Testing for a bad injector
 

re:92 400E, 140k

I have a misfire on cylinder #8. It idles rough and pulling the spark plug wire on number 8 has no impact - so I know 8 is the problem. It's getting a spark and it has good compression - so I'm guessing that I'm not getting fuel in that cylinder. How does one test for a bad injector?

For a quick and simple test, I’ve used a mechanics stethoscope to listen for a “clicking” noise coming from the fuel injector by placing the tip of the stethoscope on the injector. Compare the sound of #8 to the other injectors that are performing. I’m sure if you’ve done any searches you have seen numerous references to the engine wiring harness. What’s know as the main engine wiring harness, houses the wiring for the fuel injectors. If the wiring connecting to your problem injector is faulty, it might be the source of your problem.

Of course you probable want to perform a injector leakage test and a spray pattern test.

In addition to the above injector test, be sure to check the spark plug, simply switch with another cylinder to make sure your getting spark to the chamber

I put in a new spark plug and the wiring harness has been replaced so I'm pretty sure it's the injector that's the problem. I'll try the stethoscope to see if I can hear anything unusual. I suppose the injector leakage test and spray pattern test requires special equipment at a shop. I guess I can also try swapping injectors to see if the misfire follows the injector to the other cylinder.

When you determine the injector is the problem, you can send it to http://www.cruzinperformance.com/fuelinj.html. For $12 + shipping he'll clean and flow test it for you. The flow test will tell if it's ok to use.

Rich is the owner/operator and you can call him to verify scheduling. I'm a very satisfied customer.

Bob

Bob, thanks I think I will try that - given the cost of replacement injectors these days.