Might need a new fuel pump

**ChevyZ76** · 04-28-2014, 05:21 PM

So I picked up a 1998 Z28 today. Drove 2 hours home from the place hat I got it. I was showing a friend when I noticed a hum from the back. Pretty sure that its the fuel pump. But, since this is my first one I'll ask. Does the fuel pump normally hum on that car? Also how kph does it flow stock? I don't plan on doing any major engine upgrades right away. But Granatelli has a few pumps for the car, one flowing 255 and the other 340. I don't wanna totally murder my gas mileage either. Thanks guys

**pajeff02** · 04-28-2014, 05:44 PM

Some pumps you can hear, others are quieter. Since you just bought the car, you can test the pressure using a gauge plumbed to the fuel rail. If you see 58 psi with the ignition energized and pressure holds, then start the car and see what it does. As long as you have the correct pressure and the car starts easily I wouldn't mess with it. Once you see pressure drop, you experience starting issues, or the pump just quits, then it is time to replace it. The capacity of the pump has nothing to do with your mileage as the injectors will still only squirt the required amount of fuel into the cylinders. That being said, bigger is not necessarily better. Best to run the smaller rated pump for what you are doing with the car.

**ChevyZ76** · 04-28-2014, 05:46 PM

Thank you. My fried has a 2000 T/A and i just got ahold of him and he told me the something. Good to know. I just don't want it to quit on me like my truck did. LOL

**35th-ANV-SS** · 04-28-2014, 05:48 PM

Yea, they typically start giving you signs of starting to go out first. That's not to say one just won't quit on you without notice either though.

**pajeff02** · 04-28-2014, 05:50 PM

Replacing the pump on our car now -- the pressure falls off after you energize the ignition and under load on hot days it can be as low as 53 psi.

**35th-ANV-SS** · 04-28-2014, 06:04 PM

I see anywhere from 58 to 61psi with the Walbro pump, Jeff. It is usually pegged right at 60.

**pajeff02** · 04-28-2014, 06:07 PM

Did you upgrade the pump when you went FI, or had you already swapped it out (I can't recall)?

**35th-ANV-SS** · 04-28-2014, 11:02 PM

It was upgraded at the time of the FI install.

**Firebirdjones** · 04-30-2014, 04:49 AM

Have you been having hot days already out there Jeff?

I run the Racetronix pump in ours and see the same thing that Jon reports, pegs the gauge right at (or just a hair under) 60 psi.

Pretty common for pressure to drop on really hot days, (I'm talking 90+) especially during a heat soak situation after shutting the car off for 15-20 minutes until the hot fuel is pumped through. Today's ethanol fuel is horrible for heat soak and vapor lock issues, and the lower the octane used, the worse it is. Biggest reason you don't see vapor lock in todays cars is simply because of the fuel pressure these fuel injected engines run on. That high pressure keeps things moving. But you may see a drop in pressure if the fuel gets hot, usually not enough to cause any drivability issues though.
It's the carb applications where you fight this the most, since a carb only requires 6-7 psi. Not alot of pressure there, very easy to vapor lock. So it's even more important to keep the fuel away from hot spots, and always run a return style pump to keep fuel circulating back to the tank so it doesn't sit stagnent in the fuel lines attracting heat.

Okay, done babbling

**pajeff02** · 04-30-2014, 10:33 AM

On stupid hot days it'll stay right around 55 psi just driving around. It was our last track outing that I noticed it down to 53 psi at the top of the track. New pump is in the bucket and ready to drop in the tank this evening.

**Firebirdjones** · 04-30-2014, 11:08 AM

When you see the fuel pressure drop at the track with those high gear long hard pulls, then you know you have something that's not keeping up with the requirements.

**pajeff02** · 04-30-2014, 06:11 PM

It's all good now. Zach gave me a hand this evening finishing the swap. Just have to install the hotwire kit and all will be ready for the track.

**0rion** · 04-30-2014, 06:56 PM

To the OP......the stock pump on mine was really loud.....for 3 years. When i did the rear i went with a racetronix but the stock one was doing fine still. You can search on here for the thread about running 2 cycle oil with each fill up. That will help lubricate the pump & may quiet it down some for you.

**pajeff02** · 05-01-2014, 02:20 AM

^^ The Racetronix pump is a lot quieter than the stock pump on our car.

**ChevyZ76** · 05-01-2014, 03:07 AM

Thanks guys. The pump only seems to be making noise every once in a while. I am going to change the fuel filter out. And change the pump later down the road. Difference between Granetelli and Ravetronix? Also is the Racetronix the red pump on their site for stock to mild motors? My friend says that he runs the Racetronix in his T/A 00, he likes it.

**0rion** · 05-01-2014, 03:51 AM

yeah....be careful when ordering. The 98's have a different tank than the 99+ cars so it's a different part number. We have metal tanks with baffles instead of plastic and buckets on the pump. It's a nice kit with a really decent set of instructions. Basically walks you through it with pictures. Even sent the paper clip to push the old wires out of the plug.

That tank is kind of a bitch to get out of there. You have to lower the rear as far as it will go and then the tank comes out at an angle and you have to rotate the tank as it comes out. Do yourself a favor and take a grinder and open that area up where the filler neck passes through and it'll make life a lot easier getting it back in. I ground it down and then painted it. Makes putting the tank back in a breeze and an easy job if you ever need to drop it again.