Why the Fuel Relay is a Suspect:
The fuel pump relay acts as a switch, supplying power to the fuel pump only when the engine needs to start. If the relay is faulty, it won't send power to the pump, even if the pump itself is new.
How to Troubleshoot the Fuel Relay:
1. Locate the Relay: Consult your owner's manual or an online repair manual (like Chilton or Haynes) to find the location of the fuel pump relay. It's usually in a fuse box under the hood or inside the cabin. The manual will also tell you which relay is the correct one. They are often labeled, but sometimes you need the diagram.
2. Visual Inspection: Check the relay for any obvious signs of damage, such as burnt contacts or a swollen casing.
3. Swap the Relay (Best Method): This is the most effective test. Find a relay of the same amperage rating (the numbers will be printed on it) and swap it with a known good relay from a different circuit (like the horn relay – *only if you can spare the horn briefly*). If the Suburban starts after the swap, the original fuel pump relay was the problem.
4. Relay Testing with a Multimeter (Advanced Method): If you have a multimeter, you can test the relay's continuity and switching action. This requires understanding relay operation and using the multimeter appropriately. Online tutorials can guide you through this, but the swap method is generally easier for beginners.
Other Possibilities (If the Relay isn't the Problem):
* Cranking Speed: Is the engine cranking slowly? A weak battery or starter motor can prevent the engine from starting even with fuel.
* Fuel Injectors: While less likely if the fuel pump is working, a problem with the fuel injectors could still prevent the engine from starting. A diagnostic scan tool can check this.
* Ignition System: Issues with the ignition coil, distributor (if applicable), spark plugs, or ignition wires can also prevent starting.
* Computer Issues (PCM): A faulty PCM (Powertrain Control Module) could be preventing the fuel pump from receiving power, despite a functioning relay. A scan tool is necessary to diagnose PCM issues.
* Security System: Check if there is anything preventing the engine from starting due to an alarm system, immobilizer, etc.
Recommendation: Start with the simple and safer relay swap. If that doesn't solve the problem, take it to a mechanic or use a scan tool to further diagnose the issue. A scan tool can read diagnostic trouble codes (DTCs) that might pinpoint the root cause more accurately.
