I'm running the corvette & walbro setup too and I just experienced something like vapor lock. I drove my car to Carlisle 2 weeks ago and after 2 hrs of continuous driving the car started coughing and sputtering like it was running out of gas. I pulled over, gassed up and it didn't happen again, till I was on my way home, again after 2 hours of continuous driving. I'm replacing both the pump and filter ( if nothing else, just to eliminate them from the equation ) any ideas on what could cause this? I check the ECU, there was no codes, if I drove for 1 hour, it was fine. :wack:
I have experienced this. It's a result of high fuel temperatures and/or tank venting issues; and maybe high voltage causing the pump to overrun. I had issues with all 3.
Do you have a way to monitor fuel temp (could always use a heat temp gun on the filter/regulator)? And remind me of your pump configuration? Is your tank adequately vented?
My first experience: end of Big Bend Open Road Race (i.e. last 11 miles of a 59 mile leg doing 125 mph average at 4000-4400 rpm in OD). The AFR's would spike lean, I would take my foot out of it, wait a few seconds, and get my foot back in it and all would be ok for another mile or so. Then it would repeat.
Also, I learned more about the issue on a 1200 mile road trip. The pumps were getting really loud every 2 hours (!), so I would pull over and refill the tank. When starting the pumps back up after the stop, I could hear what sounded like aerated liquid leaving the lines and non-aerated liquid filling in place.
Part of my issue was 14.3-15.3 volts under normal operating, and 16+ volts when the AC was on. Part of my issue was just the heat from the exhaust. Part of my issue (prior to BBORR) was no vent (fixed prior to fuel issue at BBORR - had a pump failure that week - from no vent).
The final leg of my road trip I fixed the 16+ volt wiring issue with AC on, and lowered the regulated voltage to 13.3-14.3 volts. Zero issues for the last 2.5-3 hours with no stops for gas.
Additional info:
Notes from discussion with Aeromotive:
1- EPA regulations require minimal cranking when starting. Hence winter blend fuel has a higher concentration of lower boiling products in the blend.
2- 120* or less is a good rule of thumb to keep fuel temp under. Problems begin around 130-140* for a well designed fuel system.
3- most of the heat isn't generated by the pump(s) but instead by engine compartment, etc
4- ANY vacuum suction on inlet of pump drastically reduces the boiling point of the fuel at that point.
Also, he said they run a1000 pumps continuously on 3 gallon tanks and never generate enough heat to cavitate a pump.
Link to more on my specific diagnosis and issue:
http://board.moparts.org/ubbthreads...&Words=uhcoog1&topic=&Search=true#Post8130349