Fuel pressure oscillations
Hey guys,
Took my Marauder on its 1st road trip yesterday. I went 173 miles in one direction, from Chandler AZ to Show Low AZ.
The rebuilt engine, etc., had only 200 miles on it prior to the trip, so still in the shake down phase.
Everything went good until about mile 140. Then the engine stalled. As it stalled I saw the fuel pressure (AutoMeter gauge) had dropped to near zero. I got the car over on the side of the road, opened the hood and looked for anything obvious. Nothing. I attempted a restart, and the car started and I completed the trip. Yay. However...
The fuel pressure reading would oscillate very widely from 100 to near zero if the car was idling and my foot was off the gas. If I gave it a teeny bit of gas with the accel pedal, the pressure would normalize at the steady state level, which appears to be 40 psi on the gauge.
When I arrived, I pulled into the garage, took my foot off the gas. The gauge oscillated again and the car stalled.
The car has never done this in the prior couple hundred miles of running; all of my other trips were relatively short.
There is a high volume fuel pump I put on the car while it was in rebuild. The pump is powered, essentially, directly from the battery , with that power going through a relay , then the FPDM. There is a 40amp fuse on the line in. This is a wiring set up that was found on this site, and recommended by Chris at ADTR.
There was no check engine light, no codes.
After a night in the garage, the car runs/idles very normal, albeit the stable fuel pressure is at 30 rather than 40.. so maybe the problem is temp driven?
Any ideas what was causing the wild oscillations in gauge fuel pressure?
Thanks guys
'03 Silver Birch. Stock rebuilt 4.L 32V DOHC, V7-JT blower w/ADTR racing supercharger kit, Shift kit in transmission, stainless works long pipes and cat backs, Ridetech coil-overs front, shocks in back (ADTR kit). Rebuilt calipers, upgraded front rotors, OEM Mercury wheels, [boost, oil P, WB fuel/air, and fuel pressure] gauges. Build duration was Dec 2019 to Mar 2022. 8 rib serp belt upgrade i/p.