Well, I just developed a fuel pressure issue. I have been monitoring my Auto Meter Fuel Pressure Gauge and as I'm acceleratting the fuel pressure will start to rise and as soon as I get to 0 vacuum the needle starts to dance around between 30 and 40 PSI. If I stomp on it real quick it will dip for a split second and then shoot up to 45-50 PSI or so. What could this be? Has anyone else experienced this? I have Aeromotive fuel rails and an Aeromotive FPR. I'm running twin 255 pumps that came with the JDM fuel kit. Normal cruising and acceleration doesn't show any problems.

I'm thinking that it's either a pump going bad (which really doesn't make any sense because when I stomp on it the pressure goes to where it needs to), possibly the FPR going bad, clogging fuel filter, or something to do with the fuel pump resistor.

Any insight would be greatly appreciated.

 

just a thought,,,,,,it could be because you have added volume now,,,,jumper both pumps and see what the fp does

 

Did you modify the resistor setup? You can't run the twin Walbro 255s with the stock stepped voltage system and big fuel rails, because they flow less fuel than stock pumps when they are at only 7 volts. You need to modify the resistor setup so that you have about 9 volts on the low side. Then you'll have solid voltage.

Unless of course you have another issue. You should be seeing 50-60 psi when you are on the throttle and it switches to the high side.

 

It's weird because it just started happening recently. I'm sure you know a lot more about this than I do Sal. When you say modify the resistor set-up, do you mean to bypass it? You mean just cut the resistor out and splice the wires together?

 

some resistors have less resistance then others

 

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Won't bypassing the resistor cause both pumps to run full duty all the time? Is that good for the pumps? Also, won't it be diffiult to get my fuel pressure where it needs to be with both pumps at full duty?

 

That should be what your FPR is for. I dont have the walbros, but have the same problem. Big big dip in my AFR when the pumps are suppose to be at a good 12+volts. I was told that I needed to bypass the front resistor and then run a FPR to balance it out.

This info is from james @ RWTD

 

It just seems like it wouldn't be good to run the pumps at full duty all the time on a DD.

 

ive had mine jumpered for years

 

So you've never had any issues after you bypassed the resistor?

 

Did anybody ever check the fuel sending switch, if it goes bad, it will give you erratic readings.

If the fuel is fluctuating as stated, I would imagine you would feel inconsistencies from the engine responding (acceleration) to those fluctuations?


Just an opinion!!

 

I did a little more testing today on my way home. It seems that when I ease into the throttle and boost starts to climb the fuel pressure gauge needle starts to climb as well. The fuel pressure gauge needle is reaching 40 PSI right around the same time the boost gauge needle reaches 0 vacuum. Then the fuel pressure drops to somewhere between 30-40 PSI and begins to dance around. My widebands verifys that it's not the sender for the gauge acting up and it's an actual fuel issue. The whole time the needle is dancing the wideband is reading somewhere between 13.0 and 14.0 when ususally it reads somewhere in the 11.0's when I'm at 0 vacuum.

Now when I get on it hard from a stop or while driving normal, the fuel pressure will drop for a split second and then shoot up into the 50's somewhere like it should. This is telling me that it probably not the sender for the gauge acting up. I'm also not to sure if it's the regulator because of the way the fuel pressure acts when I accelerate hard.

Any ideas based on this new information???

 

You'll only know by jumping the resitor and seeing if you can then set base FP down to 39# with both pumps running full speed and then drive it. If the problem persists then it was a voltage/low speed/pump issue. If not then the regulator is bad.

 

Is jumping the resistor reversable?