Do I need a new VP44?

[Mopar1973Man]

Fuel pressure gauge?

 

Fuel pressure gauge is a very helpful friend. If there is a loss of prime typically it can be seen on a fuel pressure gauge as a lag time for pressure to rise. May also show up as a sudden dip of pressure during cranking because of loss of lift pump prime. This will give clues on where the problem might be at.

[whodat88]

Yep, that's what's next on the agenda...I drove to the PO and it wouldn't start.  Had a guy walking by spray starter fluid and it started and ran (forgot to disconnect the heater grid ).  So now I'll repair the pressure gauge that stopped working several months ago.  I'm back to suspecting it's this Raptor. 

[rburks]

did you hook grid heaters back up.. did you get Batterys charged back to full cap. and is the engine cranking slow when you start it

 

opps,,Sorry you posted 2 replays what time i was typing this....sorry i didn't see them..

 

 

As Mike stated i think we've went bout as far as you can without F/P Gauge.  you could have a problem of LP Pump sucking air or Pump Cavitation.  Could also explain why your eating Raptor LP Pumps.....bUT WE NEED A WORKING Fuel pressure gauge to proceed further

 

Stay away from the Starting fluid thats my  SPRAYING THAT ON TOP OF ACTIVE GRIDS COULD BE REAL BAD

Edited July 25, 2015 by rburks

[rburks]

OH,  ONE LAST QUESTION, now that it doesn't want to start agin, "ARE YOU SURE THE LP IS RUNNING, Could you just bump the starter to make the LP run...DONT CRANK,,Just bumping starter should activate the RAPTOR LP PUMP

 

IF ITS NOT RUNNING, JUMPER OVER THE FP RELAY AGIN and see if it runs...

[whodat88]

You guys are great...thanks for your input!  Yes the LP is running.  I installed the fuel pressure gauge and bumped the engine. With the LP running it reads 14 psi, which seems acceptable.  So now what?  Is the VP44 losing it's prime?

[rburks]

now try starting the engine while watching the gauge,,report back weather or not if it falls off drastically 

Edited July 25, 2015 by rburks

[rburks]

did your truck originally have carter LP pump on rear side of engine block behind ECM or had id had the updated LP pump installed in the  Tank by OEM dodge dealer

Edited July 25, 2015 by rburks

[whodat88]

To answer your last question first, it had the pump mounted on the left side of the engine, where the Raptor is currently mounted.  I started the engine, psi at idle is over 15, drops to around 12.5 upon reving up to 2200, then settles first back to around 12.5 then up to 16.  I cracked the injector lines of 1,3,4 while running, didn't think this would matter, and of course got a little rough idle when one was cracked, and smoothed out after tightening.  After this fuel pressure check I shut the engine down and immediately tried to restart without starting fluid, no joy. I've got plenty of starter speed, but it just needs that little extra from the fluid to work.  Anything I can do to stop the bleed down of the pressure in the pump?

[whodat88]

There must be a check valve somewhere near the inlet of the VP44 to maintain pressure in the pump, right? If that were going bad or sticking this would be the result.

[Mopar1973Man]

No. There is no check valve in the inlet. The overflow valve is at the return side.

[rburks]

There must be a check valve somewhere near the inlet of the VP44 to maintain pressure in the pump, right? If that were going bad or sticking this would be the result.

 

NO,  IT SOUNDS as if it probably the rotor,.. i could be wrong, but its not building up enough pressure to pop the injectors,,,, 

 

MIKE  your the VP GUY here, whats inside the VP that would cause low pressure to the injectors????

[whodat88]

Yeah I was looking at the exploded parts diagram and saw that...I pulled the overflow valve and cleaned, didn't matter.  However when I went to start after this I had no fuel pressure, and bumping the starter did not cause the Raptor to run.  It's a bit too hot out there now to continue, so I will continue this later this afternoon.

[rburks]

If the overflow were stuck open would it keep from building up pressure to the hp lines and injectors????  OK   ANSWERED THAT

 

 

check your relay and see if its opening with starter engaging by the bumping the key or should have power on 87 pin when starter is  bumped..if not you ave a random intermittent short somewhere

Edited July 25, 2015 by rburks

[whodat88]

That's what I was thinking...I think I have a combo problem.  Intermittent power to the Raptor, causing excessive wear on the VP44, to the point where the VP44 is not creating enough pressure to pop the injectors.  Mike, do you know where the ground is for the Raptor/stock lift pump.  Might be worth checking on that.  Once I determine the cause for intermittent operation of the Raptor and repair, then I think I'll have to bite the bullet and change the VP44, as earlier even with fuel pressure from the Raptor it wasn't getting the engine to fire without a higher RPM than the starter could provide.

[rburks]

check voltage on pin87 on relay, you'll have to have somebody crank over engine while doing this

[whodat88]

OK will do.  So my $1500 question to you guys is:  have you experienced this sort of issue before, a seemingly functional VP44 except upon starting?  I would like to be reasonably certain that changing this will repair this.

[rburks]

You really need to trace the random short in your LP power circuit..  I had the 216 deaTH CODE in mine for 1yr before i replaced it and it never failed to start fine,,, just real lazy and fuel mpg sucked...your intermittent problem maybe in the computer board on top of VP IDK...Need to see if power on relay while cranking #87 pin  if nor cross those two over and see if truck starts and hold Fuel psi.   IF IT DOES START AND HOLD FUEL PRESSURE THEN YOU HAVE A SHORT OR SOMETHING IS CONTROLLING THE RAPTOR PUMP TO NOT ENGAGE ...We will get there, but if you drop the coin for new VP and thats not it, your out $1,000.00+ cause you will not be able to return it no matter where you buy it...I know this stuff can drive you nuts but really the best thing to do is to diagnose it a little further before you start buying parts..

[rburks]

MICHAEL,, Could this be the METERING SOLENOID OR "SHUT OFF SOLENOID IN  THE VP44 Randomly killing the LP Circuit?????

[Mopar1973Man]

Only the ECM controls the lift pump circuit. The only thing that will stop the lift pump circuit is that the tach signal drops to zero or the ECM is failing. VP44 has no abilities to control the lift pump if it on or off.

[rburks]

Only the ECM controls the lift pump circuit. The only thing that will stop the lift pump circuit is that the tach signal drops to zero or the ECM is failing. VP44 has no abilities to control the lift pump if it on or off.

 

K  THANKS