LB9GTA

iTrader: (1)

Here it is.

I have a '91 GTA with 305tpi.
Last year I had the nitrous working with a 75hp dry shot.
The only thing different that I have did is 1.6 roller rockers.

The actual problem is that when I engage the nitrous,it works for a split second, the fuel pressure spikes up and the engine bogs(almost stalls) or the engine bogs and then the fuel pressure spikes. Not sure what happens 1st(it happens really fast).

Here is the things that I changed

1. Thought it was the coil(changed and worked for a while)..not the problem
2. went down to a 50hp shot and worked for a while then back to the stalling
3. thought the injectors(stock 19 lbs) were static locking, changed to 24 lb LT1, same thing
3. unhooked the vac hose off of the ZEX box and it works, so I thought it was the AFPR(homemade), put a stock fpr on and didn't help.


Any other suggestions other than going to a wet kit.

Thanks for your help.

george

Free Bird

iTrader: (1)

Put it on a dyno and get some wide band info.

LB9GTA

iTrader: (1)

No offense, but if I can't get it to run, how can I do a pass on a dyno?

When the fuel pressure spikes, it almost stalls the motor.
I don't believe that I can do a pass like that.
Besides, I am really scared that with all that unburnt fuel that I am going to blow my intake off!!

Free Bird

iTrader: (1)

So you KNOW for an absolute FACT that the motor is going way rich and boggin?

Is the n2o "hitting". Is there a solenoid in the ZEX box that opens for the n2o? Check to see if you're getting n2o flow. Is the bottle pressure low or empty? Are all of your electrical connections good? There isn't much to go wrong on that kit, it's pretty simple, don't know what you want me to do...

SmokinZ28

Your fuel pressure spike is from that FMU aka your ZEX box. It is suppost to do that on a dry kit to give you the extra fuel for the nitrous, otherwise you'd get a huge lean condition and motor go bang. I don't think your getting any nitrous from your fogger nozzle. Bad connection to solinoid, bad solenoid or empty bottle.

sleepybu

pluged nitrous filter maybe

LB9GTA

iTrader: (1)

Freebird, I apologize for coming of the wrong way.
I can't say for absolute fact that it is running rich. But the fuel pressure goes up to the normal level(60-65psi) then spikes upto 90-95psi.

I will check the nozzle for flow.
The bottle is full.

I talked to Zex. One person said that there is no way that it could be the management box and to check the fuel pump and return line.

Talked to a 2nd person at Zex, he said to send the management box in, that could be the problem. He also said that it could be the diaphram in the AFPR(even tho I said that I put another fpr in. He said that some diaphrams are not meant for the psi for a dry kit....

Anyone have any validity for these suggestions?????

LT1FUN

Had the same problem with my '93 LT1.

What kind of spark-plugs are you running? Platinum plugs and Nitrous don't mix. Get a set of NGK plug's and make sure they're 1 heat range colder than stock.

Also, as someone said earlier, check to see if the diaphram in the FPR is ruptured. That will also cause problems.

Lastly, how is the nozzle in you system hooked up?

My friend also had similar problem's in his '93Z. His Dry kit was the same as mine. On an LT1 you drill a small hole in the plastic air intake and secure the nozzle in the elbow and tighten it down from the inside with a washer/nut.

What ended up happening was the connection was loose so whenever he hit the spray, the nozzle would slightly turn in direction and face AWAY from the throttle body, thereby "blowing away" the incoming air and not allowing the motor to "breath" at al by forcing all the incoming air back out !! l.

The car would start to cut out on him and sometimes it would stall completely. While you're at it, check for any tears in the plastic intake itself.

My 3 suggestions:

- new plug's (1 heat range colder than stock)

- FPR: If you buy a new one, make sure it's a Factory DELCO unit and not some Adjustable aftermarket crap.

- Check the connection of the nozzle and make sure it's pointing in the right direction and doesn't move around when nitrous is sprayed..


Hope this helps.

B4Ctom1

there is a chance the fuel isnt causing the bog, there might simply be a lack of fuel caused by a fuel pump issue. Please try to make it misbehave as you have stated with a fuel pressure gauge connected so you can watch it when it happens. Or, do you already have a fuel pressure gauge on it?

83 Crossfire TA

iTrader: (2)

heh, I’m about to install my 3rd FPR since this spring. This one is just plain leaking, when you turn the pump off pressure drops right away (with the return blocked pressure stays up). The holley piece looks trick but so far I’m not thrilled. At least it’s easy to get it replaced under warranty.

LB9GTA

iTrader: (1)

Yes, one on the a-pillar and one underneath the hood.

The more I think about it, maybe it is starving for fuel, not running rich.

Back to the garage.........

B4Ctom1

oddly as it seems some dry manifold kits when starved for fuel do not always have the worse case scenario for a nitrous car running out of fuel with a backfire or engine meltdown. Sometimes they simply die or stall. This is usually related to the engine size being a bigger V8 and the nitorus being a small 75 shot etc...

look for fuel pressure readings in the 70 to 100 psi range when nitrous engages.

vortecracing

Kind of sounds like you are not getting the nitrous into the motor. You need to check the plugs and see if it is running lean or rich, kind of white looking means lean and smooty looking means rich. Then that will help you tell which you need to look at, whether it is fuel or nitrous. Hope this helps...

LB9GTA

iTrader: (1)

WHen I hit a 50hp shot, the guage usually goes to 60-65psi, or a 75hp shot will go to 75-80psi, but if it is not working then it will spike up to 95-100psi(too much)

Pulled a couple of plugs and they look fine

Free Bird

iTrader: (1)

You need to pull them RIGHT after a n2o pass. Find a nice empty street, make pass, then shut the motor off and coast to a stop.

B4Ctom1

if what isnt working? when the nitrous sytem is off you have the 95-100 psi?

when is this 95-100 psi seen? with the engine off and the nitrous on? If so you may have found your culprit. check the fuel filter first, if it hasnt been changed in a while (or never) then consider changing it. If you are absolutley sure it is not this, then it is likely the pump.

If you decide to replace your pump, find a walbro. Do not use some POS pump from autozone/CSK stores/advanced etc.

The cheapest 255 LPH pumps I have seen are the ones for 5.0 stangs. I paid $85 back in 2001 for my 255 LPH 5.0 stang walbro that runs my B4C now.

LB9GTA

iTrader: (1)

the WHAT is my nitrous

Like I said, when the button worksNow I will use the button and , when it only should be going 65psi for a 50hp or 75psi for a 75hp shot.


Like I said, the pressure spikes up, this is when the car is running and the button is depressed.

Oh, I have a 255 fuel pump(Carter - federal mogul is the brand, is this a cheapie??)

I am beginning to realize that I am the only person to have had this problem before!

B4Ctom1

you are not the only one, I have seen similar things happen to "FMU" type of power adders including NOS dry systems as well as blower cars with the same setup for fuel.

Inside of the Zex box is a small regulator, it takes the nitrous pressure and steps it down to just a few PSI. This nitrous is not the nitrous which goes to the nozzle and into the engine, it is just used for the fuel pressure regulator. A low enough PSI so that when it pushes against the fuel pressure regulator it doesnt burst the diaphram inside it. instead it makes the regulator work backwards and causes it to slightly and slowly close off the return orafice inside it. This causes the fuel pressure to rise.

Now here is where my zex expirience is limited so maybe you can help me, to help you. In other dry manifold nitrous systems. The amount of pressure provided is usually based on a secondary jet. Where a wet system uses a fuel jet and a nitrous jet, the dry system uses a nitrous jet as well as a fuel jet you put in the units regulator line to bypass some of the pressure fed to the fuel pressure regulator to keep it at that 65 psi for one shot and the 75 for a different shot. On your box do you have to make any adjustment or setting change at the box when you switch from one shot to the other?

I do know for a fact that alot of people are cunfused about the technology inside a Zex box and I have heard them make some pretty outrageous claims about them. Not bad claims, or bad people, but things like "it knows whats going on inside the engine and adds the right amount of timing and fuel with the nitrous...". Its a great idea and a great box mind you, but it isn't magical, its just a machine.

I have seen inside of a zex box before, I just dont remember how it regulates the shot to the fuel pressure regulator other than it uses the small pressure regulator like the NOS one inside (which is the same mini non-adjustable or spring-adjustable one that match racers use to step down the pressure of CO2 for airshifters). There is a chance this regulator has a spring in it which may have lost some of its tension on your unit. This usually happens from a couple of good high pressure bottle days.

Tell me more about this pump you used?

is it in-tank or in-line?

when did you install it?

was it included with the zex kit?

can you show me one on line (picture)?

I never heard of one, that company makes decent parts so likely it is not junk. High pressure is not a sign of a general fuel system flow problem.

Have you talked to zex yet? I bet they are familiar with this problem, especially since I have heard of it before. The NOS system fix is a new spring in the regulator. Your regulator might have different internals in it too just like different selenoids have specific types of parts in them.

I think there is a second regulatory selenoid inside the zex box, this could be the problem too. I think the answer will lie with Zex.

EDIT: I just reread the post and saw you already talked to them. so let me change my diagnosis a bit.

Lets pretend we are zex, and that every person that calls has a problem with their car but our system could never ever have a flaw, error, or failure. Lets pretend we spend all day talking to ricers and other people who will lie to us about doing the diagnostic proceedure we just asked them to because they are "sure it could never be that " and even thought they are the ones with the problem they seem to know it all. This has a distict effect of jading the outlook most of them have on future callers.

Ok fuel system; fuel pump? well we know it has enough power to jack the pressure up to 100 psi when asked to do so right? so that couldnt be the problem.

Fuel lines? well if they were plugged the pressure would drop off not go up.

fuel tank, empty? plugged? nope fuel pressure goes up not down during activation.

fuel filter? cheap so definitely worth checking or even replacing (even though a plugged filter would cause pressure to drop not rise).

line from zex box to regulator? well if this were plugged/leaking the pressure would never go up or go very little.

factory fuel pressure regulator? hmmm, good question, based on a prblem with the spring and spacer inside it (factory or aftermarket adjustable) as well as the diaphram, it could actually cause some pretty weird things to happen here, definitely say it is worth a look or maybe a change.

fuel rails? doubt it

fuel injectors? does the car run without the nitrous? yeah? I bet it does so that rules them out.

that about covers it. A failing IAT sensor could cause some crazy stuff to happen to a dry flow car, also a MAF if you try to spray through it.

Are there any other recent changes like valve stems or wiper blades for zex to blame it on? no seriously have you changed anything pertinent?

also take a look at the filter and regulator please.

B4Ctom1

please note that I edited above post

LB9GTA

iTrader: (1)

Personally, I don't know what people think of Zex, but they SUCK!! Unless you have 4 cylinders and a big wing, they don't care about the American v-8.They have never answered my questions before.
They said they never heard of this problem before!

Inside of the zex box is a small brass block(couldn't think of a better word).
The nitrous feed runs into this block.
That goes to a small passage that goes to an allen screw with a hole in it(the orfice).
That goes to the fuel jet that goes to the fpr.
The nitrous line then goes to a jet then the nozzle is in the intake tube which goes into the throttle body(about 12-16 inches away from the TB)
Hope that was clear!
There is no spring inside the magic box. I thought it was magic until I opened it

The fuel pump is a 255 carter, in tank
ZEX did not provide the pump.
I installed the pump last fall( the nitrous worked back then)
I don't have a pic of the pump, only the install of it(did it on a prev. thread)

BTW, thanks for your help so far!!

B4Ctom1

I actually like a dry kit when small shots are used, I have just never been too hot on the zex kit. Have you ever seen a NOS 5115 kit?

I love them on stock TPI cars. Its made for a mustang but loves TPI cars and other cars too. My friend had one on his probe, I had one on my camaro at one time, we even put it on a tempo once (it flew til the tranny died). Should have seen the looks on the ***** faces when it ate up their fast prelude.

anyways, if rejetting the fue jet is what you have to do that must be your decision, and the consequences yours as well

LB9GTA

iTrader: (1)

This might sound stupid, but someone said to me that just b/c there is pressure, there is not always flow(any validity to this??? )

What about the return line? what if not enough fuel could go thru it and backed the psi up to the fpr then spiked the fuel psi???

that's funny!!

B4Ctom1

I dont think it is the return line because it would be a problem when not on the nitrous.

Im sure it is the fuel pressure, just as you have described going to 100 psi at activation. It is the "why" of it though we need to find.

LB9GTA

iTrader: (1)

I tried the fuel filter. It was perfect, not the problem.

I will keep trying.
keep you posted

LB9GTA

iTrader: (1)

Checked the fuel flow. Flowed about 1/2 gallon in 30 seconds(enough to flow 255lph). Used the fuel hose at the front of the motor......all good

check the return line. I plugged off the line in front of the motor. Fuel press spiked up to 100psi then stalled the car @ idle. So that isn't the problem

Checked the n20 nozzle. Worked and not plugged

I checked the fuel pressure guage on the a-pillar and off the schrader valve, both the same.

Then we checked the return line in the front of the motor by taking it off and running it in to a jug. With the n20 on, still had the fuel spike problem!!

Running out of ideas!

Will check the fuel line in front of the motor to the afpr.
will check by putting the scanner on
will check by putting a vac pres. guage on the inline hose to the afpr.

Gotta be one of these, I hope!!!

B4Ctom1

its got to be the AFPR spring or diaphram. one member mentioned he goes through one or two a year!!!

LB9GTA

iTrader: (1)

I borrowed a buddies stock frp, and that didn't help
That included his diaphram, spring and cap!

B4Ctom1

sounds like you have narrowed it down to the Zex box. you need to call them again.

ross

Did you check the nitrous solenoid? The plunger are known to swell. And not let the nitrous flow. At least it does for use carbed people not to sure about a dry kit.

B4Ctom1

very good point! If the selenoid simply was not working right or failing to open then the pressure to the regulator would skyrocket and so would the fuel pressure!

LB9GTA

iTrader: (1)

I took the nozzle off the intake tube and turned on the n2o.

n2o squirted out of the nozzle.

Is there a chance that the orfice inside of the zex "magic" box will wear and eventually be too big?

ross

Need to take the solenoid apart and check the plunger out. It problem looks like a hard nipple. And wont flow the correct amount of nitrous.

LB9GTA

iTrader: (1)

So, I can replace this"nipple" inside of the solenoid?

Do I just take the nut off the top of the solenoid and pull it apart?

B4Ctom1

pulling off the nut on the top allows you to access the selenoid coil and coil cover. In order to access the nipple and plunger you must take the proper selenoid spanner wrench and place it into the two holes that were under the selenoid coil and rotate the center unscrewing it counter clockwise (the normal "lefty loosey" direction). people often do this with a pair of 90 degree needle nose but its not recommended because it usually takes a lot of force.

LB9GTA

iTrader: (1)

Got the problem solved!!!!

I feel stupid but here it is..

I bought the kit from a Mustang owner

I called zex tech line and they said it will work on my tpi no problem


WELL!!, This is not the case. After a very long time I called the zex line again. I talked to a person there and I was WAY over his head with the operation of the system than him, so he sent me over to Patrick(r&d, basically made the zex system). He told me that the mustang jetting was way too rich for my tpi. He told me to use the LT1 jetting charts. I did not have a lean enough jet for the LT1 system(needs a 82 fuel jet) so I used my 52 jet.

It worked much better!

He said what was happening was the injectors would only work till around 80psi then static lock, therefore closing them and then the fuel pressure would go sky high b/c it backed up the system.

SO, I need a leaner fuel jet and I should be better(I hope!)

Thanks to Patrick at ZEX!!! He knows his sh*t!

I will post times in July when I go to my 1st 1/8th mile race

B4Ctom1

that is awsome, I am very happy. I find this odd because the jetting for the dry NOS system for mustangs and used on tpi camaros for the 75 hp level works fine but the larger levels it gets a bit lean.