question for jtgh

[midtown15]

i have been reading several threads and your website helping guys out with ecu problems, so i'll tell you what i am working on.

91 geo tracker. it died on me one day driving, and now has the common no start, but has spark, and will run when you dump gas down the throttle body. i can't find any power to the injector, but it has good fuel pressure to the injector. when i turn the key on and while cranking the check engine light is on steady and doesn't flash the code 12 like you say it should. i have opened the ecu and sanded and greased the two end screws like you suggested on the website. so, my main question is, if i don't get the check engine light flashing a code, do i need to look any farther than ordering a new ecu off the ebay guy you suggest? thank you in advance. Tanner

[jtgh]

not fashing,
key on, no start. lamp on. (not false just on)
then when cranking if goes over 300 rpm (approx) CEL must go out. ( id skip this test)
place the jumper , key on , it must flash, if not the ECU is bad.
i might add you can even drive with the jumper on and see all the bad flashes that are intermittent. (not you , as DOA)

replace the corner cap. (radio shack if need it quick) .
most likely it is dry as a cracker inside and useless and Freddy mac shares.

or
the injector drivers are bad. , or wires busted or grounded out.
but the later is much more rare. try that one cap. dirt cheap fix.
digital man on ebay $70 exhange.

[midtown15]

ok, you were right. i'm sure you knew that already. lol

i replaced the capacitor with one that was rated 35v as opposed to the one that was in it was rated at 50v. it started for about 3 or 4 seconds and the capacitor blew. radio shack didn't have the 50v ones so i tried this. did it blow because it wasn't the right one, or do i have another problem?

by the way, the original one wasn't popped or anything, my guess it was dried out inside like you said.

[jtgh]

you need a 50v cap , at least.
and you prob. had it in backwards. it is polarized and will explode if put in backwards.
newer caps dont to bang trick , only split open and vent there guts,

what happens backwards is they short circuit , instantly. (that stripe is minus)

find a real electronics supplier. , RS has poor selection. i only mention it as they are everywhere. and some people do find the parts there, but some RS have limited stock others , have more.. hard to predict.

[midtown15]

will do. thanks for all the help this tracker has had me stumped for months!

[jtgh]

only hard thing if injector transistors are bad they are getting hard to find.
I do know they have them in UK. one lady here ( BEX) took hers to a shop and they found them. she used my schematic and parts page.
cost $5 or so.
she had a shorted harness so her smart mech, put an in line fuse 7amps to protect the driver xistors and new wires. been running for 6 months now.

I have no idea how or where this short can be. preplexing.

(she swapped ECU's 4 times i thing , 1 orig. and 3 new).
id measure both lines to the body and 12vd battery terminal with a ohm meter.
(pull battery neg term first or hurt meter).
make sure the resistance is infinity. ( use high ohms scan, r x 10k or r x20k range)

this precaution saves the next pair of transistors ( the 12vdc one is very like to blow).

ok,
that is what I would do , baring , exchange ECU with EBAY dude.

cheers.

[midtown15]

when you say measure both lines to the body. are you talking about the negative battery cables, or am i confused?

[jtgh]

sorry , i mean:
there are 2 injector wires.
test them this way.
1 unplug ecu
2 unplug injector at top right engine bay conn.
the injector feed is now floating.
now with an ohm meter ( resistand range high, r x 20k range)
connect neg. lead to battery minus and then touch both injector wires at the bay connector for injector at the harness side.
should read open circuit.
then move red lead to other injector pin. same deal.
then measure the continuity of both lines, with same meter on r x 1 ohm range (low)
and it must be close to 1 ohm end to end.
you can cheat and do this by shorting the injector wire pins , harness side at ecu with a paper clip bent open.
now you should get close to 1 ohm or less across the bay side injector pins.
so we are measuring the full loop in one test , other wise you need to extend the meter leads from cab to engine bay and test each line seperate.

make sure neg. lead of meter is on the black battery lug.

2 tests, shorts to ground and 1 for continuity.
that way we wont damage any new ecu you install.
a precaution.

hope that helps you .
jerry

[midtown15]

i checked the injector like you said, and everything was good. i got the ecu back today and put it in. i just got back from a test drive and everything runs perfect!!! thank you for all your help!

i'm still working on my 90. so i'll probably be bothering you again soon.lol

[jtgh]

that is good news. (who did your ecu so others will benefit)?
bring on the 90 !