Lift pump question

[Mobius1]

I believe that the CP3, thats the high pressure fuel pump that pressurizes the rail needs 20psi to operate. I am not sure about this but I seem to remember that as the magic number. If the lift pump is getting weak, especially if you are running a chip, the CP3 may not be getting enough fuel to keep the rail pressurized. If you find a reputable shop I would first make sure you are getting at least 20 psi to the CP3. Maybe someone can confirm that number here first. If you are getting enough fuel pressure to the CP3, than make sure that the rail pressure is not falling below 23000Psi at WOT. If it is than you are draining the rail. I have seen the Quadzilla drain the rail pressure even with a healthy lift pump so that would be where I would start. Good luck and let us know.

I think you should be seeing 13psi with a stock lift pump at the cp3 accroding to a reputable dodge dealer in my area. I have about 7. 5 psi at idle, 8 on a good day. I can easily pull my fuel psi to 0 on a hard run. Then the truck falls on its face. The lift pump is probably putting out more than 7. 5 put by the time it makes it to the cp3, it has loss some of its psi.



I think aroud 8-10 is an average psi for stock lift pump @ the cp3

 

[BTesluck]

My lift pump died going 70 mph down the interstate. It had NO previous signs of failure. The truck shut off just like turning off the key, but all the lights were on. Luckily it happened close to an off ramp and we coasted very close to a gas station. This happend at 65k miles on the truck. After we got into the parking lot of the gas station , I pulled the cover off the fuel filter canister and the fuel was gone. At that point I had a darn good idea the lift pump died. It was mounted on the back of the canister and the dealer upgraded the system and put the lift pump in the tank. Got 95k without any problems yet. What I am getting at is that I had absolutely NO warning !!



Bob T

 

[MickeyMiller]

Well, it happened to me today, Christmas Day! 3 miles from home, the truck stops running... I coast to the shoulder. Won't re-start. Set 10 minutes, it fires right up but stops 3 more times in the 3 miles home. Two codes:

P628 - Fuel Lift Pump Control Circuit Low (or Fuel Pump Relay Circuit Low)

P837 - Four Wheel Drive Switch Performance/Rationality



I plan to check all connections for corrosion, but expect to replace the lift pump. Ant idea why it would throw the P837???



96,541 miles/2358 hours (41 mph average)



TIA

 

[AGrubbs]

Electrical

MickeyMiller:



If you have both of those codes, it sounds more like an electrical problem than something mechanical with the pump.



Check that circuits power and ground connctions. Also the relay for the LP power.

Could be something has gotten loose or crudded up.



Let us know what you find!

 

[TGarris]

Reguardless of what the problem turns out to be, get a F. P. guage. The good news is a bad L. P. should'nt hurt your I. P. Not like the vp 44pumps.

 

[MickeyMiller]

Looks like the codes were unrelated. The '03 doesn't have a Lift Pump Relay, it's fed from the ECM. Connections look good and I do get power... so P628 looks like a bad Lift Pump. I think I have a bad position sensor on the T-Case causing the P837... more checking to do.



Once I replace the stock Lift Pump (Glacier kit due Friday) will the P628 code 'go away' or, do I have to have it reset?

 

[rbattelle]

Once I replace the stock Lift Pump (Glacier kit due Friday) will the P628 code 'go away' or, do I have to have it reset?

It should disappear on its own after 40 warmup cycles if the fault doesn't reappear. Light will go out after 5 startups without the fault returning.



Ryan