My 98 12v idles higher on oil than diesel. I think it may be a fuel pressure problem. Now if I fill the diesel tank, it won't start, hot or cold. The diesel tank pick-up screen is clean. And it starts when the tank is less than 1/4. Is the only press reg the ball and spring deal on the pass side of the pump?

 

what is your set up like? mechanical or electric LP and what are the pressures that you are running. something tells me that this has been discussed before but i just cant remember

 

Yea I searched for quite a while. The pump is stock mechanical. I replaced it, but the old was working fine. This has been an ongoing prob for 10k miles.

 

Are you using dual fuel systems? Have you checked the fuel filter on the diesel side?
Try clamping the diesel line when running on veg to see if the fuel selector valve is allowing fuel to flow around it.
Otherwise Id think youre pulling air on the diesel side. Probably from the tank pickup or metal fuel lines. Replace them all with good quality diesel fuel hose.
You can replace the rotting metal pickup tubes at the top of the tank with a vulcan draw straw. Just cut off the nylon tubing coil and replace with a section of the hose provided so the pickup sits close to the bottom of the tank when unsupported.
If you check out how the pickup assembly is put together, its pretty slick. It has a couple stages of one way valves and a float to allow positive pressure from below and negative pressure from above to draw fuel inside and retain it. Sort of makes you want to buy another for a custom veg tank.
Id also go to mcmaster-carr and get a pair of inline sight glasses so you can eyeball the fuel and the amount of air its pulling.