2nd Gen Non-Engine/Transmission vulcan big line kit and new lift pump still low fuel pressure

[Jdorfmeyer]

Ok I bought my first 24 valve, a 2001. 5 with 70,000 miles. Installed gauges and an edge ez. Fuel pressure was around 10. 5 and I could pull pressure down easily under throttle to around 5 and 6 pounds. I decided to get the vulcan big line kit, and a new lift pump from cummins. Received new lift pump 4090046 and installed with vulcan big line kit. Now fuel pressure was at 9 psi and it barely lowers under heavy acceleration. I don't even lose a half pound. Thought the pressure would be higher with new lift pump. Talked with cummins dealer here in Lincoln NE and he said he will get me new lift pump. Removed new lift pump and put original back on with vulcan kit. Again 10. 5 psi, but would pull down to about 8 even with big line kit. Got new cummins lift pump again with same part number 4090046 and still have 9 psi and it doesn't hardley change under acceleration. Does anyone know if the new lift pumps from cummins run a lower pressure. I seem to have decent pressure and no drop under throttle. I called cummins and they told me to make sure I have over 5 at vp44 and bosch says 7. I have my gauge hooked up to the port in between the fuel filter and vp44 supplied in the vulcan kit. I feel the new lift pump is very stong compared to my stock lift pump that will pull down under throttle. Is there something I am missing, or is my pressure ok. Eric with Vulcan has been great to deal with (as well as my local cummins dealer)and the kit was easy to install.

 

[Dane]

You don't need higher pressure. Not having the pressure drop under acceleration is what you want. Remember, the "lift pump" only ensures the VP44 has a good supply of fuel along with enough excess to cool it. 9psi at WOT is fine imo...

 

[Jdorfmeyer]

Thanks for your info. I know this issue gets beat to death on tdr, but I don't want to hurt the vp44.

 

[therabbittree]

do you have the lift pump mounts in front of the fuel tank with your vulcan? or still on the block with bigger lines?. . my dad's is infront of the fuel tank and its like 15psi with the vulcan big line kit and a"new" slightly used cummins lift pump from a school bus ISB. .

later

Deo

 

[Jdorfmeyer]

I have the pump back by the tank. I have the newest kit from Vulcan. Do you know the part number for your dads lift pump? Thanks

 

[CDenton]

I did the same thing to my 98,just got the cater pump from Summit 100 bucks. Runs 12 at wot.

Good Luck

 

[bullseyejack]

I had the same condition after installing the Vulcan Big Line Relocation kit and a new pump. I had also gotten a feul pressure kit from Vulcan at the same time. I found the problem to be the Isolator supplied with the gauge kit. I removed the Isolator and had 15 psi at idle and 12psi at WOT. Problem solved. If you have a isolator wit the mechanical gauge. Try removing the Isolator and see what you get. FYI I called Eric at Vulcan and he refunded me the money for the Isolator. Great Guy and good to deal with.

 

[Jdorfmeyer]

Thanks for the info.

 

[therabbittree]

forgot to mention no isolator on my dads truck... . also vulcan is awesome. . i had a connector that pulled out and he sent another asap and it worked great he was very very good customer service wise... mummn now i'm not sure if i should use my isolator on my '96 i'm just about ready to try it today. . i guess i should try it and see how it is. . but i'm measuring 12v fuel pressure. . with autometer mechanical guage and isolator. . using 4an stainless line for connections and drilled the fuel pump inlet banjo for the 1/8" 4an fitting. . interested to see how it works. .

thanks

deo