Please help.  At my wits end.   I have a 2001 Dodge the problem is,  after driving two hours on the highway if I come to a stop after driving this length of time and then accelerate again the truck will die I don’t lose my prime at the injector pump ,  I do lose pressure. but my pressure takes some time to rebuild and then it will start. I’ve pulled my tank draw straw no obstruction.  I have a raptor 100 lift pump. After I restart the truck it runs fine.  Starts fine when hot. Seems like it’s starved for fuel.  If I bump the starter after it dies the pump will rebuild pressure and the truck will start. Any ideas ? 

Is the vent on the fuel tank plugged? 

No the vent is not plugged. I checked that. And no suction when I loosen the fuel cap.  Also the problem seems to occur when I’m below half a tank. There is no crack in the draw strw or obstruction from the tank. 

Have you checked where the fuel hose/line makes the 90 degree bend going into the tank?  This is a very common place for air leaks due to deteriorating rubber fuel hose.  Are you sure the Raptor fuel pump is running properly through all of this?  It could be that it stops running intermittently due to over heating, poor electrical connection, shorted wire, etc.  

 

The only other thing I can think of is the circuit board on top of the VP-44 getting hot and intermittently losing electrical continuity.  Just a few things to take a look at that comes to mind.  Hope you figure it out.  

  I’m not 100% sure the raptor is working fine. I pressure tested from the 90 to the bottom of pickup tube and it’s good. The raptor does wine from time to time. Maybe the pressure is too high. My fuel pressure gauge  fluctuates very slightly. It does almost seem like the pump is shutting down.  I’d like to run a temporary voltmeter on the pump so I can look at it when  The truck dies.  

  Thanks for the input. 

What is the fuel pressure normally at idle, cruising on the highway, and shortly after? Do you know if the pressure is super low just before the truck starts to shut down? 

 

My first one failed after only 4 years, and for whatever reason I threw another one on there, been running good since, but time will tell.

20 psi is my fuel pressure now. My gauge in the truck is  not working and I’m waiting for a new one. I have a pressure gauge hooked up to the shradder valve  on the v44 Temporarily. So I can’t tell  if the pressure is low before it dies.  One thing I do know is after it dies and I bump the starter it takes a while for it to build pressure again. I usually have to bump it twice to build pressure before I try starting It again. 

  It also seems to happen when it is below 1/2 a tank. So frustrating. 

            Thanks for your comment ,Mark 

When you installed the lift pump, some of them have a small screen beyond the female threads down inside the inlet side that you have to remove or it can clog. Do you have a pre filter before the lift pump? Important to filter out and separate water out before the lift pump can chop it up/ mix it into the fuel, emulsifying it.

 

Also have someone watch the fuel pressure while turning the regulator up high and low at idle. Both my new Raptors on both my second gens acted up until I did this.

 

Are you powering the lift pump from the factory lift pump connection? It is wrong if you are, it will destroy the ECM. You need the factory ECM connection to trigger a relay only and lets the L/P get it's power from the batteries. 

 These are some good ideas.  I will check to see if there is a screen on the inlet side of the pump ,no I do not have a pre-filter in front of the pump. I have no contamination in my fuel tank there’s no water or any crud inside my fuel tank. 

   I will have somebody watch my fuel pressure when I turn up the regulator on the pump and see what happens.  

   I am running the lift pump with the wiring harness through a relay which was provided by raptor when I bought the pump.  I’ve had this raptor for maybe five years.

  It was whining because I had the pressure up to 30 psi.  I got it back down to about 17 to 20 pounds it’s not whining now. 

   I will check for an obstruction in the screen I hope that’s it.

  I know it’s not the draw straw I’ve pulled that sending unit out I don’t know how many times I’ve checked it twice from the top of the fitting on the tank to the bottom of the draw straw there are no leaks. 

 

   Thanks for your suggestions ,Mark. 

Yes run the regulator up and down a few times as though you were trying to help it seat or break in. I doubt that's the problem, but what can it hurt? It helped me on both rigs with unstable fuel pressures.

Ok I will try it. Thanks. 

Ok I will try it. Thanks. 

Ok. There is no screen before the raptor. And no  obstruction From the bottom of the Pick up tube to the pump. And no leak.  The pick up tube is the one which was provided by raptor with the pump. 

   I adjusted the regulator while looking at the fuel pressure gauge.  The pressure goes up and down  as it should.

  I don’t know. I’m thinking I need to hook up a temporary  volt meter  to the pump and  see  if the power is cutting out to the pump when the truck dies. 

  

 OK I have an update. I hate to admit this but my  sending unit is not working properly. At 1/2 a tank on the gauge I really only have 5 gallons of fuel in my tank.  I still should not be running out of fuel with 5 gallons of fuel in the tank but maybe my draw straw is not all the way on the bottom and therefore when I go to accelerate after stopping I suck air and the truck dies.    Thanks for everybody’s input  

Update. I hate to admit this but my truck is running out of fuel at half a tank the Sending unit is not working properly I do still have 5 gallons in the tank when does.  But maybe the draw straw is not all the way on the bottom of the tank when I go to accelerate after being stopped I am probably sucking air. 

   Thanks for all the response   

Draw straw should nearly touch the bottom. No diagonal cuts. No excessive gap.

 

There is only the thickness of a quarter between my straw. As I fill with fuel the diesel weighs about 6.3 to 6.7 pounds per gallon. Depending on cetane level higher cetane is lighter per gallon. So 35 times 6.7 pounds per gallon. That's 234 pound it will cause the bottom of the tank to deflect another 1/8 to 3/16 of inch. Adding gap but as the tank empties now the bottom comes up to the tip of the straw allowing me to suck all the fuel out. I can run all the way to the EMPTY mark and never died out.

 

I’ll check the draw straw  height.  I noticed your set up does not have a return line and draw straw going into the factory bowl/sending unit. 

No. Return to sender is HOT fuel. You do not to draw that back up. Adding more heat to the VP44. My typically fuel temp is about 110 to 120F... draw from the tank is much cooler fuel.

I’ll check the draw straw  height.  I noticed your set up does not have a return line and draw straw going into the factory bowl/sending unit. 

Ok. I have the raptor draw straw in the bottom of the gutted factory  fuel bowl module. And the return fuel goes into that bowl. Maybe should go with a set up like yours. Straight draw straw and the return fuel just dump in from the the top of the tank. 

  Thanks 

I installed my AD 09 or 10. Both my engine return and pump return go to the fuel basket/bowl and I have never had an issue with it. Still that way today.

Ok. Mine too. My problem was I thought I was running out of fuel but really my fuel gauge wasn’t working properly.  And possibly my draw straw is not all the way at the bottom of the bowl   And therefore I’m running out of fuel with 5 gallons in my tank  

Best having the straw in the tank not the sender. Returning hot fuel to the VP44 isn't good. The the measurement for inside the sender is very limited. This why I kept my draw straw where it at for over 20 years now always been able to draw the tank empty (actually empty on the gauge). All about how tight you can get the tip to the bottom of the tank as when it gets empty. When you fill the tank the bottom will deflect downward another 1/8" of so. Never measure with a tank that has fuel in it. Never had 1/4 slosh problems and always had cooler fuel temps than most. 

 

420k miles and ticking...