OMalley

My google-fu brings the suck or else I would already have the answer.

Here's my deal. I have an 02, 8.1 shoehorned into my rockbuggy that ended up having trashed factory fuel injectors. The injector place that I sent the trashed injectors to said that they couldn't be/weren't worth rebuilding so they gave me a pretty good deal on some marine injectors.

Since this vehicle is being made from scratch, I didn't have a factory fuel pump or tank so I made a tank that uses an intank Walbro pump that pressures out at 70-75psi I believe. Well needless to say, the engine ran like crap. Much like a flooded carbed engine would. Now that the engine has setup for a month or so, it wont fire at all because all the plugs have fouled out. Who'd a thunk it?

To hopefully fix the problem, I have new copper core plugs and an adjustable fuel pressure regulator. If what I have found is accurate (it was on the internet, it has to be accurate) the factory injectors flow at 32 lbs/hr and the marine versions flow at 44 lbs/hr. I believe that the factory fuel rail pressure is 60psi at idle. If I multiply 60psi times 32 lbs/hr I arrive at 1,920. If I then divide 1,920 by 44 lbs/hr I arrive at 43.6 psi that the fuel rail pressure needs to be set at so that the marine injectors flow the same amount of fuel as the factory injectors. Is that correct?

I'm not cracking into the motor to put a bigger cam in until I have the chassis complete and pulled apart for powder. When I have the bigger cam, I can increase the fuel pressure to compensate. But for now, all I have is a 3" free flow custom stainless exhaust and a free flowing intake filter. No there's not enough room for a turbo setup, sure as hell not an ideal location for a turbo either.

Cliffs notes;
Does the factory injectors flow at 32 lbs/hr?
The marine injectors flow at 44 lbs/hr.
Is the factory fuel rail pressure at idle 60 psi?
What pressure do I need to set an adjustable fuel pressure regulator at to have comparable flow or just a little bit more to keep from flooding out engine?

Thanks,

OMalley

OMalley

Bump for the morning crowd. Over 60 viewings since I posted this and no one has any thoughts or ideas that can help?

I had Jim's Performance do the computer work and he recommended that I use an adjustable fuel pressure regulator to get this to work versus trying to dick with the computer programming to get it right

Just looking for some verification that my math is correct and any additional help would be greatly appreciated.

OMalley

02_2500avalanche

Set the fuel pressure to 43psi. The factory injectors are 32lb. Adjusting the fuel pressure to try and get the air fuel ratio leaner is not the way to do this nor do I think its going to help. The computer needs to be recalibrated for the bigger injectors. The best way to do this is in person with the tuner and a wide band o2 sensor. You could atleast get away with a decent mail order tune

02_2500avalanche

The factory fuel psi is 55 at idle...60 with the vacuum line pulled

OMalley

Well, I have access to EFI Live, however neither me or the guy I loaned it too know how to use it worth a ****. Is it really as simple as recalibrating for the larger injectors? How do I go about doing that?

Off to Google to see if I can figure out how to do that on EFI.

Thanks,

OMalley

02_2500avalanche

Not exactly sure how to do it...havent bought efi live yet. I would go on the efi live forum and ask theres plently of ppl on there who know what they are doing

whippled 8.1l build

factory idle fuel pressure on mine is 43psi.. mines a 03 8.1l. marine injectors should come out for stock injectors unless you get a tune done to support the bigger injectors.. stock 8.1l injectors are a 30lb injector and marine injectors there are 3 different ones 42 43 and 44's..

the factory fuel rail also should have a adjustable fuel pressure regulator on it already.

i do have a set of stock injectors and fuel rail if your in need

whippled 8.1l build

https://www.performancetrucks.net/fo...-values-88132/

OMalley

I'm definitely confused now. My engine is an 02 and the fuel pressure regulator appears to be non-adjustable. Are you saying that the larger injectors should flow at the factory injector rate unless I adjust the tune?

After reading up on the subject, I saw where the injector pulse could be computer adjusted based on what the alternator was putting out. If that's the case, that may be the problem. My alternator has started a max charge of 17-18 volts at idle and obviously needs to be fixed. Could this be the problem?

I getting my EFI Live back tomorrow and just wandering where I need to start.

Thanks for the good information.

OMalley