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Troubleshooting a missing injector?
I am dealing with my 351W conversion. It has a custom chip by Johnson, and its a '90 EEC IV At times I wish I had just gone with a Carb. But here is what I have found. The engine is definately missing a cyl. I now believe it to be #7. I have ran many tests on the engine and haven't been able to determin where the miss was until I did a Cylinder Balance Test. I did the self test and when it started I could tell when it shut off #8 and there was quite a long pause and then the rest came in the normal sequence. So I restarted the test just to make sure that I counted right. It is #7 that is not firing, I only have a code flasher and not a digital readout so I did not get the number of the failed cyl nor did I get a pass code. I did get a code of 76 which turns out to be insufficient VAF change during dynamic test, But I dont know what it means. So I then tried to check the power going to the injector it does have 12v going to it when the key is on but I couldnt measure the pulses with my regular multimeter they were too fast for it. I also checked the resistance of the injector and it was the same as the others. I then put in new plugs in #6 an #7 I will run it tomorrow and see what they look like. In case you are wondering I have checked spark and compression, both good. I also did the key on engine off test and got a #15 which is ECA read only memory test failed and or ECA keep alive memory test failed. So I am wondering if maybe my computer is screwed up or what. I need to know if there is a good way to tell if the cylinder is getting fuel. And any other ideas anyone might have.
Thank You very much. ------------------ '90LX powered by ('69 351 EFI) [This message has been edited by MuscleStang351 (edited 04-09-2001).] |
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I'm wondering the same thing, jimberg. Also, you can test injector pulses with one of those noid lights. It's basically either an LED or a neon bulb, I don't know which, but it'll flash if it's getting the right pulse. How did the plug look that came out of #7? Wet or dry? You shouldn't be getting a code 76 from a 1990 EEC-IV computer, either. VAF was never used on Mustangs. This makes me wonder if the computer or that chip is messing something up. What's the Ford part number on your EEC-IV computer?
------------------ Capri306, Moderator, The Mustang Works Online 1979 Mercury Capri, 5.0L -- C4 -- 2.73 1987 Mustang LX Notch http://smilecwm.tripod.com/net3/wink2.gif |
I got a noid test set, I was able to try the left side injectors today at lunch time. They all pulsed the same :-( Then I listened to all of them with a screwdriver and they were all clicking (all 8). Without the custom chip it runs the same but just hunts at idle and stalls more. The computer is the stock gA9L. I put two relatively new plugs in #6 & #7 today they looked about the same and were dry after driving about 10 miles. I think I will try to pull the fuel rail off with the injectors in it and try to turn it over to see if they squirt. I just dont know if I can do it wothout them cumming out of the rail under pressure.
Later and thanks very much for helping. Bruce [This message has been edited by MuscleStang351 (edited 04-10-2001).] |
This may sound simplistic, but when I had a bad injector I found it by starting the engine cold and feeling for a header pipe that doesn't heat up as quickly or as hot.
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PS - another way I've found to tell a less hot header pipe is wetting them and seeing which one steams longer or starts steaming later, or spraying a dab of WD40 on each one and see which one cooks off slower & later
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Well I am now confused, I tried the water trick on the headders and they all dried off at the same time. I wonder if I should try the WD40 now too see if its just a little less hot on the one cylinder?
Thanks for the help Bruce |
Ok check it out, I put oil on all the headers out of each cyl. I ran it and the oil cooked off all of them but cyl #5 and #7. So now I am going to start all over and do another compression test and get new plugs and run it and then see what I get. I feel like I am going in circles....
Thanks again Bruce |
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