2.5 and 2.8 fuel pumps (Page 1/2)
handymanpat JUN 22, 11:23 PM
Ok, so I dropped the tank on my newest fiero, an 87 2.5
The tank, pump and sender was wrecked.
I had another tank, sender and 3 pumps.
All 3 pumps look the same and I cannot see any way to determine if they are for the 2.8 or 2.5.
These pumps look almost new and I am sure I did buy one or two of them new and for some reason we’re not used very long.
I would rather use one of the good pumps I have instead of spending another 50.00 for another new pump.
Here is my question.
Can the 2.8 pump be used in a 2.5?
I would imagine the 2.5 pump might not be strong enough for the 2.8 engine but is the 2.8 pump ok to you in my 2.5?
Since I cannot tell what the pumps are I do not know which engine they are for.
Thanks for any help.
If I have to, I can just use the new pump from autozone but I would like to use one I already have.
Thanks Pat

pat moody

Patrick JUN 23, 03:21 AM

Originally posted by handymanpat:

Since I cannot tell what the pumps are I do not know which engine they are for.

It wouldn't be all that difficult for a handy guy to stick each pump in a bucket of something, connect 12v, and measure what the pressure is. Seriously, it's pretty easy to do.

My feeling is that if a higher pressure fuel pump would've worked fine long-term with a duke, then Pontiac wouldn't have bothered messing with two different pumps on the Fiero assembly line.

[This message has been edited by Patrick (edited 06-23-2021).]

handymanpat JUN 23, 04:52 AM
Yes, that sounds like a good idea.
I was hoping that the higher pressure pump would run the 2.5 but I was sure the weaker pump would not run the 2.8
The people at autozone were the ones that said the pump they sold me would work for both engines, that’s what got me to thinking it would.
Well, thanks for letting me know.
I will test the pumps to find the pressure they have and then mark each one so I know which ones I have.
Thanks again for everything and my little handyman guy says thanks also!
fierofool JUN 23, 08:04 AM
Think about people doing an engine upgrade and rather than changing out the pump, just increase pressure at the regulator to flow more fuel. That's the effect the higher pressure would have on the 2.5 injector. I don't know if you could possibly put an adjustable regulator on the Duke and throttle down the pressure.
Dennis LaGrua JUN 23, 09:06 AM
The Duke fueling system was made to produce a steady 15 psi of pressure. If you install the 2.8L pump it could be said that the fuel pressure regulator would keep the pressure to 15 psi but there is always the possibility that the high pressure that the 2.8L pump will put out may damage the regulator. Testing the pump with a pressure gauge is the best idea but what liquid do you use? I would not use gasoline out of the tank. Using water should be safe short term.

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handymanpat JUN 23, 09:14 AM
Thanks you guys!
I knew there were people who whorls immediately know the answer and have the solutions.
I do not want to damage the regulator for sure.
I did change out the filter along with the sender and the pump but I was not getting any fuel from the injector.
The gas was dripping a little from it but there was no spray.
The car sat for a few years but supposedly did run back 2019.
I bet the injector or fuel line is gummed up and clogged!
Thanks again for letting me know
Patrick JUN 23, 12:21 PM

Originally posted by Dennis LaGrua:

Testing the pump with a pressure gauge is the best idea but what liquid do you use? I would not use gasoline out of the tank. Using water should be safe short term.

Yes, I'd shy away from using gasoline for safety reasons. It was probably varsol that I used when I was testing fuel pumps outside of the gas tank. I think using a solvent or kerosene or something along those lines would be fine. Personally, I wouldn't use water... just in case it corrodes the inside of the pump if the pump isn't immediately put into service afterwards.
handymanpat JUN 23, 12:32 PM
I will use something besides water or gas.
I do have kerosene from a lamp I can use.
It will be good to know what pumps I actually have.
Thanks Pat
theogre JUN 24, 10:11 AM
The regulator for TBI on 2.5 will likely peg w/ 2.8 pump.

Not only pumps are make for pressure but volume too.
Likely won't "damage" the reg but force all the way open for volume and high pressure will make 2.5 for have problems.
Even setting DTC 45 at random because ECM sees "Rich Engine." Even w/o setting DTC, Fuel Map is pegged rich most to all of the time as viewed by ECM scanners. As is, Many are setup so Engine Idle near/at the limit for BLM number.
See my Cave, Scan Tool Help and More on Tools

Might be hard to test on a bench w/o something to restrict flow and gauge to see pressure.
2.5 system pressure is 9-13psi via regulator and their pumps "top out" at 18-20 psi to make sure engine get right system pressure.

Don't restrict flow for long to see the "top out" or "stall" pressure. Electric Fuel Pumps need constant overflow to lube and cooling.

Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 06-24-2021).]

handymanpat JUN 24, 11:47 AM
Here is my new solution.
I’m going to just eat the 55.00 for the new pump and not bother with the others.
I will test them at some point but now I’m afraid I will end up making more problems and have more time and trouble into Messing with the existing pumps.
I bet I had put on a 2.8 pump and it maxed out the system because it was just a drip from the injector!
I will put on the new pump and repost my results.
Thanks everyone!