TBI Quarter Mod

[1SLOS10]

I just got done grinding the lip down on the bores of my tbi, and thought about doing the quarter mod. My question is, where exactly do I put the quarter? Does it go between the spring and diaphragm, or spring and spring cup, or does it go between the cup and the actual can that they all sit in? Is it worth doing, or should I just leave it alone? Thanks for the help!

[dagen_1]

banannabrain did this mod... msg him

[1SLOS10]

Anybody else? I sent a message to bananabrain, but havent heard back yet. putting this thing back together in a hour or so, and really need to know where to place the quarter. Thanks

[GreaseDog]

On the side with the spring.

[1SLOS10]

I had it between the bowl and the spring seat and it ran like shi*. I just took it out and left it stock.

[silverado_lover]

I used to have 2 quarters in mine, it ran fine till I upgraded my fuel pump...ran like shat after that.


My solution was to replace the engine :aniteef:

[1SLOS10]

Yea I been wanting to put a ls motor in mine. I looked through your build pics on ls1truck, just wish I had the money to go through with it.

[silverado_lover]

Just save up, buy parts as you get the money, and before you know it you'll have a room full of parts :D

[1SLOS10]

I think I tore the diaphragm up trying to get the quarter in the right place. Injector pouring fuel now..

[UnderCover W/T]

That sucks.....Can you explain the quarter mod?

[1SLOS10]

Turns out it was a bad idea. From what I understand you take the torx screws out of the top of the injector assembly, turn it over and remove the 4 smaller torx screws, remove spring and spring cup and put a quarter between the two, then reinstall in reverse order.

[1SLOS10]

Culprit was a torn injector o-ring.

[Customization]

My 95 tbi seems like its dumping fo much fuel on a stock set up could this be an inyake manifold gasket
Meaning that iys using more fuel to keep ot running. bevause there isnt a good vacum from tni unit done

[1SLOS10]

Not sure I understand what you are saying, but have you checked the plugs to see if it's running rich?

[1SLOS10]

Could be a vacuum leak, and the o2 sensor is seeing a lean condition and giving it more fuel to correct it.

[Customization]

How could i check for vacum leak an plugs are good engine runs great

[1SLOS10]

Use a small propane torch not lit of course, and pass it along vacuum lines and ports, motor will idle up if you pass over the place where there is a leak

[Customization]

Ok could it be manifold leak

[1SLOS10]

Exhaust manifold is likely, that could cause a lean condition.

[1SLOS10]

Proper place for the quarter is between the spring and the spring cup that sits in the bowl. Got it together this morning, with new regulator diaphragm and a injector o-ring. Runs great now!

[Customization]

Its a pig on fuel maybe 10 mpgs bit just the fiel mileage isnt theee

[UnderCover W/T]

Proper place for the quarter is between the spring and the spring cup that sits in the bowl. Got it together this morning, with new regulator diaphragm and a injector o-ring. Runs great now!

Can you explain that? Like better throttle response, low end torque or like fuel economy?

[1SLOS10]

I can't tell you which did more or if they both compliment each other, but I did the ultimate tbi mods,where you cut down the ridges around the throttle bores, added the quarter and injector pod spacer. I would think it would help throttle response with the added pressure.

[1988 GMC 355]

Throttle response is much improved, low end is a bit better and you will see a rise in MPGS

[Doober]

http://tbiparts.com/index_links/TBI-AFPR.pdf

A (slightly) more scientific approach for more pressure... the quarter thing is a shot in the dark and a mod I wouldn't do myself. I have and adjustable regulator on mine from a seller I thought was named 'xtreme fi' or something like that on eBay, but can't find it now... it's a machined aluminum part with a port for vacuum reference. Along with this you can get a fuel pressure gauge/adapter at Autozone for around $40-50, and set pressure to a proper level. Also advance base timing a few degrees for a little more snap in throttle and some kick off the line.

[GreaseDog]

http://tbiparts.com/index_links/TBI-AFPR.pdf

A (slightly) more scientific approach for more pressure... the quarter thing is a shot in the dark and a mod I wouldn't do myself. I have and adjustable regulator on mine from a seller I thought was named 'xtreme fi' or something like that on eBay, but can't find it now... it's a machined aluminum part with a port for vacuum reference. Along with this you can get a fuel pressure gauge/adapter at Autozone for around $40-50, and set pressure to a proper level. Also advance base timing a few degrees for a little more snap in throttle and some kick off the line. why not try it? Doesn't cost anything but a quarter. Money back guarantee if you remove it. :lol:

[Doober]

Indeed :lol: guess I'm just anal about some of that stuff :)

[Quyonmob]

My 92 was really finnaky about fuel pressure. I ran the XFI adjustable regulator and plumped and inline gauge. 12.5-13psi was perfect for the stock L03, over/under that it lost mpg/throttle response noticeably.

Stock was a dismal 10psi.

[Customization]

How can u gey a pressure guage plumpef off the stock regulator

[Doober]

Autozone carries them, Actron brand. My store had one in stock.


http://www.autozone.com/autozone/accessories/Actron-0-60-PSI-36-in-hose-GM-TBI-fuel-pressure-tester/_/N-25eb?itemIdentifier=232719_0_0_

[Quyonmob]

How can u gey a pressure guage plumpef off the stock regulator

I meant plumbed... but just like this;

http://i80.photobucket.com/albums/j195/Quyonmob/92%20BLUE/TBI%20rebuild/DSC01044.jpg

Installed;

http://i80.photobucket.com/albums/j195/Quyonmob/92%20BLUE/TBI%20rebuild/DSC01046.jpg

[Customization]

Is there any way to pkumb it into the cab kike just ibctease the line ibto the cab

[Quyonmob]

Is there any way to pkumb it into the cab kike just ibctease the line ibto the cab

You would have to use an electronic gauge and sender, a pressurized fuel line in the cab would be a great way to burn your face off.

[silverado_lover]

He must be sipping on Canadian Club :lol:

[Quyonmob]

He must be sipping on Canadian Club :lol:

Alternate way to burn your face off... poisonous cheap rye. :D

[Customization]

Im just asking ok. so i could keep an eye on it under load conditions

[GreaseDog]

You would have to use an electronic gauge and sender, a pressurized fuel line in the cab would be a great way to burn your face off.

Much beyer than a crazed maniac high on bath salts chewing it off. Just saying.

[Quyonmob]

Im just asking ok. so i could keep an eye on it under load conditions

TBI fuel pressure doesn't vary much.


Much beyer than a crazed maniac high on bath salts chewing it off. Just saying.

Flaming face or eaten face... Cooked medium well before serving.

[drifterdude]

You can get a JET adjustable regulator from summit. I have one its machine billet and anodized. Works great. It has a hex bolt in the bottom to adjust with using a allen wrench. Just before you install it drill a hole between the fuel line adapters so that you can turn the bolt without removing the TBI so you can adjust it easily. Mine works great.

If you are going to do the quarter mod get a new diaphragm while your at it as its easy to tear a older one thats been in there.

[Doober]

So was the one I got, and it was $33 less.

[Quyonmob]

So was the one I got, and it was $33 less.

+1.

Probably the same one I posted, which is adjustable from the bottom with a whole drilled in the TBI housing.

[Doober]

Yeah, the hole is there to drill/tap for vacuum refegerence.

[Quyonmob]

Yeah, the hole is there to drill/tap for vacuum refegerence.

Yes it is, but is not the hole anyone was talking about. Both were talking about the hole that needs to be drilled in the TBI housing (not the AFPR) to access the adjuster.

This hole.

http://i80.photobucket.com/albums/j195/Quyonmob/92%20BLUE/TBI%20rebuild/DSC01025.jpg

[ryan_thompson87]

Alternate way to burn your face off... poisonous cheap rye. :D

Amen.


I run the XtremeFI regulator using vacuum too, works great, I just didn't like the way they tell you to epoxy a nipple onto it for the vacuum port... I drilled and tapped mine and used a fitting. Used they're inline pressure port too, but after I got mine set I took it to work for testing pressure on TBI Trucks, it's a pain in the ass to pull the filter out to test one :lol:

[cupkicker]

Looks like an interesting mod

[Customization]

Has any body made there own afpr

[Doober]

I'm sure there's a thread or two on here.

[Customization]

I have found some sites but still not sure so after I put the screw in the stock housing. After that I am confused on what to do

[Customization]

I think I have figured it out :) so more pressure on the diagram the more fuel pressure

[Doober]

Yes, that's correct.