jackballs529

I have new 24# Accel injectors but suspect a problem. Iratic timing along with a miss. How do I check them? Another big issue is I can only get to a few of them since I have a Superram intake. I would need to pull the intake to get to the rest.

3.8TransAM

First:

pull the connector to the inj. and ohm them out, not sure what accel should be at, but stock inj, were around 16-17ohm.

Your should be 12+ohm more than likely and just look for a good grouping, they should be all near 14 or 15ohm. Not one a 10 and one at 15 etc.

Hook up a FP guage.

Get some hose clamp pliers

Turn the key on and block off the feed and return lines(where they turn to rubber on the bend to the fenderwell).

See if your fuel pressure holds steady. If it drops its losing it at the injectors(bledding down)

Then unhook the one to the fp and see how well it holds pressure.

the less the drop on either test, the better off u are.

Completely sealed injectors should hold for 45-1hr or so.

If u have to take them off, pull the rail as a unit and prime the car and try and see what one(s) are leaking. (laying some paper towels under the inj. might help spot it, at least catch the drip)

later
Jeremy

porkyzilla

iTrader: (1)

accels are 14.2ohms,

HalfInchWrench

It's not always a leaking problem or something you can find with a multimeter. Sometimes they are just plugged up with dirt.

Vader

12Ω is right. The resistance test of the solenoid coils only determines if the injectors are electrically viable. It says nothing about pintle actuation, inlet screen contamination, leakage, inadequate flow, poor spray patterns (dripping or streaming), and whether the injector actually even opens. All of those will affect how the engine runs, and an ohmmeter won't give you a clue.

Perform the resistance test using Porky's numbers, just to be sure the coils are good. Test the leakage as 3.8 suggests. Then keep your tools handy and finish up with a power balance test. Make sure you have a good tachometer with a lower RPM scale for better resolution.

You can perform a power balance test with a tachometer. Don't rely on the one on your dash, since it isn't graduated precisely enough to register any significant difference.

1. Start the engine and allow it to reach full operating temperature.

2. Stop the engine.

3. Bypass the EST circuit to prevent the ECM from trying to correct for any changes while you temporarily disable each cylinder.



4. Locate the ALDL connector under your dash panel.



5. Insert a jumper in the ALDL connector between terminals 'A' and 'B', then turn the ignition to RUN without starting the engine.



5. Wait at least twenty seconds for the IAC stepper motor to extend fully, then disconnect the IAC electrical connector.



6. Turn off the ignition and remove the ALDL jumper wire. This will force the engine to run only on throttle body bypass air and will again prevent the ECM from adjusting the idle speed or timing to compensate for your disabling of cylinders.

7. Connect your tachometer.

8. Restart the engine and allow it to idle. If there is any difficulty in getting it to maintain idle, you may have to temporarily increase the minimum air position of the throttle plates by turning the adjustment screw - just count the number of turns since you'll have to reset it later. Try to set it at a nice round number, like 600RPM or so. (See diagram above)

9. Unplug the electrical connector from one injector and monitor the engine RPM as it is disconnected. Wait at least ten-twenty seconds to make sure any liquid fuel can be cleared out and won't affect your readings. The drop in idle RPM should be relatively equal through the firing order. Replace the electrical connector and go on to the next injector. Understand that the ECM will sense the RPM drop and attempt to compensate by adjusting the IAC, which is why it was disconnected in the first place.

10. Reset the throttle stop screw if you moved it, and reconnect the IAC, EST bypass connector, and anything else you may have disconnected to perform the test.

Compare your results from each cylinder. If one or more injectors caused little or no change in RPM, it is not flowing fuel at the correct rate. NOTE: This test will not be accurate if the ignition system is not in good order or compression is low on a cylinder.

This test allowed me to identify two defective injectors, and test results after removal of the injectors confirmed that - two of them had very poor spray patterns and low flow rates. The engine had 18,000 miles and I had already tried several types of injector cleaner in the fuel tank with no improvement.

As always, if you discover a bad injector, I would recommend contacting Cruzin' Performance or another reputable injector service.

jackballs529

All awesome info. thanks...

Some further thoughts. Vader, your tests will mostly not work as I can't get to my injectors due to the Superram. I think I might be able to get to 4. Front drivers side and rear passenger side.

I was thinking about pulling my plenum and dueing the quick leak down test by pulling the fuel rail with the injectors and prime the system.

I would like to do the OHM test, exacty how do I do that? If I have it apart obviously I can't run the car, can I still do the OHM test to rule out electronic failure? I would like to check to see if the ECM is sending the correct pulses, could ecm failure be possible?

By the way my 355 rebuid has about 300 miles on it so cylinder issue should not be likely. Also, the car does not want to start cold. I have to open the throttle blades and play with it then it fires and I get a cloud of fuel out the exhaust. I think its an injector leak down problem. A lot of guys talk bad about the excel injs. I am so frustrated that I am thinking about buying the Ford SVO 24#er's and be done with it.

Vader

In order to perform the resistance test, you need to have access to the electrical connectors on the injectors - just as you would for a power balance test. You may be S.O.L. on that one.

As for the ECM, it fires all the injectors in a bank at the same time. As long as the wiring is intact (here we go again with access to the connectors) the injectors will all get the same firing signal. The injectors are actually all fired at the same time, provided both INJ fuses are good.