Ford Mustang Forums banner

1 - 20 of 21 Posts

·
Registered
1991 Ford Mustang 5.0 gt40p heads trickflow upper and lower intake 24lb injectors, non nitrousnoturb
Joined
·
8 Posts
Discussion Starter · #1 ·
I have gt40p heads, trickflow upper and lower intake , 24lb injectors , e303cam cam. What are the negative affects to using a bigger pump? Will it hurt anything?
 

·
Registered
Joined
·
4,712 Posts
190 LPH is more than enough for your engine. I still use a 190lph with Boost-A-Pump at over 600HP. Even a 155lph would work, but then you might end up having to swap it again if you upgrade power as most people end up doing. There is some heating of the fuel as the pump gets larger and possibly fuel backing up (pressure increase) at idle with the 255lph and certain aftermarket fuel pressure regulators, but neither of these is likely or much of an issue as thousands of people run with a 255lph on the street.
 

·
Registered
Joined
·
578 Posts
I run a 255 LPH on a HCI 5.0. I haven't had any problems with it. If you have a stock fuel pump in there now there is a good chance you aren't pumping enough fuel to supply your engine you have now. I think the stock pump was something like 90 lph.
 

·
Registered
Joined
·
1,400 Posts
I just replaced my 255 with a 190 and happy I did. I hated the noise, even over my exhaust I could still hear it.

the 255 moves too much fuel and is noisy as hell. if you don't need it don't use a 255. The 190 is more than enough.
 

·
Registered
1991 Ford Mustang 5.0 gt40p heads trickflow upper and lower intake 24lb injectors, non nitrousnoturb
Joined
·
8 Posts
Discussion Starter · #7 ·
I run a 255 LPH on a HCI 5.0. I haven't had any problems with it. If you have a stock fuel pump in there now there is a good chance you aren't pumping enough fuel to supply your engine you have now. I think the stock pump was something like 90 lph.
I have a 195 in it now but it’s going bad
 

·
Registered
Joined
·
2,411 Posts
install another 190lph, change the filter. inspect all the wiring.

First, why do you think its going bad? they either work or they dont.
 

·
Registered
Joined
·
1,757 Posts
First, why do you think its going bad? they either work or they dont.
I kind of thought this too, but we had a 90 model fox we were working on with the factory fuel pump. The car would run alright, but then start to run like **** and die after a few seconds. We hooked up a fuel gauge on the rail and it would slowly drop from around 34psi to where it reached the low teens. Filter wasn’t it, we changed that. Put a new pump in it and off it went.
 

·
Registered
Joined
·
9,084 Posts
I'd stick to a 155 or 190lph pump for your setup.


The downside to running a higher volumn pump than needed is that the fuel circulates much more than needed and may cause it to warm up. Also, when using the stock fuel lines, as your flow rate increases, you may find pressure in the lines increases as well due to resistance to flow. This may or may not translate to increased pressure at the fuel rail. I do have experience in putting a 255 in a mostly stock car (not my choice) and finding that we could not dial in the fuel pressure any less than 42psi vacuum off after the change (was previously 39psi). Unsure if this was unique to this car due to the type of regulator it had, but just something to keep an eye out.

Because of the above, i tend to suggest to size the pump for your needs, vs just sticking the biggest pump you can get in there. I have a 190lph in my car, and feel I would have been fine with a 155 for my combo.
 

·
Registered
Joined
·
2,411 Posts
I kind of thought this too, but we had a 90 model fox we were working on with the factory fuel pump. The car would run alright, but then start to run like **** and die after a few seconds. We hooked up a fuel gauge on the rail and it would slowly drop from around 34psi to where it reached the low teens. Filter wasn’t it, we changed that. Put a new pump in it and off it went.
I shouldve worded it different. Fuel pumps either work properly or they dont work properly. Fuel pumps like you described are sometimes pinta to diagnose. surprised that when the fuel pump was going bad it wasn't pulling enough amps to blow thr fuse or the link.

good old days of banging on the bottom of the tank to unfree a sticking pump. I haven't done that in a long time.
 

·
Registered
Joined
·
4,712 Posts
I do have experience in putting a 255 in a mostly stock car (not my choice) and finding that we could not dial in the fuel pressure any less than 42psi vacuum off after the change (was previously 39psi). Unsure if this was unique to this car due to the type of regulator it had, but just something to keep an eye out.
Similar to what I saw using a Magnafuel regulator with the 190lph if I activated the Boost-a-Pump at idle. Pressure would shoot up to 45 psi when I did so. Has to do with the size of the return orifice in the regulator.
 

·
Registered
1991 Ford Mustang 5.0 gt40p heads trickflow upper and lower intake 24lb injectors, non nitrousnoturb
Joined
·
8 Posts
Discussion Starter · #13 ·
I replaced the fuel pump today and still a misfire right when the tach gets to 3500 rpm tach jumps like crazy, fuel pressure is at 40 while at 3500 rpm staying steady while under load, I’ve replaced the fuel pump 190lph, new adjustable fp regulator, new ignition coil, 2 new distributors , new plugs and wires, has anyone heard of anything causing this?
 

·
Registered
Joined
·
4,712 Posts
Will the engine rev higher than 3500 RPM, or do the misfires start there and get worse as RPMs rise?
 

·
Registered
1991 Ford Mustang 5.0 gt40p heads trickflow upper and lower intake 24lb injectors, non nitrousnoturb
Joined
·
8 Posts
Discussion Starter · #15 ·
Will the engine rev higher than 3500 RPM, or do the misfires start there and get worse as RPMs rise?
It starts at 3500 and keeps missing through the power band
 

·
Registered
Joined
·
4,712 Posts
It starts at 3500 and keeps missing through the power band
I forget everything from your previous post on this, did you ever look at the valvetrain? Bad injector? Bad sensor - MAF, O2, something else?
 

·
Registered
Joined
·
9,084 Posts
I had a similar issue with my car. Misfire after 3000rpm. Chased fuel, didn’t have any codes, checked sensors, etc.

On a whim I changed out my Accel coil to a good OEM unit abs problem solved.
 

·
Registered
Joined
·
7,751 Posts
Another vote for 190.
 

·
Registered
Joined
·
24,697 Posts
I replaced the fuel pump today and still a misfire right when the tach gets to 3500 rpm tach jumps like crazy, fuel pressure is at 40 while at 3500 rpm staying steady while under load, I’ve replaced the fuel pump 190lph, new adjustable fp regulator, new ignition coil, 2 new distributors , new plugs and wires, has anyone heard of anything causing this?

doesnt it feel good when you change parts, without diagnosing, only to have the same problems!!

close your eyes and play some darts with your best friend
 

·
Registered
Joined
·
4,712 Posts
doesnt it feel good when you change parts, without diagnosing, only to have the same problems!!

close your eyes and play some darts with your best friend
:ROFLMAO: you're a bad man
 
1 - 20 of 21 Posts
Top