Fuel pressure question from a dummy...
 

After searching sooooo many threads - I have a question. 1998 Blazer, 4.3L Vortec engine - runs like poop. Gas consumption became a problem 2 days ago - what used to take up 1/4 of a tank is now taking 3/4...recently replaced distributor cap due to miss (didn't use AC delco and miss is still present - going to get one tomorrow) but....did pressure check this evening and key on/engine off 65psi which IMMEDIATELY dropped to 10psi (within seconds). One of the threads I read stated this would be a fuel pressure regulator problem. (Going to NAPA to get one tomorrow) Would this be the most likely problem or the only problem? Could there still be a leak (fuel) somewhere (no apparent leak is visible...no drips, etc)? Thanks for any help....

this should have all the information you need

https://blazerforum.com/forum/tech-a...agnosis-23038/

THANK YOU! You will let you know what I find out!

I want to thank you, again, for your help. Ended up taking it to the shop after all the tests WE did did not reveal a leak (other than the smell of gas and the dropping fuel pressure) and it turned out to be a carboned up MAF. (Cause was the "new" spark plugs that were put in - they were not AC Delco...) Shop cleaned the MAF and husband put in Delco platinum spark plugs. This was a frustrating and time consuming lesson learned!

Your welcome im glad your trucks running again

Grrrr......we are back at it. Same as original post....gas is dumping into cylinders and consumption is awful. Took it back to the shop and they are at a loss for what it could be? We have now replaced the MAF - still blowing back smoke and eating fuel. Has misfires. The truck is throwing codes : PO102, PO154,PO174,PO300,PO440,P1153. Shop did a "smoke test" and found nothing. Husband replaced the fuel filter last evening. When he tried to put the AC Delco distributor cap/rotor in vehicle, the vehicle ran worse than it did prior! (Shook so much on start up he thought bumpers would fall off!) Funny thing is....when he drove it to work after jumping it (Battery dead from light being left on) - the truck ran like a champ for the first 50 miles WITH NOT ONE STUTTER. Then, the horror started all over again. Any ideas would be most helpful....

Spark plugs won't cause a MAF sensor to get 'carbon'ed up :S

MAF sensor isn't even on the engine, it's in the air intake.. 65psi is borderling high for these engines (engine off/key on)

If you're having a rich condition, I wouldn't spend money on ignition! Take a look at the fuel side of things. Shouldn't drop from 65psi to 10 psi in seconds. Supposed to slowly decrease over a period of time... I'd take a look at the fuel pressure regulator, or perform an injector balance test to see if you're getting an injector that is stuck open.

Don't waste any more money picking parts and replacing them! :)

-OSS

Maybe they got confused. Carboned up MAP, maybe. Would be pretty unusual but MAF... no

But the obvious answer to your problem considering it runs fine often and crappy rich sometimes and Fuel pressure may be too high is the fuel pressure regulator.