I think so. I will go with a 190 and report back. Damnit, have to drop the darn tank again. I’m a tank dropping expert now. Sheesh.
Resolved Fuel pressure high at 52 new FPR same thing
- Thread starter afjLX
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I think so. I will go with a 190 and report back. Damnit, have to drop the darn tank again. I’m a tank dropping expert now. Sheesh.
For reference, In my combo:
347
heads
cam
KB blower that pulls between 6 and 8 HP at idle.
42s
Be advised: There are low pressure and high pressure 190L pumps as well.
I generally recommend the high pressure no matter what. I don't know if it's still true or not but the low pressure Walbro 190L LP pumps would "pop-off" internally at around 60 psi. So, no boosted apps with FMUs. The HP pressure versions have a much higher internal pop-off (90 to 100 psi IIRC).
347
heads
cam
KB blower that pulls between 6 and 8 HP at idle.
42s
Be advised: There are low pressure and high pressure 190L pumps as well.
I generally recommend the high pressure no matter what. I don't know if it's still true or not but the low pressure Walbro 190L LP pumps would "pop-off" internally at around 60 psi. So, no boosted apps with FMUs. The HP pressure versions have a much higher internal pop-off (90 to 100 psi IIRC).
I was gonna order the gss242 from summit and reuse the filter sock off the 255 unit. Is the gss242 the right pump?
Specifications:
- Fuel: Gas
- Horsepower: 300-400
- Flow Rate: 190 lph
- Flow @ 40 psi: 50 gph
- Fuel Pressure: 50 psi
- Maximum Working Pressure: 137
I dug this up for you to checkout when you have the inclination.
It explains what I talked about above with graphs and tables and things...
Note the [Download] Button in the upper right. It's an old magazine article:
It explains what I talked about above with graphs and tables and things...
Note the [Download] Button in the upper right. It's an old magazine article:
I dug this up for you to checkout when you have the inclination.
It explains what I talked about above with graphs and tables and things...
Note the [Download] Button in the upper right. It's an old magazine article:
Thanks!! I’ll check it out!
For some reason summit only lists a gss242BX for the pump only??it Looks like the right one?? I couldn’t find just a gss242 listed.
It should drop right into the hanger you have for the 255. They should be physically similar.
I have run a 255 lph high pressure pump for over 15 years in my Coupe with three different motors and had zero issues getting the pressure down to 39 psi. At idle the fuel consumption difference on a stock 302 versus one with all kinds of bolt-ons and with both of them being NA is going to be minimal. Larger displacement or boosted applications will use a little more. Where things differ is when the foot hits the gas pedal.
Not being able to adjust the pressure up or down is like the return line has an orifice in it upstream of the pressure regulator so it basically negates the regulator. Is there an obstruction in the fuel rails? I just cannot see this being a fuel line size issue as thousands of these cars run 255 lph pumps with no issues.
Not being able to adjust the pressure up or down is like the return line has an orifice in it upstream of the pressure regulator so it basically negates the regulator. Is there an obstruction in the fuel rails? I just cannot see this being a fuel line size issue as thousands of these cars run 255 lph pumps with no issues.
No orifice or restrictors or check valves, etc. anywhere. Did fuel line size change at all throughout the years? This car was an 87 4cyl before a 5.0 swap. Could the fuel lines be smaller on an older mustangs or 4cyl?
Okay, that is something we need to know. When I swapped my car I installed V8 lines due to the 4 banger lines running on the driver side and the V8 lines running on the passenger side. Line size between the V8 cars and the 4 cylinders are the same which are 5/16" feed and 1/4" return. My guess is whoever did the conversion swapped to the V8 lines on your car?
Lines run down the psssenger side so they appear correct. One question though, how are the stock lines routed? Do they make a 90 at the back near front of the rear wheel towards the center of the car then outback to the fuel filter? It looks like a stock setup but you never know.Okay, that is something we need to know. When I swapped my car I installed V8 lines due to the 4 banger lines running on the driver side and the V8 lines running on the passenger side. Line size between the V8 cars and the 4 cylinders are the same which are 5/16" feed and 1/4" return. My guess is whoever did the conversion swapped to the V8 lines on your car?
They run down the passenger side and about midway down they move to the drive shaft tunnel and run along it until it gets to the rear axle area. From there they run along the sheet metal to directly over the rear end and then it switches to rubber lines from there over to the tank and the filter.
I verified the routing using LMRs diagram, they appear to be correct v8 lines.
You proved the regulator will regulate in Post #26 and that there is a restriction somewhere past the steel line that connects to the fuel rail.
The two plastic lines that go from the hard lines just in front of the passenger wheel then over to the two hard lines that connect to the fuel rails have a hard foam / rubber protective covering around them from the factory. Does your car still have them? If so are you sure the return line under it is not kinked?
The two plastic lines that go from the hard lines just in front of the passenger wheel then over to the two hard lines that connect to the fuel rails have a hard foam / rubber protective covering around them from the factory. Does your car still have them? If so are you sure the return line under it is not kinked?
I pulled the rubber off both. The supply line had a slight kink. Return line was ok. Fixed the kink and then eventually tested with return line dumping into a bucket.
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Update:
Well, installed the walbro 190 and cranked it up. Fuel presssure was at 30psi and I was able to adjust it to 40 without vacuum. So it does appear the 255 was overloading my return line. Maybe I got a really well built 255 that was pushing 99% efficiency and flowing every bit of its rated flow?
The Walbro 190 is on and I can now adjust fuel pressure. Thanks to everyone for their help!!
Well, installed the walbro 190 and cranked it up. Fuel presssure was at 30psi and I was able to adjust it to 40 without vacuum. So it does appear the 255 was overloading my return line. Maybe I got a really well built 255 that was pushing 99% efficiency and flowing every bit of its rated flow?
The Walbro 190 is on and I can now adjust fuel pressure. Thanks to everyone for their help!!
It not actually the first time I've seen this happen but it's been rare.
The trouble is that if the return side is just [barely] able to handle the volume then the pressure rise accumulates fast (hydromechanics are a beeoch).
The good news is that you're not burning much fuel at idle.
it takes a little bit to get one's head wrapped around the difference between pressure and volume in a closed hydraulic system. I could probably take your return system, put it on my car, and it would be just fine.
gkomo
now i can hopefully expect to receive the shaft
Don't be. I've run mine for ten plus years ,no problem with pressure,stock regulator.
All I have to say is glad you got it figured out and this is the first time I have ever seen or heard of this but I have never thought to research a 255 being too large based on my experience and other cars I have been around with them. Kinda crazy how you can run an intank 255 plus an inline 255 and not over pressure the stock lines with a supercharger or turbo car at idle. IDK but still really glad you got yours figured out.
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