The Test To Find The ‘Spider’ Problem

When I read Jim's e-mail, I knew the next step (for him) was to see if the ‘Spider’ injector assembly was injecting fuel.

This is what I e-mailed him back:

There is a way to see if the spider fuel injectors are clogged and not spraying and I have done it several times but this is not a test for everyone. This method is used at the shop were I work quite a bit, and it's done by taking several important safety precautions. This is the test:

1.) Remove the plenum.
2.) Reconnect the metal fuel lines to the spider assembly (if you disconnected them).
3.) Disconnect the ignition coil's and ignition module's electrical connector -THIS IS CRITICAL- do not proceed without doing this.
4.) Pull one fuel injector from its cavity in the intake manifold.
5.) Have a helper crank the engine while you observe the fuel injector. if it's not clogged, it will spray fuel. You should have a rag somewhere between it and the engine so that the fuel sprayed will not spray all over the engine.
6.) Repeat this test on the remaining injectors (nylon fuel lines).

Now, you need to make sure that nothing falls into the the open ports in the intake manifold, 'cause the only way to fish anything that falls into to them is to remove the cylinder head.

This test works to check them, now having said that, it's a bit risky for the reasons mentioned above. So if you try it, take all necessary safety precautions. Your safety is your responsibility and I offer this test only as advice and as an opinion and therefore assume no liability.

If you do find they are clogged, the only viable option is to replace the whole assembly once again.

The steps to see if the ‘Spider’ is actually injecting fuel are pretty straightforward and in the reply to Jim (above), the steps are pretty much self-explanatory but I'm gonna' add some more thoughts on the subject.

Here are the main points of the steps listed above:

  1. Remove the upper intake manifold plenum.
  2. Disable the ignition system (ignition coil and ignition control module).
  3. Reconnect the ‘Spiders’ injector's electrical connector.
  4. Remove one and only one fuel injector nylon tube from its place on the intake manifold.
  5. Have helper crank the engine to see if the nylon fuel line sprays fuel.
  6. Once you've verified if the injector is spraying or not, RE-INSTALL the injector back into its cavity (in the intake manifold) and proceed to the next one.

It's a pretty simple test, although I can't claim that it's easy to do (since quite a few things have to be removed to do it) AND you have to keep in mind the following important safety precautions:

  1. Prevent objects from falling into the lower intake manifold.
    1. Since the upper plenum has to be removed (for this test), this opens up the possibility of something falling into the open lower intake manifold ports.
    2. If something does fall into them, it'll usually end up inside the engine cylinder and usually the only way to retrieve it is by removing the cylinder heads.
  2. Fuel is extremely flammable.
    1. You need to have the nylon fuel line pointing to a rag (shop towel). The shop towel's job is to get hit by the fuel being sprayed and keep the fuel from soaking the intake or the valve covers.
    2. You need to test them one at a time.
  3. Disable the ignition system.
    1. This will prevent spark from reaching the spark plugs and causing a back-fire thru' the intake manifold.

As you see/read above, this test does have some inherent risks which are fire and engine damage (if something falls into the open intake ports without your knowledge and you crank the engine). These can be overcome with a few precautions but the risks remain. So you might be asking yourself: Is this the only way to test for a clogged ‘Spider’ assembly?

The answer is: No, this is not the only way to do it. The above test works (I personally have done this test several times as have my fellow techs at work and well, Jim did it too without any dire consequences). But, this method might not be your ‘cup of tea’. In this case, there is a different method and it involves using a fuel pressure gauge and the OTC 3398 Fuel Injection Pulse Tester (like the one in the box on the right).

Why didn't I recommend this other way in the first place? These are the main reasons:

  1. You might not have the tools.
  2. The tools are expensive.
  3. You're an experienced ‘wrench-er’ and have removed the intake plenum before and are comfortable working around and in the engine.

Let's turn the page and find out about the second method.



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