04.5 LLY Fass 165 troubles

brycejhnsn100

New member
Dec 14, 2019
10
0
1
Hey guys, recently bought a 04.5 LLY that has a fass 165. Issue is on cold start sounds horrible injector knock and smoke until it warms up for a few. Injector rates are perfect when warm. Issue is when warm at idle my actual rail pressure is about 8500-9000 and desired is 4500 or so. I believe my fass is sending to much fuel as ive heard its an issue. Have not hooked a mechanical gauge to test yet. Pressures are fine under a load to. Anyone have a part # for a spring that will lower the psi?? Thanks
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Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
2,838
246
63
Neenah, Wisconsin
Check what the supply pressure actually is. If it's too high it will cause the issues you're seeing. To fix it, call FASS and they will get you squared away with the proper spring at usually no charge. You will need your pump's serial number handy when calling to order parts.
 

brycejhnsn100

New member
Dec 14, 2019
10
0
1
I did email them they want to hook up a pressure gauge and said between 8-10psi


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Ron Nielson

Active member
Oct 11, 2009
376
27
28
Berryton, KS
I would think that FASS would know what pressure would result from a given spring. if the pressure is say 14 currently vs 10 currently, would there be a different spring to make the adjustment??
 

MMLMM

Tunergeek
Mar 2, 2008
4,085
1
36
40
Reno, NV
www.dyncal.com
As stated already, check the pressure with a gauge. Your theroy of too much pressure is correct. It will cause the regulator to not close off correctly, which will cause higher 'actual' rail pressure. It could also be the regulator itself starting to fail. Do you run any fuel treatment in the winter the time?