Injector efficiency test?

[BHaner]

Question... Does yours only have this miss, and smoke when it has been sitting for about 4 hours or so?



Or will it do it at random times? Hot, cold, etc.

 

[steved]

Only after its cold soaked overnight... getting worse now its gotten colder.

 

[steved]

OK, I got a technical question... since this is nothing more than a electrical solenoid, can it be tested by the home mechanic?

I have access to the terminals on the head (and even if I need to pull the valve cover to get better access)... if I read ohms across the terminals, would I see any difference between one that is weak and one that is good??? Would it be worth looking at?

There has to be a way to test it, or the ECM would not be able to do this efficiency test either...

On rethinking this, I may pull the valve cover this weekend and simply see if there is any difference. I will also talk to my father, who is an electrician and see what his thoughts are.

 

[Wayne M.]

OK, I got a technical question... since this is nothing more than a electrical solenoid, can it be tested by the home mechanic?



I have access to the terminals on the head (and even if I need to pull the valve cover to get better access)... if I read ohms across the terminals, would I see any difference between one that is weak and one that is good??? Would it be worth looking at?



There has to be a way to test it, or the ECM would not be able to do this efficiency test either...



On rethinking this, I may pull the valve cover this weekend and simply see if there is any difference. I will also talk to my father, who is an electrician and see what his thoughts are.

Steve, yes you can check for resistance,but that may not tell you much other than a good/bad test. I am led to believe that these injectors are fired just like gasser injectors. If this is true, there is full voltage going to the injectors and they are fired by completing the path to ground. The computer controls this by varying the grounding time in milliseconds. You might want to look at the voltage going to the injectors (I believe 12V, not sure, could be more) when things act up. Possibly there is something going on with the drivers that power the injectors. In any event, be careful because this is a delicate circuit.

To give an example of how low voltage can effect things, at work I have a series of trucks that have an elaborate PTO system that watches for low oil level, blocked filters, etc. If the alternator stops charging, the first thing to go is the Hydraulics. If someone tries to diagnose a no PTO problem, woud they go right to the charging system? I doubt it. We found it the hard way, but sure enough this is a pattern failure. Our guess is that when the alternator stops putting out, the first thing to go is the relay that controls this circuit. It still starts, runs fine etc. but you'll loose PTO. I believe you have a problem that needs "thinking outside the box". I could be wrong too, but you saying that it acts up only when the grids cycle- that raises a flag to me.

 

[steved]

Steve, yes you can check for resistance,but that may not tell you much other than a good/bad test. I am led to believe that these injectors are fired just like gasser injectors. If this is true, there is full voltage going to the injectors and they are fired by completing the path to ground. The computer controls this by varying the grounding time in milliseconds. You might want to look at the voltage going to the injectors (I believe 12V, not sure, could be more) when things act up. Possibly there is something going on with the drivers that power the injectors. In any event, be careful because this is a delicate circuit.

To give an example of how low voltage can effect things, at work I have a series of trucks that have an elaborate PTO system that watches for low oil level, blocked filters, etc. If the alternator stops charging, the first thing to go is the Hydraulics. If someone tries to diagnose a no PTO problem, woud they go right to the charging system? I doubt it. We found it the hard way, but sure enough this is a pattern failure. Our guess is that when the alternator stops putting out, the first thing to go is the relay that controls this circuit. It still starts, runs fine etc. but you'll loose PTO. I believe you have a problem that needs "thinking outside the box". I could be wrong too, but you saying that it acts up only when the grids cycle- that raises a flag to me.

I posted this in my other thread...



I just spoke with a CTD tech at the local garage... I explained the issue, the mods to the truck, and what I had done already. These are his thoughts:



1) DC can do a balance test, where they turn individual injectors off, but he was not aware of an efficiency test.



2) Test the resistance of each solenoid, see if one is low/high when compared to the others...



3) Pay particular attention to the under-valve cover wiring and connectors to see if one is cracked/stripped.



So I now have a starting point. I can at least start to methodically narrow the issue down with some sort of testing that will provide actual numbers. I fully plan to pull the valve cover off sometime this weekend, but I need to install a radiator in my DD first.





I am going to assume, for the time being, that nothing is wrong with the ECM controlling the injectors, and that it is something in the injector circuit since that was the only thing that has changed in the past year.



If I cannot determine a potential culprit by measuring resistance, I will most likely be forced to take it to Dodge and have it diagnosed. That's if I don't trade it first...

 

[AH64ID]

That's if I don't trade it first...

You're not going to trade because of this are you?

 

[steved]

You're not going to trade because of this are you?

If its not resolved by the first of the year, this truck will be peddled. We need a new 4-door for the wife, and I'll trade this truck without batting an eye. We were going to keep it, but not if I can't cure this issue... I'm tired of spending $$ and amassing spare parts on a truck that should not have an issue before 200k.



And then I'll revert back to my original plan, a 12-valve... that's if I even buy another dodge or diesel after this episode. My co-worker's Hemi looks better everyday I deal with this POJ.



Hind site is always 20/20... I should have never traded my 1999 on this POJ...

 

[Bob4x4]

I would say do not try to power up the injector. It uses a hi volt low amp very short duration pulse. you will fry it. As far as the resistance of the coil they have a wide range of acceptible limits. Seeing that it is intermitant good luck reproducing the failure. I doubt the dealer will be able to find the issue in 2 hours time. If it hasn't set a code yet,I doubt checking resistance will help much. The ECM cks current flow through the injector ckts. Have you disconnected your grid heaters before starting it cold?



Bob

 

[Bob4x4]

If your origional injector issue was due to contamination did you replace all the system or just injectors?

 

[Wayne M.]

I would say do not try to power up the injector. It uses a hi volt low amp very short duration pulse. you will fry it. As far as the resistance of the coil they have a wide range of acceptible limits. Seeing that it is intermitant good luck reproducing the failure. I doubt the dealer will be able to find the issue in 2 hours time. If it hasn't set a code yet,I doubt checking resistance will help much. The ECM cks current flow through the injector ckts. Have you disconnected your grid heaters before starting it cold?



Bob

All good info here. It's intermitemt, but happens predictibly. Disconnecting the heaters would be real good, might set a code if it's a load monitored circuit. It would single out a power distribution problem.



What mods does this truck have?

 

[steved]

The original failure was from worn out injecctors. It was from water (possibly), but the damage happened well before the actual replacement. The system was flushed prior to installing the rebuilt injectors... keep in mind, the non-replaced pieces of the injectors have 170k on them.



I got very similar readings tonight... background was 0. 2 to 0. 3, and all the injectors were 0. 4 ohms, but my meter isn't that precise either.



Although it was almost 45*f today, it did miss tonight when I started, but the injector was quiet. I did get it on video... its hard to hear, but its definitely missing. I am going to see if it does it tomorrow... and get a video so everyone will be able to see I am not nuts...

 

[steved]

The truck is more/less stock... the injectors are the only performance mod...



I have a granetelli monitor and fass... but no chip or programmer.



Unhooking the grids... at the grids themselves? The miss was occuring more when the grids kick on tonight, but its rough the entire time... the injector starts snapping when the grids kick on and the temps are cold...

 

[CoastyAV8R]

How about pulling the fuse for the grid heaters? What you would be eliminating is the large electrical load the grid heaters place on the electrical system by doing this so you could atleast cross this off of your list of possibilities.



How many miles do you have on the truck? It sounds like you have quite a bit if you had 170,000 miles when you changed the injectors.



When you checked the resistance on the injectors, did you disconnect the wiring to each injector to eliminate reading through something other than just the injector?



You obviously know your truck better than anyone else and if you hear a miss, then it most likely has one. Chasing a problem down like this sucks, there is no doubt about it. If you come up with a plan of possible causes and check the ones that don't cost anything first, it will have the least financial impact.



Good luck and believe me, any guy who has ever chased a problem like this can appreciate the frustration you feel.

 

[steved]

The truck has 170k on it, the injectors only have around 30k since being redone. I have replaced all the recommended parts at this point... FCA, CamPS, CrankPS, cleaned the IAT, cleaned the harness connections, etc...

I did not remove the wiring from the injector, however I did unplug the injector harness at the valve box which does essentially the same thing.

The truck is being taken back to the shop, I feel at this point that he has a better chance of solving this than I do. With it being colder, it seems to be consistent in the symptoms.

It definitely has a cold-start miss... I posted a video of it in my other thread. It is one of those things that every time it happens you wonder if it will clear up this time... or if you're going to be calling a wrecker.

 

[Gus's 03]

You might want to look at the voltage going to the injectors (I believe 12V, not sure, could be more) when things act up. Possibly there is something going on with the drivers that power the injectors. In any event, be careful because this is a delicate circuit.

.

the injectors are driven @ 80v and pull in current is usualy around 14a.





yha... . thats alot... .

 

[Wayne M.]

the injectors are driven @ 80v and pull in current is usualy around 14a.





yha... . thats alot... .

80V@ 14A?! Are you sure? That's heavy! we have some electronics to be switching that at that rate!

 

[Bob4x4]

Voltage is correct ballpark,I think a decimal was dropped for the amps

 

[steved]

I assume you could just check voltage at the terminals on the injector?



Unplugging the injector pairs and plugging them back in, results in a delayed firing of the injectors... takes a few seconds for the injectors to come back on line? Normal?

 

[Bob4x4]

I assume you could just check voltage at the terminals on the injector?



Unplugging the injector pairs and plugging them back in, results in a delayed firing of the injectors... takes a few seconds for the injectors to come back on line? Normal?

I doubt you have anything fast enough to see the injector signal :-laf



Bob