Tayloe08

Just got home from work and on the way in noticed the FP gauge at 4-5



The gauge would jump back up to 14-15 and then back down to 4-5. The LP is about 3 or 4 months old. Could it be shot already? Or could it be the gauge which is only about 5 months old? Thanks

Andy505

if it is an electrical guage then try making sure that the wiring is secure. I had the same problem....the fuel pressure was all over the place...i check the wire to the sender and it was loose. tightened it up and all is well

Tayloe08

I am thinking it may be the gauge because of the different readings on the gauge. I don't see how the LP could go from working (15 psi) to not working (5 psi) and back again. It seems that it would drop to 5 psi and stay!!!

Bob H

Could be a leak in fuel line. Mine was sucking air where the steel line from the tank and the rubber to the lift pump join. Two hose clamps solved the problem


bob H

Tayloe08

Waiting for store to open and just wanted to check a few more things.

1. The gauge is mech. Could it still be bad?

2. Am I correct in thinking if the LP is bad the pressure would stay at 5 psi?

3. It is a Carter LP. That is all the store has and I really need my truck today. Is there another brand that is better? I am going to order the Vulcan relocation kit and bigger lines. Should this solve or at least help my future LP woes?

Shovelhead

There are several threads discussing a replacement for the stock lift pump in the general Diesel Discussion forum.
My last two lift pumps have done the same, low pressure until over ~1,000 rpm them jumps to 15 psi.
As soon as rpm dropped back to idle, pressure would drop like a rock.
New pump brought pressures back up to acceptable levels.
There have been reports that the plastic bushing that connects the motor to the impeller might be culprit causing some of the failures.

HOdiesel

I had the same problem. It was the mechanical gauge. I replaced the whole gauge system and it is back to normal.

HoDesel

atch

What type of isolator are you using?
I had trouble with the cylindrical one, went to the diapram type and the problem went away.

Tayloe08

Just got home from work and truck seems to run fine (I was being easy with the skinny pedal) The only difference from before is at idle it was 15 psi and now it is only 12.5 - 13 psi. I could not get it below 10 or even to 10 before and now I stopped when it dropped below 10 on the interstate. Any suggestions???

crobtex

Check all your fittings and then you will probably replace the lift pump.

Mine done the same thing on a fairly new LP....replaced it with a FASS II and all is well. There are other option then the FASS>

phox_mulder

Are you measuring pre or post filter?
I'd check the filter, something might have just gummed it up.

Then start thinking about the LP dying.


phox

Tayloe08

The gauge is post filter. I did replace the LP this morning and getting the numbers above. So the LP did help but it does not have the pressure it had before. The pumps are exactly the same. Would the above readings cause concern to you all or am I ok? Thanks!!

Shovelhead

All lift pumps are not created equal.
My old one read 16 psi @ idle.
The new one reads 14-15 psi at idle, but I still can't pull it below 10psi at full boogie.

Bad Ramer Jamer

When you installed the isolator, did you put anything like antifreeze in the line. I didn't on mine and all's well. Just a thought.

Tayloe08

I did not use an isolator on my setup but thanks for offering advice. I guess I will just order the relocation kit with bigger lines and see how that works. At least I know that is one thing that should be well worth the money! I would not be so worried about the lower reading at idle but it drops to about 8-9 at WOT (or at least that is when I let out but that seems about as low as it will go) We'll keep foot out of it for now. Thank everyone for your helpful advice.