What is the proper PSI for Diesel vs Veggiefuel?

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VeggieFuel1's picture
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Joined: 03/24/2007

Hey Everyone...
I have a 6.5 liter diesel suburban.   I put an inline sensor on the fuel line.  Here are the stats/issue:
On start up I get 7 PSI while the LP is priming the IP.
When running it drops down to 5 and sometimes 2 or lower when stepping on the peddle.
Switching to veggie works fine (co-pilot) but the PSI is 10 to 12 PSI.  I have had this adjusted to this PSI since purchasing 3/8" hose and Raptor pump kit back in 2010.
Switching back to diesel while on the road is fine. But when it slows down the car seems like it is miss firing.  I had relocated the PDM so I think that is not the problem.
I have come to the conclusion that it is either the IP or the PSI on the diesel side needs increasing.
I have already changed the filters twice within the last two months.  I had some veggie get in the diesel tank because the return valve ground got loose and dumped about 10 gallons of veggie in the diesel tank this last summer.  About three months ago the warning light came on for checking optical sensor.  I immediately checked the filters and found them extremely dirty.  I then changed them and it did not come back again.  I also had an OPS go bad about 4 months ago and had that changed also.
Any thoughts are appreciated.
Thanks -
 
 
 
 
 
 
 

veggpwr's picture
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Joined: 09/27/2010

""""The most common symptoms of lift pump failure are slightly harder starting and low power.

This pump is located underneath the driver's seat area inside of the frame rail and should produce around 4 PSI of pressure to the injection pump. You should be able to hear and feel this pump running. Another method to verify the pump's operation is to open the fuel filter water drain in the engine compartment with the engine running. If fuel sprays from the end of the hose and the truck continues to run, the pump is still working. If the truck dies, you may need a new pump.

Continuing to operate with a failed lift pump causes overheating and eventual failure of the injection pump and PMD (if you have not graduated to a remote mount PMD).

Before replacing a lift pump that is not working, be sure to check for 12 volts at it's terminals with the truck running. Use paperclips to back probe the connection instead of unplugging the pump since an unloaded circuit will give a false reading. If 12 volts is not present, the problem may lie with the oil pressure switch located at the back of the left cylinder head. The pump receives power through this switch with the engine running, but through a separate relay with the engine cranking.""""
 
The above is a copy and paste info from the internet.
Check your diesel lift pump operation.
Also check and clean your fuel pickup strainer inside the diesel tank if you have one. Most likely it's partially clogged.
Veggie is a good detergent inside the diesel tank. It would break loose the sediment inside the tank.
That's why you had two extreme dirty filters.
I would drop and clean the tank to make sure.
 
After making sure the strainer is clean and the fuel pump is fully functional, install a new fuel filter and notice
the fuel pressure at idling. Use this number as a reference number for fuel pressure concern in the future.
The number at different pedal position is hard to use as a reference.
Recommend to install a fuel pressure gauge right before the injection pump so you can monitor the operation
condition of your fuel system (diesel pump, veggie pump, diesel filter, veggie filter) on the run.

__________________

'05 Cummins CTD 24V HPCR RAM 2500 QC SLT SB Black 4X4 48RE  325 hp  610 ft.lbs
GC Kit  + 3rd Tank WVO(80%)/RUG(20-30%)  +  Co-Pilot 
3-Tank Operation managed by Co-Pilot: Blending(warm up) / Veggie(hot run) / Diesel(purge for next start)
Smarty Jr  40/70/100 hp (Timing Map Modification)
 

VeggieFuel1's picture
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Joined: 03/24/2007

Here is an update,
Thanks for the update and comments.
Just wanted to make it clear that I already have a pressure guage as indicated above as this is where I collected the PSI info.
So it sounds like the diesel is at the correct pressure.  Mine is running around 5 PSI and the LP is definitely working.
I drove it today just on diesel (60 miles) and had no problems.
I will definitely check into cleaning out the diesel tank.
Thanks  for the information!
 
 
 

VeggieFuel1's picture
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Joined: 03/24/2007

What is the correct PSI for the veggie side ?  Should it be the same as the diesel?

veggpwr's picture
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Joined: 09/27/2010

What is the correct PSI for the veggie side ?  Should it be the same as the diesel?
NO, usually not the same.
Usually the veggie side is a little higher than the diesel side, to compensate for the efficient delivery
of higher viscosity of veggie before it's HOT, IMO.
The correct PSI would be the one that is high enough to do the delivery job without hurting the injection pump.

__________________

'05 Cummins CTD 24V HPCR RAM 2500 QC SLT SB Black 4X4 48RE  325 hp  610 ft.lbs
GC Kit  + 3rd Tank WVO(80%)/RUG(20-30%)  +  Co-Pilot 
3-Tank Operation managed by Co-Pilot: Blending(warm up) / Veggie(hot run) / Diesel(purge for next start)
Smarty Jr  40/70/100 hp (Timing Map Modification)