Injector Cleaning at Home
Derek and I pulled the head off the car last week. Among the list of to-dos while the head is off is to service the fuel injectors. Like most cars, the Miata has sealed injectors, but there’s still a bit an average person can do to keep them in top shape.
I initially was looking for a local place near San Jose, CA that could flow test, refresh, and retest the injectors, but I didn’t find anyplace (I also didn’t look very hard). There are a few well known shops that you can mail the injectors to, they service them, then mail them back. We’re putting the head back on in six days, so there isn’t time for mail turnaround — and I’m too cheap to pay for FedEx.
I came across this article on Pelican Parts’ website that detailed a procedure for reconditioning the injectors on a Porsche 944. Fuel injectors are similar in function and operation across most cars, so I figured I could give it a go on the Miata injectors.
The procedure entails forcing carburetor cleaner through the injector using compressed air. It sounds kind of hairy, but in reality it was really straightforward.
The first thing I did was to remove the rubber seals from the injectors and give them a thorough external cleaning. After I did this they basically looked new.
I cut a 2 foot length of 8mm fuel hose and used a hose clamp to attach it to a valve attachment on my air compressor’s hose.
Take the other end of the fuel hose and spray carburetor cleaner into it until it’s more than halfway full. Use a hose clamp to connect it to the fuel injector supply side.
Since the injector will not flow without current applied, it’s necessary to involve some electricity here. I then took the injector wiring harness from the car and probed one injector connector to see where the wires came out on the other side. Each injector has two pins. The other side of the harness has eight pins, so it was a short exercise to see which of the 8 pins I should use. I hardwired one of the pins to one terminal of a 9 volt battery, and crimped a terminal onto the end of the other wire so I could touch it to the other battery terminal to “pulse” the injector.
Here’s the whole setup:
So the compressor feeds the fuel hose, which is filled with carb cleaner. I set the regulator on the compressor to 40psi or so. After filling the fuel hose with carb cleaner, I’ll open the valve from the compressor hose to pressurize the fuel hoze. When the circuit connected to the battery is closed, the injector opens, spraying carb cleaner into the plastic tray.
I did each injector forward, backward (feeding the cleaner in through the ouput end — be gentle), then forward again. They all sprayed the same from the beginning, so I don’t think it will be a night-and day difference. But on the other hand I won’t be left wondering how it could have been.