I just moved a very good DIY thread into the DIY section.

DIY fuel pressure regulator on Blazer 4.3L CPI engine

The purpose of this thread is to discuss this submission. If anyone sees anything that needs correction, please post about it here.

Thanks kerander for your submission!

 

Yep, that's exactly what a normal good working94-97 plenum looks like inside. That's what mine looked like 160K miles ago and I didn't touch my FPR or spider or nut kitbecause I could not see or smell any fuel leaking.

"After changing mine, the truck runs smooth again, got its power back, and vastly improved fuel economy (went from 2 to 20 mpg ). "
kerander (new member)

You were only able to go 36 miles on a tank of gasoline?

 

That is NOT what a normal intake will look like. That cleaned off aluminum is from the fuel leaking from the FPR. If it did not have the fuel leak, the passenger side would have the copperish color all over it.

 

When I was told that my FPR/spider injector assembly was gone about 160K miles ago. I opened the plenum and it looked just like KERANDER's did when he opened his. I smelled no more gas than what I would expect. There were NO puddles of fuel and the FPR was copper colored and dry. Passenger side of plenum was very clean and drivers side all carbon. I did NOT change anything. It still runs super.

I just think you need to be absolutely sure that you are changing the correct parts because these parts are costly and if you break the mounting holes for the FPR, you are buying a $350 spider injector. There is a member asking now for a used one because he did just that.


I am posting pictures of what an ACTUAL LEAKING FPR looks like when you pull the plenum off.

Notice that the leaking fuel causes the FPR to get a carbon coated burn on it.
Notice that the fuel is actually all over the passenger side of the plenum.
Notice that after it is cleaned, the copper color is NOT washed off the plenum.
Notice that the FPR is actually wet from the gasoline.








Photos courtesy of member 93LT from previous post in 2006
https://blazerforum.com/m_7118/tm.htm

 

It all depends on how long the leak was present as to how much the plenum will be cleaned. Now, look at the pictures in the DIY post. Looks like there is gas pooled on the plenum, but it is very hard to tell with the pictures how they are.

As always, it must be verified that there is an internal leak in the plenum either visually by pressurizing the system or with a fuel pressure guage, but to blindly dismiss the potential for a leak with a WELL documented, leak prone, spyder assembly such as is used in the CPI by simply looking at pictures is ridiculous.

*EDIT* - Never once have I just blindly recommended that the CPI unit be replaced. I have always recommended having the fuel pressure leak down test performed and/or removing the upper plenum and actually visually inspecting the lines and other components of the fuel system internal to the intake. A small leak may be present, but have no impact on driveability. Doesn't mean it is OK.

Just as sticking poppet valves may not be easily diagnosed, but without proper maintenance, the poppet valves will start to stick. I suspect with your truck because of the sheer number of miles you accumulate in a week, the poppet nozzles don't get a chance to varnish.

But just because something has gone for 340k miles on your truck doesn't mean that your voice is any louder than the thousands (understated) that have had their FPR leak at under 100k miles. This problem is a wide spread problem. Some make it longer than others, but it is a problem none the less. But being as wide spread as it is, many driveability concerns may be inappropriately linked to a bad CPI unit. That is why I stress the proper diagnostic procedures be completed. If you must use a mechanic, always get a second opinion unless it is someone you trust.

 

does this same thing happen on later versions of the 4.3? Im getting horrible gas mileage on my 97, and i was wondering about some causes for this. Im cleaning the EGR and MAF sensor today.

 

The poppet nozzles are of the very same design on the CSFI spiders as on the CPI. I'd run some fuel injector cleaner through the next few tanks of fuel.

It is quite possible that you don't have a problem with the injection at all and that it is the O2 sensors causing a problem, but that is a discussion for a different topic.

 

The carbon build up on the FPR is not from it leaking, it is from the normal by-products of combustion, hence the rest of the intake being covered in carbon. When the fuel leaks out it cleans the the carbon off, just like it does it the picture above. Every one I have replaced looked brand new, not all carboned up. This is of course the customer always waits until they are fed up with poor fuel economy, and the hard starts. I have replaced a ton of the FPR, and the nut kits, but only one spider assy.. And that was only due to the main injector being dead. Korey

 

swartlkk
If you look at the picture in the DIY post where he is showing the FPR through thehole in thetop of the plenum, it is actually dryer around the FPR than on the drivers side. How do you look at that and think that the FPR is bad (leaking)? I absolutely agree that thousands and thousands of spider injectors have been replaced on the 94-87 Blazers under 100K miles. If the FPR is so fragile on these Blazers, how come it is a special order part at Auto Zone, Advanced Auto and NAPA? Not even stocked at their warehouses, a special 2 week notice , pay in advance, buy it with no returnpart.
I don't even think that mine is anything special.



This is what seemed to be wrong with mine. This wire was broken. $95.00 at Chevy dealer for connector and 1 foot harness. Yikes.

 

Blasir, the intake being so clean like that in the DIY picture is what tells you the FPR is leaking. My NAPA, Autozone, and Auto-Valuestocks the FPR. I replace these all the time. If one side of the intake is clean there is a leak on that side. The reason it looks drier is because by the time you look at it the fuel has dried on/ around it. And around the 2 intake bolts on the left side of the picture, if it was not so bright, you probably would see fuel sitting there. Your picture looks as though someone cleaned it, or you run some sort of cleaner through your fuel system an a regular basis. Every one of these motors I have had apart look like the pictures in the DIY section. Either the whole intake looked like the right side, or the side that has the leak was clean like the left side. Korey.