Troubleshooting a missing injector?

MuscleStang351 · 04-09-2001, 10:22 PM

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.

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'90LX powered by ('69 351 EFI)

[This message has been edited by MuscleStang351 (edited 04-09-2001).]

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04-09-2001, 10:22 PM	#1
MuscleStang351 Registered Member Join Date: Apr 1999 Location: Killeen TX, USA Posts: 113	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).]