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OK so i have a 99 chevy blazer with a 4.3 in it. well a couple weeks ago out of the blue the thing just dies. initially we thought it could be the fuel filter, as i was still hearing the fuel pump running, well replaced that and still wouldnt start. my husband gets home from working out of state and he tries to figure out what it is. well thought maybe it wassomething electricals so thought maybe the fuel injector connector replaced that. still nothing. we have pressure and everything. has new spark plugs and wires, and they have spark, replaced the mass air flow censor not to long ago, now we are thinking it might be the spider. reason saying is scanned it about a month or so before this incident and came up with a random miss fire code, cant remember exact code. but ive been reading a few things and think that its one of those injectors are clogged. im just wondering if anyone knows of a good way to clean them? have it all torn out of the manifold and apart, thinking about soaking it down in seafoam, is there any other method that might be better?
 

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Check these first:
P0300 is almost always caused by a fault in secondary ignition. These are the secondary ignition parts that must be correct before continuing with diagnostics:
Spark plugs: AC Delco 41-993 with a gap of .060"
Distributor cap & rotor: Needs to be AC Delco, (yes, it does make a difference). It needs a dab of silicone dielectric grease on each terminal, inside and out.
Plug wires: AC Delco, Autolite professional series, Belden, (good quality parts, no AZ stuff).
Ignition coil

P0300 can also be caused by incorrect camshaft retard, worn distributor shaft bushings, and low fuel pressure.

Camshaft retard streaming data is viewed on a capable scan tool, . Preferred spec is zero degrees with a tolerance of +or- 2 degrees. It is adjusted by rotating the distributor, and it's part of the job when installing the distributor to check and adjust it. If it's out of spec, crossfire will occur inside the cap causing the engine to misfire. The farther off it is, the more crossfire. The only DTC that might be set, is P0300. If camshaft retard is off ~27 degrees or more in either direction, P1345 will set in memory and turn the SES light on.

Distributor shaft bushings: There must be no radial play. Best to check it with an oscilloscope.

Fuel pressure: Key ON, engine OFF, (fuel pump will run for ~2 seconds and shut off). Fuel pressure must be checked when the pump is running: Pressure must be 60psi to 66psi. It must remain above 55psi for at least 10 minutes after the pump shuts off.

Cleaning injectors manually:
http://www.instructables.com/id/Poor-Mans-Repair-Guide-For-ChevyGMC-Vortec-Fuel-I/

Upgraded MPFI spider replacement:
http://www.amazon.com/ACDelco-217-3028-Fuel-Injector/dp/B000NW8ES0/ref=au_pf_ss_1?ie=UTF8&Make=Chevrolet%7C47&Model=Blazer%7C420&Year=1999%7C1999&carId=021&n=15684181&s=automotive
 

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I've seen engines run poor because of a bad spider but not just quite and not start again.

I wouldn't condemn the spider before I knew what the fuel pressure was. It culd be a leaking fuel regulator.

On my trucks and my customer trucks I've had P0300's for a bad MAF, vacuum leaks and low fuel pressure. All of them would start and run.

Fuel delivery problems are common with our trucks.

Put a little fuel down the throttle body and see if it fires up.

Have you checked for spark?
 

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Discussion Starter #4
yes we have spark. and when we spray starting fluid into the intake, it starts and runs and then dies in a few seconds. we starting cleaning the spider yesterday, the thing was soooo filthy. at this point it wouldnt surprise me if that did turn out to be our issue because it had so much build up on it. we have fuel pressure, i dont remember the exact specs on it but i know it was in the good range. This blazer was never really maintained before i got it. Now i started running regular maintenance stuff on it and shes screaming at me!! lol right now this is our only vehicle and arent even living in the same state that its in anymore. having to come down on weekends off from work and try to do a little bit at a time. Im at wits end with this thing if this doesnt work!!
:rotf:
 

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The factory method uses a pressurized cleaner made by 3M. It's a standalone system that attaches to the Schroeder valve...fuel pump is disabled. It's available in the aftermarket. There is a TSB on the procedure.
 

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Do yourself a favor and replace the spiders with the mpfi assembly. Took me about 2.5 hours total and isn't hard. The hardest part is bending them damn plastic lines to get the injector into the port. That and getting the plenum down over the new assembly. Gave me a lot smoother acceleration, idled better, and I got 23 mpg hand calculated on a road trip the other day.
 
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