How do I troubleshoot the dead tachometer?

[jjgolf]

I understand the tachometer must work or the ECU cuts injectors. My tach. does not work, killing my injectors. I do have spark. I tried the jumper wire at diag. conn., cranking for 10 sec., but only get code 12. Bad ECU? Am I beating a dead horse and just need a new ECU? You mention in my other thread something about no tach. feed? Brown wire? Suppressor? I did find the suppressor. Can I check it? My chilton's does not show anything about the tach. I know.. I need FSM. I see a brown wire at the suppressor, and one at the back of the instrument cluster. Maybe I just have a bad tach.? I did notice what looks like junkyard marker pen #s on the cluster when I pulled it. Just point me in the right direction. Thank you for any help/advice. (I also know I need to learn how to maneuver/respond/reply
in these forums. Forgive my ignorance.)
jjgolf

[fixkick]

im sorry what car is this, 8v, 16v, (89 or 95 year)? i forgot...... which of the 3 generations of sidekicks.
ignore the tach, just trust, code 12 cranked,
no code 41/42 , checked off, good.
spark good, bingo.
if suppressor is there, and plugged in, it's good, they cant fail, no way, for a resistor and small cap to fail there.(inside,)

my be bad tach, but if the tach sorted you'd get code 41s. for sure.
Noid lamp tests failed on all 4 injectors (16v answer)
if the noid test failed the next test before condeming the ECU, (fuses all good)
is THE TPS.
the TP pin must not be at 4v or more, 3.5? or more or the ECU cuts fuel (1 more feature ) this is the unflood mode, and does this is the TPS ground is cut. (open)
there is no ignorance here, please..... be good to self !!, this is arcane, ECU logic. , dont worry , we can fix it, (find it)

to get injection , you need only have good tacho wire, (brown tach wire pulses, aka: code 41 pulses, YOU DO HAVE THEM, your tach is old and slugish, no surpise there)
and TP must read, 1v (about)
and have fuel pressure.
and The NOID must flash.
and last the injector must not be clogged.
if all that is good, the ECU is bad or you lost 12v to the injector (16v answer) 8v, has 2 wires, and both pulse and love to fail. bad ECU on 8v if either injector wire is dead and NOID is dead.

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please post car spec... year and if below 1996 , 8v or 16v.

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Lets do it !!

[fixkick]

all EFI Gas engine cars do this.
cut fuel for many reasons, we can find, it.
just need year, and engine option.

because i dont know year/engine , in your car , i can not post exact pins to test and how.

[jjgolf]

O.K. I have a 1995 Sidekick JX, Manual, 4x4, 16v. Compression-175 on all 4. I seem to have intermittent problems. (YAY). Injectors are now working, but are flooding. Fuel pressure @ 38. Maintains 35> for hours. Good spark. I'll keep tinkering and update when I have more info. Thanks, jjgolf

[fixkick]

16v 95 (is the the symotoms NO STARTS, you didnt say) so below is Nostarts, and flooding.. help.
no start
floods. but injectors do NOT leak, passes leak test.

code 12, 5sec, cranking, the tach can be near zero due to low battery voltage cranking, it only moves at tiny amount if at all, but no code 41 or 42 means the ECU likes the tach sig , and i trust that.
ever put in new CAPS in that ECU?
the TP pin on the TPS must not be near or over 4vdc cranking, ever. or the ECU cuts fuel, but you are flooding
id have spark strobe light on spark timing very fast, if way off the cam belt slipped. or worse) but 175compression says it didnt slip (1 person out of 100 get good compression but the dizzy timing, is all over the map, and crank key is sheared. Bouncing back and forth, some times the compression is good, from pure luck of the bounce.. rare but seen it 1 time.
I check that bolt for 94 ft/lbs, first. if found loose, bingo. the crank pulley bolt.
this car needs that and good caps to run. the 2 things to check first. on all sidekicks. 95 and older for caps. newer kicks never fail for caps ,ever....

if the ECU is ok, you can do this test
FLOODING:
get it dry. pull the fuel pump relay or the pink wire connector behind, the left rear tail light. this KILLS all FUEL.
now crank it. it must start. if not spark timing is wrong. (weak or dead)
must start and run till the old fuel leave the engine.
then when dry, test fuel works , each time you spray for 3 seconds... spray , runs 3 seconds, spray and repeats, this proves 2 things, the engine is good, and spark is good, and ECU
can make spark each time.

fuel pressure 38 (running or not)
spec: 30-37 PSI running
36-43 not running.
the key on pressure is like 43 and once started (sealevel) the pressure drops 10 psi to 33.. that 10 psi drop is the vacuum going active on a good fuel pressure regulator.

Get the engine to run on test fuel, repeat until happy engine sounds good, then put back the fuel pump relay and we can fix flooding.
The first tests. are all using a voltmeter, (no scan tools for 95, so hard way)
ECT (2 wire coolant sensor)
ECT reads what ohms , parked cold. (connect unlocked and meter on pins of ECT)tell me outdoor temps.?
key on MAF output voltage?

fsm
Next move the probe to the output pin. Gray-black wire, the voltage key on, no start is 1.0