So I was having problems starting...(Mainly I'd have to prime the system before starting). My fuel economy dropped from 20 mpg local to 12 mpg local, this was significant and that much of a drop I could not attribute to winter gasoline formulas. I knew it was the CPI

This how-to will focus on changing out of the regulator only though it can be applied to swapping the entire CPI... Typically it's the regulator that goes bad, but because of how detrimental this part is to running, I wouldn't advocate buying this part online. Since the regulator is now available at most autoparts stores from Help! Part #55162, it's much easier to swap out a defective unit.

Tools needed.

10mm deepwell socket (Must be a deep well)
8mm socket
T30 Torx Bit
Paper towels
Either a complete CPI
or
Help! Part # 55162 (the reugulator) Includes the needed Torx security bit for retainer removal. (About $40.00 at Autozone, Pepboys, or Advance autoparts)
New plenum gasket.

First remove your intake air feed and disconnect the air temp sensor. Then remove the 2 bolts holding the VORTECH cover on. (The bolts holding this on are T30)

Here you can see where I disconnected the air intake temp sensor and started loosening the cover bolts
http://www.pghconsulting.net/teal/cpi/cpi1.jpg

Next Disconnect the linkage from the throttle butterfly and remove the 2 8mm bolts holding the top of the cable bracket to the upper intake.

Disconnect all sensor connectors and move them out of the way.

Using your 10mm deepwell socket, Starting with the bolt holding the bracket, work your way around the plenum. There are 9 bolts to be removed. As you get to the bracket holding 1st the coil bracket and then on the opposite side the fuel recovery module, you 1st need to remove the 2 top nuts then set the bracket out of the way then remove the bolt(s) holding the plenum down.

As you remove these bolts (and nuts) Lay them out in order. Several of the bolts are different sizes, so if you lay them out in order, you can simply put them in reverse.

Disconnect the small vac hose from the back of the plenum, then the larger hose at the brake booster.

Lift the plenum straight up.

Here we see that the passenger side of the upper plenum is very washed (note the gold covering)

http://www.pghconsulting.net/teal/cpi/cpi2.jpg

Here we have the lower intake. Note that the passenger side is almost clean while the driver's side with the nutkit is nice and dirty.

http://www.pghconsulting.net/teal/cpi/cpi3.jpg

Next I stuffed all the intake ports with paper towels. Why? Becuase you DO NOT want to take the chance of dropping something down there. (Last time I did I destroyed a motor, :D)

http://www.pghconsulting.net/teal/cpi/cpi4.jpg

Here is a shot of the regulator SImply remove the 2 screws holding the retaining ring on. (Help! was thoughtful enough to provide the security Torx bit needed to do this)

http://www.pghconsulting.net/teal/cpi/cpi5.jpg

A shot of the retainer ring removed
http://www.pghconsulting.net/teal/cpi/cpi6.jpg

A shot of the new regulator (left) and the old one (right)
http://www.pghconsulting.net/teal/cpi/cpi7.jpg

Here is the new regulator on the CPI (pre retainer installation)
http://www.pghconsulting.net/teal/cpi/cpi8.jpg

Now make sure that the mating area is completely clear of any old gasket material. If needed, use a razor blade to scrape the mating surface. For some areas if too difficult, use sand paper.

A final shot prior to putting it back together w/ the new plenum gasket
http://www.pghconsulting.net/teal/cpi/cpi9.jpg

Simply reinstall everything in reverse

Starting at the bolt at the bracket, torque in circular patter to 8 ft pounds

Wala your're done!

Note: Prior to putting it back together, it's a good time to pull the distributor cap and check the condition of your cap and rotor. The reason I mention this is because of how difficult it is to get to that front screw.

great pics and directions.
wish this thread was created a long time ago. for me i had a busted regulator and nut kit so i just replaced the nut kit and complete cpi unit. if i could i would like to get ur opinion on the gas mileage. i replaced my cpi/nut kit in august. before winter i was getting about 15-16mpg (98% city stop and go driving). when the winter gas formulas went into effect, economy dropped to 13.5. this seems very low to me even with the winter gas formula. what are the odds of a new regulator (one that comes with the cpi) going bad. i did a tune up at the time of the cpi replacement. any thoughts? the only thing i can think of is that it might be time to pull the egr again.

wish this thread was created a long time ago. for me i had a busted regulator and nut kit so i just replaced the nut kit and complete cpi unit. if i could i would like to get ur opinion on the gas mileage. i replaced my cpi/nut kit in august. befor winter i was getting about 15-16mpg (98% city stop and go driving). when the winter gas formulas went into effect, economy dropped to 13.5. this seems very low to me even with the winter gas formula. what are the odds of a new regulator (one that comes with the cpi) going bad. any thoughts?

Only real way to find out is to re pull the upper plenum and check (its worth a 7 dollar gasket replacement)... Fouled the hell out of my plugs too..

actually that gasket is 11.50. yea that would be the easiest way, as pulling the intake only takes only about 5-10 min. the only thing is i installed a pcv catch can not long ago with prevents the upper intake area from guming up with oil and such, making a leak harder to detect. So i guess i will have to turn the key on with the manifold off to prime the system, then look for leaks. i may pull the egr again also and give it a good cleaning.

Good job, this is the first how-to that I've seen with instructions for only replacing the regulator..... should save people some money.

Good job, this is the first how-to that I've seen with instructions for only replacing the regulator..... should save people some money.

Well, when everyone kept saying buy the reg from lindertech, I was always against that. The reason being is that if it goes out, you have to send it back, wait for them to approve a replacement, then wait for the replacement. This puts your truck out for up to a week, sometimes even more. Where as if you bought the CPI locally you could just catch a ride up to where you bought it and exchange it only being without your vehicle for maybe a few hours at worst. Now that everyone is typically keeping the regulator in stock it makes life much easier, and cheaper... :)

Only real way to find out is to re pull the upper plenum and check (its worth a 7 dollar gasket replacement)...

That comment got my butt moving. I've been "over diagnosing" and not getting anywhere. I have a 93 S10 Blazer, 4.3 CPI, W and have had hard starting, black soot coming out the exhaust and other symptoms that I've posted.

Here's some pics that I think show a bad regulator. they're not as clear as the rlith pics inasmuch as the color/contrast differences but that may be because of different lighting/camera/flash etc.

Experts! What do you think?

http://members.cox.net/leadalto/Top_LowerIntakeManifold.jpg

http://members.cox.net/leadalto/Bottom_UpperIntakeManifold.jpg

Yeah, your CPI is goin, and you're nutkit looks like it's leaking too (albiet a pin hole leak, it needs replaced)

Damn, I *might* have gone with a plain old regulator swap if the option were available. However, when I actually got INTO my intake, the bitch was falling apart in between my fingers. All of the tubes to the poppet vavles were brittle and the nut kit disintegrated upon removal of the fuel line clip. In my case, outright replacement would have been the way to go.

Now that I know everything under the intake is new, if something comes up with the regulator, I will try to locate and fix that first.....in another 5-7 years that is. *laugh* Good work guys!

Wow that was a great read and pics! Awesome!

Yeah, your CPI is goin, and you're nutkit looks like it's leaking too (albiet a pin hole leak, it needs replaced)

I took a picture with another camera looking straight down, Adjusted the image for contrast, color , etc.

Is the small washed area, as pointed, what you suspect is a pinpoint leak in the nut kit? If so, it looks like it's on the return line side.

There is also a big difference in the color of the spider tubes (and nut kit plumbing) from the passenger to drivers side.

http://members.cox.net/leadalto/KIF_0138_a-iC_b.jpg

I took a picture with another camera looking straight down, Adjusted the image for contrast, color , etc.

Is the small washed area, as pointed, what you suspect is a pinpoint leak in the nut kit? If so, it looks like it's on the return line side.

There is also a big difference in the color of the spider tubes (and nut kit plumbing) from the passenger to drivers side.

http://members.cox.net/leadalto/KIF_0138_a-iC_b.jpg

Still washed on the nut kit side a bit... Replace it...(Yes, the nut kit is the inbound/outboud fuel lines...They come as a set)

You're quite fortunate Rlith... I looked like hell for just the regulator and could only find the Vin Z and the 96 version.

Very nice pics. The effects (clean vs dirty) are quite pronounced in your case. Should serve as an excellent example for anyone wondering!

Rlith,

Didn't you just replace your whole cpi injector only less than 2 years ago with a new unit?

Still washed on the nut kit side a bit... Replace it...(Yes, the nut kit is the inbound/outboud fuel lines...They come as a set)

I hooked up the fuel pressure guage and by using the key-on, ign-off or connecting the fuel pump pigtail connector direct to the + battery terminal, I get 60 psi which holds "forever". I cannot see any signs of gas leakage (pin hole or otherwise) on either side of the plenum (regulator or nut kit side). What gives? Shouldn't there be gas spilling into the plenum or a strong odor of gas if I have a leak? I'm looking right into the open plenum!

I pulled the plugs and they are not fouled but all were just sooty, as they would be from running a very rich mixture as I reported (black smoke in exhaust). The plugs on the left and right banks look the same.

I'm very reluctant to pony up to $350 - $450 in parts to fix a leak that I'm not seeing or smelling.

I cleaned the EGR a few days ago because I had an EGR code. That did not fix the problem. I'll do it again because it's so easy to do with the upper manifold removed. As a matter of fact, it's so easy to remove the upper manifold and the gasket is relatively inexpensive that it may be worth it (to service the distributor or even the EGR unit), to avoid needless aggravation.

I'm anxious to solve the problem but not to throw money at it.

I hooked up the fuel pressure guage and by using the key-on, ign-off or connecting the fuel pump pigtail connector direct to the + battery terminal, I get 60 psi which holds "forever". I cannot see any signs of gas leakage (pin hole or otherwise) on either side of the plenum (regulator or nut kit side). What gives? Shouldn't there be gas spilling into the plenum or a strong odor of gas if I have a leak? I'm looking right into the open plenum!

I pulled the plugs and they are not fouled but all were just sooty, as they would be from running a very rich mixture as I reported (black smoke in exhaust). The plugs on the left and right banks look the same.

I'm very reluctant to pony up to $350 - $450 in parts to fix a leak that I'm not seeing or smelling.

I cleaned the EGR a few days ago because I had an EGR code. That did not fix the problem. I'll do it again because it's so easy to do with the upper manifold removed. As a matter of fact, it's so easy to remove the upper manifold and the gasket is relatively inexpensive that it may be worth it (to service the distributor or even the EGR unit), to avoid needless aggravation.

I'm anxious to solve the problem but not to throw money at it.

A lot of times the leakage happens when underload, not always when you just prime it... That said, the regulator is only $40 bux and the nut kit runs about 60.00

Rlith,

Didn't you just replace your whole cpi injector only less than 2 years ago with a new unit?

Yep....Entire CPI unit..

Yep....Entire CPI unit..

Wow, I wonder if this is my problem.

I am suffereing with some serious low city mileage but it is cold up here and I do a lot of short trips.

Highway mileage is still over 21mpg so I am wondering if it is this or just poor driving conditions and lots of short cold driving trips.

It is weird that you are bringing this up seeing I to have had some poor starting if I don't prime it completely everytime.

Wow, I wonder if this is my problem.

I am suffereing with some serious low city mileage but it is cold up here and I do a lot of short trips.

Highway mileage is still over 21mpg so I am wondering if it is this or just poor driving conditions and lots of short cold driving trips.

It is weird that you are bringing this up seeing I to have had some poor starting if I don't prime it completely everytime.

Rlith, excellent posting. I wish I new about this a year ago. I could of saved some money.

LT, I replaced a whole CPI unit and nut kit on my "94", then about a 14 months after my regulator was leaking. So I replaced the CPI again. Had I known that the regulator could of been replaced. I would of done so. So I think I'm going to have to keep a regulator on hand as spare parts around the house.

Rlith, Thanks again.

My city economy is 12-13mpg with a lot of stop start driving and cold weather nothing higher than 32f so the engine is never really getting up to temperature.

Rlith, not trying to overstep my word here, but I would take a toothbrush and some TB cleaner and scrub that TB butterfly, it looks a bit grubby.

And maybe consider the PCV catchcan to stop that oil and gunk getting into your intake if you want.

Just a thought, nothing implied.

I have a 96 w-code 4.3L in m blazer. It doesnt look anything like this. Does this problem also occur in my style of 4.3L?

You can have a leaking regulator but in most cases it won't show the same problems as the 1992-1995 as is stated in this thread.

http://www.babcox.com/editorial/us/us30098.htm
http://www.asashop.org/autoinc/feb2000/techtotech.htm
I know i posted these awhile ago but in case people dont search here they are again incase you are confused and want to read up on it.

Rlith,

Notice any performance improvement?

Sorry to bring this thread back up, but I need to see who has done this and what improvements they have seen?

Does your city mileage still suck BLT?

And are those HELP parts any good? I've often looked at them but never bought any thinking that they look cheap.

Only improvement was gas usesage went back to normal as well as power and pressure.

just a thought...anyone know the likelyhood of a newer ac delco replacement cpi w/regulator going bad within a year of being replaced? i forget how long they are under warranty but they are "suppose" to last 5-7 years.

Does your city mileage still suck BLT?

And are those HELP parts any good? I've often looked at them but never bought any thinking that they look cheap.

Actually, I think is has gone up rather significantly.

80% city and I will be getting close to 18mpg which is not bad at all.

It is just weird sometimes. Somtimes the truck seems to be peppy, and others it seems to be a dog.

Wonder if it is the regulator or the coil?