weinerschizel

I built up a LQ9 from LM7 parts. Long story. Injectors I got leaked. They were just standard LQ9 / LM7 OEM injectors. Long story short, I got a set of Denso's of a generous guy here on the forum.

Part# Denso 25326903

I cannot find much info on these injectors.

A few searches show they are 32 lbs/hr. However at what pressure?
Is the flex fuel pump the same pressure as the regular pump?

I blew up an engine meddling with injectors and want to make sure I get everything right this time. Thanks!

strutaeng

They are probably the L59 flex fuel version of the LM7. I'm running a 2004 swapped L59 with my 99 Silverado NBS, but with a 2000 ECU. It runs fine, but around 11% rich consistently across any RPM. Just enough to throw 2 bank rich codes.

I'm not savy enough to adjust the tables and whatnot on HP Tuners, so I just disabled those 2 codes. Engine is all stock and I've got around 12k miles on it over 2 years now. No problems.

weinerschizel

Oh interesting. Once I get it all figured out I'll throw what I did up on here.

DId you use the same fuel pump? I'm trying to figure out if Flex fuel pressure is same as Gas pump.

strutaeng

Yes. I did a V6 to V8 swap on that truck. The fuel pump is the original. They are the same between the V6 and V8 on those trucks.

I don't know anything about the flex fuel vehicles though. The L59 engine came from a 2004 Yukon XL. The guy was parting it. He bought it with a blown transmission from his friend.

weinerschizel

Thanks for the details on it being L59 engine. I found this post here with more specs. Combing through it now... L59 Specs

BigBlackCamaro

The 903 injectors are 33 lbs at 50 psi and are used with a vacuum referenced fuel pressure regulator. Used 2002 to 2004. Plastic rail.

The 426 injectors are 36.6 at 58 psi and are used with a returnless rail from 2005 to 2007
Both are flex fuel injectors and use the EV6 connectors.

jetech

HPT calculator says 903 injectors flow 35.5lbs/hr@58psi. I am running these in my LQ9 swap. 230* cam LT headers TEA 243 heads milled .030. It runs very strong

weinerschizel

Welp, ready to pull my hair out and scream bloody murder till my lungs explode. I finally got some time after work to install the new to me injectors Denso Part# 25326903, 2002 flex fuel injectors. I cleaned them up, installed new o-rings, ran carb cleaner through them, and puled them with a injector tester at same time. All good so far. Then tore down fuel rail. Held new injectors next to old injectors. They are same height and appeared like they will fit...

Went to put fuel rail back in with flex fuel injectors. They don't fit. The outside diameter of injector is 0.150 larger than the bore on the intake where injector sits.

I don't know how this happened. I compared all the part numbers prior to taking this on. The part number for intake and fuel rail is the same between flex fuel L59 and gas engines LM7 (I have intake off a 2001 5.3L gas engine yet compared part numbers as well between everything and was the same). Yet these injectors don't fit. I'm I crazy, am I doing something wrong?

Those of you that have done this swap, what the heck, how do I get around this issue. I thought maybe spacers between rail and intake, however, then the injector won't be all the way down in the airflow.

Video of what I'm talking about

BigBlackCamaro

Those injectors are taller. The correct flex fuel rail has mounting tabs that are lower. You could use a spacer or washers with the right size bolt.

I prefer to use the flex fuel rails with the fuel pressure regulator that was meant to go with those injectors.
Do you have a return style rail on it now?

weinerschizel

@BigBlackCamaro thanks for your help. I've been surfing web here since my last post trying to find L59 (flex fuel engine) part numbers.

Parts in my engine build are from a 2001 LM7 (gas 5.3L), only thing different are the injectors flex fuel injectors.

So the intake manifolds is the same between L59 and LM7? And the fuel rails are different?
Do you know what part number is for the flex fuel injector, L59 engine, fuel rails? GmPartsDirect shows same part number for fuel rails?

Don't want headache of converting to return-less. I only need bit higher flow injectors that don't leak (my current injectors I'm replacing leak).

I have the gasoline engine fuel pressure regulator with return line. I'd think if the pressure is correct, the higher flow would be fine?

Right now I just need to get these injectors to fit.

I've been digging through google images, etc. etc. etc and do see this picture of flex fuel take w/ fuel rails on. There does appear to be a rail that mounts lower down.

The arm that mounts to the intake is flush on mine, the LM7 rails. I just cannot for the life of me find a part number for this fuel rail. Did GM not make very many L59 / flex fuel engines?


My fuel rail

BigBlackCamaro

I just get fuel rails from a junkyard. Not sure if they still sell them new.

The rails you have will physically work with spacers to take up the gap. BUT those non flex rails have a regulator that runs at 58 psi and you can't put the 50 psi flex fuel regulator in it.
jetech posted that those injectors flow at 35.5 at 58 psi so you could just program that into your tune and be good according to jetech. I have never tried it.

weinerschizel

@jetech do you have any tips to impart on my Flex Fuel injector swap? I'm going to run the 58 psi regulator / Gas fuel rails for now.

Thanks! I have a 2002 Flex fuel BIN / tune for HP Tuners. Was going to pull the injector config from it. I'll have to modify it slightly per your advice. I didn't realize the regulator for the flex fuel injectors was lower PSI. That actually works even better, as I hoped to generate more power than the flex injectors would support but haven't tuned for any of it yet. I just needed something to quick fix my leaky injector issues.

Separate question, I assume all that extra clearance is accommodated in the Flex Fuel fuel rails? Nothing additional in the intake (Flex fuel intake and gas fuel are same)... Reason I ask is, it almost appears as though the tip of the flex fuel injector sits higher up in the intake bore and not in same place / intake track as the gas injectors...

I took my measurements and put them on a little image here...

_Red_SS

Yes the flex fuel rails will allow those injectors to bolt right up on the same manifold like factory.

weinerschizel

Awesome thanks, I assume the fuel lines are same fitment too on the gasoline versus flex fuel?

jetech

@@weinerschizel Yes the flexfuel injectors will work very nicely. If I remember correctly all I did was use a different O-ring and spaced the rail. It's hard to see here, this is the best pic I can send right now. Zoom in if you can

I had to purchase new rails. The original ones started to leak. I think the seals dried out from sitting to long with out fuel inside them. They are not cheap! About $90 each
II

jetech

I'm not sure about the fuel pump differences. I don't think you would need a flexfuel pump for any reason. Find O-ring that will seal the flexfuel injectors inside the non flexfuel rails. Fit it on the engine and shim the rails to the intake manifold as needed. If this is a stock engine you will need to tune the pcm for the larger injectors

weinerschizel

@jetech awesome thanks for clarifying. Beautiful build too... I only painted my block, now I feel ghetto haha.

Okay, so I used flex fuel o-rings on the injectors, not the gas o-rings. They did fit in the bore, and I pressurized the rail. There were no visible leaks... Are the o-rings smaller for the flex fuel?

I've got the config for the L59 injectors. I assume I mostly copy that config then raise the Flor Rate vrs KPA to 35.5# instead of 33.0#

Sidenote:dang that is one clean engine bay! Is that a truck? I notice the steering gearbox. I'd love if my engine bay was cleaned up like that.

jetech

I didn't do the tuning so I can't help you with that.
Thanks for the accolades. It's my '71 Camaro. It's in the bodywork stage now

weinerschizel

Ah spacer H.E. double hockey stick . I'm going bug nuts trying to get these bleeping injectors adapted. On my SECOND spacer kit and several weeks now w/o my truck.

I ordered a kit from ICT Billet. Kit is simple enough. Bolts w/ rail spacers... and here's where the drama starts... O-Rings. Bag w/ o-rings says, "MUST USE Change Lower Oring". These were only instructions but kit seems simple enough so I changed the o-rings.

I measured factory flex o-rings and compared to factory gas o-rings and the factory gas o-rings are 0.014" larger OD... so a larger o-ring in the kit makes sense...

There's no way in hell though I can fit the injectors in the intake now. I cut my hands all up swapping the o-rings in the kit with the rail in the truck. I assume they are intended to go on the land where the factory o-ring went.

Here's the crux... Are there different intake manifolds for flex fuel versus gas? I'd be really suprised if that was the case... why all this drama with orings? I had test fit the flex fuel injectors w/ the factory flex fuel o-rings on them. They fit snug in the bore. I'm super confused why the only instructions say "MUST USE" and have o-rings that don't fit.

Anybody have any further info on this swap?

jetech

I just took plastic bushings and cut them to fit the dimension I needed. If the orings you tested with no leaks worked I would've just used them. I think they give those orings because some people would install the original orings and have fuel leaks