symtoms: low vacuum at idle, hard hot starts (have to floor the gas to turn off injectors for it to start hot), fuel pressure gauge shows rapid drop of fuel pressure when car is turned off. car runs well under WOT. my fuel mods are supra TT fuel pump, 4x850 injectors, and SX FPR with gauge. runs 42 psi static pressure and the first time time we saw the fuel pressure drop, it dropped to 0 in about 3 seconds.

so far we have taken off the intake manifold and fuel rails to test the injectors since we thought that they could be leaking. they dont seem to be leaking however, we found one of the seals (not sure if its just a dust seal or what on the top of one of the primary injectors to be FUBARed). we did however also find a vacuum leak on one of the capped off vacuum nipples on the LIM (cap had a large split in it). now I know that when you use 850 cc injectors in the primary rail, you either need to machine the rail or use 2 O-rings. in my case we used 2 O-rings... if that helps to diagnose it.

please share any ideas you may have as to what is causing these problems. thanks in advance.

 

anyone? is the fuel pressure supposed to drop off that fast? or could it just be the vacuum leak causing all this mess...

 

How old is your motor? Did you do a compression test?

 

Fuel Pressure Regulator , (the vacum line to it) may be disconnected.

 

motor has 15k on it. I will check the vacuum line on the FPR.

 

FPR is bad. or you have a leak, that is releasing the pressure.

*edit: 42psi might be to high, I had to drop mine to 38, when I had 850 primaries...do you have a FPR solenoid?

 

no, im running microtech so I pretty much dont have any solenoids or anything. its just fuel line to FPR to fuel rail.

 

I hope its not the FPR... anyway I can test it?

 

you just tested it basicly. If FP is dropping like that... FPR is more then likely bad.

 

pull the vac line off the reg. if fuel is in it it is bad.

 

ok, fixed vacuum leak and reinstalled everything including 2 new "insulator" seals for the primaries from mazda and a new UIM gasket. car now idles at proper vacuum, BUT hot start problem is still there. gonna take apart the FPR tomorrow and see if there is anything visibly wrong with it. also going to inspect spark plugs and change if neccesary.

 

Maybe the vacuum line running to the FPR is cracked or leaks? or maybe it is the FPR itself

good luck