Chrysler Repair: continuously blowing a fuse on a 97 plymouth voyager 3.0L, plymouth voyager, blown fuse

Question
QUESTION: Roland,

I have a 97 Plymouth Voyager with the 3.0L engine.

You helped me back in June by pointing me to a blown fuse for "Engine."  This is the one that feeds trough to the ASD Relay.  It is labeled as #12 for 96-97 and #17 for 98 on my diagrams.

http://en.allexperts.com/q/Chrysler-Repair-807/2008/6/1997-Voyager-quit-oil-1.ht

Since then the fuse has blown two other times.  The first I replaced it, and weverything was fine.  Yesterday, I replaced it and it immediately blew when I crenked the car again.  I tried this a couple of times, and it blows the minute we crank the car.  I am suspecting a short somewhere downstream from the ASD relay.  I am not sure where to go from here, but I did try a few things, and I'm not sure that they are relevant.

I tested for continuity between the fuse and ground strap.  On one of the posts, the multimeter would jump from no continuity to like 170, then back to none.

I also tested for continutity between the open post on the relay and the ground strap.  This post is called 87 in my Haynes manual on page 6-17.  I am a beginner at wiring diagrams, but it seems to me that the open post should not connect through to ground when the system is not running.

Anyway, all help and ideas are appreciated.  And if I just need to take it to a shop, I'll do that, but money is really tight so that is really a last resort.

Thanks

Dave

ANSWER: Hi Dave,
Thanks for the explanation and for pointing me toward different numbers for that fuse over those years (I have a '95 and a '98 manual and have assumed that the '98 applied to the '95-6 model years). I would believe that one of the very many items fed through the ASD is shorted to ground, but you could pull the relay and try to start it just to verify that it isn't the wire from the fuse to the relay, and also if you suspect the relay might be shorted try exchanging that for another one in the box with the same part number. But I believe if you will measure the resistance between pin 87 in the relay socket and ground you should find it to be flat out shorted (it should read at least 0.7 ohm or the fuse will blow). If it reads less than that then you have to find the short:
fuel injector rail plug
alternator
powertrain controller
ignition coil
upstream and downstream oxygen sensors
In all cases it is a dark green/orange wire that is connected to pin 87, What I would do is disconnect these items one at a time and keep checking until you find one that causes the resistance to jump up to more than 1 ohm. Also try shaking the harnesses. Somewhere in that list you have a short to ground. My first suspicion would be one of the oxygen sensors because of their delicate wires and high temperatures to which they are subjected.
Please let me know when you find the short!
Roland
PS Use the "thank/rate' tab below to get back to me with a follow-up question. There is a space for comments.

Thanks Roland. I am a little confused. You say that if I measure the relay socket 87 to the ground strap, I should get at least .7 ohms? Did I interpret that correctly? And the next step is to unplug stuff on that circuit until the resistance goes up? So, I am looking for a shorted component? I guess I assumed that I was looking for a bad wire. If I find that all components are okay, will I have to replace all the wires in that circuit? Or is that scenario unlikely? Thanks for the clarification. I really appreciate it. My email address is david.millard.kc@gmail.com if you care to contact me directly. Thank you again for your time. (PS too bad I can't nominate you for volunteer of the Year)

Hi David,
The 0.7 ohm figure just represents the minimum resistance necessary to keep the current below 20 amp which is the limit for fuse. I would expect it to be much higher than that when you fix it. It could be one branch of the dark green/orange wire is shorted to ground so gently flexing the harnesses to all those components is reasonable, but my bet is that the wire connection at the item or the item itself is shorted when you identify the faulty one.
You said that it blows when you try the starter? Are you sure it dosen't blow when you simply turn the switch to "run"? I ask because the starter circuit is not part of the #12/17 fuse supply.
Roland

---------- FOLLOW-UP ----------

QUESTION: Is it possible to check the injector connectors without taking off the air intake plenum(sp?)

It seems that it is too tight to get in there.

Answer
Hi David,
I don't suggest that you deal with the injectors individually, rather just check what happens at the 14-pin plug (with only 7 wires) that supplies the injectors. Simply unplug that connector and see if that raises the reading of the resistance that the dark green/orange wire shows as measured at the ASD relay to a significant extent. If not then the injectors are not the short problem and you need to look elsewhere.
Roland

Thank you so much for your advice and encouragement. The culprit is the electrical connector to the ignition coil. I pulled it off, the circuit showed much more resistance. Then after jiggling it around and plugging it back in, the resistance stayed higher. So, the van started, but it's not really fixed, right? I need to replace the connector, I think. Do you have a part # for that? I tried searching Advance, O'Reilley and Napa but didn't find anything that looked relevant. Thank you again so much.


Hi Dave,
That is great that you found where the short it located. I don't have a parts catalog for that engine so I would suggest that you go to a Chrysler dealer to see if they list that ignition coil plug as a separate part or not. You may find that it is not sold separately but rather as a part of a pre-fabricated wiring harness. If that is the case in may be prohibitively expensive.
If that is the case I would be inclined to try flexing the cable starting at the plug to locate where you can show the resistance reading will jump up and down which is where the insulation that separates the two wires that service that coil plug has deteriorated.
At that point I would examine how to reconstruct the insulation with rubberized gasketing compound or electrical tape, whatever it takes to eliminate the short between the two wires which is why the fuse blows. One of the wires as you know (the dark green/orange) has 12V on it whenever the engine is turning over. The other wire is the spark coil 'driver' which is being intermittently oscillated by the computer between ground and 12V to cause the sparking. So whenever the spark is generated (grounded) right then and there is the reason that the dark green/orange is grounded and that is a short circuit that blows the fuse. So you will need to do some delicate "reconstructive" surgery. If the breakdown is just where the wires enter the plug it may be impossible and you will have to improvise, or better go to a pull-it-yourself junk yard and find any Chrysler with a 3.0L and cannibalize a replacement plug with its wires, and then buy a connector to splice the existing harness to the replacement plug/wire.
Roland