I just read the topic about upgrading your CPI to a MFI. I was wondering if this could be use on my truck. I have a 93 s10 v6 CPI vin w truck and I am worried it will start to leak fuel soon.`Any help would be great.

 

This does not apply to the CPI motors, but rather the 96+ SCFI motors. The MFI spider is different in that it moves the 6 electronic injectors from the fuel metering body down to the location of the poppet nozzles on the SCFI spider, removing the problem prone poppet nozzles from the system.

Sorry... But you're stuck with the single batch fired injector and poppet nozzle setup...

 

OK Thx from what it looked like to me it was just an upgraded cpi injector with better tubing.

 

what are you guys talking about? What will this do for you engine?

Thanks.

 

What are we talking about?...

Well, the first post asks about an upgrade from the CPI spider which utilizes a single batch fired injector feeding 6 individual, pressure actuated, poppet nozzles to an MFI spider with 6 injectors, one in each intake runner fired sequentially. That is not possible for a few reasons; parts do not interchange and if they did, the computer does not have the capability to fire the injectors sequentially.

Now for the 96+ SCFI motors which already have 6 individual electronic injectors that are fired sequentially, but also have 6 problem prone, pressure actuated, poppet nozzles at the intake runner, there is an option. In late '02, GM started installing true MFI spiders into the 4.3L and 5.7L. This spider was a direct replacement for the old SCFI spider.

You will not gain performance from this change. One thing that has been noted with this is that the SCFI spider has higher lb/hr injectors than the MFI and some have run into problems when they've turbo'd or supercharged their 4.3L on the newer MFI spider. If you currently have a problem of sticking poppet nozzles and or injectors, then the MFI spider will cure those problems and keep them from returning far longer than a new SCFI spider would.

Before I traded in my Bravada, I had replaced my SCFI spider and I regained a bunch of lost performance. But before I just replaced it, I verified that I had a problem with my injectors. I had 2 leaking electronic injectors and 4 sticking, partially clogged poppet nozzles. This on a SCFI spider that was just professionally cleaned not 6 months prior. It was cheaper to purchase the MFI spider ($200 from my local dealer) than it was to purchase the individual injector that needed replacing.

 

How can you tell if the injector is bad? Is it a feeling like running on 5 cylinders instead of the 6?

 

I wish it were that easy... For me, I have a scan tool that allows me to do individual injector tests. I removed my upper plenum and reinstalled my fuel supply rails. Then I pulled each of the injectors out of their bores and put them each into a small glass jar. Pressurized the fuel system and looked for leaks at the poppet nozzles. There were the ones that leaked quite steadily, then there were the ones that had a crappy spray pattern when I activated the electronic injector.

You can do a leak down test by cycling the individual injectors and seeing how the pressure changes, but even that is sorta subjective...

 

So I just bought this 2000 Blazer (rest of spec's in my sig) earlier this year. It currently has a hole in the muffler, sagging driver side door, possible bad rotors/pads, and I already put a new air filter in it, will be putting new spark plugs and wires on it in a few hundred miles when I hit 80k. Would it take very long to test the injectors and is it something I should consider checking?

If I had a bad injector what would it rob me of? From the way I have it in my head I would guess power as the big one, I would not think it could lower gas mileage....?

 

I picked up 2mpg and much smoother operation from the repair. And I have no doubt I would have gotten the same results with a new SCFI spider as well. However, I had verified leaking and sticking injectors/poppets. If you currently don't have drivability concerns (misfires, hesitation, etc) and/or haven't already tried a professional injector cleaning, I would not recommend dropping the $$$ on the MFI spider.

 

The only hesitation I had when I first got the truck left after I put the new air filter in. How much would the injector cleaning cost and is there a certain mile marker when you should get them cleaned? (Will be easier to let my dad get em done depending on price)