LT1 Walbro 255
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LT1 Walbro 255 fuel pump is a Walbro 255 with Hotwire kit
Fuel pressure when primed with key on: 30 psi
Fuel pressure when primed with jumper under the hood: 40 psi
shouldn’t these read the same?
pressure bleeds down 10 psi fast then slowly to 0 psi.
i have the fuel rail pulled up with the injectors intact to check for leaks.
i have checked the FPR (stock) vacuum line for fuel and there is none.
any help is appreciated
Fuel pressure when primed with key on: 30 psi
Fuel pressure when primed with jumper under the hood: 40 psi
shouldn’t these read the same?
pressure bleeds down 10 psi fast then slowly to 0 psi.
i have the fuel rail pulled up with the injectors intact to check for leaks.
i have checked the FPR (stock) vacuum line for fuel and there is none.
any help is appreciated
Pretty sure the fuel pressure shouldn't bleed down like that. It seems like I remember reading there is an internal check valve on the fuel pump that can go bad. If you can safely eliminate the fuel pressure regulator and injectors as culprits, about the only other thing I can think of would be a tiny leak near the fuel filter, a bad check valve on the fuel pump, or maybe the clamps on the flexible hose in the gas tank going from the pump to the fuel lines.
My 97 Camaro suddenly became very hard to start. It would run normally once it finally fired up, but I had to crank it excessively to get there. When I hooked a fuel pressure gauge up I noticed the pressure would drop rapidly when the pump shut off, just like you described. I installed a new fuel pump and the problem went away. I briefly considered installing an inline check valve near the fuel filter as a cheap/easy fix. heh..
Chad
My 97 Camaro suddenly became very hard to start. It would run normally once it finally fired up, but I had to crank it excessively to get there. When I hooked a fuel pressure gauge up I noticed the pressure would drop rapidly when the pump shut off, just like you described. I installed a new fuel pump and the problem went away. I briefly considered installing an inline check valve near the fuel filter as a cheap/easy fix. heh..
Chad
More importantly, what is the pressure when the engine is running and the vacuum line off the FPR? Doesn't the jumper keep the pump running constantly? IIRC I think the 255 pumps bleed down as described. Is your FPR adjustable?
Pretty sure the fuel pressure shouldn't bleed down like that. It seems like I remember reading there is an internal check valve on the fuel pump that can go bad. If you can safely eliminate the fuel pressure regulator and injectors as culprits, about the only other thing I can think of would be a tiny leak near the fuel filter, a bad check valve on the fuel pump, or maybe the clamps on the flexible hose in the gas tank going from the pump to the fuel lines.
My 97 Camaro suddenly became very hard to start. It would run normally once it finally fired up, but I had to crank it excessively to get there. When I hooked a fuel pressure gauge up I noticed the pressure would drop rapidly when the pump shut off, just like you described. I installed a new fuel pump and the problem went away. I briefly considered installing an inline check valve near the fuel filter as a cheap/easy fix. heh..
Chad
My 97 Camaro suddenly became very hard to start. It would run normally once it finally fired up, but I had to crank it excessively to get there. When I hooked a fuel pressure gauge up I noticed the pressure would drop rapidly when the pump shut off, just like you described. I installed a new fuel pump and the problem went away. I briefly considered installing an inline check valve near the fuel filter as a cheap/easy fix. heh..
Chad
30# of fuel pressure is too low so that right there is telling you something. You should get a slight increase in pressure if you pull vacuum from the regulator but 30 is to low. These cars should be a bit over 40 running iirc. I think mine is about 49 actually.
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Injectors are not leaking. FPR is OEM
but not the original one. Maybe 2,000 miles
I have the rail pulled up with the injectors attached.
pump is a Walbro 255 from Racetronix
with the Hotwire kit. Hose is the teflon
one and I am aware of its problems as the
first hose was split from packaging.
Racetronix sent me a replacement.
I see that the Racetronix kits come with a
different looking pump now (purple ends).
is this an improved pump? Mine is about
5 years old but doesn’t have 2,000 miles
on it. Guessing I just need to buy a new
pump and see if the pressure changes.
but not the original one. Maybe 2,000 miles
I have the rail pulled up with the injectors attached.
pump is a Walbro 255 from Racetronix
with the Hotwire kit. Hose is the teflon
one and I am aware of its problems as the
first hose was split from packaging.
Racetronix sent me a replacement.
I see that the Racetronix kits come with a
different looking pump now (purple ends).
is this an improved pump? Mine is about
5 years old but doesn’t have 2,000 miles
on it. Guessing I just need to buy a new
pump and see if the pressure changes.
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As previously mentioned and what I agree with, is the possibility of the Fuel Pump/Sender check ball. The ball is there to retain fuel pressure for a quick prime at startup. I have only had this issue twice on my own personal vehicles in the last 20 years. But when I worked for a dealership I've maybe seen it 5 or 6 times. Its one thing that is severely overlooked when diagnosing a hard start with Rapid Bleed off and lack of Fuel Pressure with KOEO.
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As previously mentioned and what I agree with, is the possibility of the Fuel Pump/Sender check ball. The ball is there to retain fuel pressure for a quick prime at startup. I have only had this issue twice on my own personal vehicles in the last 20 years. But when I worked for a dealership I've maybe seen it 5 or 6 times. Its one thing that is severely overlooked when diagnosing a hard start with Rapid Bleed off and lack of Fuel Pressure with KOEO.
Before I'd explore the FPR first. If it were me I'd get an aftermarket adjustable. I can't remember which on to avoid if it's Holly or some other brand. Plenty of threads you can search that suggest the correct one. Install it and try to adjust it to 43.5psi with no vacuum at idle. Then take it for a drive with a pressure gauge taped to the windshield. Go through a few gears at WOT and see if your needle stays right around 40 to the 43.5 peak adjustment. If it dips to 30 then there's inadequate pressure somewhere. I do remember I had a 255 (many years and probably two fuel pumps ago) that would bleed off quickly. Car started right up and it never ran lean. Have you contacted Racetronix to ask them? There may be someone there who knows. Not sure these days.
I dunno, to me it seems normal. Especially if you aren't experiencing hard starts(?).
I dunno, to me it seems normal. Especially if you aren't experiencing hard starts(?).
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FWIW I have a Walbro 255 (pump only) I put in at least 15 years ago. It has always bleed off within 10 min. Car starts instantly. You hear the fuel pump prime for a few seconds when you turn key on
with a FP gauge when you turn key on FP should "immediately snap" to the correct FP..if it doesn't (read slow low needle climb) than pump is likely getting tired, clogged filter
I have a adjustable FPR I bought at O'Rielys. Stay away from anything Aeromotove
with a FP gauge when you turn key on FP should "immediately snap" to the correct FP..if it doesn't (read slow low needle climb) than pump is likely getting tired, clogged filter
I have a adjustable FPR I bought at O'Rielys. Stay away from anything Aeromotove
FWIW I have a Walbro 255 (pump only) I put in at least 15 years ago. It has always bleed off within 10 min. Car starts instantly. You hear the fuel pump prime for a few seconds when you turn key on
with a FP gauge when you turn key on FP should "immediately snap" to the correct FP..if it doesn't (read slow low needle climb) than pump is likely getting tired, clogged filter
I have a adjustable FPR I bought at O'Rielys. Stay away from anything Aeromotove
with a FP gauge when you turn key on FP should "immediately snap" to the correct FP..if it doesn't (read slow low needle climb) than pump is likely getting tired, clogged filter
I have a adjustable FPR I bought at O'Rielys. Stay away from anything Aeromotove
Was just reading a post by Shownomercy/Man-Crush on another thread suggesting a "genuine 255 Walbro" pump. I googled those words and got this link:
https://www.highflowfuel.com/i-23904...fuel-pump.html
Which states:
https://www.highflowfuel.com/i-23904...fuel-pump.html
Which states:
A common side effect of high volume (and OEM) intank fuel pumps are their inability to maintain static fuel pressure when the vehicle sits for any extended period of time. This leads to a "hard starting" condition where the starter must engage continuously for 3-4 seconds (or longer) before the motor will finally start. This side effect is commonplace with all high performance, high volume fuel pumps including Walbro, AEM, Aeromotive, and Quantum fuel pumps. Our check valve resolves this issue once and for all, and can be used either intank, or externally. It features a high-flow design which uses viton seals and stainless steel internals which are compatible with modern pump gasoline as well as E85. This check valve will not significantly alter the flow capabilities of your pump, but it will make sure that the car starts instantly, every single time. We recommend installing an inline check valve even with a brand new pump, so the tank doesn't need to be dropped again a few months later.
