Finished up today on my EGT, boost and my Fuel pressure

Fuel pressure gauge problem:
My fuel pressure reads 34 at idle and when I rev it at idle it doenst move...I took it out on the road and the fuel pressure while cruizing stays at 34 as well and spikes up altitle bit when you gas it but goes right back down. wheN I bring the car up alot it goes all the way to 100 and starts to come back down...it also does a fluctuating thing//...if im cruizing it will bounce back and forth between 40-60
Its an electronical auto meter gauge with the black box thing..i wired everything correctly..also when I unplug the sender from the wires in the engine bay, the gauge slowly creeps up to 100...im tryin to pinpoint where the problem is..BTW, the Sender is on the top mount of the AEM FPR

Now for the Boost Gauge problem...
The boost gauge is reading a constant 20 vaccum..when I throttle alittle bit i see no movement at all...Cruizing I see 20 vaccum...I get no boost in first and second the most i saw was 5...
I had the back line coming off the boost gauge off before i installed it because it was crimped right at that fitting...i took that off and cut it, and moved that little ball up to a new spot on the clear plastic line...I ahve the plastic line going to the vaccum source by the throttle body

-matt

 

anyone have any feedback at all ??

 

use the vacuum source off of your blow off valve.

 

- start the car and pull the vacuum line off the cartech fpr and check what the base fuel pressure is set at 0 psi.

- where are you tee'd in at for the boost gauge?

- make sure u dont have any kinks in the vacuum system

 

I have a 5 way splitter off where the stock fpr got vaccum from...that vaccum source is supplying the BOV, Cartech FMU, AEM FPR, and the vaccum tank for the mevi.
I have the Boost gauge going to its own vaccum source at the manifold right near the throttle body

I took off both vaccum lines off the catech and the fpr and the fuel pressure went up to 50psi or so...and did move alittle when I gased it abit with the vaccum off of both..its jumping around quite a bit when I take it out on the road with the vaccum on and when I lay into the throttle, it shoots to 100psi and slowly dropps down. ?? maybe the gauge is malfunctioning
When I took the vaccum lines off the AEM and cartech, the boost gauge moved from 20 to 15 on the vacuum...reving at idle the boost gauges doesnt move at all

-matt

 

bump...any help

-matt

 

You should probably lower the base fuel pressure on the cartech for starters... do this by pulling the vacuum line on the cartech and dropping it to about 45 psi or so... This should alleviate that fuel press. spiking issue.
Also, try turning down the fuel on the brass **** on the side... Sounds to me like it hits 100 psi and the fuel pump can't flow that much for very long... pressure starts dropping because of that... i could be wrong on that one though.

Also keep in mind -injectors run the risk of locking up 100+ psi... this means that you run the risk of leaning out/ detonating... so be cautious.


I wonder if your mevi vacuum line requires its own vacuum source.... seems like there's a lot of devices that are working off of that one T.

 

Yea but im barely hitting the throttle at all, and the fuel pressure spikes right to 100...its a very strange thing....its almost like its not hitting 100 but a false 100 and the gauge isnt working, but I may be wrong...

I see alot of guys running 5 way splitters when they have sc...I could try capping one off and tryin that...it could get getttin messed up

What **** will lower it to 45 ??

-matt

 

You can't lower base fuel pressure with the Cartech fmu. You need to do that with your adjustable fpr.

Here are the instructions for the Cartech fmu:

http://www.bellengineering.net/Pages...struction.html

In order to help you further, it would make matters simpler if you could take a series of pictures of your entire fuel system, including fpr, fmu, pressure gauge sender, and the lines leading to and from each, sort of like what I've done here:

 

Well I have no means of taking pictures But I can explain my routes of everything....

Gas:
Off fitting off the fuel rail ====== AEM FPR With FP Sender ====== Cartech FMU ===== back to the tank
Vaccum:
Stock frp supplying vaccum.....MEVI tank....AEM FPR.....Cartech FMU....Greddy BOV...

I havent messed around with the setting on the fpr or the Cartech at all...If i take the check vavle off of the cartech the gas pulsates...I have the little setting on the side of the cartech, vaccum, set 3 turns in from all the way, and the top setting on the cartech less then 1/2 way in...

When im at idle and I rev it up a bit, I get little to no movement on the Fuel pressure...I go out for a ride cruizing it will osolate from 40-60psi and if I lay into the throttle the slighest bit it shoots to 100psi fast then creaps on back down...if im at idle and I unplug the fuel pressure sender, my gauge slowly moves up and up

-matt

 

I just noticed in the pic that there's an adjustable FPR working in conjunction with the Cartech. Crap, so I need that too or can I go with the stock fpr? What fpr is recommendable or does it matter?

 

Does your mevi tank have a check valve? If it doesn't or isn't working right, then strange things are going to happen.

Something to check. As a matter of fact, maybe the first thing you should do is disconnect the mevi vacuum tank from your five-way tee. Don't forget to block off the resulting open port.

 

Yes, you need a separate adjustable fpr if you want to adjust base fuel pressure. You can use the oem fpr if you don't need or want to adjust base fuel pressure.

 

My MEVI tank does have a check valve...ist the Black Napa Unit

I just took the car out for a ride and its acting really weird...I had to turn around and come home..
Threw throttle I am experiencing weird blips in the car...the hole car jults at certain rpms...the fuel pressure gauge continues to ocilate back and forth and when I lay into the throttle it jumps with no hesitaion right to 100psi...
Im really confused on what this could be I need major help

-matt

Stephan, my top setting on my Cartech is alot lower (inside of the unit) more than yours ?? would that make all these problem prevelant

 

The center bolt determines the onset of fuel pressure increase relative to boost. In other words, you use that setting to control when the fuel pressure increase occurs. You can set it so that the fuel pressure starts to rise at, before or after the manifold pressure reaches zero (gauge). In addition, it will control the maximum fuel pressure achieved. The farther in it is set, the higher the fuel pressure is going to be at full boost. So maybe that is your problem.

I would try and do a scientific process of elimination to figure out what is wrong.

First, disconnect the vacuum line from the mevi tank, just to eliminate it as a source of problems. Go for a drive and see if the problem persists.

Second, back the center bolt all the way out of the Cartech fmu, and disconnect the vacuum line.

Now go for a drive, but don't do any boosting above about 4000 rpm, just a quick boost up to 4000 rpm. See if your fuel pressure behaves more normal or not and report back.

If the problem persists, we'll go to the next step. If the problem goes away, we've pinpointed the problem to how the fmu is set.

 

Ok....taking the vacccum off the T that supplied the MEVI supply tank did nothing..
I backed the center bolt all the way out of the cartech, took off the vaccum line from the cartech, plugged it and went for a ride. The Fuel pressure gauge is staying right around 30-40 and no ocilating back and forth at all..I took it to 3500 and the most Fuel pressure I saw was 40 but it crepped to 40...didnt shoot like before.....idle it was at 32 like before but this time it didnt shoot to 100 either....
Now what ...

-matt

 

Okay, good. So the problem was with how the Cartech fmu is set. While you have the fmu disconnected, use your adjustable fpr to adjust your base fuel pressure to 34 psi at idle.

Reconnect the vacuum line back to the fmu. It is best to make adjustments with a wideband O2 sensor, but we can shoot for a safe fuel pressure. What size pulley did you say you had?

If it is the 3.125 incher, then you want to shoot for about 85 psi max. That's probably a little on the rich side, but not too much.

The safest way to make initial adjustments is to get a Mityvac and connect it to the fmu so that you can pressurize the fmu while the car is idling to simulate boost pressure. Start with the bleeder valve all the way in and the center bolt all the way out. Pump it up to about 10 psi and see what your fuel pressure gauge is reading.

If it is over 85 psi then back out the bleeder valve until you get to 85 psi. I doubt this will be what happens.

If it is less than 85 psi, screw in the center bolt till you get to 85 psi.

Take it for a drive and see if the fuel pressure behaves in a stable way. It should increase from 34 psi to 43 psi as soon as you go WOT, and then gradually increase to 85 psi as you build up boost.

There is more to it than that to get to a final setting, but this will get you to a reasonably safe fuel pressure until you can get to a dyno and do some fine tuning with a wideband O2 sensor.

 

yeah - like I was saying, sounds like the base fuel press. on the cartech wasn't set right - maybe i came out confusing - i wasn't talking about base fuel press in the sense of idle - but at 0 psi... anyhoo, sounds like your problem is fixed? Just gotta set the side **** for the fuel press. ratio....

 

whats a Mityvac ??

-matt

 

Go to sears.com and do a search on mityvac.

They sell them at just about every auto parts store. If you are going to be a boosted playa you gotta start accumulating tools...

 

Ah! My apologies. I thought you were talking about setting the base fuel pressure at idle. Looks like you were right on target.

 

any other uses for a mightyvac...things like $50 so I dont wanna spend that for one use

-matt

 

Sure. But I gotta ask. How much is safe boosted operation worth to you? I suppose you can just have the dyno operator make the required adjustments, but is that really how you want to live your life?

Besides, you can find them for ~$30 at Autozone or Pepboys.

 

I went out and bought a mightyvac
So the bleeder valve, (valve on the side with the vaccum and check valve off of it) always stays "All the way closed" ??

-matt

 

There's two kinds of Mityvac - Silverline and Automotive Tune-up. Which one should I get?

http://www.sears.com/sr/javasr/searc...&gobutton.y=13

Unfortunately Sears Canada does not carry many of the automotive tools that are found in Sears.com so I'll have to look around.

 

Doesnt really matter...as long as it has a hand pump, and a gauge then your set
The one at Sears is $70 and I called some places around here and found it for $30-$45

-matt

 

Thants not right is it ??
Im really only gettin 5-6psi ?? what gives

-matt

 

What the bleeder valve does is bleed off boost so that the fmu doesn't build up fuel pressure as high. It controls the rise rate of the fuel pressure. The standard Vortech fmu has only one rise rate which you control by what size disk you use in it. The Cartech fmu has a variable rise rate that is easily changed by opening or closing the bleeder valve.

So, back to your question. You start out with the bleeder valve all the way in and the center bolt in far enough to give you about 85 psi of fuel pressure at 10 psi of boost. This will most likely result in a rich afr (you need to check this on a dyno, though). When you go in for dyno tuning, you can adjust the bleeder valve out to give you less of a rise rate, resulting in a leaner and hopefully more optimal afr.

This is a pretty simplistic method of tuning, but it is the safest way to do it with the Cartech fmu. There may be more optimal settings where you screw in the center bolt farther and use more boost bleed off to get to an optimal afr throughout the rpm range. Hopefully your dyno guy has experience tuning with a Cartech fmu.

But! I will repeat what I said earlier. What you need to do to get your car roughly tuned to where you can safely drive it until you get to the dyno is to
1. Screw the bleeder valve all the way in.
2. Disconnect the vacuum hose from the fmu and block the hose
3. Attach the pressure port of the mityvac to the vacuum port of the fmu
4. Start your car and pump the mityvac until you get to 10 psi.
5. Check your fuel pressure gauge. If you have less than 85 psi, screw in the center bolt until you get to 85 psi. If you have more than 85 psi, screw the center bolt out.
6. Reconnect the vacuum line to the fmu and go for a test drive. Gradually work your way up to full boost. Have a friend call out fuel pressures while you're checking boost pressure. You should be at about 43 psi of fuel pressure as you pass through 0 on your boost gauge, and your fuel pressure should rise smoothly with boost pressure. You will have to be at wide open throttle when you do this, so it's best to do a run to 3 psi and check maximum fuel pressure, then a run to 5 psi, etc. until you get to whatever full boost is for your pulley. Listen for detonation and if you hear anything that sounds like marbles rattling in a tin can, shut down immediately.

Have fun but be safe.

 

Good thread, very informative.

 

UPDATE::PROBLEMS
Ok I bought the pump hooked up and started screwing the top set screw in and got NO repsonse from my fuel pressure gauge...on my mightyvac there is a reading on the outside that in "in HG vac) ?? That reading goes up to 30 so i figured 10 on that readign was correct = 10psi ??

I have to pinpoint the problem now...fuel pressure sender, black box for the guage or the gauge...but the thing is The Gauge Works.....or my AEM fpr is in backwards or the cartech is no good....
When I give the car power (ACC) but dont turn it on, the FP guage goes to 40 without turning the car on....then i start it and it stays at 34...I give it alittle gas when its warm and itll shoot up a tiny bit but not much..ie. 36-37.....that top set screw did nothing for me even with 10hg I put on the Cartech FMU.....the most fuel pressure I saw inside on the gauge was 48 and thats when the top screw was all the way in and the bleeder was ALL the way in..Something is wrong

-matt

p.s. I had the cartech in backwards this entire time till yesterday and I figured that would solve all these problems... maybe i have the FPR in backwards to and its unable to get a reading on the sender thats on the FPR...
FPR IS SET UP LIKE::
I have the OUT gas line off the FPR on the port accross from the set Screw...the IN is in the other port and the sender is on the top port...

PLEASE HELP I wanna drive my car already

 

hg is vacuum pressure

you have to pump it so it goes to the other side of the gauge

 

Well the "in. Hg vac" goes up to 30 and theres a smaller inside reading on the same scale that goes to -100 which is "kpa" ??

The part # on the mightyvac is #07000
http://www.sears.com/sr/javasr/produ...id=00947058000
There is the top port that creates pressure and the front port creats vaccum...
This is how I have my FPR hooked up...I think its correct..
3rd Post Down from the top (not my car but thats what I followed) (could be writen down wrong)
http://forums.maxima.org/showthread.php?t=301674

Im clueless now

-matt

 

To the top...please help..I wanna drive this thing

-matt

 

kpa is pressure, but in metric?

who knows what the conversion is?

i know that someone here does

 

I just need to know what to do....The mightyvac has two connections...one for vaccum and one for pressure..but when I hook up to create pressure, and hook it to the cartech, I pump is and nothing is coming across the gauge thats on the mightyvac

-matt

 

Yes, the mityvac gauge won't register any positive pressure. You have to tee in a second gauge in order to be able to tell how much pressure your pumping up to.

Sorry, I should have mentioned that to begin with.

Your other problems I'll look over tomorrow when I have more time.

 

http://forums.maxima.org/showthread.php?t=337083