I was hoping a quick question I asked in my other thread would save me the trouble of creating a seperate topic, but I'm still having issues with fuel pressure on my 3800 swap. It seems to be the only thing keeping me off the road at this point.

Here is the thread. It started off as an IAT question and ended up asking about the fuel pressure regulator.
https://www.fiero.nl/forum/F...093536.html#lastpost

I think that either my pump is shot, a walbro 255 that I ordered brand new and has maybe an hour or two run time, or the fuel pressure reg isn't doing its job and fuel runs right back into the tank without building pressure.

I replaced the slide-in coupler between the feed line and the pump with a piece of hose and secured both ends with fuel hose clamps. I really don't think that's leaking.

I just purchased a new fuel pressure regulator... I build pressure for a moment, but after starting the car it died in about 5 seconds. I again have no pressure.

Is it possible to install a fuel pressure reg incorrectly? Seems straight forward enough...

could this problem be electrical?

Is there an inline fuel pressure reg, or any other adjustable reg, that you would recommend in addition to or as replacement for the stock reg?

Not to be an ass, but do you have the fuel lines backwards? it goes... supply line (from tank).... fuel filter.....injectors/rail.....press reg... return line(back to tank)
maybe you have the suppy and return lines backwards if the press reg is correct?

Check to see if your fuel pump has 12V to it while the engine is started/starting. If not check the fuel pump relay/wiring. BTW what did you do to defeat the Passkey antitheft from activating? You did shut the code off in the PCM program, right?

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 07-28-2008).]

It can be so easy to miss something obvious.Do you have fuel in the tank (2-1\2 Gallons)?As for the engine, the large fuel line is the feed, and the smaller fuel line is the return.Some fuel pump manufacturers will reverse wire there fuel pumps. Example:stock Fiero Fuel pump small prong hot+ and the big prong negative--. An after market fuel pump like the walbro MIGHT BE big prong hot+ and the small prong ground--.Exactley opisite of what the stock Fiero Fuel pump is.Might check your fuel pump fuse while your at it.Back to your question Is it possible to install a fuel pressure reg incorrectly,(someone correct me if Im wrong),but no.You could try disconnecting the fuel line and see if fuel is pumping.Do you hear a 3 to 5 second buzz when you first turn the key?

I would be surprised to see 2 fuel pressure regs fail. I am willing to bet you have a wiring issue such as maybe having some of the 2speed wiring screwing up on you.

I'll say this again because it happened to me. Did you replace the short 2-3" tube between the pump and the fuel line inside the tank? I tried to re-use the old one (don't know why) and exploded the line right away. Somehow I was still getting 14lbs of fuel pressure but when I opened the tank again I saw the old line had exploded. I have this same pump and it flows a ton.

Another thing could be the fuel filter on backwards?

Could it be possible your regulator is not getting vacuum?
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-Kyle
Email: kakagiraffe@gmail.com
Aim: Littlechugger
1988 Notchback 4.9 V8, 5spd Isuzu, Spec Stage 4
True Dual Exhaust, Delta Cam
1996 Grand Am 3100
2001 Honda CBR 600 F4i

[This message has been edited by arte444 (edited 07-29-2008).]

From your description it starts but then looses pressure. Sounds to me like the pump is being turned on by the ECM for the usual 2 sec priming run when you first turn the key but then after it starts (I think) it's the oil pressure switch that keeps the pump relay engaged (based on my DOHC swap). Sounds to me like that part of the circuit is not working.


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Dave

www.ltlfrari.com

[This message has been edited by ltlfrari (edited 07-29-2008).]

quote Could it be possible your regulator is not getting vacuum?

Would just give him a small amount of extra pressure, wouldnt hurt anything.

quote From your description it starts but then looses pressure. Sounds to me like the pump is being turned on by the ECM for the usual 2 sec priming run when you first turn the key but then after it starts (I think) it's the oil pressure switch that keeps the pump relay engaged (based on my DOHC swap). Sounds to me like that part of the circuit is not working.

It just looks for tach signal and the PCM turns it on, no oil related switches. Although the PCM commands low speed mode after it starts up, so if he had that system hooked up, but hooked up wrong, then it would shut the pump off.

I replaced my pump, and all the rubber EXCEPT that small 3" piece between the pump and the metal tube running out of the tank. Got no pressure at the fuel rail, tried everything, and finally dropped the tank. Found the small 3" hose with a 1/4 inch hole in it. Fixed the hose and now have 42psi at the rail.

Rob

Here's what I'd try. Hook up the pump directly to the battery and try it. If it works you know the pump is not staying on under normal conditions so look at that part of your wiring (as described above, not the bit by me!) If it still doesn't run then suspect the pump.

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Dave

www.ltlfrari.com

I have had two Walbro 255 pumps fail on me in the past 4 months.
What I have found is that the stock wiring for the pump is inadequate for the High Pressure - High Volume Walbro pumps.
What I also found was that the pump would run (in the case of the High Pressure pumps) but pump nothing.
This would only happen if the car was running for more than 15 minutes or so, basically, enough time to heat up all the wires and engine compartment.
Once the car and engine compartment cooled down, the pump would work fine as long as the temperatures were comparatively low.
The pump wasn't getting the power it needed to run efficiently.
I will be rewiring with 14 awg wire and getting my source from the alternator + feed.
I am also re-wiring the in tank wire with Teflon coated 14 awg wire for the ground and pump.
I love the pump, but the stock wire (in my case) won't support it.
My 2 pennies...

[This message has been edited by IFLYR22 (edited 07-29-2008).]

Wow, lots of help in this thread and I thank everyone.
I finally got to drive it... it runs great.

Lets start from the begining, and explain why I'm a little stupid when it comes to cars sometimes.

-Replaced the slip coupler/whatever it's called from the pump to feed line with fuel hose and fuel hose clamps. Still no pressure. Measured with a gauge
-Ordered and installed new fuel pressure reg. Car still would not run, so I assumed still no pressure. BUT I did not measure it with a gauge, since the gauge was at my neighbor's and he works days, I work evenings.
-Finally got to mess around with it last night, this time with the gauge. I indeed had fuel pressure, but the car would not run more than 2 or 3 seconds. (first stupid thing I did- made and assumption)
-Unplugged the mass air flow sensor for shits and giggles. The car ran!
-Removed MAF. Behold! A small piece of cotton had got in there and caused the car not to run. (second stupid thing I did. Worried about debris getting in the TB, I stuffed a rag in there while dropping the cradle to work on the throw out bearing. That's where the cotton came from.)

Now the only thing I have to do is remake the bracket that holds my shift cable. On my test drive it came loose, and I only could go into 1st and 3rd. Still, it was fun. Such a relief to finally see that car go down the road.

quote Originally posted by IFLYR22: What I have found is that the stock wiring for the pump is inadequate for the High Pressure - High Volume Walbro pumps.

I haven't had any problems and I have the 4cyl wiring. Anyone else have any problems?
I'm not doubting that the wire could be inadequate size, and that being 20 years old is unsafe. Seems like it would pop a fuse before the pump would quit or anything horrible would happened.

------------------
-Kyle
Email: kakagiraffe@gmail.com
Aim: Littlechugger
1988 Notchback 4.9 V8, 5spd Isuzu, Spec Stage 4
True Dual Exhaust, Delta Cam
1996 Grand Am 3100
2001 Honda CBR 600 F4i

I have found stock wiring to be very big, and being its a short run, it loses little power.

I would save the "I dont have fuel pressure" description for when you have a gauge on it next time. IIRC you have quite the mod list, I wouldnt be driving it at all untill you have a tuner on it, and mail order tunes do not count.

Yea I was frustrated that it wouldn't run and jumped to the no fuel pressure conclusion. Stupid on my part. Sorry to everyone but hopefully this thread is helpful to someone later on...

Dark, I do not have a tuner myself. I sent the PCM to Loyde with a complete list of what will be done to the motor, and I trust that will get me into a safe zone at least for granny driving.

My neighbor has a nemysis (sp?) type scan tool, but I believe it is read-only. We watched values for KR after letting it warm up in the garage. 0* the whole time. I have not scanned it, nor taken it to wide open throttle down the road. But I intend to have the scanner whenever I do (waiting to break the clutch in)

You wouldnt ever knock in the garage... even if you did it wouldnt be dangerous..

The only values that would let you know how far out the tune is would be your LTFT's. If you are seeing numbers greater or less than 10 and -10 respectively, you could be in trouble. Idle values are sorta meaningless, but if you are seeing + or - large numbers I would be concerned. You should also see your o2 values bouncing around to every value between 200 and 800 briskly and randomly.

After you take it in and out of boost a few times, you will need to watch your ltft's and KR values to see what sort of shape you are in, then you can reference o2 voltage for a ballpark idea of how you are running.

DO NOT assume your close enough for granny driving!!!!! its not hard to sneak into low boost, and even that could be dangerous with a completely off tune, which is very possible.