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Agreed. I couldn't really tell how the relay was inserted originally, because it was a bit warped. I used some DeOxit on the contacts for the panel and put a new relay in. It seemed to fit properly, but I will keep an eye on it.
Originally Posted by Mrmerlin
First thing to do is put the relays in the proper positions
fuses that are melted are not making good contact
CPS grounds into computer, computer grounds at valley. Tach behavior during intermittent ground failure, stutter and no start is impossible to diagnose from because it will behave intermittently.
I blamed cps many times, replaced them, and had satisfaction...but only because I disturbed bad ground wires in the process of replacing them. CPS didnt fail, their ground connection failed.
Valley grounds need to be clipped and resoldered, which is pretty easy. Known issue on east coast S3 and S4 cars. Done that yet? Can reuse the same ring terminals.
Else car has engine ground strap loose.
That doesnt solve it, swap your computers into similar car. I'm near Richmond VA, if you are anywhere within 150 miles I'll bring it to you to try it, and tools to fix it.
Only other thing I can offer is that I have a scab box with numbered pin outs for monitoring computer connections while driving. You and Dr Bob could perhaps figure out how to use it to rig and monitor his test lights. Or a portable oscilloscope.
Let me know, sir. Your pain on this has got me reliving my own trials.
There's some general guidance somewhere on inspecting and cleaning ground points as the second step, right after "relay-relay-relay" per 928 sage Jim Bailey. 928 sage Wally Plumley shared a similar bit of guidance as part of his "928 Annual Electrical Maintenance" paper, hosted on the 928 Specialists website. It seems we go through cycles of forgetfulness, and of course there are new owners cycling in continuously. Know that there are some great nuggets of legacy knowledge lurking in the shadows of time. The annual electrical maintenance doc is a wealth of detailed info that will help avoid nuisance glitches and gremlins. Clean The Ground Points if you haven't already. Log the effort in your car's maintenance logbook, so you can reference the date later when you think "I just did that a few months ago!". It's a fall ritual here, even in our very dry climate and a car that's lived its whole life in a dry desert climate.
Shirley there's mention of this in our "new visitors" thread.
I did check/clean those valley grounds, and the main battery ground strap. The valley ground wires seemed in decent shape...ironically, the battery ground strap was in fact loose, but it's cleaned up and rock solid now, with no change.
I got my parts for the "Dr Bob Telltale Diagnosis Light" but haven't had much time to do anything with it yet, due to work.
It's a good point, about the documentation on routine ground maintenance, etc. I remember reading that when I first bought my car and going through a lot of that at the time, but it's not a terrible idea to go back through it.
That breakout box is interesting. Would certainly make it easier to check out various signals coming in to the computer.
Check my logic: I constructed Dr Bob's telltale device and hooked it into the seat heater fuse location. No power there until ignition is on. I put the ignition switch into the ignition position, press the button, the light comes on. Turn the ignition switch off then on, light goes out and stays out until I push the button again. The telltale device is working as designed.
Start the car, press the button, light is on. Wait for it to die (tried it yesterday and it wouldn't die, but this morning it did) and...light is still on. This tells me the ignition circuit is not cutting out. This may or may not be a surprise to anyone, but I think at the least it means I can stop wondering about the ignition switch harness, etc.
I'm wondering what other fused circuits I might check in this manner. If I have a momentary short in the ignition harness, or the CPS connector, or a ground failure in the V, etc, does that shut the car down in such a way that it removes power to the EZF (as an example?). That would be pretty easy to check with this thing, I just am not sure if that's they way those failures happen. Obviously, if the EZF or LH has some sort of internal failure, it won't trigger this, but if I can rule some of those other things out with this method that would be really helpful.
Maybe I'll take a pic of the telltale device later so you can all have a laugh at my terrible soldering skills
I believe your scenario involved temperature, right? Mine doesn't... It's happened numerous times within a minute or two of starting, and also all the carpet, etc is pulled back right now and it still happens. Of course, that doesn't rule out the LH, but it's not the scenario I remember you describing.
I'm definitely interested in ruling out anything I can. I'm just not sure how to do that. People often suggest swapping in a known good one, but I don't have one.
So here's the thing. I'm not a big fan of fixing stuff that "might" need fixing. If my valley grounds are bad, there should be some way to prove that. I mean, sure, I could do it...but I think there's a better-than-even chance that I make things worse, not better, and it ends up having nothing to do with the problem at hand. Where do I snip? What evidence is there that the problem is on the snipped end of the ground wires rather than the other side of the snip? I'm not opposed to doing that if there's real evidence that that is the problem. I AM opposed to doing it because it "might be the problem," with no real evidence. I'm not trying to be a **** or discount your experience, but how can I pinpoint this before I make a change like that? Am I wrong? I'm open to a throng of people telling me I am.
Location is South Florida...just west of Fort Lauderdale.
Originally Posted by Landseer
Location?
Snip, strip and resolder valley grounds. Cheap and relatively easy.
You cannot assess this by eye, nor by measuring resistance to ground.
Last edited by bureau13; 10-25-2020 at 03:20 AM.
Reason: Adding location
Easy. Just run a second ground from point to point in parallel to the existing ground. The current takes the path of least resistance and by bypassing the old ground it'll tell you if the problem is solved.
Easy. Just run a second ground from point to point in parallel to the existing ground. The current takes the path of least resistance and by bypassing the old ground it'll tell you if the problem is solved.
I was actually wondering about how to rule out the LH, but this is good too...I'm not sure off-hand where the other endpoint is, for the wire which ends up grounded in the V. I suspect it's for the injectors, CPS, ISV, any of that stuff under the intake? I think the brown wires just disappear into the harness, so I'm not really sure what that end of my extra wire would attach to.
For "wires that disappear into the harness", often the best test is to inspect, clean, tighten, and see of the symptoms change for the better. The alternative for injection ground is to test from the controller connectors and see if you can see a higher resistance to ground from there. Challenge with this method is the high-impedance DMM, with test leads and their connections that could easily have enough resistance to give you a reading of an Ohm or too, which you might dismiss. In the high-current injection circuit though, that's enough to mess with the actual functionality of the controller. It really needs a solid ground. I went through a tangent of this when I was testing for charging voltage. The ground strap at the battery tested fine, no measurable voltage drop across it with engine running. Yet a new good one solved the symptom I was chasing. Lifting and cleaning the ground point in the valley is easy after the airbox is removed. Look at the wires and connectors. Small brass detailer's toothbrush is used to polish the ring terminals, the boss on the block, and clean the bolt. Look at the conductors that go into the wires that disappear into the harness, and decide if they are corroded to the point where it would make sense to trim back to fresh copper and install new ring terminals.
A lot of the testing we do is inspect, evaluate, measure if it's practical, repair or replace if needed. Sometimes we repair/replace easy and inexpensive things to eliminate them from the possible-causes list. Poor grounds and other electrical connections are responsible for a tremendous percentage of the symptoms reported in the forum. I suppose it would be rude to start off every response with the relay-relay-relay recommendation, clean ALL the ground points, clean all the related sensor and final-element connections, treat them with Deoxit, clean the battery posts and minor terminations there, replace the ground strap, charge the battery, clean the inside of all the window glass... ONLY THEN, tell us what's still bugging you after all that is done.
For over a dozen years, I taught classes in logical problem solving in the industrial environment. Expansive fishbone diagrams on several whiteboards, then a sorting through the matrix of possibilities. Look at history (what caused it last time?), look at ease of testing, and work to divide the list of symptoms in half with every test. You can cruise through a list of 100 possibilities with maybe a dozen tests. Some of the tests are as simple as verifying a ground to eliminate a whole family of possible causes. Good reasons to look at those fabulous logbook entries. More, good reason to maintain our archives of symptoms and causes here. Experience is a very tough way to be educated, although the memories are usually burned in a little deeper. You get the test before the lesson, opposite of the way learning-from-others works.
10-19-2020, 11:35 PM
