real quick Question on fuel pressure

[Aaron R.]

I have looked in my Chilton, Mitchel, and even All-data. I can not find a fuel pressure spec for my SHO. Its a 94 3.2 and its at 29 psi with it Idling and I have nothing to compare it to. I think I need to replace my fuel pump but I want to be sure.
Thanx,
Aaron

 

[Rockledge]

According to my '93-'94 Ford Workshop Manual:

KOEO = 37-43 psi

KOER = 30-45 psi

 

[Rockledge]

I've seen some different numbers kicked around here, as well.

My '93- '94 Ford Workshop Manual says that for the 3.0L SHO (SFI) motor:

KOER = 28-33 psi

KOEO= 30-45 psi

I assume the 3.2L would have the same specs, so according to my manual, your fuel pressure appears to be OK.

 

[AutoSHO]

28-32 PSI At Idle
38-42 PSI With the FPR Vacuum Line Disconnected
Fuel pressure should jump immediately if you blip the throttle with the FPR connected normally. Should stay at 38-42 psi with vacuum disconnected.

If the Fuel Pressure lags or drops and then rises when you open the throttle, look into replacing your fuel filter, and if that doesn't solve it, your fuel pump.

 

[Rockledge]

28-32 PSI At Idle
38-42 PSI With the FPR Vacuum Line Disconnected
Fuel pressure should jump immediately if you blip the throttle with the FPR connected normally. Should stay at 38-42 psi with vacuum disconnected.

If the Fuel Pressure lags or drops and then rises when you open the throttle, look into replacing your fuel filter, and if that doesn't solve it, your fuel pump.

Hi Chris,

When I first looked at the fuel pressure specs you provided, I thought they might be in conflict with those that came out of my Workshop Manual, but upon further review, I think they are in fact quite consistent. The numbers I passed along regarding KOER seem somewhat general, while yours are more specific as to idle and also when the engine is at WOT (FPR Vacuum Line Disconnected). But I don't see any inconsistencies there.

The numbers I gave included KOEO specs (after cylcling the key a few times) and your numbers did not include KOEO. In your experience, are the KOEO specs from my Workshop Manual correct? If so, then I think will finally have a full grasp of the what the fuel pressure specs for the SHO are, which would be great.

Thanks.

 

[AutoSHO]

KOEO Should be the same as The engine running with no vacuum applied to the FPR, 38-42 psi. In my experience you observe this while the car runs, but the FPR does not react quickly enough when the pump shuts off to hold quite that pressure, so it drops a bit right when the pump ends its cycle.

KOEO, pump on, should be 38-42 psi, because the FPR Vacuum Signal is atmospheric pressure, which equates to 38-42 psi, same as what WOT or no-vacuum would be.

 

[Rockledge]

KOEO Should be the same as The engine running with no vacuum applied to the FPR, 38-42 psi. In my experience you observe this while the car runs, but the FPR does not react quickly enough when the pump shuts off to hold quite that pressure, so it drops a bit right when the pump ends its cycle.

KOEO, pump on, should be 38-42 psi, because the FPR Vacuum Signal is atmospheric pressure, which equates to 38-42 psi, same as what WOT or no-vacuum would be.

Makes sense now, thanks.

FWIW, my SHO tested out at KOEO = 37 psi after cylcling key, and KOER = 32 psi at idle, with a notable pressure jump as I blipped the throttle. So I seem to be OK...

 

[AutoSHO]

Yup, should be fine.

Mine had some really funny readings with a bad FPR.

Cold:

KOER, idle, 45 psi
KOER, no vacuum, 60 psi

Warm:

KOER, idle, 20 psi
KOER, no vacuum, 30-32 psi

Replaced it, problem solved. No wonder it was having trouble idling when cold