spectre6000

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Adding fuel to the confusion fire...

I put the old boost sensor back on. It was hesitant to start, but it did. Usually it fires off after the first starter revolution, this time it took 3-5 or so. Then I pulled out of the driveway, and didn't get out of the parking lot. It was lurching like crazy. It was NOT doing this Saturday. Saturday, I could drive it just fine (if down on power) below the 5/6th ports, and it would cut out (lurching, not like a rev limiter) above that if I was in the throttle.

New boost sensor (an S5 unit if it makes any difference), and it's as good as new.

Next time I go to drive it, it's like crap again and pretty much like before.

Next time (today) it's cutting out slightly at low RPM, and completely hitting a limiter-esque wall at the 5/6th.

I put the old boost sensor back in, and it is lurching at low RPM like it used to at high RPM. Probably couldn't get to the 5/6th if I wanted to.

I put the multimeter on the old boost sensor in the car, and everything tests out PERFECTLY (only 3.53V instead of 3.55V); I did not blow/suck on it.

I put the new boost sensor back in, and this time it started back up (it took a full starter rev), it'll drive again, but it's clearly losing power at lower RPM. Maybe worse than before, maybe the same.

WTF???

spectre6000

iTrader: (1)

Other things I can think of just on the off chance there's anything related I'm not aware of:

- AC compressor clutch doesn't engage. Too low of a priority to have made any effort to figure out why.

- CPU is still wonky as hell. It doesn't beep constantly, but it does weird things intermittently.

- Wipers only work on one setting. Pretty sure it's just the switch. Too low a priority to have investigated.

- EGR was removed by PO.... (I'm grasping at straws), cold start fluid was removed by me as per TSB.

- injectors are new, fuel lines in the bay are new, filter sock is new, high pressure filter is new, vacuum lines are nearly all new, coolant was flushed, oil kept up with, gear and diff oil are new (and lots of other things like that)

- I recently had the dash and all it's associated electrical things out. I resoldered the CPU, AC control unit, and the diagnostic cluster. The clock on the latter still didn't work right, and I got another used one (wherein the clock doesn't seem to work at all).

- Save this particular malady, it's been beautiful. This malady seems to be progressively getting worse.

- I back probed the ECU thoroughly Saturday morning. Everything read like it did the last time I did it save the relief valve solenoid and the boost sensor. Both have since been replaced. I tested the boost sensor again at the sensor itself to spec, but not the relief valve solenoid.

- I can't think of any more pertinent or non-pertinent bits of history to add.

- I'm Stumped and frustrated and have a headache.

- Oh! and I took out the fuel pump shutoff switch. I spliced the wires back together where they were cut for the switch with a butt connector...

spectre6000

iTrader: (1)

The fuel pump shutoff switch was just a little metal rocker switch that cut two blue/brown wires right before a relay. When I removed it, I just spliced them back together from whence they came. I'm trying to make sense of the wiring diagrams, and there doesn't seem to be any color code key...

I'm looking at page 50-36, and the fuel system isn't all that complicated. There's a relay in the schematic, but I have no idea what leads go where without testing for continuity all over the damn place. There are three possible colors that could correspond to "B": blue, brown, and black. The two "B/W" wires could be three different combinations. BR, could also be three brown/black/blue combinations, and L could mean purple (lila) if it were a German car, but it's not... None of the possibilities as I see it are blue with brown stripes. What's going on here?

j9fd3s

iTrader: (3)

in the beginning of the wiring diagram book, there is a how to use this book section, and in the first page it has the wire color codes. then it goes on to explain electricity in quite a bit more depth than you'd expect.

B = black
BR = brown
L = bLue, as the b's are taken.
W = white
Y = yellow
R = red
G = green

so b/y is black with yellow, BR/R is brown with red, etc

spectre6000

iTrader: (1)

You must have a different version than I do. There's a lot of stuff in the front, but I went through it several times (and again just now) and there is no explanation of the color key... There is a list of non-color abbreviations, and a list of colors explaining resistor ratings, but nothing about their color key... Regardless, now I know.

Unfortunately, it doesn't help with what I'm seeing. The wires coming out of what I assume is the fuel pump relay (under the steering column) that had a switch spliced into them are blue with brown stripes, or R/BR by that key, and there are two of them. In the schematic, the options are B/W X2, L, BR, and B.

If I read it correctly, the B/W wires are powers high/low, the BR goes to the AFM to shut it off when there's no air flow, the B is a ground for the low, and the L goes to the fuel pump itself which ultimately grounds back there. For some reason that last wire bifurcates temporarily... ???

My car differs from the diagram in that there are two identically colored wires (blue/brown) that go into the relay into the same terminal on the plug. Maybe that bifurcation takes place right at the plug, and the brown stripes were an '86 thing? That would explain what's going on there. Obviously this is about the only theory I have going right now for this mess.

spectre6000

iTrader: (1)

Operating under the fuel delivery theory, I could be looking at a pump or a relay. In the event it's a pump, it's a pretty straightforward fix. I've already been in the tank to replace the sock, and should have no issues with the screws being difficult.

Should it be the relay, that's a helluva pricey relay! It's got signal in and signal ground, then power in and it goes to either the pump or the AFM, which I understand shuts the pump off in the event there's no air flow. I further understand that that "feature" did not exist on later cars. It seems to me, omitting that wire would allow the use of a more conventional (and less expensive) relay. Thoughts?

spectre6000

iTrader: (1)

I just went and quintuple checked the fuel pump relay.

- I pulled the relay itself apart and verified that everything inside looked happy and healthy.
- I verified my wire colors against the schematic (they don't line up 100%, but they're close enough to get an idea).
- I tested continuity of my splice.
- I tested resistance of my splice.
- I started it up and verified that full line voltage was getting from the power-in on the relay to both power out wires.

The relay appears to be healthy. My clue box has officially been drawn down to where the ONLY thing I can think of is the fuel pump. It doesn't correlate to any pin on the ECU (which I'm about to go back probe again to make sure everything is happy and healthy after I replaced the solenoids and the boost sensor), but short of the heat hazard switch (which reads bad at the ECU), CPU (clearly having issues), or diagnostic cluster (new/used, no idea if it works) somehow mucking things up, I have no other ideas for what to chase down next.

spectre6000

iTrader: (1)

https://www.rx7club.com/2nd-generati...-test-1085193/

spectre6000

iTrader: (1)

I'm pretty thoroughly convinced at this point that it MUST be electrical. Something mechanical would have the decency to fail either wholly and completely to your face or gradually with grace and dignity. None of this off and on intermittent nonsense.

Given the plentitude of seemingly non-drivetrain related electrical maladies I have otherwise, I think the best course of action will be to go around and systematically relieve them of their spite. Hopefully, getting everything to function will either turn up whatever it is that's causing my problems or cause said problems to cease being problematic.

Things like this are why I'm designing and building a custom electrical system from the ground up in my truck... The old military harness had a ton of completely useless (to me) things gumming up the works and causing problems. In the new system every switch is on a relay, all breakers, no fuses, wired closed loop ground, dedicated and isolated drive and house electrical systems, and I might even go so far as to loom it all in some sort of stainless steel mesh for shielding, abrasion, and good measure and why the hell not. Add to that the fact that it's a 100% mechanical diesel (sum total electrical components on the engine include a few senders for gauges, glow plugs, and a single solitary solenoid to shut off fuel), and I dare a gremlin to show its ugly green face!