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The short answer is "YES" and any of the L98 pumps can be used. Your fuel pressure is set by the regulator in the Cross-Fire injector system... the one on the driver's side IIRC.
a new fuel pump will not add fuel pressure past the regulator
Yes, and it will make sure your FPR is operating at 100% of capacity. If the "old" pump is operating at less than spec, your FPR will deliver less than spec. A slightly higher pump (delivering higher than spec) will make sure that the FPR is at 100% operating efficiency.
To follow up on this thread, I went back to the stock Crossfire pump. All my driveability issues are GONE. It runs leaner and smoother. The 45 psi pump addition was a mistake. It ran so rich it made eyes water in following vehicles. It was always searching for idle, almost NEVER hit the intended idle, stalled at traffic lights, stumbled on accel- just a mess.
One good thing that came out of this last pump change was a the discovery of the biggest conflict between the edges of the sender flange and the hole in the body above it. I removed about 2" of the curled edge of the flange with a Dremel. Installation took about 5 minutes and I did not scratch any more paint.
BTW I had replaced my sender unit with the 85 fuel pump because my sender always stuck at 1/2 tank. TO unstick it I had to hit a hard bump in the road taking a left turn with a full tank of gas. After 20 years of that I decided to kill two birds with one stone and buy a C4 sender with the C4 pump- a cheaper option than separate. My gauge worked but it was very inaccurate. It showed empty at 1/2 tank. So this time when I replaced the pump with the stock unit I also replaced the sender with the stock unit. While on the bench getting prepped I compared the two. Guess which one is the C4.
Always glad to help with observations of my incredible mistakes.
Steve
To follow up on this thread, I went back to the stock Crossfire pump. All my driveability issues are GONE. It runs leaner and smoother. The 45 psi pump addition was a mistake. It ran so rich it made eyes water in following vehicles. It was always searching for idle, almost NEVER hit the intended idle, stalled at traffic lights, stumbled on accel- just a mess.
'84 owners should take heed as those preaching the upgrade to an '85+ pump are misguided, IMO. As I have posited in other posts, this theory that the Chevy engineers spent five years redesigning the entire car to arrive at the C4, but somehow screwed the pooch and under-sized the fuel pump simply doesn't hold water. The TBI's on the CFI are designed to be supplied by a low pressure centrifugal pump whereas the '85+ C4's use a positive displacement pump. These are two completely different pumps and are not in any way interchangeable from a fluid mechanics, engineering design or any other standpoint.
When purchased, my '84 CFI had the classic stumble when I put my foot into it, particularly when I was coming out of a hard left turn. I did two things. I rebuilt the TBI's (regulator and compensator diaphragms were indeed completely shot) and I replaced the fuel pump with the OE spec ~14 psi pump. It runs beautifully and is extremely responsive at any speed. Simply put, it's a joy to drive. No idea what the result would have been if I'd followed the surprisingly popular advice to second guess the design engineers and 'upgrade' to an over-sized positive displacement pump; but the above update sounds about right as it's clearly not a wise move.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Originally Posted by Livin_as_Luther
'84 owners should take heed as those preaching the upgrade to an '85+ pump are misguided, IMO. As I have posited in other posts, this theory that the Chevy engineers spent five years redesigning the entire car to arrive at the C4, but somehow screwed the pooch and under-sized the fuel pump simply doesn't hold water. The TBI's on the CFI are designed to be supplied by a low pressure centrifugal pump whereas the '85+ C4's use a positive displacement pump. These are two completely different pumps and are not in any way interchangeable from a fluid mechanics, engineering design or any other standpoint.
When purchased, my '84 CFI had the classic stumble when I put my foot into it, particularly when I was coming out of a hard left turn. I did two things. I rebuilt the TBI's (regulator and compensator diaphragms were indeed completely shot) and I replaced the fuel pump with the OE spec ~14 psi pump. It runs beautifully and is extremely responsive at any speed. Simply put, it's a joy to drive. No idea what the result would have been if I'd followed the surprisingly popular advice to second guess the design engineers and 'upgrade' to an over-sized positive displacement pump; but the above update sounds about right as it's clearly not a wise move.
This is an old thread, but I'll bite.
There is nothing wrong with installing a later 85-87 TPI pump in a CF. The pump is rated in flow, either lph or gph...NOT psi. That is regulated. If GM got it right and engineers are correct, why is the range for ANY CF 9-13psi regulated? To prove a point, set your FP at 9psi and nail it. It may stumble and It WILL run out of power and fall on it's face at or around 4k rpm. Now set the FP at 13psi which is still GM spec and perform the same test. The motor WILL pull at the way to redline every time in every gear. This is also dependent on if the pump can provide the correct flow at WOT and provide the wanted psi and the voltage is correct to support that.. So, Did GM engineers get that wrong? How dare they!
You do not have to regulate the FP anymore than 13psi for any stock CFI motor. Mine is not stock, but I run 30psi with a 255lph pump and run mid 12s. The new tune I'm working on hopefully will put me into the 11s, we shall see.
Last edited by Buccaneer; Jul 17, 2021 at 09:57 PM.
