454 TBI Fuel Pressure
 

Hello, on my 1992 454 motorhome, when i turn the key to on position the fuel pressure builds up to about 12 psi, I can hear the pump coming on then after two seconds roughly the pump turns off and the pressure drops back own to zero. I pinched off the fuel return line and it still does it. I pinched off the feed line after it builds up and it still drops after the pump turns off.

My sources say that pressure should stay up even after two hours. Well, the pump is brand new, the regulator is new and so is the fuel pump relay! The car runs fine. So my sources say there must be a leak either outside or inside the tank but if so why when I pinch off the feed line does pressure still drop?

Any ideas anyone? Thanks for your input ahead of time.

Kaweh
Spanish Guitarist San Francisco Bay Area
www.kaweh.com

Re: 454 TBI Fuel Pressure
 

It is normal for a TBI system to not hold fuel pressure once the pump turns off.

RBob.

Re: 454 TBI Fuel Pressure
 

WEll, the manifolds glow when under load within 30 seconds. We cupped the tbi close and glow goes away. what to do?

Re: 454 TBI Fuel Pressure
 

Connect a scan tool, read the data stream under various operating conditions, but especially under load.

In your position, I'd want to know O2 sensor readings, O2 cross-counts, short- and long-term fuel trim numbers, along with coolant temperature and manifold pressure sensor readings.

Knock sensor activity, and spark retard would be useful info, too.

When was the last time this vehicle had a proper tune-up, with inspection/replacement of the distributor cap, rotor, plug wires, plugs, etc? Ignition timing? Compression test results?

For the record, farm trucks with BBC power will routinely glow the manifolds under prolonged load. They just make that much heat.