What These Parts Actually Do
I've had my hands inside more LPG converters than I care to count. The heart of any LPG system is the vaporizer—a small aluminum block with a diaphragm and a coolant-heated chamber. Gasoline runs at atmospheric pressure, but LPG is stored as a liquid under about 10 bar. That pressure has to drop to near zero before the engine can burn it, and that's the vaporizer's job. It uses engine coolant to heat the liquid, turning it into a vapor that the mixer or injectors can handle. The diaphragm inside is a delicate piece of rubber that responds to pressure changes, and when it gets hard or cracked, everything goes sideways.
Beyond the vaporizer, you've got the solenoid valves—those click when you turn the key, shutting off fuel when the engine dies. There's also the regulator, the mixer (if it's a carbureted setup), and the injectors on sequential systems. Each one has a specific task, but they all share one thing: they're mechanical parts that wear out. And when they fail, they don't do it quietly.
Common Failure Symptoms
The most obvious sign of trouble is the engine running rough or stalling at idle. That's often the diaphragm in the vaporizer losing its flexibility, so it can't hold the right pressure. You might smell gas—not the rotten-egg odor of gasoline, but a faint, sweetish smell that's unmistakable if you've been around it. Another red flag is the engine backfiring through the intake, which can happen when the mixture goes lean because the vaporizer is delivering inconsistent pressure.
On sequential injection systems, you'll get fault codes for individual injectors. Those injectors are tiny solenoids that pulse open and closed, and the coil windings can short out or the needle can stick. You'll notice a loss of power and fuel economy, and the check engine light will drive you nuts. Solenoid valves, on the other hand, often fail as a stuck-open or stuck-closed condition. A stuck-open valve means fuel leaks into the engine even when it's off—not a good day. A stuck-closed one just means no fuel, so the engine cranks but won't start.
Used OEM vs. Cheap Aftermarket
Now here's where I get preachy. I've seen guys slap on a $30 aftermarket vaporizer from the internet, and it works for a month, then the diaphragm swells and warps because the rubber compound is garbage. You might save a few bucks upfront, but you'll be doing the job twice. A properly inspected used OEM part, pulled from a wrecked car that had 60,000 miles on it, is a different animal. The OEM engineers spent millions testing that diaphragm material—they know exactly what rubber blend handles LPG's hydrocarbons and the heat from the coolant. The aftermarket copy might look identical, but the tolerance on the valve seat is off by a few microns, and that's enough to cause a leak or a pressure fluctuation.
I'm not saying every aftermarket part is junk. There are reputable brands that make good stuff. But the cheap no-name stuff that floods eBay and Amazon is a gamble, and the odds are stacked against you. Used OEM gives you the original design, the original materials, and a part that was working when it was pulled. You just need to make sure it was inspected properly—that's the key.
What to Check Before You Buy
Before you hand over your cash, ask the seller for specifics. Was the part pressure-tested? A good seller will have tested the vaporizer with nitrogen or at least checked the diaphragm's condition. Look at the condition of the mounting flange—if it's corroded, that's a sign the part sat in moisture, and the internal valve may be pitted. Check the solenoid coil resistance if you can; it should be within the OEM spec, and you can usually find that online.
Also, check the date codes if they're visible. LPG parts have a service life, and a vaporizer that's been sitting on a shelf for ten years is not the same as one that was in service. The rubber degrades even without use. And don't forget the hoses—if you're buying a kit, the hoses should be rated for LPG, not just any rubber hose. LPG will eat through standard fuel hose in no time.
One more thing: make sure you're getting the right part for your system. A vaporizer for a 100hp engine won't flow enough for a 300hp truck, and an injector from a different model might have a different spray pattern. Get the exact OEM part number if you can, and cross-reference it.
So, you've got a failing LPG part, and you're weighing your options. Take it from someone who's seen the aftermath of cheap parts—go with a used OEM part that's been inspected. It'll save you money in the long run, and you won't be stranded on the side of the road.
Check the current listings for LPG parts on this site—they're all inspected and ready to go.
