so i installed an inline fuel pressure gauge

idle fuel pressure = 28-32psi

shorted out the FP/GND lead on diagnostics, 36-38psi

clamped down the engine side of the fuel line going to the gauge to simulate MAX pressure

48psi

so that means when i go WOT, my fuel pump and or filter is causing my power loss + lean condition, right?!

edit: i have a new fuel filter + supra fuel pump awaiting installation tomorrow

 

I could look up the base idle fuel pressure in my manual, but it's in the car, covered, but I think its 43 psi at idle, then adds fuel pressure at a 1 to 1 scale so at 10 psi it should be around 53 psi. That's just going off the top of my head, correct me if I'm wrong.

Tim

 

i checked robrobinette's website for the install and pressure readings

 

Stock fuel pressure at idle is around 30 psi. The base pressure (what you get with no vacuum signal on the FPR) is about 38 psi. Add 1 psi for each pound of boost, e.g. at 10 psi, your fuel pressure would be about 48 psi.

-Max

 

okay max, so let's assume i clamped the engine side of the hose shut, which should make the pump do all it can (and filter assembly)

would the 48psi reading i get mean that it would handle 10psi no prob, but 12-13psi would be a problem?

that's what i'm thinking at least

 

I've done this test, lets see if I can remember all the workshop manual instructions - ie. verify these numbers but they are close.

If you clamp off the return, you should only put power to the pump for 5 seconds and see approximately 70-110 psi. After 5 min. pressure should be no less than approximately 20 psi.

For my test, the pressure instantly jumped to 110 psi then after 20 minutes I had approximately 25 psi. When I installed my fuel system, I was worried about the fast drop in pressure after the car was shut off. It passed the test per the workshop manual. My set-up has an RP/Nippondenso fuel pump with -6AN feed/return, Kinsler fuel filter, SX FPR, and SPA gauge.

Jack

 

FP gauge IS a plus.
While driving, I got a huge bucking in the engine. I noticed my fuel pressure would drop straight down to zero. Now I can't even crank the engine up cuz of no fuel pressure. I haven't had the chance to check it, but at least I'll be on the right track as opposed to trying to figure out what it could be

 

Yeah Brian if you clamp the return your pressure should skyrocket over 100 psi.

 

I agree with the other posts -- it should be way higher than 48 psi if you clamp the line. The workshop manual says 70-100 psi or so, as Trout says. If it can only make 48 psi with the hose clamped, it isn't going to be flowing enough to maintain pressure under any boost, most likely.

The FD has a two-speed fuel pump control circuit. At low load/RPM, the power flows through a resistor pack and the fuel pump. When the load/RPM increases, a relay shorts the resistor so that the fuel pump gets full voltage. Does the test procedure run the pump at full voltage? Could the problem be with the relay that shorts the resistor? I would expect that it would produce less static pressure at the low voltage, perhaps significantly less.

-Max

 

could this be a power issue? the batt is enough to crank the car, so i would assume fuel pump would be no prob

 

Thanks for the clarification for me, I thought I had it wrong to begin withm but wasn't sure. I'll check your logged runs and see what the battery voltage is at high rpms. Also, check the fuel pump like Max posted to see if its kicking up a notch.

Tim

 

well i installed the supra fuel pump, new fuel filter, fuel pressure seems to be OK

i'm still leaning out like crazy on your map tim, so i had dan at batlground richen it up, before you know it we were at 100% injector duty, and still running lean on the high end, definitely richer, 12:1 at some points

blew an AST hose, overheated like crazy, and so now i'm back to the drawing board

i'm going to swap the high flow for a midpipe, and check all the vaccum lines going to the FPR and FPD

what else could it be? i suspect a faulty thermostat or bad coolant cap on the temp issues

running lean doesn't help

 

Did you check that relay? I'm not sure switching the pump will fix it.

 

i don't think that's the problem

i'm thinking fuel pressure regulator, dirty injectors, or possibly a dampner?

 

could this be bad turbos?? or high flow cat related?

 

I'd continue with the fuel side. Check the fuel pressure regulator. Does it increase fuel pressure with boost?

Running lean shouldn't have to do with the turbos currently. If they are making the 12 psi its set for (unless they are making more boost) then the mods you've done to the fuel side should be more than adequate for 12 psi and not be pushing the injectors 100% to achieve a 11:5 to 1 or richer A/F ratio.
If you add the MP, you'll be even leaner since it will flow better than the hi-flo and place more demands on your fuel system.

I'll send the logged runs for you to look at and compare to the wideband runs. They seem to correspond with each other concerning the stock O2 also dropping to a low voltage at higher RPMs.
Your battery voltage during the runs were 13.3 to 13.5 through out the runs with no apparent correlation with the O2 voltage. Check all the grounds...all of them...can't hurt.

Tim

 

well i will keep that in mind

it would spike to 14psi or so and drop down to 12-13ish

i do have the holley jets which could be causing a problem