Injector Lock up due to High Fuel Pressure
 

Hello, I have a question regarding our HPFP and fuel lines. From my research the fuel system is designed to operate and maintain up 2900psi if you are running the LT4 fuel system.

I own an 1LE and recently I did a heads/cam swap with a 32% fuel lobe and my car cannot get bellow 22-23mpa in the higher rpms (above 5.5k) with the LT1 pump and lashcap on 93 octane.

My tuner warned that this high of fuel rail pressure can lead to the injectors locking up if the pressure rises too high due to my fuel bypass selenoid not being able to keep up. I was wondering if this is a common issue people run into? What fuel pressure are other setups normally seeing in the higher rpms?

I see people recommend LT4 pumps and injectors on heads/cam builds all the time and never heard of complications from getting too much fuel.

Any insight would be appreciated.

Why are you running 2900 psi on an LT1 HPFP? That’s supposed to be set at 2175 psi. Did your installer check the fuel pump travel after installing the lash cap…?

It is targeting 2900 psi because I was originally running a full lt4 system but was advised to switch back to LT1 to see if it reduced fueling. Still running lt4 injectors which requires the 2900psi.

Both setups have had a lashcap with limited preload and do not bottom out on top stroke. It is the .060" lash cap slightly machined.

What is your build? Are you still NA?

Correct still NA
Texas Speed Heads cam (231,243 116), 2" headers, Rotofab intake, LT2 ported IM and ported TB.

What were you putting down for power? At first glance it wouldn’t appear that you needed LT4 fueling in the first place…

That's what I was going to say. Maybe his pumps are on the weaker side.:noidea:

On 93 octane you shouldn't need more then the LT1 fuel system at LT1 pressures. On E85 you would probably be close to the limit of needing the LT4 stuff depending on target AFR.

That being said I have never had a issue running LT1 style pumps @ 2100-2900psi in the past. I have ran 3 different LPE big bore pumps(based on LT1 pump) that high and never had issues. And I also know some guys have ran LT4 stuff as high as 3400psi without issues.

If pressure is too high for the injector they will misfire. I ran into this on a set of gen 2 FIC +30's. They don't like 2900psi. Had to turn rail down then they were fine.

Moral of the story I think you are fine either way.

Tuner wanted to me try some things to see if pressure would drop. Added e85 and zero changes in fuel rail pressure. Removed lashcap with e85 in the car, zero changes in fuel rail pressure. Car is still hitting 22-25mpa and holding with rpm. At this point idk what to do to get it down.

Did you tuner adjust the high pressure pump angle in the tune? I don't remembering ever having any trouble with mine hitting target fuel pressure when I put my cam with fuel lobe and lash cap on before I edited my cal, but just a thought. Mine seemed to be right on and right on after I adjusted the angle.

Funny, I expanded my search and I was reading a post you replied to on HPtuners earlier today about adjusting this file. First posts I've found discussing this issue.

Checked the compare files of the stock file vs latest file and the angles have been adjusted but they don't appear to be by 1.32 like stated on the forums. Maybe the values were not properly adjusted?

I am tempted to try it myself but have raised the question to the tuner.

Thanks for the insight,

I owe you a beer. Thank you!

Once we adjusted the tables slightly and issue has been resolved. Why this wasn't attempted before idk but I'm glad it is working now. Hits and holds 20mpa until redline now.

For anyone who may come across this thread from search.

You needs to adjust the table under Fuel Pump --> "High Pressure Fuel Pump Leading Angle" and edit the Y axis to match the new flow numbers to properly calculate fuel pressure.

That is good info! Nice catch Cmitchell!!