Testing WOT Fuel Pressure

Everyone should know that testing their fuel pressure during WOT is not only the best way to determine if there is any issue with the fuel system, but it is often the cheapest, quickest and easiest.

Unfortunately, people think it’s a nearly insurmountable task and its last thing you'd ever do when diagnosing a suspected fuel system issue. The whole process isn't very hard, in fact, it’s very easy and NO, you don't have to buy some ridiculous racer in car gauge. However, you should have the means to test fuel pressure at the fuel rail before you ever think about installing a fuel pump.

First off, get yourself a decent gauge. Not a liquid filled, cheap 1/2" diameter play toy you find on most regulators. Get a real gauge- 2.5" diameter or bigger, 100psi minimum. Every autoparts store has one type or another in stock and you'll find them all over Ebay. Should be less than $40. Even this cheapo from Harbor Freight will do.

If you have a 2003 SRT-4 you're pretty much done. This is because 2003s already have a Schrader valve port on their fuel rails. On 2004-2005, the fuel rail won't have a pressure sensor port, if you simply look in the Factory Service manual, you'll see Mopar's nifty solution--> Miller Tool 6539. A quick Google search finds the exact part you need for less than $35.

You're not quite done yet. You need to see the gauge while driving but most gauge kits you'll find for less than $50 only have ~2ft hose, which won't get the gauge out from under the hood. Luckily, old R12 refrigerant hoses use exactly the same fittings and are practically indestructible. Note: size 3/16” 45 deg flare, 3/8-24 thread. IT IS NOT A -4!!! THE SIZE IS 3/16” 45 DEG FLARE.

A 3/16” 45 deg flare splice from your local hardware store or a $10, 36" long R-12 A/C hose, either new or off an old A/C charging set, works great to extend the fuel pressure gauge to wherever you need it. I prefer just to tape it to the windshield to test WOT fuel pressure.

If you have already run new supply lines but didn't provide yourself an easy way to test fuel pressure, something like this little gem is exactly what you need.