Fluctuating / Vibrating Fuel Gauge And Pressure Drop Across Injectors

[03cobra#2]

I worked on a little project that I wanted to share. I noticed that after I got my fuel system together the liquid filled gauge on my fuel rail vibrated like crazy when the engine was running...same thing with the electric gauge in my cabin that used a sender on the fuel rail as well. When the engine is off and key on (return fuel system) everything is nice and steady. I decided to ditch the liquid filled gauge on the rail and relocate the sender for the electric fuel pressure gauge to the fuel regulator which is located in the drivers fender well. Fuel pressure gauge reads nice and smooth now and doesn't jump around like it used to. Maybe related to the cams / choppy idle? Which gets me thinking.

What if the FRPS which is located on the rail goes through the same vibration? When I the FRPS it's fairly stable but does jump around a bit in a datalog. Has anyone moved the FRPS off the fuel rail and relocated it in the engine bay, like remote mounting it? car runs good, just doing some tweaking.

 

[TP03]

Maybe check this out. After I went to a return fuel system I was remote tuning and had a lean spot around 2k rpm that was consistent and annoying. Tried a bunch of revisions but couldn't tune out the lean spike. Finally after some research I installed a pulse damper on the rail and wouldn't you know it the damn car ran great. It might smooth out your "vibration"?

Fuel Pulse Damper, Direct Mount Kits

The Radium Fuel Pulse Damper Kit helps regulate and maintain safe and consistent fuel pressures. Erratic fuel pressure is commonly associated with random lean air fuel ratio spikes that are difficult to tune out.

www.radiumauto.com

 

[TP03]

 

[cj428mach]

Maybe check this out. After I went to a return fuel system I was remote tuning and had a lean spot around 2k rpm that was consistent and annoying. Tried a bunch of revisions but couldn't tune out the lean spike. Finally after some research I installed a pulse damper on the rail and wouldn't you know it the damn car ran great. It might smooth out your "vibration"?

Fuel Pulse Damper, Direct Mount Kits

The Radium Fuel Pulse Damper Kit helps regulate and maintain safe and consistent fuel pressures. Erratic fuel pressure is commonly associated with random lean air fuel ratio spikes that are difficult to tune out.

www.radiumauto.com

Did Malcolm tune your car? He believes in the pulse dampers and it made a world of difference on one of my cars. I'm glad he recommended it to me.

 

[TP03]

No he didn't. I went with Decipha. However I did buy my fuel system from Malcolm. Great dude. Yeah, a damper in my fuel system made a big improvement to drivability. Surprised you don't hear about them more often? Made me a believer.

 

[01yellercobra]

Maybe check this out. After I went to a return fuel system I was remote tuning and had a lean spot around 2k rpm that was consistent and annoying. Tried a bunch of revisions but couldn't tune out the lean spike. Finally after some research I installed a pulse damper on the rail and wouldn't you know it the damn car ran great. It might smooth out your "vibration"?

Fuel Pulse Damper, Direct Mount Kits

The Radium Fuel Pulse Damper Kit helps regulate and maintain safe and consistent fuel pressures. Erratic fuel pressure is commonly associated with random lean air fuel ratio spikes that are difficult to tune out.

www.radiumauto.com

Was your lean spot while you were cruising or when you passed by 2k while accelerating?

 

[01yellercobra]

FWIW, I went ahead and ordered one of those dampners. I have a lean spot just off idle I can't get rid of. I've adjusted everything possible to try to get rid of it. The weird thing is it's only there when there's full E85 in the tank. If it's closer to pump gas the lean spot isn't there.

 

[03' White Snake]

View attachment 1762083

Did you run just one of these or add one to each rail?

 

[TP03]

Just one next to the FRPS but I do have a balance line connecting the two rails.

 

[TP03]

Was your lean spot while you were cruising or when you passed by 2k while accelerating?

Just when I passed by 2 - 2.5 k

 

[TP03]

Sorry for the late replies. I’m elk hunting. Just happened to get some reception up here.

 

[01yellercobra]

Sorry for the late replies. I’m elk hunting. Just happened to get some reception up here.

So you're supplying dinner?

 

[03cobra#2]

Thanks for the pulse damper idea. Ill throw one on and see how it goes.

 

[cj428mach]

Did you run just one of these or add one to each rail?

I have just 1 in each of may cars. I can't say there was any big improvements in my cobra but it didn't really have any problems. I have a 64 falcon with a 331 and massflo based multiport EFI with a mega squirt computer. In order to keep it more stockish looking I have a single feed line going to the rails in a dead head configuration. It was untuneable.

My VE table looked like a shotgun pattern rather than anything smooth. At around 2k rpms at low load I had a cell almost at 180 to try to combat a lean miss, every cell on either side of it was half that value and I still had the lean miss. I put on the pulse damper at Malcolms recommendation and my VE table completely smoothed out. It was at that point I ordered one for everyone of my modified efi vehicles.

 

[03' White Snake]

I have just 1 in each of may cars. I can't say there was any big improvements in my cobra but it didn't really have any problems. I have a 64 falcon with a 331 and massflo based multiport EFI with a mega squirt computer. In order to keep it more stockish looking I have a single feed line going to the rails in a dead head configuration. It was untuneable.

My VE table looked like a shotgun pattern rather than anything smooth. At around 2k rpms at low load I had a cell almost at 180 to try to combat a lean miss, every cell on either side of it was half that value and I still had the lean miss. I put on the pulse damper at Malcolms recommendation and my VE table completely smoothed out. It was at that point I ordered one for everyone of my modified efi vehicles.

Good to know. My cobra is dead head, I’m having issues with the car bogging and sputtering from a stop, so I might add one of these to see if it helps. I need to get the car back to the dyno, just trying to figure out charging issues first.

 

[96dreamer]

Late to the party but I am also running the radium engineering pulse dampers. I have one on each fuel rail. I was having a nightmare tuning out a lean spot around ~2500rpms and a little over 6500. The pulse dampers cured almost all of the issues. I added one to the driver rail and was still having issues on the passenger side in the same spot. Added a second to the passenger side and it cleared everything up. Didn't have the passenger side on yet in this picture.

for what its worth my system is a fuel lab 42401 pump/filters feeding a Fuelab regulator in the fender running the fuel rails in dead head with a crossover in the front. I also have bosch 220lb injectors which I think contributed to the harmonic issue.

 

[01yellercobra]

I installed the dampner today, but won't have a chance to drive the car until next weekend to see if it helped.

 

[cj428mach]

All of mine are inline ones from Radium and plumbed close to the rails

 

[DSG2003Mach1]

interesting, i thought ya'll were talking about the old KB burst discs for the FRPS and was highly confused

 

[01yellercobra]

interesting, i thought ya'll were talking about the old KB burst discs for the FRPS and was highly confused

That wouldn't help me much since I'm not running an FRPS anymore.