94 4.3 CPI Blazer is getting on my last nerve

[towbar]

Hey guys, I bought this 94 CPI 4X4 Blazer with 104k miles on it a few months ago, it was running great but gradually started running rich and was hard to start. I checked the fuel pressure regulator by looking through the plenum divider in the top of the intake and the regulator was leaking (dribbling and puddling). So I pulled the upper intake and replace the regulator with a new Dorman part and FelPro gasket from Autozone. Fired up and ran great that day, the next day while driving the engine shut off. Tried to restart and it was hydrolocked with fuel. Hauled it home on the trailer. Looked into the intake and the intake was filled with fuel, once i got the upper intake back off and cycled the pump I saw that the new regulator diaphragm had ruptured and would actually spray fuel on the garage wall. So I pulled the regulator, returned to Autozone for refund, went to Orielys and got a Borg and Warner regulator. Spun the engine over with the plugs removed to make sure there wasn't any obvious internal damage and to get the fuel out of the cylinders.....everything seemed fine. Installed the new regulator yesterday and buttoned everything back, changed oil, installed new plugs, it fired fine and idles smoothely for about 10 seconds but then started missing and ran terribly, no power, missing horribly at part throttle, occasional backfiring through the intake, lean O2 code showing.

I dont think there is any internal engine damage, it idles pretty smooth with an occasional miss, no noise from the engine. Dosent overheat or puke out antifreeze. No oil in the water. Have not done a compression check though.

I did verified the firing order making sure it wasn't cross wired.
No obvious vacuum leak showing up but there must be one to cause the lean condition.....any ideas??
Should I have replaced the day old intake gasket again??
Could it be leaking?
how many # of vacuum should it hold at idle? gonna hook up a vacuum gauge tomorrow.

there is a tear in the rubber boot that connects the air filter assembly to the intake throttle body but its been there since I got the Blazer...maybe its a little bigger now from repeated on and off....could that tear be causing the lean condition?

think I'll spray the intake down with soapy water and put some compressed air in the intake through a vacuum port and see if i get any bubbling

thanks in advance...any help or suggestions would greatly be appreciated!!!!

[Lee H]

Does it have the spider injectors, seems like I had to replace those every 15k miles on my 92 blazer.
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[towbar]

thanks Lee H, yep, its a spider injector (vin W) Blazer, thing was running great but just on the rich side till I put the new regulator on and its been all down hil from there. Last night I did a intake leak test and didn’t find and vacuum leaks. So I thought if it’s not too much air then it must be lack of fuel...and the only thing different is the regulator. So I did a fuel pressure test again...originally did one to figure out the original regulator was leaking, that test showed 60psi key on, and about 58 wit the engine running. The fuel pressure test I did last night yielded about 46 psi key on, and about 41-43 running which is way too low.....so I started doing some research as to it the replacement fuel pressure regulators are adjustable, should have been pre-set from Borg Warner? No mention of it being adjustable n the regulator papers that came with it. Papers said nothing about that I need to check and adjust fuel pressure prior to buttoning everything up?? Low and behold I find some threads on another forum stating that they are indeed adjustable buy a trox screw in the center. So this evening me and my step son will pull the upper intake, again, and see if I can adjust the FP up to the 60psi range and see if that improves the running of it.

Stay tuned.

[Lee H]

Good luck!

[Low Elco]

Might also check EGR, known trouble spot, makes 'em do all kinda weird things.

[towbar]

figured it out, the new regulator fuel pressure regulator was set too low from the factory, has an adjustment screw in the center so I turned it up from 40 psi to 60 psi and it purrs like a kitten now.

[jayman68]

Originally Posted by towbar

figured it out, the new regulator fuel pressure regulator was set too low from the factory, has an adjustment screw in the center so I turned it up from 40 psi to 60 psi and it purrs like a kitten now.

Congrats! Good job on finding that.

I had a fuel pressure regulator problem on an Astro that I had, not knowing what the problem was I ended up changing the engine(using the same TBI unit) and still had the problem. Eventually found a failed spring in the regulator.