QuestionQUESTION: Hi Roland, this is Dave again with the ASD relay / ECU problem of before. I couldn't figure out how to follow up, so I'm reposting. I apologize, the van is a 1991 Dodge B250 with the 3.9L / 6cyl TBI engine (not 3.6).
ANSWER: Hi Dave,
If you have a copy of the first question please send that to me as a follow-up question as I can't pull it up again. I will then see if I can give you an answer based upon the wiring diagrams used on other TBI engines of that timeframe. I don't have copies of the full-size van manuals but there are consistencies in the engineering at Chrysler. Thanks
Roland
---------- FOLLOW-UP ----------
QUESTION: Thanks, Roland. Here's the original question:
I apologize for the lengthy description. I'd be extremely grateful for any pointers. My 1991 B250 van (3.6L V6) with 170k has been in storage for six months. Got her out and she was doing fine.
Prior symptoms that may/may not have anything to do with this:
Fuel and speedo gauges erratic. speedo normailized after a couple of miles, fuel gauge continued to wander. Dashboard lights not working but attributed that to a failed fuse (in the aftermath, all of the fuses are okay).
Symptoms:
One day after work, I tried to start her up, experienced the usual lights, then the motor cranked very briefly but died abruptly, along with all interior lights, gauges and buzzers. accompanied by a loud "tock". It seemed I had lost all power.
I checked fuses, battery, tried a remote starter, tugged on the fusible links, which appear to be fine. I began to suspect the ASD relay, tested its power supply lead (red) and got a good 12V. I undid the large connector through the firewall to check the corrosion situation in there, cleaned it up and reconnected. Connectivity there to the ASD leads was good. I assumed the relay was bad, went out and got a new one, installed it, relinked the negative to the battery (which I had removed for continuity testing) and turned the key to "on". The interior electricals were functional again. I cranked the key around to start ... same reaction ... "tock", sudden loss of power to the interior, motor stops cranking. (I cursed myself for not having raised the window while i had the chance, with a storm coming through).
I then attempted to jump the ASD harness (connecting the hot - red - lead to the adjacent one - dgr/blk), hoping to at least be able to raise the window. Still no power to the interior. I had to leave for the day.
When I returned I tested the other leads on the ASD harness. The dkg/blk to my surprise was also reading 12V to ground (battery neg). Unfortunately, I don't recall whether I had tested this lead before. To my surprise, I now had power to the interior again, with no asd relay in place. (I didn't forget to close the window this time).
Assuming a short to hot some where, I successively disconnected peripherals connected directly to the dgr/bk lead, according to my Chilton, in which the wiring diagrams aren't very concise. Coil, Injectors, alternator, hot oxygen sensor. No luck again. I disconnected the ECU harness, the reading dropped to about 6V. After that, I had to leave again for the day. I have yet to check the fuel pump lead and the ignition switch.
I'm afraid it might be the ECU itself, but don't want to blow a pile based on suspicion.
ANSWER: Hi Dave,
You may have a misunderstanding about the ASD relay. It has nothing to do with the starter motor function. It is strictly for the purpose of fire safety in that it controls the power for the spark plugs, fuel pump, and heated oxygen sensors so that in the event of an accident in which the engine stops running there will be neither fuel or spark or heat to cause an engine fire. It requires the engine to be rotating (either on its own power or via the starter motor) for the relay to close.
But what you are describing (the starter motor dropping out, the interior lights going out, suggests to me either that you likely have a basic issue with the battery connections to everything, e.g. that you have a loose ground wire (the one or more from the - post clamp that go to the chassis metal and the engine and maybe a third wire?) of that the ground post/clamp interface is dirty/loose, of the wire connections to the clamp are corroded OR
similarly that the + post clamp is dirty/loose or the wires connected to the clamp are corroded/loose, or the fat red wire from that post to the starter motor is loose/shorted along the way from the battery to the starter motor.
That is my impression of what you describe rather than something having to do with the ECU. The global shutdown and the noise sound to me like a major current path issue, not something related to just the engine control circuits.
So give those a try. The interior lights are typically powered all the time directly from the battery so when those get flaky you have to think 'battery connections'.
Roland
PS Sorry for the delay in getting back to you, but I hope this will prove helpful.
---------- FOLLOW-UP ----------
QUESTION: Roland,
That all sounds very sane, thanks for the concise answer. I'll rethink my approach & check the spots you mentioned. One quick question, though. I'm still a bit worried about the voltage reading on the receiving end of the ASD relay plug, (at the socket for pole 87). Do you suppose that that in itself is indicative of anything or might it just be a result of another issue (eg. the ones you mentioned in your answer.)
I was able to obtain up to date and exact wiring diagrams at the local library (they have an account with alldatapro.com ... great resource!), that should help.
I realize how difficult long distance diagnosis must be. Many thanks to you for you help.
AnswerHi Dave,
Without having the wiring diagrams in hand so as to be able to see everything that dark green/black wire is connected to I can't comment. And exactly what was the status of things when you say 6v would be important. Presumably if it had 12v showing it was because the relay was closed as that is what the relay does...connects the 12v red wire to the dark green/black wire. What you also might try, by the way, is to get any fault codes out of the ecu using the ignition switch:"on-off-on-off-on and leave on" doing that in 5 seconds or less elpased time. Then watch the check engine light, which remains 'on', to see it begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat the process to be sure of an accurate set of flash counts. Tell me the numbers in order of appearance and we'll go from there to see if anything specific to the problem is called out.
Roland
