Fuel pressure?

[Talesin]

Just wondering what the stock fuel pressure tends to be on a 1ga (if anything else is different)... been having classic 'running rich' problems, and couldn't figure out why for the longest time. Then I realized that with the number of 'hidden mods' that prior owners had put into the car, it wouldn't be unimaginable for one of them to toss in a high-volume fuel pump, even though the FPR is stock.

Just had it checked... apparently I'm running at 35psi with vac, and my mechanic isn't sure if it's supposed to be 27psi (VIN U) or 35psi (VIN R).
Now I know that I have a VIN U, with a GSX. What I'm not sure of is if they did the rewire mod at the same time.

So, 27psi at optimal stock. (nobody gets 'optimal' though, why I asked for pressures up top)
Anyone have a 155lph pump? A 255? A 255HP?

Trying to figure out what I've got without cracking open the tank, more or less. And picking up an AFPR today. Hello again, good gas mileage!

 

[1SloColt]

37psi stock

 

[DSM90AWD]

Just had it checked... apparently I'm running at 35psi with vac, and my mechanic isn't sure if it's supposed to be 27psi (VIN U) or 35psi (VIN R).
Now I know that I have a VIN U, with a GSX. What I'm not sure of is if they did the rewire mod at the same time.

37-38psi with the vac line disconnected from the FPR.

Rewire mod is easy to check, just pull the floor from the hatch and look for non-OEM wires running to the pump access panel.

You would not notice the diff with "smaller" upgraded pumps (190lph), but with a SupraTT or 255HP you'd see 5+ psi over stock and run super rich.

 

[psychlow]

- 1 PSI =~ 2.04 inHg
- Stock vacuum is 18-20 inHg
- Stock FPR is rise/fall at 1PSI:1PSI ratio.
So, 18/2.04 = 8.82PSI, 20/2.04 = 9.80PSI

Stock FP with no vacuum = 37PSI, so stock FP with vacuum should read 27.2 - 28.2PSI.

Your FPR is being overrun, otherwise you may have an N/T FPR on the rail.

 

[Talesin]

It's likely being overrun. The guy who had the car before me didn't exactly know what he was doing, from what I've found. Haven't pulled the pump to look, but the high-pitched whine has always annoyed me since I got the GSX.. and KNEW it wasn't there on the GS-T.

It's 35psi with vac, 42-45 without vac. Possibly a N/T FPR, true. But still running really rich.

Picked up an AEM AFPR once I found out, so that's going on tomorrow... picked it up for $100 under retail list. Only reason I didn't go with the IE-FPR kit, as the AEM doesn't look to have an extra in/outlet for an underhood gauge. :b Though it *is* a lot beefier than I'll likely ever need... rated to 1000lph total.
Hmm. Mental note, check injectors. :b

Also supporting the theory that it's a higher-volume pump than stock is the starting problem. I figured it was just flooding due to the FPR, but was reading through the FAQ, considering pulling it to look.. and at the end it noted that if you screw up/tear/mis-seat the o-ring, it'll cause a delayed start by a few seconds, but still allow an immediate restart if you shut it off and retry. Which happens with me. So I might as well pick up the rings from Autozone or the like, on my way over to the garage.