Delphi Aftermarket Fuel Pump FAQ – FG0407, 597338, and Getting It Done Right

Before you spend money on a fuel pump, I answer the questions I get most

I'm the guy who reviews fuel pump modules before they go out the door. I've been doing this at Delphi for over six years, and I've rejected my share of deliveries that didn't match spec. People assume that if it's a Genuine Delphi part, everything checks itself. It does—on our end. The friction happens when someone orders the wrong part, buys from a third-party marketplace, or tries to save a few bucks on shipping when the truck is already down.

Here's what I actually answer when customers ask me about the FG0407, the 597338, or swapping a trailer hub. No marketing fluff.

1. Is the Delphi FG0407 the same as the 597338 fuel pump?

No, they're not the same assembly, even though they look similar in photos. The FG0407 is a module assembly—meaning it comes with the mounting flange, level sender, and inlet tube as one unit. The 597338 is the pump-and-sender assembly that fits a specific set of GM applications. The plastic flange geometry is different, the pump internals are tuned for different fuel pressure curves, and the electrical connectors aren't interchangeable.

I've seen people order the 597338 because it's $40 cheaper, then try to stretch the wiring harness. That's how you get an intermittent fuel gauge and a low-pressure code two months later. Check the OEM interchange for your exact VIN substring. If the listing says it replaces both FG0407 and 597338, treat that as a red flag—unless the seller specifically states they ship the correct module for your VIN after you message them. A true Delphi application tag matters more than the listing title.

2. How do I know I'm getting a genuine Delphi part?

Look at the retail packaging first. Genuine Delphi aftermarket fuel pumps ship in a white-and-blue box with a holographic label that reads “Delphi” in the center. The pump body itself will have a laser-etched part number with a date code, not just an ink stamp that rubs off with brake cleaner.

Here's the thing: counterfeits are getting better. I recently got a sample from an online marketplace that had the same color sleeve and a similar connector. But the fuel outlet barb was 0.5 mm thinner than the print spec. On a 60 psi system, that's a leak waiting to happen. We don't advertise that check in our marketing materials because it's not a defensible claim to say “all fakes have thin barbs.” But it's one of the first dimensions I measure.

Per FTC guidelines on advertising, a claim like “100% genuine” is a legal assertion that can be substantiated. If a third-party seller can't provide an invoice from an authorized Delphi distributor when you ask—not a screenshot, an actual invoice—then you're gambling. I'd argue that an $18 discount isn't worth an engine fire or a tow bill.

3. My fuel pump just died. Should I pay extra for rush shipping?

I get asked this more than any other logistics question. And here's where I'll be opinionated: yes, if the vehicle is a daily driver or a work vehicle.

I had to make this call myself in March 2024. Our van needed a fuel pump module on a Tuesday, and a local parts house said “probably Thursday” if the warehouse transfer went through. A next-day freight quote was $210. Standard ground on the same part was $28. I've been burned by “probably” before—the last time, a promised three-day part took eight days and cost me two scheduled jobs. I paid the $210. The part arrived at 9:30 AM the next day. I installed it by noon and didn't miss a single appointment.

When you do that math, the rush charge isn't about paying for speed. It's paying for certainty. A missed deadline for a delivery truck or a camper rental costs more than the $180 difference in shipping. To be fair, if the car is parked and you have another vehicle, ground shipping is fine. But if you're counting on a specific day, don't let a salesman tell you “it'll probably make it.” I'd rather hear “no guarantee” upfront than have to make angry phone calls later.

4. Can I use an oil barrel pump to prime or pressure-test a fuel pump?

You can, but I don't recommend it for fuel system work. An oil barrel pump is designed for viscous liquids at low pressure—typically 5 to 20 psi. A Delphi electric fuel pump pushes fuel anywhere from 45 to 60 psi depending on the application.

I've seen one mechanic try to use a manual oil barrel pump to push gasoline through a fuel rail for a leak test. The pump seals aren't compatible with ethanol-rich fuels; the rubber swelled and contaminated the test fluid. Not to mention the safety issue of pressurizing volatile fuel with a pump that wasn't rated for it. If you're bench-testing a fuel pump, use a proper fuel pressure test kit with a clean container. Don't improvise with shop equipment that's meant for motor oil.

On the flip side, if you're working on an off-road diesel rig and need to transfer fuel from a 55-gallon drum, a quality manual barrel pump is a reasonable tool. Just don't cross the streams between that pump and your EFI service kit.

5. Does replacing a trailer wheel hub have anything to do with a fuel pump module?

Not in terms of parts. But I get this question more than you'd think, because both jobs show up on the same weekend to-do list for boat owners and camper owners. A worn trailer wheel hub can cause a vibration that feels like a fuel delivery problem. If your trailer is handling poorly at highway speed, a fuel pump won't fix that. The hub needs to be repacked or replaced.

The biggest mistake I see in that job is not torquing the spindle nut to the manufacturer's spec. For most 3,500-lb trailer axles with a 1-1/16" spindle, the spec is around 50 ft-lb while rotating the hub, then back off 1/4 turn. If you just slam it tight, the bearing will overheat and seize. That's a $30 trailer hub failure that turns into a $400 spindle replacement.

For the record, if you need a wheel hub for a trailer, don't look in the Delphi aftermarket catalog. We do stampings, forgings, and fuel systems—not trailer hubs. But I mention it because a surprising number of home mechanics email us expecting a universal answer.

6. What about the “delphi aftermarket” quality reputation? Is it overhyped?

I'm biased, but I'll give you the straight version. The reason fleet managers spec Delphi aftermarket fuel pumps is rooted in the parts we make, not just the name. Fuel pumps are one of those components where first-tier OEM manufacturing experience matters. Delphi supplies original equipment fuel pump assemblies to several automakers. The aftermarket parts run on the same assembly line to the same dimensional tolerances.

But I won't claim that every Delphi aftermarket part is perfect on the first build. We had a batch of FG0407 modules in Q1 2025 where the level sensor float sat a couple degrees off, which caused an intermittent low-fuel light in deep interiors. We caught it in the audit, quarantined 800 units, and recertified the line. No recall, no field failures. But it's a good reminder that even the best brand relies on inspection protocols—not faith.

When you buy a cheap white-box pump, you're buying whatever a distributor could source. When you buy a Genuine Delphi part, you're buying the documented quality process. That's the real difference. On an integrated assembly like a fuel pump module, you don't save money by skipping the verification step.

7. How fast should I expect delivery on an FG0407 from an online seller?

Realistically, two to five business days for ground if it's in their warehouse. If the listing says “ships from a local warehouse” and your address is within the same state, three days is reasonable. Beyond that, you're at the mercy of the carrier.

I'll tell you the same thing I tell my own purchasing contact: a dealer that stocks the Delphi parts in the FG0407 and 597338 footprint is more reliable than a drop-shipper. Ask directly if the item is physically on their shelf. A vague answer like “normally ships within 24 hours” doesn't mean they have the part in hand. If you're in a hurry, order from a source that can send you a photo of the actual box. It's not a guarantee, but it's a better signal than a stock status text.

As of January 2025, the USPS First-Class rate for a letter is $0.73, but that has nothing to do with shipping a fuel pump module—a part like this goes via UPS or FedEx ground because of the size and weight. Online sellers who quote USPS for a pump module are usually shipping the wrong thing or padding the delivery window.

8. Bottom line: what's the safest way to replace a fuel pump module on your own?

Take the five-minute safety check before you drop the tank. Relieve the fuel pressure by pulling the fuel pump fuse and cranking the engine for 5 seconds. Disconnect the negative battery cable. Work on a level surface with a fire extinguisher nearby—not because the task is dangerous, but because mistakes happen. Then follow the service manual for the exact torque sequence on the tank straps and the pump module lock ring.

If you've never done a fuel pump replacement, I'll be honest: the job takes longer the first time than you think. The lock ring tool is worth buying instead of using a hammer and screwdriver. You can finish a Delphi FG0407 module swap in about two hours on a 2005–2008 Chevrolet Silverado if the tank is not full. On an F-150, it's a bed-off procedure, and that's a bigger project.

I'm not going to add a fancy conclusion. You already found the part number, you're deciding who to order from, and you need the rig fixed before the weekend. Buy the genuine part, pay for the shipping certainty if your schedule depends on it, and don't cross-contaminate your shop pumps. That's all the advice I'd give a friend.