Ok I just got my car together about a month ago. I have two fuel pumps run off relays that are directly wired to the battery. I had originally taken out and jumped out the resistor in the stock fuel pump wiring and was using it for a trigger. Since I wasn't boosting on the new engine and there was no need for a whole lot of fuel pressure I wasn't having any problems. I was slowing trying to work in a little boost and I found that whenever I would get into the boost the fuel pressure would drop off. I am not sure that it is related to the wiring but I want to check that out first but I need a trigger source to activate and run the pumps while the car is running. Any help would be appreciated. Thanks.

(The pumps are run seperately all the way to each rail and then brought together in the FPR. This shouldn't cause a problem would it.)

 

thats my setup..... trying it shortly


input on this would be appreciated


G

 

using the stock fuel pump wiring to trigger the relays should not cause the problem. I would check the connections, and what size wire do you have the pumps wired with to the battery??

 

I run dual 280 lph in tank pumps and run them off a single 60 amp relay vs two 30 or 40 amp relays. I have it fused with a 60 amp inline glass fuse and triggered off a 12 volt switched source. I run 10 gauge wire on the heavy sides (battery and fuel pumps). Reason I didnt run two relays is because if one relay decides to take a crap, I wouldnt know and would loose fuel pressure under high boost...vs loosing all at once and car would just die...which it did because I was running them off a 40 amp relay and trying to pull it through a 30 amp fused circuit, which it didnt like and melted things, lost all fuel pressure. So I rewired everything to handle it now.

 

I use the fuel pump power wide as a trigger. Not sure if our cars have a switch to cut power in a roll over but using this wire will insure that feature is still functional if there.

Jack

 

Thanks for the info. You guys with the wiring done this way, did you modify the high low voltage relay in the front relay box?

I dont see a need to with this principle, since a signal is a signal be it 5 V or 14.6V.... right?

Thanks

 

make sure your fuel pumps are isolated in the tank (put some rubber around them so they dont make contact with the flange deal...)

 

No need to modify the relay when done this way. I've since gone back to stock wiring with Chuck Westbrook's wiring mods. My Nippendenso pump burned up pretty quick running constant 13V and the Apexi pump I use now flows so much there's no need.

Jack

 

thanks... i will be running to walbros 255s. they are ment to operate at 14 V so as such it shouldnt be a problem......i hope.....

 

you can also just make your own signal switch...

 

Just and update. I made my own signal switch directly from the battery this weekend and I found out that it isn't a wiring problem. I get to about 4 psi and the fuel pressure drops dramatically. I am pulling the pumps tonight and using two stock ones a friend is lending me to see if that will solve the problem. If it still does the same thing I guess I am going to have to look at the plumbing.

Does anybody know if a FPR can handle two seperate fuel pressures from two sources? (Aereomotive 1:1) Each fuel rail is fed independently from its own pump and it comes together at the FPR. Is this ok?