lkaras99

I am looking to find out what the fuel pressure specifications are for a Sequential Port Fuel Injected 454. For my vehicle I took the following Data and trying to judge whether this is within specifications.

At Key On - Surges to 58 psi and then drops back to 52 psi
At Idle - 49 psi
Upon Light Acceleration - 53 - 55 psi
At WOT - 58 psi
Upon Engine Shutdown - Surges to 58 then drops back to 52
Very Little Pressure decay after shutdown - 51 psi at 10 minutes 49 psi an hour later

Does this look "normal" for this engine with SPFI? I had engine troubles on a trip. I replaced the fuel filter on the road which seems to have solved the issue based on no issues on my return trip but am trying to be proactive to determine whether I have a weak fuel pump or not. Any help would be greatly appreciated.

lkaras99

I did one more test. I removed the fuel filter and connected the pressure gauge to test the maximum pressure developed by the fuel pump. I got 85 psi. It would appear that the pump is capable. I have recently heard that the normal pump pressure for Key On - Engine Off is 55 - 62 psi. Per my earlier post, I get 58 but only for a few a second then it backs down to 52. I know it's only a few psi but might this be an indication of a pressure regulator going bad? Can anybody comment on the "normal" failure mode of a pressure regulator if any? Is my getting 52 (Vs 55) psi possibly an indication of a regulator on it's way out? OR Do they typically just outright fail?

lkaras99

I would like to ask another question about the fuel pressure specification. When the spec says 55 - 62 psi, at what point does it apply? Mine surges to 58 at Key On - Engine Off but within a second falls back to 52. Does my system pass because it surged to 58 or does it technically fail because it settled back to only 52 psi?

kevinkpk

You have a pressure regulator in the system, that is what you are seeing.

lkaras99

Thank you for your input. I assume though that the spec is to verify the proper function of the pressure regulator. From the dynamic readings in the first post, it looks like the pressure regulator is doing something as it is responding to engine vacuum and changing the fuel rail pressure. The real question I have is whether the regulator is controlling to the right pressure. I am not sure how the spec applies. Does the system surging to 58 count as a pass against the acceptance criteria (55-62) or is the real controlled pressure considered to be where it settles back to? i.e. 52 psi which in that case is 3 psi low to the spec?

I may be stressing over nothing but I want to avoid a stranded on the road in the RV situation. It wasn't fun when the engine stalled and I lost power steering and shortly thereafter vacuum brake assist with the weight of the rig plus a towed vehicle. I changed the fuel filter after that event and things SEEMED OK but I thought it would be prudent to do whatever I can to assess total fuel delivery system functionality. The vehicle is 12 years old but it only has 16K miles on it. Any more thoughts or comments?

kevinkpk

I think you have no problem. You have to realize thses are mechanical devices,so expect some reaction time.

MDTAHOE

Yours is working correctly, nothing to worry about. The pump only runs for a few seconds when the key is turned on, when it goes back down to 52psi the pump is no longer on. Unless you have a high end pressure tester the gauge probably is not all the accurate anyway. As far as the regulator, pull the vac line off of it while it is running if the fuel pressure increases the regulator is working correctly. After it has not been running for at least 30 mins pull the vac line off the regulator if there is raw fuel in the vac line the regulator is bad. You can put a new reg or it or even a pump however new does not necessarily mean good.

Blake Hillhouse

98 Chevy k3500 454 vortec5 speed


Hey guys I'm bought a 98 Chevy from a family member who's had trouble with it. When I test drove it down the gravel road only it would cut out like the injectors or valves missing. I think it might be a fuel pressure regulator problem because lack of power and he said he plugged it into a code reader idk which code reader he used but he thought it was missing off 5 and 7 he also highly recommended that we towed it home .
Is this, or even could this be the problem . Very much help is appreciated thanks.

lkaras99

Silly question but when was the fuel filter last changed?

Jim Heidrick

Where is the fuel pressure regulator? And, what voltage should be coming to the injectors? and is 58psi normal on the fuel line at the carb? On a 1992 Chevy 454 injected motor