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My memory is not to place an oath over, but I think I recall all of the injectors have a light buzz for each test of each solenoid. Only the tested solenoid is loud. So... if you hear only a light buzz when you should hear a loud buzz, that is likely the opposite head doing its thing.
One other buzz under the hood would be the vacuum pump - particularly if you have a vacuum leak. Is your vent stuck on defrost?
Just an idea , But maybe do the buzz test at night with engine compartment is dark. Might be able to see a spark.
There was nothing sparking at night. IT sounded and looked just the same as during the day. This was a good idea though that I would not have thought about. Thanks for the suggestion.
Originally Posted by Bonanza35
What did you find?
Originally Posted by Tugly
My memory is not to place an oath over, but I think I recall all of the injectors have a light buzz for each test of each solenoid. Only the tested solenoid is loud. So... if you hear only a light buzz when you should hear a loud buzz, that is likely the opposite head doing its thing.
One other buzz under the hood would be the vacuum pump - particularly if you have a vacuum leak. Is your vent stuck on defrost?
I did the buzz test while under the hood and what Tugly said here appears to be what is happening. The light buzz is coming from the passenger side injector solenoids. I did not get the chance to apply the dielectric grease yet. I thought I had some at home but I couldn't find it. ( probably put it up somewhere so I wouldn't lose it. Happens all the time. ) I stopped at the auto parts and bought some so I will do this tonight. Hopefully that will be something revealing. thanks for all the suggestions. My only thoughts is that it has to be something in the wiring that I am missing. I am going to take the harness apart from the IDM to the 42 pin connector and see if it is something in there.
I would start taking readings from the 42-pin connector because it's easier to reach and not make errors. There's a good link in my signature that covers this.
Some quick thoughts...
If you have both valve covers off try switching sides with the UVCH see if anything changes.
When you pulled and checked your harness did you use continuity check or apply 12volts to each wire to see if they would actually carry a full 12volts.
When you ohmed from 42 pin connector did you shake the harness while taking the readings? ( Easier to do with a helper )
You said you tried a new injector , did you swap it out individually for each of the injectors on the left side, and then clear codes and retry buzz test?
You could probably just switch the solenoid as the buzz test is strictly electrical anyway.
Is there a chip on this truck? I see you switched PCM's so will assume it is stock.
Some quick thoughts...
If you have both valve covers off try switching sides with the UVCH see if anything changes.
When you pulled and checked your harness did you use continuity check or apply 12volts to each wire to see if they would actually carry a full 12volts.
When you ohmed from 42 pin connector did you shake the harness while taking the readings? ( Easier to do with a helper )
You said you tried a new injector , did you swap it out individually for each of the injectors on the left side, and then clear codes and retry buzz test?
You could probably just switch the solenoid as the buzz test is strictly electrical anyway.
Is there a chip on this truck? I see you switched PCM's so will assume it is stock.
Just some ideas ,
I do not have both valve covers off but I do have 4 brand new UVCH two of which are FORD and two are cheapies. I have tried all of those to no avail.
I did a continuity test on the harness. Applying 12 volts is a good idea. I will try that.
I did not shake the harness but I took it apart and traced each individual wire to make sure there were no bare spots. I suppose there could be a break inside the insulation though. I will try that.
I only tried the injector in the #4 hole. Since it did not make and difference at all I did not try the others. I do have a full set of injectors I could put in if I could get the buzz test to work at all.
Your assumption is correct, this truck is stock with no chip.
Thanks for the ideas. I will try these when I get home tonight.
I am still curious as to why 2, 4, 6, & 8 ohm out at nominal. What are the odds that bad circuits to those injectors would have the correct resistance?
Another thing to try is to unplug each injector one at a time and try to start
as I understand it One injector with an open or low ohm reading can shut the whole bank down.
If unplugging 1 gets the other 7 to work you've at least narrowed it down
To illuminate further what Rich mentioned, during the buzz test all injectors get a light buzz, but the sequence 1 thru 8 gets a stronger buzz. I read this protects the injectors but I don't know how. So what you are listening for is a strong buzz (cylinder 1-8 in order) vs a light buzz that all the other 7 injectors are getting every time.
At this point I'd pull the PCM and IDM connectors and look for a distorted pin. IDM will shut down a bank and throw a P1316 code when it's not happy. And since both were swapped recently that was an opportunity for a bent pin. And continuity check wires from both connectors to 42 pin. These may help.
Speaking of 42 pin, any sign of chaffing on the underside of the harness where it crosses the valve cover?
I am still curious as to why 2, 4, 6, & 8 ohm out at nominal. What are the odds that bad circuits to those injectors would have the correct resistance?
That is what is puzzling me. I am testing the ohms from the IDM plug. That would indicate to me a good circuit all the way to the injector and back. This is why I am stumped as to where to go next.
Another thing to try is to unplug each injector one at a time and try to start
as I understand it One injector with an open or low ohm reading can shut the whole bank down.
If unplugging 1 gets the other 7 to work you've at least narrowed it down
I tried this. I was thinking the same thing you are. I unplugged each injector one at a time and cleared the codes in between. Still not working. I then plugged each injector on that side in one at a time with the other 3 unplugged to see if just that one injector would start firing. Still nothing.
To illuminate further what Rich mentioned, during the buzz test all injectors get a light buzz, but the sequence 1 thru 8 gets a stronger buzz. I read this protects the injectors but I don't know how. So what you are listening for is a strong buzz (cylinder 1-8 in order) vs a light buzz that all the other 7 injectors are getting every time.
At this point I'd pull the PCM and IDM connectors and look for a distorted pin. IDM will shut down a bank and throw a P1316 code when it's not happy. And since both were swapped recently that was an opportunity for a bent pin. And continuity check wires from both connectors to 42 pin. These may help.
Speaking of 42 pin, any sign of chaffing on the underside of the harness where it crosses the valve cover?
Yes I get a very light buzz on 2,4,6,8 and a loud buzz on 1,3,5,7.
I have done a continuity test from the IDM to all the injectors and back to the IDM plug. They all come good. My thought is that if there was a bad connection from the PCM to the IDM then the other 4 cylinders would not fire either. Is that wrong thinking? Is there a separate circuit for each side from the PCM to the IDM. I am also thinking the issue must lie somewhere with the IDM or PCM plug not making good connection. I have tried 3 different IDM modules in this truck which all work in my other truck so I am fairly certain it is not the IDM or PCM since I also have 3 different PCM modules that work in the other truck. It is nice to have another truck to try these parts in.
I have checked the wiring where it crosses the valve cover and there is no chafing there.
I am leaving for a 1.5 week vacation so I will not be able to work on the truck for a while. I appreciate all the ideas you are giving me and I will pick this up when I get back from vacation.
Thanks for all your help. This forum is GREAT!
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) I stopped at the auto parts and bought some so I will do this tonight. Hopefully that will be something revealing. thanks for all the suggestions. My only thoughts is that it has to be something in the wiring that I am missing. I am going to take the harness apart from the IDM to the 42 pin connector and see if it is something in there.
