thanks for taking the time to read this message... i have searched and cant find much...i am having some fuel problems and here is a list of what is on the car and what is going on with it...

Vortech Supercharger 3.3 pulley
Stock Injectors
Utec
Walbro 255
JWT Oil Pan spacer
Vortech Fuel Management Unit... no return

At first my car was running lean... so we knew it was a fuel problem... come to find out when we first installed the walbro we didnt do a couple of steps according to the TN instructions...we drilled the 7/64 hole in the FPR, drilled the 2 holes in the plastic bottom and popped out the yellow cap...

Now when i start the car it is backfiring... and running horribly rich... around 8.5 at idle then when i put it in drive and give it a lil gas it drops down to 0.3...

The car is shaking at idle and is also at low RPM...

THe driverside exhaust is blowing cool air and the pass side is blowing hott...we checked my plugs and they are fine... they are NGk Iridums 1 step colder...

my question is were the TN instructions on the Walbro installation inacurate or made for bigger injectors? my fuel pressure is about 56psi which is better than what it was when it was too lean (70 psi)... SHould i stop stressing and just get a tune?? any guidence would be great!

 

yeah if you search the tn stuff most people who have it post not to do it im not really sure but you could search and im sure you will find your answer

 

^ i have searched bro... it is all mixed reviews...

 

Anybody?

 

You replaced the S.S.Box for the UTEC but still have the Vortech FMU/Aux fuel pump? Does the UTEC have the ability to turn the Aux fuel pump on? The TN comes with larger inj's but this shouldn't account for what you are describing..You definitely should have it tuned before damage..

 

um.... you need a tune. that is it. your car shakes b/c you need to raise your idle. did you drill the holes for the fuel pump regulator, and bottom assembly? if you drilled the holes in the assembly you cant run the car under a 1/4 tank. also you DO NOT need the vortech fmu and inline if you have a walboro 255.

 

SS is replaced by the UTEC... i am using the Vortech FMU without the aux pump since i have a Walbro 255... I am also on stock injectors...using 3.3 pulley... Basically everything is out of the box except the Aux pump and EMU...

 

At first i was figuring that i needed a tune but now i am second guessing the way the fuel is set up... can the FMU only be controlled by the SS box or does a ECU reflash take care of it?

how would you set this up and should i get a new fuel assembly so i wont have the holes drilled? Should the Fuel pressure regulator in the fuel assembly still be drilled out to 7/64.

 

The S.S. Box controls fuel during boost. Under boost (via the vac line attached to it) the FMU sends fuel at a ratio of 8:1 (boost pressure:1) to the Aux fuel pump which in turn is energized by the S.S. box which raises the fuel pressure to the inj's.
Not sure how your set up with the utec controls or substitutes for the S.S. Box? What does the FMU do?

 

^ THe utec should only control boost and the stock ECU takes over when the car isnt in boost... The FMU should be sending fuel when the car is in boost via the walbro 255... im thinking...

 

You need a schematic of the fuel system.. The FMU is downstream of the Walbro..Look at the Vortech install manual..

 

The vortech manual doesnt do anything for me since it only gives guidence on installing the FMU w/ Aux pump (which i am not using)....

 

Your first thread say's you have the Vortech FMU. Your last thread say's your not using it. Very confusing in understanding what you have.. Again a fuel schematic would help you. The Walbro alone will not provide sufficient fuel during boost.. Tuning will not help..A fuel return will if all you have is the Walbro and nothing else..

 

if you have the walboro 255 just take out everything the vortech kit has for the fuel system and return it to stock. It will work fine.

the FMU is not controlled by the ss box it just reduces excess fuel pressure created by the inline fuel pump by reserculating it. since you have the walboro 255 you will have enough fuel pressure on a 7psi setup.

yes you need to drill out the fuel regulator. but do not need to drill the bottom fuel pump assembly. you will regret it like me if you do. I cant drive my car under a 1/4 tank. it sux till I find another fuel pump assembly from a junkyard. but you need to take the syphen out of the bottom of the fuel pump assembly. it is yellow.

 

sorry for the confusion JC... I do have the FMU but i am not using the aux pump that is supplied with it... i am using the 255 instead...

 

Muzzy... i think you might have the correct answer... I am running a stock SC setup excpet for the Utec and the 255... so you are saying that the 255 is enough to push the stock injectors for 7psi?

I am going to buy a new fuel assembly so those holes arent drilled out at the bottom of the plastic..

 

i pmed you back about probably what is going on there...



get a stock fuel assembly , remove the yellow piece, put in the walbo and use a stock system with some bigger injectors...

 

Yeah, I seems your fuel system and EMS are all confusing each other. You can't run the FMU without the AUX pump, and the AUX pump cannot work with the UTEC, and stock injectos wont work without the complete Vortech fuel/EMS system. Sooooooo...best bet is to put in some larger injectors..440's or 550's, the walbro pump, and make the TN mods to the assembly.

Or do a return fuel system with larger injectors, and you wont have to drill out your fuel pump assembly, and ruin it, if you decide to go bigger later.

 

Sharif,, are you sure the Walbro w/mods and larger inj's will suffice? I am skeptical!!

 

For maximum precision, we always recommend a return fuel system. But at low boost, and on a linear based SC kit (low boost), you should have a fairly good result.

Since many people intend to build their motors and go for bigger power later, they usually get an RFS from the start. An RFS makes for a super consistent tune..day after day...after day.