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05-10-2011, 09:01 PM #1Registered User
- Join Date
- Dec 2007
k3500 silverado vortec 454 possible fuel pressure regulator?
I have a 97 silverado 3500 with the vortec 454 in it. It has 200k on it, and has a horrible low throttle input miss and a high idle at times. It is also way down on power and stumbles until you really give it some gas, but even then, you can tell its low on power. Unfortunately, this is how I aquired the vehicle with this condition. I changed the plugs, wires, fuel filter, and even the distributor for the common worn out gear, and man was it worn. Everything I changed was extremely worn out and each time, I though for sure I found the issue. but the issue is still there. In fact, it seems to hesitate even worse now. I do now have a p1345 code (crankshaft/camshaft correlation) since I changed the distributor, but have read that it can only be adjusted with scan tool. I do wonder though if the distributor was the issue and I have it one tooth off. I made sure to mark everything and put it all back. But I don't know 100 percent sure it was correct to start with.
My main question now is: what is the fuel pressure suppose to be? With the fuel pump on, it registers around 50 psi. As soon as the fuel pump shuts off, it drops to 20 psi. But will stay there for hours. I have read that it should not drop at all and if it does, the FPR or injector could be the issue. I have read these engines need to run at least 60psi, but have also read lower psi.
I guess I need to buy a service manual. But if anyone has had any experience with these engines and can point me in the right direction, I would greatly appreciate it.
2005 CBR 1000RR..."mostly stock".
1968 camaro... "in the works".
05-11-2011, 10:31 AM #2
OK lets start with the basics. (1) Check your compression, the fastest way to see if they are all at least even with each other is to disable the ignition and roll it over with the starter. If it sounds like a nice even rhythm its probably ok. If it has a spot where it skips or sounds like it speeds up, pops out the exhaust or intake you got problems. (2) check your timing (if it's been doing this since you got it who knows what "they" did). the computer will have to be disabled to properly check it (usually it requires unplugging the input wire(s). (3) I don't know the exact fuel pressure, but if you call your local dealer/truck shop and ask real nice, they usually will help you out, it's not really the pressure thats the problem, but the volume...if it works at full throttle under load conditions (this is the most taxing on the fuel system) this is probably not the problem. If this truck is what I think it is, it has a "octopus" type injection system, making it virtually impossible to isolate any one injector at a time, they also take a sh-t quite often and are expensive to replace. Also, if you are thinking ignition, which is the next likely target, if it works at full throttle (again, the most taxing condition) then it probably has ENOUGH spark. All this being said (very long winded I know) if your compression and timing check out I would look towards fuel delivery system/ major air leaks between mass airflow sensor and throttle body, cam timing, worn cam lobes..... let me know how it goes question: does it have individual injectors (electronic) / TBI or octopus type injectors?
05-11-2011, 12:25 PM #3Registered User
- Join Date
- Nov 2004