grim

so i was in the middle of a 3 hour drive when i notice my fuel pressure has dropped down to around 1 or 2. i normally have a consistent pressure of 4 or 5. Upon accelerating or while under a load it would seem to drop to zero or just above.
As soon as i could i changed both diesel filters (i have a secondary). When idling ill have 5 PSI but when driving itll go back down to 1 or 2 and randomly itll be at 3 or 4 sometimes and stay there for a while but then will go back down. I have a mechanical pressure guage, and it seems unlikely that it just started malfunctioning.

I also am running on veggie oil. I changed my veggie filter and the pressure reads the same for diesel and veggie oil.

are these symptoms of my lift pump dieing? Should i stop driving until my pressure is regular?

#2isgreen

Do you have the stock diaphragm pump? If the diaphragm is failing fuel could be getting into your crank case. If the dip stick smells like diesel or the oil level looks too high you should look for a new pump or a piston pump and eliminate the diaphragm.

Onemoparnut

That low amount of fuel pressure wont hurt anything except performance, but like #2isgreen says make sure it is not leaking into the crank case.

grim

ya i have the stock pump. Wondering if i should try the volume test in the manual? is that an accurate way of telling if my pump is goin bad? or what is my next move? im kinda nerous drivin around like that with pressure dropping to zero sometimes.

grim

also i dont have fuel in my oil (that i can notice anyway) and my prime lever works.

grim

update:
i unhooked the output hose of the lift pump and cranked it into a bucket and measured a litre of fuel. manual says .75 is normal so i got that.

it seems my pump is fine. not sure what to check now.
could anything else cause low pressure?

grim

update again. I installed a new pressure guage. and my psi is normally running above 3 but does drop down to 2. manual says bellow 3 needs replacing. still wondering what yall think?

deanhinsley1963

If you can afford it do the piston pump replace should get things going good again.

Santaclaus

You might do a static pressure check to see if the spring in the lift pump has gone bad. Just my two cents, Mike.