CPI '92-'95: Why it leaks and How to fix

[j894]

http://www.s10planet.com/gallery/data/503/medium/51PICT0052c.JPG

As you know CPI stands for Central Port Injection.

Look Familiar?


http://www.s10planet.com/gallery/uploads/51/11110900823d8010fd90.jpg (http://www.s10planet.com/gallery/uploads/51/1111110900823d8010fd90.gif)

As you can see, the CPI is located under the upper intake
manifold. The CPI assembly itself consists of an integrated Fuel Pressure
Regulator (FPR), 1 injector, with 6 poppet nozzles branching off to
each intake port. When its fired, fuel is delivered to all cylinders at the
same time, regardless of whether or not they are on the intake stroke or
not. The injector pulses once per complete engine cycle (2 revolutions). It
Also has a set of plastic inlet/outlet fuel lines (AKA, the "nut kit"), going into
the injector assembly on the drivers side.


This fuel system usually fails in 2 different areas.
1. Diaphragm inside the Fuel Pressure Regulator ruptures, leaking fuel into the intake manifold. (passenger side)
2. The Inlet/Return fuel lines (aka "Nut Kit") are made of plastic, and
over time are known to bust open or develop pinholes, where they then
leak. (drivers side)

http://www.s10planet.com/gallery/uploads/51/tt3.jpg

If you remove the upper intake manifold (10 bolts, 10mm deep
socket), a leaking fuel system will have washing on either side where you can
see the gold. This is where the fuel has leaked into the intake and cleaned
the inside. Your able to determine which component is leaking by which side
has the washing. If the drivers side of the intake is washed the fuel lines are
leaking. If the passenger side has washing the FPR itself is leaking. Its not
common, but it is possible for both items to fail and leak.

The fuel lines can be easily replaced for around $60.
According to GM, the CPI unit is not serviceable & if your FPR is
leaking you must buy a whole new unit. We all know that
is Not so, you can purchase the FPR itself off the fallowing
sites or off ebay. It requires security torx bits to remove it.

Here are a few sites where you can purchase replacement parts
including a new FPR, and fuel lines.

http://robstark.com/cpi.htm

http://www.lindertech.com/reconinj.htm

Some pics are from autozone.com

I will be going into more detail and adding more in the days to come.

[rlith]

I'd like to add...

Well, you know I have railed against getting the FPR from online sources (or any critical part) because of whats involved time wise getting a replacement if it goes bad under warranty. Basically you have to take time to ship it back (usually at your cost) wait till they test it, then send a new one. This can be from 3 days to a week without your vehicle. When you buy locally, just catch a ride up to the local parts store where you bought it and swap it out. Well, I'll rail no more about buying just the FPR.

Advance autoparts, should you live by one, now carries the FPR for our trucks (The FPR is usually what leaks on the CPI unit, somone did a FPR change how-to around here, maybe they can re-link it) The cost is $43.00 with no shipping charges! I called several of our area advance autoparts and they all said they keep a few of these in stock...

Motormite part #55162

Link to website http://www.partsamerica.com/ProductDetail.aspx?mfrcode=RNB&mfrpartnumber=55162

Hope this helps some of you. Far better than having to pay the whole 270.00 for the injector unit. Since motormite is a common product line, I would find out other parts stores that carry it. (Autozone, napa, etc)

[j894]

Cool, didnt know advanced stores carried it locally

[Beko]

First off i would like to say thanks for a great site, I just bought a 95 4x4 for $1000, the blazer looks like new but it skipped and had a strong smell of gas so the owner opted to buy a new vehicle and I bought this one, well after lurking on this site I pulled the plenum off today and sure enough the passenger side was washed clean and even had a puddle of gas laying in there, the driver side had a small puddle of oil (not gas) that looks just like the above pic so I assume this is normal? (the oil) thanks for any input, also the ses was flashing under a heavy load while driving it home but I would assume it was the fuel dumping causing that, I will have the regulator on tommorow but wanted to make sure the oil was normal before putting it back together, thanks again, Kevin

[j894]

Its probably gasoline, & just seems like oil because of
all the carbon mixed in.

[Rob_0126]

I have bounced this idea around in my head, if I should buy an ss s-10, fix this problem even if it's not apparent, and enjoy the ride. I think the trouble to fix it is well worth the performance of the engine.

Now I have the money to do so, but I cant find an ss s-10 :(

[dagwoods4x4]

Does anyone know the part number of the nut kit for the injector. I already have have motormite PN for the regulator(55162) and I was going to change the nut while I was in the intake????????

Thanks Dagwood

[Rotzy]

Nut Kit Part numbers:

GM: 17112705
GP Sorensen: 800-9116A

[Stanthaman]

Nut kit:motormite: 55163

[j894]

Thanks for the part #s
Fell free to discuss it more in the 4.3 section.
or pm me if you wish to add more to this thread

Also. Dont forget to checkout Rlith's Thread:
http://www.s10planet.com/forum/showthread.php?t=4695