TBI Adjustable Pressure Mod

[mudbuggy]

Hi. All. I got a spare tbi from my local pullapart this spring, then this summer got the gasket set for this unit, I was going to rebuild the spare then swap out for the original after I got my pressure gauge installed. Which I finished this past weekend. I installed the gauge for. Reasons. First my youngest daughter (seven years old of 6 kids) likes to work on my truck with me, I am suspecting that the fuel pump is original, next I wanted to known what the pressure was and lastly,for a baseline of when I start to bolt on mods. Which by the way I'm at 9.5 psi and I also double checked the electric gauge with a mechanical. My next purchase will either be the cfmtech spacer or the aldl cable, right now I am thinking the cable so I can see any changes in system then the three wire O2 sensor then the O2 tuner setup. I really am trying to avoid doing any mods that change it from the oem setup until I habe all of the sensory equipment need to read all mods in the future


So with the background out of the way I have a few stupid questions about thbe was and lastly,for a baseline of when I start to bolt on mods. Which by the way I'm at 9.5 psi and I also double checked the electric gauge with a mechanical. My next purchase will either be the cfmtech spacer or the aldl cable, right now I am thinking the cable so I can see any changes in system then the three wire O2 sensor then the O2 tuner setup. I really am trying to avoid doing any mods that change it from the oem setup until I have all of the sensory equipment need to read all mods in the future


So with the background out of the way I have a few stupid questions about the pressure regulator. How does the adjustment stem get changed? Does it stick through the base, if so what happens to the vacuum port on?

Thanks,

[EagleMark]

I think you have a TBI conversion on something? Vehicle, motor and information would help.

Making a stock TBI regulater isn't hard. Here's an article from ThirdGen.org
http://www.thirdgen.org/tbi-afpr

But a stock regulater will usually run 13 PSI. I have yet to see one stock that does not with proper fuel pump, lines, clean filter, enough electrical power, big enough wires from relay power good grounding to frame, frame to motor, motor to body. Yours at 9.5 PSI is very low. I'm not sure a adjustable regulater is going to help, I think you have another issue.

If you have not rebuilt your TBI then that would not hurt and you would have it apart to do the Mod. Get the injectors serviced while out!

[mudbuggy]

OK now that I'm home I can use the laptop, not the pda, a lot easier. I am rebuilding another tbi unit and I am installing the adjustable fuel regulator on it. That way I know that everything is up to oem specs or above once I bolt it on. Everything will be done on the rebuilt one not just a clean up and regasket, why do half the job when its apart it a lot easier to do all of it and there is less to worry about down the road.

Once I got the pressure guages installed I checked the relay for power there, it was .6 volts off of the battery, I don't want to cut, or 'scrape' a wire going back to the fuel pump just to get a power reading. I'm sure that in the next year, hopefully longer but Murphy has a thing for me, I'll be changing the fuel pump. At that time I'll do something that will make it easier to test connections and/or change out the wiring to the fuel pump, just because it's 25 years old and there's salt used here for the snow. When I do the fuel pump I am also going to add the shackle flip when I have the tank out, and cut a hole in the floor (clean and with a fabricated cover that fits tight) so I don't have to drop the tank for a fuel pump swap or even to change out the sending unit all together.

The fuel filter was changed when I installed the sending unit for the electric guage this weekend. I made a hydraulic line with the fittings that I needed to just hook into the fuel system between the filter and the tbi so I know that the filter is beginning to get clogged, or whatever. At first I thought that I would leave the old filter on, then I figured that I would change it out that way I don't have to crawl under the truck twice. So I did.

I did notice on the original tbi unit that the tab in the fuel regulator bowl is bottomed out. That is its the furthest away from the hood. I figure it was just set low from the factory, but you guys are the pros at this stuff, I'm learning.

The original reason I began to post here was that I have seen some of the fuel regulator setup in the past that have an adjustment that is inside the spring housing, and it is adjusted by removing the housing off of the tbi unit turning the set screw then bolting it back on and checking pressure, if it not right then rinse and repeat. Others I have seen (this is where I am having my question) have an adjustment screw that protrudes out the bottom of the 'can' it also drilled thru the tbi base. What happens to the vacuum source on the back of the tbi base? Is it just capped off is it ported or what? I am assuming that what ever is hooked up to that port, then I just relocate to another vacuum port?

[EagleMark]

Don't worry about a vacuum adjustable regulator unless you have built a big HP engine and are running lean top end. They are very hard to tune. Just do the mechanical adjustable regulater.

.6 volt loss at relay is not bad. loss at pump would be better reading, with you mentioning slted roads a ground issue is likely.

If you make the regulator adjustable, first don't drill the plug to far, you can easily take out the head of threaded bolt in there. When you get it out and slot it of find an allen to put in. When you get the injectors back in and the injector pod is done, don't put it on TBI. Hook it up to fuel lines and turn on key and watch pressure, you get 2 seconds. Then adjust, then 2 seconds, then adjust till 13 PSI. Then reinstall on TBI and try it out.

I just looked at three here in my shop and none of the tabs in regulator are bottomed out?

[JeepsAndGuns]

A much easyer way to adjust the fuel pressure is to just grab the knob with plires and turn.
See here:
http://www.binderplanet.com/forums/show ... post298293 (http://www.binderplanet.com/forums/showthread.php?p=298293#post298293)

[mudbuggy]

JeepsAndGuns
That's a lot easier then tearing it all down and rebuilding it. I'll look at mine in the shop tomorrow and mighj tinker with it after I get the bills paid for the day.

EagleMark
In the picture below I have seen other modified tbi units with the adjuster going from the can through the tbi base and exiting the bottom of the tbi about were the vacuum line is at. Isn't that for a sensor? Is that a pressed in fitting? I have mine apart and I am looking for the correct bolt to use for the adjuster screw. I guess I could use a allen flat tapered head screw leave it inside of the can. But the adjusters that stick out of the bottom really make me wonder, I'm really interested in that, since my fuel lines are steel lines up top, if I would attempt to set and adjust I would only make a mess of things with fuel spraying all over.

I can only imagine how cautious I will be when I get the cable and then need to solder, I'm nervous just thinking about it. Not really, but a heat gun isn't a torch!

[EagleMark]

Fuel does not spray when key is turned on for prime. Only when you hit crank. I always set up adjustable regulaters this way.

That vacuum line in picture is for MAP. I have seen people T into it with vacuum for fuel pressure regulater but I would find somewhere else. Don't like to mess with vacuum to the most important sensor of system. Somewhere on here is a picture of one a guy drilled through the throttle body down to I guess the IAC vacuum port, brazed in a vacuum fitting and ran an elbow to the line he drilled in. Most TBI units have a direct vacuum line on front, so I don't know what would be best.

Truthfully I have never seen a stock or near stock motor need more then 13 PSI. Unless your a big cam big horsepower high RPM engine the VFPR is a pain to tune because when vacuum drops it adds pressure. Changing your tune. I think this is better left to race cars.

I just did a big block Mopar over 400 HP and only needed 17 PSI with Big Block Chevy injectors to keep VE in check at high RPM WOT. With these built engines you need enough fuel at WOT high RPM first! Then tune idle and mid range. If you do idle and mid range first without doing math then you go lean WOT. Not good!

[mudbuggy]

I don't think you understand what I'm attempting to ask and I don't know the correct termmanology to ask another way. I want to extend the adjuster past the bottom of the tbi bottom unit so that I can adjust the pressure of the bypass spring while it is attached to the unit. My biggest fear is that I will drop a screw through the paddles and I won't be able to retreive them and/or they will damage an valve. So I am attempting to come up with a way to avoid having to remove the top of the tbi to adjust the pressure.

[EagleMark]

Oh! Yes just run it through that hole in the picture.Some you have to drill hole, just looked at 2. It's just metal base for air cleaner about 1/4 inch to drill through. Easier to get to but not a lot of room there with the MAP hose.

When I said to hook it up to fuel lines and test pressure you do this when the entire TBI is off being rebuilt. When the injector pod is back together hook it up and test. Adjust pressure, then disconnect from fuel lines and install on TBI unit. Then put the entire unit on truck.

Even on vehicle you need to remove fuel lines, remove adapters into injector pod, remove air cleaner bolt, then there is only three torx bolts to remove that will not fall through closed throttle plates and to easy to hold on to so they don't. Most adjustable regulators and almost impossible to adjust on TBI. I did one once by drilling the hole, but then need an allen wrench trimmed half way, then I could do it 1/8 turn at a time... pain.... half turn is about half pound... then there's the spring. I don't know how far it will bring pressure up before needing aftermarket spring.

If I hadn't said it I have never made one from stock. If I needed one I bought one. Just saw an polished aluminum one on Amazon for $58.

I know some guys want to play with fuel pressure while tuning but I don't. 13 PSI will handle stock to plus 50 plus HP with tuning. Big HP motors I start at 1/2 pound over what math says it needs to be. Hardly ever touched one again this way.

Maybe there's a better way. Build it and they will come!

[mudbuggy]

I'll take pictures of what I have done so far tomorrow, don't think I'll do it from my pda, I'll wait until I get home and do it from the laptop. It was all factory, I have the adjuster freed up and moveable if the base wasn't in the way so I figured out where to drill and hogged it out to a 5/16" hole with the mill. Don't know how much of the return fitting I can get into so I just played it safe. I am wondering what I can do with the vacuum tit on the base if I can move it or relocate it to another port just so I can get the adjuster to extend further down. Guess in my old age, and smashing my hands with my 3lb sledge means I can't get my fingers in the tight spots as easy as when I was younger. Now I guess I could cut the tit short and add a 45 degree elbow on the fitting to allow more room under there just so it can be adjusted while it's running. At least that the idea that I had when I started this part of the tbi rebuild.

On a different topic but the same subject what does removing the radius of the bowls accomplish?
Does the tbi spacer help atomize the fuel air mixture?
Should I get a replacement fuel pressure spring while I'm doing all of this?
Has anyone ran into a fuel pressure regulator spring loosing compression over its service life?

Sorry to bore anyone, but as I have said before Murphy gets a hard on for me! lol

[EagleMark]

I'll take pictures of what I have done so far tomorrow, don't think I'll do it from my pda, I'll wait until I get home and do it from the laptop. It was all factory, I have the adjuster freed up and moveable if the base wasn't in the way so I figured out where to drill and hogged it out to a 5/16" hole with the mill. Don't know how much of the return fitting I can get into so I just played it safe. I am wondering what I can do with the vacuum tit on the base if I can move it or relocate it to another port just so I can get the adjuster to extend further down. Guess in my old age, and smashing my hands with my 3lb sledge means I can't get my fingers in the tight spots as easy as when I was younger. Now I guess I could cut the tit short and add a 45 degree elbow on the fitting to allow more room under there just so it can be adjusted while it's running. At least that the idea that I had when I started this part of the tbi rebuild.

On a different topic but the same subject what does removing the radius of the bowls accomplish?
Does the tbi spacer help atomize the fuel air mixture?
Should I get a replacement fuel pressure spring while I'm doing all of this?
Has anyone ran into a fuel pressure regulator spring loosing compression over its service life?

Sorry to bore anyone, but as I have said before Murphy gets a hard on for me! lol
Sounds like he got the best of you? Hard on your fingers, it's all tight spots. Looks like another old gu here with me and projecttomany...trying to hold our own against these young guys.

But the easy way to get to 13 I told you above.

MAP line has to go there! If you could shorten it and use a GM elbow from a MAP line it would be fine if it gives you room. Spring will be fine to 13. My 1990 Sububan TBI has never been touched 149K miles, still has 13 PSI. TBI spacer is snake oil unless it's A CFM Tech one that has an opening at bottom was tested to give more power, but very small... also their hypertech power charger works, and you will never guess what else is on this page?
http://marine-performance-parts.com/gmt ... mance.aspx (http://marine-performance-parts.com/gmtbiperformance.aspx)

[Six_Shooter]

Running MAP and FPR off the same vacuum line is perfectly fine. Many OEM applications are set-up this way.

People forget that vacuum in this sense is not flowing air, but more like a spring or cushion of air, that only moves a little bit, or rather gets stretched under more vacuum.

[EagleMark]

Darn smart kids! :happy:

All I know is vacuum sucks! :innocent2:

[mudbuggy]

pics This is what I have as of now. I am also have had my brain working overtime today for the tbi. How do I test the tps and the iac while it's disconnected from the vehicle?

[mudbuggy]

more pics

I am thinking that I can attach a piece of elbow to the port fitting coming off of the tbi housing then run it to the map sensor. Then I can drop the adjustment screw out the bottom without a lot in the way.

[mudbuggy]

Running MAP and FPR off the same vacuum line is perfectly fine. Many OEM applications are set-up this way.

People forget that vacuum in this sense is not flowing air, but more like a spring or cushion of air, that only moves a little bit, or rather gets stretched under more vacuum.



I'm not trying to to a vacuum regulated fuel pressure thingy, I'm attempting to make mine adjustable with a thumbscrew underneath the unit so I don't have to take the upper part off to adjust it. I wouldn't know how to do that

[JeepsAndGuns]

I have made the regulators adjustable on about 4 diffrent tbi units, all of them that little screw was brazed into the part sticking down. And that part is held in with a snap ring and then glued into place. I have simply grabbed it with a pair of vice grips and spun it, only one I had to heat just a touch to loosen the glue. Once freed I could spin it all the way up or down.
The tbi unit on my engine right now is like that, all I have to do is remove the air cleaner and turn it with some needle nose plires.
All the machine work and custom screws and whatnot seems like the hard way to do it :confused: Just my $0.02 worth

[EagleMark]

Or you could buy one, or copy one...

http://marine-performance-parts.com/images/products/detail/cfmtechadjregulator.1.jpg

Have you ever checked the fuel pressure with a test gage? Wonder if that electric is lieing?

[mudbuggy]

Before I installed the electric gauge I installed a mechanical set. Dead on! The adjustment tab is all the way on the bottom of the hat. That is the one that is one the truck!

[gregs78cam]

I have thought about getting a pair of these, they might help in your case but those steel lines can be pretty tough. I had a heck of a time getting a couple of them out of one of my TBIs.

http://www.eastwood.com/ew-brake-formin ... liers.html (http://www.eastwood.com/ew-brake-forming-tool-pliers.html)

http://www.harborfreight.com/tube-bendi ... 95782.html (http://www.harborfreight.com/tube-bending-pliers-95782.html)

I know two ends of the scale.

[EagleMark]

I've got flare tools and tubing benders but sometimes it's not sharp enough bend. Would really like a set of those plier type benders for 3/8 and 5/16... the ones listed do 3/16 and 1/4///

[mudbuggy]

When I get home I will try and adjust the tbi that is on the truck how you said. No heat, don't feel like going in orbit (just filled up this morning). I am having a brain fart on the map fitting can't remember when I stored those elbows, only 10 of them. I as of yet have been able to remember to dig out test info for the tps and iac. Hopefully ill do that before the weekend

[EagleMark]

http://www.thirdgen.org/tpimod2

[mudbuggy]

I attempted to move the base of the fuel regulator this evening with needle nose pliers, didn't budge, but I didn't crank the shit out of it either. I did pay attention to the tps and the map. I realized that the tps that is on the other tbi is of another style, and the map is nonexistent, I mean it's not there. I have an 89 I should have one if not in that position, then someplace right? My back was knotting up on me so I didn't spend a lot of time, but I will look tomorrow at lunch, I have a much larger flashlight and my meds will be in full effect at that time too...

[JeepsAndGuns]

The map sensor is there to the left of the tps in the 2nd pic, it has a green connector on it.
When I said I had to apply heat to one, I ment when it was out of the truck and on the bench, tbi and fpr disassembled. I dont think you gonna break it loose when its still on the truck using needle nose plires. I have always had to remove the top of the injector pod and put some vice grips on the nub to break it loose. Will probably needa new gasket.

[mudbuggy]

I understand, I wasn't going to use heat on the truck anyways, I just filled the tank up and I don't feel like ending up in orbit!!! I am thinking that I might this weekend just rebuild the top half of the tbi unit, depending on the weather and how I feel, I need to get a flat tapered head torks 1/4" x 28 tpi bolt idk maybe an inch or 3/4" long. Once I have the bolt then I have all of the parts. I'll just use the back up tbi upper pod section, I have a leak from the upper pod or from the regulator so I'm only a breakdown away from having to rebuild it anyways. Besides firewood season is coming up and I'd hate to miss a day of playing at the cabin because I have to rebuild the tbi.


If that is the map then it is plugged into the fittings on the front of the tbi. The line that comes off of the back is to the 'service' equipment, cruise, hvac, vacuum gauge. The one with a green plug, I thought was the egr solenoid, I'm going out to look I'm curious now! Nope your right, but it is tied into the intake vacuum port. Now I'm wondering who said the map was suppose to be in the rear port of the tbi that is slowing me from installing the adjustable fuel regulator knob on the back. idk I'm so confused now?

[EagleMark]

Sure looks like the MAP vacuum line runs to back of TBI from here. The port between fuel lines is for MAP.

[mudbuggy]

Mark,

That line from the back of my tbi goes to the cruise, vacuum guage, vacuum ball (?), and the hvac. That's it. That's how I bought it too, for 25 bucks!!! I put a battery in it and drove it the next day to work!!!

[EagleMark]

The line on the back of TBI goes to MAP sensor only!

[mudbuggy]

Ok, look at the last post that I made that has two pictures in it. The first picture has a green glove holding the vacuum line from that fitting. Do you see the white tee, then the cruise control can, then the smaller vacuum line that runs to the left in the picture? So what now is a person to do? What does this mean, that someone has really redone the vacuum lines on my truck? I am starting to wonder how it is suppose to be from the factory? If it's working I'm not really sure I want to mess with it too much, then again, if it is less then effecient then I would rather it be better. I really am getting more and more confused on what to do?

[JeepsAndGuns]

You say the map sensor is hooked to a vaccume port on the intake? If so, then it sounds like someone in the past had them off at one time and simply put them back on incorrectly. Attach the map sensor to that port on the rear of the tbi and hook the vac hose thats running all that other stuff to the intake port.

[Six_Shooter]

Using a port directly off the manifold will result in the same reading as the proper port on the TB. Manifold vacuum is manifold vacuum.

[EagleMark]

Pictures here may help.
viewtopic.php?f=9&t=21 (http://www.eagle-mark.com/Forums/viewtopic.php?f=9&t=21)

[mudbuggy]

More I think about it, it makes me wonder if that's the reason the cruise won't work. I need to move the map anyways, the closer it is to the vacuum source the quicker it will tell the ecm what to do. I think I can get rid of a foot and a half of vacuum line. I'll just make a bracket to mount the map on the firewall, might even mount it on the air cleaner housing just to try and keep the line as short as possible.

[Six_Shooter]

More I think about it, it makes me wonder if that's the reason the cruise won't work. I need to move the map anyways, the closer it is to the vacuum source the quicker it will tell the ecm what to do.

Really? Since vacuum is more like a fluid than flowing air, the change in pressure happens very quickly over a long distance.

I've mounted MAP sensors inside the passenger compartment, and had no noticeable lag or issues with the long (about 3') of tube between the TB port and the MAP sensor.

[EagleMark]

He's right, just have to get good vacuum line! Notice he said tubing, like what comes on a Chevy to begin with. Don't want cheap/wrong vacuum hose to collapse or kink!

I know one rule that came from Detroit engineer was MAP should be very close to MAP vacuum port level. Meaning same height. I don't know why but have never tried any other way. Where your MAP is, is where it came from GM. No need to change location.

[mudbuggy]

Just going by my mechanics at my shop on the map
. They were saying that the closer the better and that's why the are mounted on the intakes now adays. They also stated that the tbi stuff is not what they are dealing with daily

How many tps styles are there for the 'truck' series? Are they (the tps) interchangeable on all of the tbi units? Reason I ask is the tbi I am rebuilding doesn't have the same plug ( 3 prong micro pointed toward the ps fender) as the tbi that's on the truck ( 3 prong weatherpack style pointed toward the hood). No I haven't compared to two, it was raining and I didn't want to float away. Thanks guys

[EagleMark]

Three that I know of on TBI. 3 prong oval pointing up and three prong oval out are interchangable. The 3 prong round is not. You will have to repin a new plug onto your harness.

There are also 2 differant IAC and the small block, big block have 2 wires changed.

MAP on the intake may be better when it gets down to micro engeneering, but won't change a thing on your truck. Also most newer cars that have AMP mounted on intake only use it for a split second between key on and crank to get Barometric reading. Then they run off MAF.

[mudbuggy]

Holy shit was that a pita. I switched out the units, at least the upper housings, and then I couldn't get any pressure. Took it apart, made sure that the regulator baffle was sealed, retightened the upper housing and tried again. Still leaking. Well maybe a half a dozen tries later, I finally figured out that the replacement spring isn't strong as the oem spring. So I cleaned up the oem unit and put it back on. I now have 10.5 psi, apparently I had a small leak, where I was loosing 1.5 psi constantly!!! 10.5 is with the oem regulator, and I can't move the bottom of the regulator to attempt to adjust it. I did try, even dripping with gas and brake cleaner I thought about heating it up just for a second. I just went out and looked at it, it's still dry, it was always damp around the bowls and down the back of the tbi unit. Now I just need a replacement spring and I can redo my redone regulator. Yea!!!