Installed a Walbro Pump and Fuel Pressure Gauge yesterday.

Trying to figure out if these 2 things are normal:

1) When starting the car, even if it's totally warmed up, the FP goes to 40PSI for EXACTLY 33 seconds, then drops instantaneously to 32PSI at idle.

2) Now here's the weird part - WHen driving at let's say 10% throttle then going up to approximately 33% throttle and holding it I go from 34-40PSI for a good 5-8 seconds, then it JUMPS to 48PSI instantaneously.

Is it normal for this to happen?

What's the normal Fuel Pressures?

(I am NA right now because I'm re-doing my entire boost system)

Thanks!
IanS

 

Ah - found the specs in the FSM.

regular is 43PSI at idle when starting, then it drops to 34PSI.

So I guess that's normal....I'm at 40/32 however - 2-3 PSI off....this normal with a Walbro, or should I even care?

Anyone have an answer for #2 above however?

IanS

 

The GS342 (hipres version) pump should actually be higher than stock #'s... I've heard it would be around 42-43psi normally at idle. I can't attest to this as I put in my SARD with the FP gauge at the same time.

 

Well, I'm 34 at cold start-up and 32 at idle after it gets warm.

Something wrong here?

 

Yeah, I got 38-40 psi at idle, about 50 psi at WOT after installing the Walbro pump, no other changes.

 

On anybody else's car I'd say there was a problem, like maybe the pump you bought wasn't what you thought you were getting. Strange stuff like this seems to be the norm for your car, though, so

 

Like Stephen stated...can you verify which version you have? Here is the GSS342: (you can make out the "342" if you look carefully at the pic)

 

The top one....of course.

I verified it said "Walbro" on it before installing it - but it didn't say the model number on the pump.

Maybe this SUnday I'll take it out and look at it again.

 

Correction - ebmorgan is going to take my car tomorrow while I'm at work and take the pump out and take pics for me and verify the installation (zip ties holding on the strainer and all)

 

Just had a thought.

I have the Cartech FMU on there and I'm not boosting. As I understand it, the Cartech only changes Fuel Pressure under boost.

Am I wrong?

I'll try messing with it and seeing what happens to the idle FP before removing the pump if you guys think that may be the case.

 

Someone said that the Cartech did NOT have a base fuel pressure adjustment... If so, the Cartech should not increase FP unless there is boost.

 

Checked the pump today - it does definately says "GSS342".

Now it's doing something even stranger!

idle cold - 34PSI
idle hot - 32PSI
WOT - 3000 RPM - 43PSI
WOT 5000RPM - 50PSI
WOT 6000RPM - 20PSI!



Car sounds fine when it does this however....no smell of fuel coming from the back seat either.

Anyone have an idea what this is?

 

Let's assume that you FP gauge is accurate...

You would be running lean... Don't boost!

Sounds like your Walbro is malfunctioning....

 

Well, it didn't do this at all until after we took it out and looked at it and put it back in today. It was doing the weird jumping thing, but not this.




I'm not boosting anything until this is 100% solved.

Guess I'll take it out AGAIN on Sunday and check the hoses and electrical connections on the pump.

You'd think however even NA if I was running only 20PSI at 6000RPM, I would detonate....

I'm not.

Any ideas anyone on any of the above mentioned issues?

 

Maybe your stock fpr is on its way out?

 

You would think.

But because the car doesn't lose power, stutter, or detonate when it does this, I'm wondering if it's an install issue with the pump or something.

I'll tear it down Sunday and try and figure out wtf is happening.

I suppose it could be the gauge, but since it didn't do this yesterday, I'm thinking it's got to be an install issue or something.

Anyway - either way, a new gauge is on the way - should be here early next week.

 

Anyone else have ideas as to why this would happen?

 

Plugged in the T-Rex Aux pump today.

Still having the same problem.

Vacuum looks good, EGT's look fine, but the gauge still reads 20PSI at WOT at 6000RPM.

Grrrr.

Didn't have time to take the pump out again - but the way it's acting makes me think the Fuel Pump is fine. It works great until x RPM, then drops fuel pressure. I thought bad Fuel Pumps usually either just don't work or are very random.

This is very specific.

 

OK - now it gets even stranger

Went for another drive.

At idle, WITHOUT the T-Rex Aux Pump plugged in, the car goes to 40PSI for 30 seconds then drops to 32PSI. This is somewhat normal.
But what's not normal is that the fuel pump makes a girgling sound during this 30 seconds and the gauge bumps inbetween 36-40PSI. After that 30 seconds is up and the needle drops to 32, it's dead steady.

With the T-Rex plugged in, it goes to 40, stays there steady, then drops to 34 after 30 seconds.
Then, when driving around, with the T-Rex plugged in, it doesn't drop FP at high RPM like it was (I have no idea why it did it once earlier like that).

But it never goes above 40PSI. When I first installed the pump it would go to 40, then the needle would jump fast to 48.

Anyone? It seems pulling the pump and making sure it was the GSS342 caused alot of problems. Any ideas? I was thinking maybe a leak in the tank or something where the hose meets the pump, but since it acts better (not fine, but better) with the T-Rex plugged in, I think the hoses are fine.

IanS

 

Check or try replacing fuel filter with a larger flow unit.
Try installing one from 300zx or maybe 350z.

 

Already have the 300zx one in - only 10k on it.

Besdies, since it works better with the T-Rex running, I don't think it's a clogged line or filter. If a line or filter was clogged, it would continue I think to do what it's doing under both conditions (T-Rex on and off)

 

Just a long shot... but did you make sure the pickup assembly for the intank pump is on securely and not leaking?

 

Well, I just took a look at the way all the pics on the How2's show the pickup assembly hooked up, and that's exactly how I did it.

(If you mean where the strainer meets the pump)