I just installed fuel, boost, and pyrometer gauges. Truck is pretty much stock besides a cold-air intake. after the guages were intalled i noticed my fuel pressure was at about 7psi at idle. When i punch it on the highway it almost reachs 0psi. My lift pump was replced a few years ago with the in tank retrofit pump. The shop that installed the guages told me that it should be ok, but the next time i am in the shop i should get the lift pump tested. I am wondering if the guage was calibrated when they put it in, or if it even needed calibrating. The guages are auto-meter. just looking for some thoughts or ideas. ive pretty much decided that the lift pump needs attention but i'm fairly new to diesels and hey, i'll admit it, i don't know everything. not yet anyways. thanks.

 

I think that your gauge is correct and your in-tank fuel pump is not very good, like most of those types the dealer puts in. This is why many people throw those away and install an aftermarket kit.

 

any suggestions for aftermarket pumps?

 

Going to be hard to beat the FASS systems. Any of the FASS systems. I put the HPFP without the aftermarket filters, and use a draw straw. Good pressure ALL the time. Something like a 6 year warranty also. Just a little noisy. Installed mine in the middle of the bed on a rail, so it is not quite so noisy.

Kip

 

thanks i'll look into it.

 

The Airdog is a popular system also. You might check it out. I have heard good things about the Airdog and Fass both. But i hear FASS does deal with warranty's too good. Just my

 

For what its worth I have the newer version carter pump not the air tex and its still in the factory spot and I have a solid 13psi idling and no less than 8pis at 2500rpm pull a load. Been strong for 2 years now don't know why only thing I can esplain is that I don't have major fueling mods.

 

OK, so far ive talked to a diesel tech at the dealer. He is saying that the in tank retrofitted pump on my truck (chrysler pump) cannot be read by a pressure guage. It is based on volume only so any psi reading will be inaccurate. Anybody out there heard of this before. I don't want to have to change out the pump if i don't have to. By the way the dealer dude told me to change the fuel filter as i told him the truck seems a little sluggish.

 

Dodge went to a flow measurement instead of PSI as they were replacing too many pumps.

Free flow measurement tells you how much the pump flows, but does not tell you if it will maintain any positive pressure at the point of delivery.

You could have a 500GPH pump, but it may only make 1 psi. Which is better, pressure or flow?

I stick to pressure. Flow comes with it based on the size of the lines. The larger the line at a given pressure, the higher flow potential. However, pressure is resistance to flow.

Bottom line is, I don't like the in tank pumps. In many applications they simply cannot keep up and the result is low power at least and lack of fuel at worst.

Dave

 

Makes sense, thank you very much!

 

on an aside, the dealer also said it sounded like the truck has had a performance chip in it before(i bought the truck used two years ago) because i had a stored code(can't remember the #) that said i had an over boost on my turbo. This doesn't make sense to me. I would think (and i'm about as sharp as a boiled weiner when it comes to disels) that insufficient fuel flow could indirectly affect turbo boost under load. thoughts on this? am i out to lunch or what?

 

Jay Jay:
I had the same low pressure problem after my in tank pump was installed.. I installed a "Vulcan Big Line Kit" and now 60k miles later I still have 9psi at idle, and 7 /7.5 psi at WOT. The vulcan kit, replaces the very restrictive banjo bolts with larger fittings and lines, and allows flow and the pump pressure to get to the VP44. I also eleminated the cast alluminum block that Dodge puts were the old pump went. So I replaced 5 restrictive banjo bolts and now have fuel line dirrect to the inlet of the filter and then from the bottom of the filter housing direct to the inlet of the VP44. So I have 2 of the fittings left.(vulcan supplys 5 fittings ,I used 3 of them.)
And my fuel pressure gauge is tapped into the fitting on the VP44.The Vulcan is cheaper than replacing the whole system. Just my $.02.

 

The dealer is playing word games. If the pressure measured at the VP44 ever goes to zero, it means that as soon as that point is crossed, the lift pump will not deliver any more fuel, it has plateaued at its max flow capacity. Flow and pressure are very closely related.