Lift pump fuel press.

[Ball54]

I installed a Raptor 100 lift pump last year and have been having pressure loss problems on warm days.Idle press. is set at 15psi when the engine is cool.On 80 plus degree days I've seen the idle press as low as 6psi.when the engine thoroughly warmed up.When the truck is parked I've checked several hours later as it cools down the press. will gradually go back up to 15psi with the passage of time.The fuel system is set up as follows,stock fuel module,3/8 hose throughout,Chrys.H/D fuel filter head with high flow banjo bolts in and out,Raptor pump,stock fuel filter housing with GDP adapter and Wica gauge,GDP 2Mic filter,then in to CP3.Fuel filters are,Fleetguard FS 1001,Baldwin 7977,Donaldson P551313.Originally the F/W separator was a Chrys.68020642AA but I changed to the FS1001 for the standpipe.It seems to have helped some....Any thoughts suggestions?

 

[Ball54]

Forgot to mention the tank vent is OK.

 

[RDeFayette]

Forgot to mention the tank vent is OK.

do you notice any difference when the tank has more fuel in it?
Possibly you are returning so much (hot) fuel to the tank you are decreasing the viscosity enough to drop the pressure. More fuel in the tank will decrease the effect (More fuel to dilute/raise in temp). anytime the fuel is warmer viscosity will decrease, inverse of gelling in the winter. Just a thought.

 

[Ball54]

A couple weeks ago I went on a 250 mile trip running lite.With a full tank temps in the lower 70's and no A/C on at the turnaround point the press. was 14psi.I thought FS1001 had solved the problem.Return trip temps.were above 80 so I turned on the A/C.Back at home the press. was 7psi with 5/8 of tank.The next day checked it by bumping the starter. The press. was again at 7psi and it struggled to get to 15psi before the pump timed out.Vaporlock,suction leak,low viscosity?I'm thinking of getting rid of the high flow banjo bolts on the F/W separator.
2004.5 2500 4X4 SLT Quad Cab SWB 48RE 3.73LS Banks cat back Ex.Raptor 100. Chrys.Svr duty filter. GDP 2Mic.filter

 

[hcole]

ball54, I would check your gauge, especially the isolator. When the antifreeze in the line to the gauge gets low on my truck, it will give those type of readings. I just refill the line with a hypodermic needle.

 

[PWong]

I had a Raptor pump problem similar to yours two and half years ago. It was a Raptor 150 for WVO operation. It was installed near the firewall above the exhaust manifold, in a vertical position. Problem showed up one year later in around 10000 miles. Before engine was warmed up the pressure was good at set 11 psi at idle. After the engine reached operating temp the pressure would drop to 5 psi at idle. The WVO temp can be as high as the coolant temp. So the pump operated HOT.
The replacement Raptor 150 was installed under the hood in a cooler location and installed horizontally. So far there is no problem for two and half years and 50000 miles.
I would say your pump is retiring if your gauge is good.

 

[TJJEEPER]

ball54, I would check your gauge, especially the isolator. When the antifreeze in the line to the gauge gets low on my truck, it will give those type of readings. I just refill the line with a hypodermic needle.

^^^ This
My pressure gauge dropped to zero after the truck had been setting for a while. First thing I thought was algae in the tank. Bought some Biocide and changed the filters. Still nothing. Cracked a fitting and there was diesel squirting everywhere. I found my isolator was near dry. Injected some antifreeze and refilled and bingo, proper pressure.

Doesn't explain why you're getting good pressure when cold though...

 

[Ball54]

I don't have any in cab gauges yet.My fuel press.gauge is a mechanical gauge on the side of the stock fuel filter housing.I spoke with a fellow a local shop that does work on diesel pickups and he suggested 1/2 inch line and getting rid of the banjo bolts on the fuel water separator.Probably be a few weeks before I get that done.Thanks for all the feedback so far.



2004.5 2500 4X4 SLT Quad Cab SWB 48RE 3.73LS Banks cat back Ex.Raptor 100. Chrys.Svr duty filter. GDP 2Mic.filter

 

[PWong]

suggested 1/2 inch line
Size of fuel line should have nothing to do with the low lift pump output (5 psi) at idle.
The demand of fuel is mininum.
Also it has nothing to do with the reading of the pressure.
Your problem is temp related. (temp of pump motor)

 

[Ball54]

My fuel pump is only 2" from the transfer case so that might be the problem. I could make a heat shield. Do you think that would cure it.



2004.5 2500 4X4 SLT Quad Cab SWB 48RE 3.73LS Banks cat back Ex.Raptor 100. Chrys.Svr duty filter. GDP 2Mic.filter

 

[PWong]

fuel pump is only 2" from the transfer case
I don't a lot of heat there unless it close to the exhaust pipe.
I just try to say in my case it could be heat related, position (vertical or horizontal) related or just a defective pump motor.

 

[PWong]

installed a Raptor 100 lift pump last year
Should get a free replacement within 12 months.
I would call them.

 

[Blakers]

Are there any negative effects other than observing the pressure drop?