how to test the fuel injector - PeachParts Mercedes-Benz Forum

bpaz_ph · #1 09-21-2006, 10:23 PM

190e 87 2.3 8v.

Is there a way for a backyard mechanic to check the spray pattern of the injectors.

Thanks in advance.

Gilly · #2 09-22-2006, 05:03 AM

Maybe take the injector out, bend the line, and have someone crank the car while you watch the injector. I don't think they recommend bending those lines too much though.

Gilly

bpaz_ph · #3 09-22-2006, 12:45 PM

I had the same idea but what steps should I take to make it right. Like unplug the ignition control. Do I unplug the fuel pump relay and jump 7 & 8 pin. Stuff like that.

tvpierce · #4 09-22-2006, 01:34 PM

Here's my shade tree injector cleaner/spray-pattern tester:

Materials:
Air compressor with regulator & blow gun (or some kind shut-off valve)
2 foot length of 3/8" clear vinyl tubing
1 Brass plumbing adaptor to go from the blow gun threaded outlet to a 3/8" barbed connector
2 small hose clamps
1 bottle of Techron fuel injector cleaner.
1 clear soda/beer bottle

Set your compressor regulator to the spec for the fuel system on your car. (I think about 70 lbs... is that right Gilly?)

With injector removed from car, attach the vinyl tubing to the threaded end of the injector. (3/8" is intentionally too small -- it has to be tight, you have to stretch it with a pair of needle nose pliers, then twist the tubing on the threads of the injector to pull it on.) Then put one of the small clamps over that connection. This connection will drip a few drops while pressurized, but nothing of any consequence.

Next put the brass barbed plumbing connector on the other end of the tubing, and clamp that connection.

Fill the tube with Techron.

Thread the brass plumbing connector into the blowgun.

Hold the injector in the mouth of the soda bottle.

Squeeze the trigger on the blow gun. The air pressurizes the fluid and pushes it out the injector into the soda bottle.

Refill tubing with Techron and repeat as necessary.

This will show you the spray pattern, while at the same time, running straight Techron through the injector to clean it.

Granted, this is not going to give you the results you'd get if you send them out for professional cleaning. But it's a pretty good system for shadetree work.

Jeff Pierce

danwatt · #5 09-22-2006, 02:16 PM

When I worked at the auto parts stores, we would have some slow days. One Sunday, with an average of 3 customers an hour, we decided to clean the injectors on a co workers Honda Accord.

We got a fuel pump, a 12v battery, some wire, hoses, and a bottle of fuel injector cleaner. Then we would apply 12v to the solenoid on the injectors, turn the pump on, and ran it through. Worked out pretty well, his car was definetly a little peppier after that.

However, this is probably very bad advice, we just thought it was worth a shot.

Kestas · #6 09-22-2006, 03:49 PM

I was told that 12v is rather risky to use to energize the injector... 4-5v ought to do it.

Otherwise I like both ideas.

I have access to an ultrasonic cleaner at work. I fill the bath with alcohol, fill a clear tube with alcohol and connect it to the injector tip, hook up a power supply to open the injector, and blow to reverse flush the injector.

I just rejuvenated 8 injectors that were gummed up from 10 years of sitting on a junk car. I think reverse flushing and ultrasonic cleaning is a superior way to clean the injectors before testing the flow pattern.

bpaz_ph · #7 09-22-2006, 05:12 PM

Hi kestas,

How were you able to reverse flush the injector. Aren't they one way valves? Anyway I think mine is since it's mechanical injection. I don't even think mine has gummed up. Any ideas would be a great help for us DIYers.

When I tried to flush my injectors with carb cleaner and then I shook out the excess on a piece of white paper, dirt marks were left behind when the cleaner dried up. I researched further and found that each injector has a filter to catch any debris that might have excaped the fuel filter. So I guess the only way to clear the filter is by reverse flushing.

Thanks for the info.

Kestas · #8 09-22-2006, 06:15 PM

There's no one-way valve in the injector. They're just pintle valves... much like a spray gun. Other cleaning methods will remove soft deposits, such as wax and varnish. But if there are hard particles in the system, reverse flushing will (hopefully) move them back the same path they came from, out the inlet.

I got the idea from reading the info from on-line injector cleaning services. They too use ultrasonics and reverse flushing. They also check the flow balance among the injectors to make sure each set flows the same amount.

The beauty of tvpierce's setup is that - if done carefully - one can use this to check the injectors for flowrate and perhaps identify an oddball. Then you've done everything a professional cleaning service can do.

Bob Weir · #9 09-22-2006, 06:58 PM

A little off topic, but fyi.

I had Cruzin Performance clean & test injectors for both my Scorpios. It's my understanding that the flow rates should be very close to each other for proper performance. $12 ea. and a few dollars for shipping, I felt was a good investment. And if you have a bad injector, he might have a used one within range of your others.

http://www.cruzinperformance.com/fuelinj.html

Bob

Gilly · #10 09-22-2006, 08:51 PM

In regards to my "poor mans" method of doing it, just disconnect the coil wire.
Gilly

Arthur Dalton · #11 09-22-2006, 09:53 PM

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.. yup...and stick the injector into the top of a glass mayo jar.. then you catch the gas and can see the spray pattern...........just drill a hole into the lid a little larger than the injector diam.