector pump needs is 10 psi or more. Is that right? If so, why in the world do they only check for volumn? Any thoughts??

 

[Mak]

I just read pizzilla's message about the internal pump verses the external pump. I neglected to mention that the dealership made that change on my truck. So I guess I can expect "0" psi wot..... Geez, that sounds crazy!!!

 

[SnoKing]

My granddauther use to ask we when our 29' SeaRay was in the air in the launch at Edmonds, Wa "Grandpa, how do their do that?" and I would reply "It's magic!" Anyone that can believe that there is more fuel available a zero lbs of pressure at the inlet to the VP44, than there is at 10 lbs, could maybe explain that to the rest of us.



On the other side of the issue. My VP44 is getting replaced this weekend, and has never seen low pressure, but got a 216 code and dead peddle recently. SNOKING

 

[NoSeeUm]

...

Anyone that can believe that there is more fuel available a zero lbs of pressure at the inlet to the VP44, than there is at 10 lbs, could maybe explain that to the rest of us.

...

Here you go Snoking, its Pure Funny Magic? :-laf



The debate about volume (for DC and the dealers) and pressure (for the consumers) rages on. Most knowledgable consumers prefer pressure, because like in my case I can see pressure on an in-expensive gauge. If I see pressure than I know that the VP44 is not pulling more fuel than my LP can deliver. That way I can be more confident that the VP44 is staying filled and not cavitating.



At 10 psi or 0 psi the volume flow rate can be the same, and that is the dealers postion. Guess what, they are right. But the trouble is that, unless a compound gauge is used that displays vacuum, zero is zero. If the VP44 is attempting to pull more volume than the LP can deliver then the pressure would be at a vacuum. So in that case only a compound pressure gauge would show that fact.



If the dealers can prove that there new system results in less VP44 failures then the consumers might start to believe. :{



Jim

 

[WestTN]

I think the Dodge spec' of checking for volume is valid for a stock system. With the known restriction of the stock system you will have the adequate pressure if you have the specified volume. Modifications to any part of the system or to the engine which changes the fuel demand or flow characteristics will invalidate that specification. And that is not their problem. They warrantee only a stock system.

As owners who desire more performance, we should make whatever modifications necessary to complete our objectives on our own dime and not the dealers. If you modify, you are your own warranty station.

 

[Doug1810]

Are They Sayin How Much Flow ? You Could Get A Flow Gauge And Check It Yourself . How Can You Have The Same Flow Rate At 0 And 10 Psi Because You Have The Same Size Hose And Or Restriction ? This Just A ? Not Startin A Fight .

 

[Thomas]

Are They Sayin How Much Flow ? . . .

The Factory Service Manuals 1998-2002 specify two pressure tests for evaluating the transfer pump—cranking and idling. Here is what is said regarding idling: Start engine and record fuel pressure. Pressure should be a minimum of 69 kPa (10 psi) at idle speed. When the operation of the transfer pump is described here is what is said: With the engine running, the pump has 2 modes of operation: Mode 1: 100 percent duty-cycle with a minimum pressure of 10 psi except when the engine is cranking. Mode 2: 15 percent duty-cycle with maximum pressure of 7 psi with the engine cranking.

The first mention of "flow" as a diagnostic tool shows up in TSB 14-002-03, likely because Daimler/Chrysler was tired of replacing transfer pumps based on the pressure specifications.

http://dodgeram. info/tsb/2003/14-002-03.htm

 

[Doug1810]

Thanks Doug

 

[Mak]

The flow rate was measured at 46 oz in 25 seconds. Spect says 45 oz in 25 seconds (how convenient is that?) Also measured 11 psi with engine off.

 

[Misenheimer]

I think that SNOKING is correct. The pump needs pressure to circulate fuel. The return fuel pressure regulator has a small (2 mm) hole in the side of it to return fuel to keep the pump cool. Diesel engines do not like warm fuel (big problem on boats). The pressure regulator should not pop off at 10 psi but open about 14 - 15 psi. My lift pump pressure was intermittent but before I replaced the pump I turned the vanes around and put it back on. The pressure was as it should be (10 lb) After thinking about what was going on I have come to the conclusion the lift pump must have been sucking just a bit of air from the fitting at the pump and I sealed it when I lubricated the fuel line to reassemble it. I think that a $0. 75 O ring has killed a lot of V44 pumps.

Robert

 

[WestTN]

SNOKING is correct. Unfortunenately Dodge has decided to make only a static check under no load at idle as the sole requirement to validate the LP. The dealer will therefore not bother with anything else.

 

[rgordon]

I too live in Prescott Az and just had the same experience at the same DC dealer last week. Fuel pressure red light always coming on, yet the dealer says everything is within spec's. I did my own testing with a fuel pressure gauge and found 5 PSI at idle and 2 PSI under load. I then installed a 7 PSI carter pump in front of the fuel tank with a filter between the tank and new pump. Fuel pressure at idle is now around 12 to 13 PSI and 8 to 10 PSI under load.

 

[SAndreasen]

as preasure goes up flow goes down this is a hydraulic principal

 

[SnoKing]

as preasure goes up flow goes down this is a hydraulic principal

HOWEVER, with zero pressure or negative pressure not much fuel is going to be flowing!!!! SNOKING