Fuel pressure question.

[finesse49ers]

I have a fuel pressure gauge that was originally attached to my return line. I know that's not where it supposed to go but my man didn't wanna take a chance and cut the feed line. Anyway, the gauge would read at 100psi at start up and as a drive the car for a while it would slowly go down to around 5-7 psi. Today at RIPP I had it put on the feed line and now the gauge reads at 100psi at startup and stays there when driving and 106psi is the max on the gauge. I was told that when I give it gas the psi is supposed to rise. I also have a Walbro 255 fuel pump installed with a cold air intake. Is the fuel pump the reason the psi is so high or do I have a faulty gauge?

[estraw]

if you get an aftermarket fuel pump, your typically going to need to get an aftermarket fuel pressure regulator or else yes, you are going to have unusually high fuel pressure and your engine will run rich

[icemanrld19]

i was wrong

[PharmEcis]

Originally Posted by icemanrld19

the gauge should go after the FPR. Your gauge is just reading the continuous pressure from the fuel pump

Wrong.

The gauge goes before the FPR because you want to know the fuel pressure on the rail.

100 psi is WAY too much! I can't believe that your car is actually drivable in that state!

[icemanrld19]

Originally Posted by PharmEcis

Wrong.

The gauge goes before the FPR because you want to know the fuel pressure on the rail.

100 psi is WAY too much! I can't believe that your car is actually drivable in that state!

im explaining it wrong

[finesse49ers]

Originally Posted by PharmEcis

Wrong.

The gauge goes before the FPR because you want to know the fuel pressure on the rail.

100 psi is WAY too much! I can't believe that your car is actually drivable in that state!

Wow! I have a regulator that will be put on Monday morning. Thanks. PharmEcis I've been meaning to call you but I've been busy getting these cars worked on the past 4 days. I still want to do the 6G74 block with a turbo kit.

[Chato]

Just to give you an example, my fuel pressure @ idle is 40psi. 100psi is crazy high.

[Clipse3GT]

Idle at 40 psi is what it should be.

Get a good FPR along with a accurate gauge. Aeromotive is what most guys here use for the FPR.

[finesse49ers]

Originally Posted by Clipse3GT

Idle at 40 psi is what it should be.

Get a good FPR along with a accurate gauge. Aeromotive is what most guys here use for the FPR.

I was just looking at some regulators. I'll check out these aeromotives. What I'm gonna do on Monday is put the stock fuel pump back in. Will I still need a regulator for the gauge to read properly?

[Bitter]

you sure thats not reading in Kpa? or something else?

[finesse49ers]

Originally Posted by Bitter

you sure thats not reading in Kpa? or something else?

Nah, it's definetly reading in psi. I have a Walbro 255 installed on a stock GTS motor. That's why the pressure is sky high. I'm gonna put the stock pump in tomorrow. Would an aftermarket regulator still be needed?

[Bitter]

hopefully you didnt damage the fuel injectors any, 100psi is double what the stock pump does at full pressure!

[icemanrld19]

Are we talking about your sds eclipse?

[finesse49ers]

Originally Posted by icemanrld19

Are we talking about your sds eclipse?

No, not that one.

[PharmEcis]

Ok... Let's analyze this.

Which car is this? Why is there a FPR if it's not boosted? If there is no power adder on the car, a walbro in the tank is fine on the stock FPR. I'm running that combination right now in my car. Your fuel pressure should be 39psi base at idle.

Is the malpassi in there? That's the FMU that Ripp sent out w/ their units. If so, that is probably causing your issues.

[Bitter]

i had heard that theres 2 versions of the walbro 255lph pump, a high pressure and a standard pressure. is it possible he got one of the high pressure versions by mistake?

[finesse49ers]

Originally Posted by PharmEcis

Ok... Let's analyze this.

Which car is this? Why is there a FPR if it's not boosted? If there is no power adder on the car, a walbro in the tank is fine on the stock FPR. I'm running that combination right now in my car. Your fuel pressure should be 39psi base at idle.

Is the malpassi in there? That's the FMU that Ripp sent out w/ their units. If so, that is probably causing your issues.

No, there's no regulator on it or anything else. I just have the Walbro.

[icemanrld19]

so you dont have the stock fpr on it? can you post up some engine pic of this car?

[finesse49ers]

Originally Posted by Bitter

i had heard that theres 2 versions of the walbro 255lph pump, a high pressure and a standard pressure. is it possible he got one of the high pressure versions by mistake?

Yeah, I think you might be onto something. I have the high output version. This info is from walbrofuelpumps.com:

Pressure Types:

OEM (Original Manufacturer Specs) - 190LPH and 255LPH Walbro fuel pumps are ideal for original manufacture replacements of faulty fuel pumps. When your fuel pump goes and you don't want to spend hundreds of dollars getting a new fuel pump from your vehicles manufacturer or local auto store, OE spec Walbro replacement fuel pumps are a low cost, high quality, and reputable replacement.

HP (High Pressure) - If your vehicle is used for racing purposes, heavy hauling, or in high powered turbo vehicles, OE spec Walbro Fuel pumps may not supply enough fuel to satisfy your engines needs. The Walbro 255LPH high pressure fuel pump is highly recommended for vehicles with engine performance purposes. Installing a Walbro high pressure fuel pump in a non-performance vehicle will not damage your motor. All fuel first passes through fuel injectors and a fuel pressure regulator which only send the required amount of fuel into the intake manifold, sending the unused fuel (usually more than 1000%) back to the fuel tank.

If I decide to leave the Walbro in will I need an aftermarket regulator? I was going to put the stock pump back in but seeing that I'll need to purchase an aftermarket regulator anyway down the road I might just do it now.

[finesse49ers]

Originally Posted by icemanrld19

so you dont have the stock fpr on it? can you post up some engine pic of this car?

The stock regulator is on it. I meant there is nothing aftermarket on the motor except a cold air intake.

[Chato]

Originally Posted by icemanrld19

so you dont have the stock fpr on it? can you post up some engine pic of this car?

Randy, Aren't you using a high pressure Walbro fuel pump with the stock FPR?

[icemanrld19]

yes sir. Thing is i also have injectors that will handle it as well as a tune.

[PharmEcis]

Originally Posted by Bitter

i had heard that theres 2 versions of the walbro 255lph pump, a high pressure and a standard pressure. is it possible he got one of the high pressure versions by mistake?

The pumps are identical except for the fact that at higher pressures, the HP version will have a greater flow rate. Pumps lose flow at higher line pressures and the HP version was designed for guys running 25+ psi to keep flow up at those line pressures.

Again, I have a Walbro 255 HP in my car w/ a stock fuel pressure regulator and my fuel pressures are just fine. It could be that your stock FPR is damaged and is being overrun. This means it can't return enough fuel back to the tank hence increasing pressure on the rail.

[MattS00]

I say it is probably a bad gauge.

If the gauge is good, then did you modify the nipple on the end of the return line on the fuel pump? That nipple is crazy small and could cause a rise in fuel pressure for everything before it. If that is ok, then look to the stock FPR for problems or check the fuel lines for clogs, restrictions, pinching.

[MattS00]

This thread is actually unusual. The norm for a walbro instalation is a broken gromet and low pressure.

[finesse49ers]

Well I found out that the gauge is working correctly by hooking up another gauge and it read the exact same psi. What I'm gonna do tomorrow is install the original fuel pump. If that doesn't change the reading then I'll have to replace the stock regulator.

[MattS00]

Did you enlarge the fitting on the end of the return line? This is a known problem.

[rc_maniac]

Are you all aware that there is a recall for a blocked fuel return line that would cause high fuel pressure? I don't believe there should ever be pressure built up in the return line EVER since it is just a drain back into the tank.

Technical Service Bulletins & Recalls
About half way down the list, SR-03-003 Recall - Fuel Pump Return Line Restriction.doc

[finesse49ers]

Originally Posted by fasteclipse00

Did you enlarge the fitting on the end of the return line? This is a known problem.

No, haven't touched it.

[finesse49ers]

Originally Posted by rc_maniac

Are you all aware that there is a recall for a blocked fuel return line that would cause high fuel pressure? I don't believe there should ever be pressure built up in the return line EVER since it is just a drain back into the tank.

Technical Service Bulletins & Recalls
About half way down the list, SR-03-003 Recall - Fuel Pump Return Line Restriction.doc

Thanks, this is good to know. I'm gonna check to see if the gauge is wired correctly.