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Thread: How To: Test fuel injector spray patterns

  1. #1
    Moving on DMage's Avatar
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    How To: Test fuel injector spray patterns

    Did this a while ago and didn't take any pics. Not a hard job to complete, but a good thing to check if you are having engine troubles (or just to check if you want to do it for maintenance).


    Tools:

    Flat head screwdriver
    10mm socket wrench
    6 glass mason jars
    Jumper (12-14 gauge wire with two prongs crimped on the ends)


    Steps:

    (1) Remove air filter box from intake to give you easier access to everything.

    (2) Pop off retaining clips from all 6 fuel injectors.

    (3) Remove injectors and place each one in a mason jar. Will take a few minutes to get everything sitting right around your engine bay if you are doing this by yourself.

    (4) Get into your electrical compartment, remove RPM relay, jump pins 30 & 87.

    (5) Turn key to 'acc' position (to power up everything without cranking the engine).

    Now your fuel pump is running because of the jumped wire. Go look at your spray patterns. Go look at pictures over on http://www.specialtauto.com showing the reference of how the injectors spray should look and what exact wires to jump.


    Stats:

    Electrical knowledge required: 4 (out of 10)
    Mechanical knowledge required: 3 (out of 10)
    Time: 30-45 minutes
    -Derek

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  2. #2
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by krs09 View Post
    I am getting ready to attempt this tomorrow and it seems to easy. Is this still the best way to check injectors? When jumping the RPM relay, will the jars fill with gas quickly or will it be just a slight mist if the injecttors are in good shape? My one concern is my fuel pump has a dedicated ground wire that attaches to the frame, will this effect how the pump will react when jumping at the relay? Wordy I know.. just really hope it as easy as it sounds.
    A couple corrections

    3) will take more than a few minutes - the forward injectors on the driver side are a pain

    5) no need to turn on the key. The RPM relay jumpered from brown to white/purple will power up immediately

    NOTE fuel will not (should not) should flow out of the injectors until you press on the air plate. Wide open should fill 6-ounce jars evenly in about a minute, at other flow rates look for spray pattern and even-ness across the 6 injectors.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  3. #3
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    Additional step when bad injectors are suspected:

    6) If some injectors are displaying a poor spray pattern or releasing anemic amounts of fuel compared to other injectors, DON'T automatically assume that you must have a bad injector(s), as it very well could be the fuel distributor causing this and not the injector(s) at all. To source whether the problem is indeed a bad injector(s) or actually the fuel distributor, change around the ports on the fuel distributor feeding each injector and re-run the test. If the same bad performing injector(s) from the first test setup continue to perform poorly while being fed by a port on the fuel distributor that previously showed OK with the injector originally hooked up to it, then it is indeed a bad injector(s). If an injector that showed OK during the first test setup performs poorly while being fed by a port on the fuel distributor that was originally feeding a suspected poorly performing injector during the first test setup, then your fuel distributor is at fault and will either need to be rebuilt or replaced.
    Last edited by NightFlyer; 08-19-2013 at 02:58 PM.

  4. #4
    Admins Never Retire Ron's Avatar
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    Or, you can simply take the injectors off and run the timed test. The volume delivered will be very close to the same amount (6 oz each)....tests the lines too.

    Mentioning the obvious, you should confirm that you have ~72 psi (5 bar) primary pressure first before all the above.

  5. #5
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    Quote Originally Posted by Ron View Post
    Or, you can simply take the injectors off and run the timed test. The volume delivered will be very close to the same amount (6 oz each)....tests the lines too.

    Mentioning the obvious, you should confirm that you have ~72 psi (5 bar) primary pressure first before all the above.
    Good point

  6. #6
    Junior Member TimD's Avatar
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    Quote Originally Posted by DMCMW Dave View Post
    A couple corrections

    3) will take more than a few minutes - the forward injectors on the driver side are a pain
    Hey Guys,

    Just thought I would share this to save owners some time and reduce worldwide cursing:

    I just moved into a new house and my garage is ill-equipped. After fighting for almost 40 minutes, I made a loop with some mechanics wire in order to release the clips. Works awesome! Did the driver's side in about 4 minutes (a few). So have at er!
    2014-02-13 21.27.04.jpg

  7. #7
    Senior Member
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    I sent my injectors to be cleaned out by John Hervey at Delorean Special T and he did a great job. Said he had to redo them several times to get the properly performing. The Delorean had not run for at least 7 years and it runs great now. I would recommend that if you thing they are not properly operating to have them cleaned anyway. Cheap to do and insures it is not a problem.

  8. #8
    Custom DeLorean Builder Rich W's Avatar
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    Quote Originally Posted by DMCMW Dave View Post
    NOTE fuel will not (should not) should flow out of the injectors until you press on the air plate. Wide open should fill 6-ounce jars evenly in about a minute, at other flow rates look for spray pattern and even-ness across the 6 injectors.
    Attaching a photo of Dave S. at work (before he "went pro", back in 2004) while testing the injectors (in jars) for the DCS 2004 Raffle Car.

    Fuel-Metering-Jars.jpg

  9. #9
    Senior Member OverlandMan's Avatar
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    I'm in the middle of doing this right now. I've got one injector that isn't spraying but rather just dripping. Another one sprays but is a bit sporadic. Can I just swap injectors between the one that isn't spraying and one that is to rule out the injector or fuel dist as the culprit?

    Also, wasn't aware that the air plate needed to be fully depressed. Is it supposed to have some resistance when you press it? Mine did when I pressed it in about half way. Then the resistance never recovered in the 5-10 minutes I was messing with it last night. I can check it again today when I get home.

    Here's a video of my test last night. You can clearly see the 1 injector not working correctly and the second one that is more sporadic. These two offenders are at the #1 & #2 cylinders.


  10. #10
    Ryan > Ruben Ryan King's Avatar
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    Bump.

    Any tips on cleaning the injectors?
    Living The Dream Since 2005 - VIN#3997

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