So the weather finally looked good and so I drove it to work. The car was recently tuned by Steve Kan 2-3 weeks ago and it ran flawless. Anyway, as I was driving I was checking my gauges and my fuel pressure gauge was reading 18-20psi...typically it's 38-40psi. To add to this, my AFR seemed a little off. Typically when warmed up and sitting at idle, I'm at around 13:1. When I was stuck in traffic/idle, it was sitting at 12.3-12.5. When I was cruising at normal highway speeds, typically I'm at 14-15, but it seems when I tried to cruise, I was around 12.5.

Thinking that something was wrong with my fuel, I drove very easy and kept a close eye on my fuel pressure and AFR. Made it to work and the fuel pressure never showed over 30-32psi at some moments. Pop the hood and my FPR is reading 38-40psi so I'm not too worried about that as there may be something simple as something blocking the sensor or something as easy as that but what are your typical AFR during idle/cruising/driving?

 

The AIT comp map should be good for colder temperature but I don't take out as much fuel out if the AIT gets above 50C. You could see richer reading if AIT is above that range.

 

If you have a weak pump or a dirty filter pressure will vary greatly due to flow.

So basically if you need more fuel - that's when your pressure can bleed off rapidly (system can't keep up).

Voltage can also play nasty tricks.

 

Oh I don't know if you saw it, but my FPR reads the typical 38-40psi, it's my actual fuel pressure gauge (interior) that is not reading right.

 

You sure it wasn't closer to 28-30psi while driving in vacuum?

 

Well obviously I can't see my FPR gauge while driving. So when sitting idle, I checked the gauge on my FPR which reads a 38-40psi and then I'll check my fuel pressure gauge inside and it's reading 18-20PSI so there is something wrong with my gauge.

 

Yeah threw me off when you said "as I was driving...18-20psi" ...

 

Oh well yea, while I was driving the gauge was reading the same 18-20psi even when I got on the gas a little, the pressure didn't raise. So that is why I checked (at idle) the readings of my FPR fuel pressure gauge against my interior fuel pressure gauge and noticed that although my FPR gauge was reading 38-40psi, my interior gauge was still only reading 18-20psi, so it's something with the interior gauge and not an actual fuel pressure problem thankfully.

 

I would start there and try to fix that problem first.

They might be reading from two different locations and very possible that they are two different pressures.

Of course the guage could be wrong also but they are usually fairly reliable. I'm not sure what type you have but they usually require a good 5v supply to the sensor so would check that your getting your 5V since that is quick and easy test.

 

Let me guess. You have an Autometer fuel pressure gauge.

Yes, you have to make compromises.

 

The interior fuel pressure gauge was reading fine before, 38-40psi which matched my FPR gauge so something is wrong. The sensor is tapped onto the FPR itself so whatever the FPR reads, the gauge should be reading that too. See picture. Don't mind what the pressure is at in that picture. I took that picture when I was having trouble with fuel pressure cause I had a fuel leak.

 

Ugh double post