heinrich

That sort of diagnostic advice is the best you can get!

Scott M.

Fraggle;

Would you let me know how you like the Picotech 'scope?

I need to upgrade scopes and that has promise.

Scott

fraggle

OK, just worked some more.

I've got voltage in all the right places, I believe. The LH isn't grounding out the LH relay. I can jumper it but still don't get any start.

Fires up on starter fluid. NO movement on the tach. AC VOM hooked up directly to speed sensor, I get ~3.2V - looks right on.

When I hook up the same stuff (either the DVOM or my old suspect scope) to pin 1 I get "something". It sure doesn't look like a square wave. More like a 12V impulse with a decay.

I am able to just about get what I should on the scope for the EZK speed sensor input now - 3+ V P-p waveform, so I'm getting more confidence in my ancient equipment (though I still can't wait for my picoscope).

I'm beginning so suspect the output stage of the EZK brain. ick.

Does the tach get its signal from the LH or does it share this output from the EZK?

John Speake

I think you mean LH doesn't ground FP relay ?

Anyway, the rpm signal from the EZK to pin 1 LH is also fed to the tach.

And to the kickdown relay for an auto.....might be worth pulling the kickdown relay if fitted...check feed from EZK to LH pin 1.....also check if here is a short or very low impedance from pin 1 to chassis ground.

fraggle

I've got a 5 speed.

Yes, I meant the LH doesn't ground the FP relay, sorry.

I've got continuity in the harness from LH pin1 to EZKPin 13.

It is ~100 ohms from either spot to in the connectors ground. I'm guessing this is the path through the tach?

John Speake

That 100 ohms seems too low. Did you measure that with LH and EZK connected ?

I don't have a car here to measure for you. But I can tell you this -

input resistance of LH on its own = 500k ohms
output resistance of EZK on its own = at least 10k ohms

I can't believe the tach is a low impedance device. The EZK has quite a high resistor in series with the pin 13 output, so it appears it isn't designed to be loaded with 100 ohms !

I think you are getting close to the problem :-)

fraggle

Measurements as follows:

Just EZK connected: ~100ohms
EZK and LH disconnected: ~100ohms (same)

... so I'm assuming I'm only measuring the tach at this point or some wierd short. I will get solid numbers this afternoon after the F1 race.. what an ugly start!

I've also gone over the central wiring with a fine toothed comb and plan on disconnecting J11 or W11 to fully isolate the computers from the tach. I figure if I pull the right wire there should have infinite resistance from either LH Pin1 and EZK Pin13 connectors (when disconnected from the computers) and ground.

Thanks for the tips so far...

John Speake

OK, good luck, let us know what you find.

So did your O2 short damage something else.....?

fraggle

I may have damaged something else. I did some rather poor road-side testing applying voltage to the fuel float (duh) thinking it was the pump contacts - I was 150miles from home and 30 miles from cell service so I was trying anything I could. I should have known better there. At least I used a lead with a fuse in it!

Haven't gotten a chance to take look yet. What an F1 race! now its rolex...

fraggle

OK GREAT NEWS.

Pulled W11 and she STARTS! What a wonderful sound. No functioning tach, though. SO....

Interesting enough, the fuel gauge doesn't work, either, though the car SHOULD be only down 10 gallons or less). I'm pretty sure I fried something extra through my weak side o the road trubleshooting. (i.e. I thought it was relay X and the connectors at the fuel sender were the fuel pump contacts)

Short in the tach? Have to study the central E some more to see if fuel sender is grounded through the tach somewhere. I'm not looking forward to pulling the POD but at least the vehicle RUNS!

If so, it is possible I damaged something when applying 12V the wrong way through the sender.

Lesson 463: Don't troubleshoot from memory.

John Speake

OK, looks like something in the dash is damaged.....at least it starts :-)

SharkSkin

Good to know... but... what is an O2 sensor and why would you want one?

fraggle

Got my Picoscope AD40 today. I'll be playing with it a lot this weekend. Pretty nice package so far on the install. I've just got to watch things to make sure I don't blow it up (+-5V range) I have a 10x probe so it should be OK in the car...

fraggle

OK I love the picoscope. Haven't fixed my problem, but immediately upon hookup I could produce this:

(with W11 unplugged)



Plugged in it is definately a no-start. I unplugged the fuel sender and still have a no start, so the short is probably in the dash. uh.

SharkSkin

Can you post a link to more info on that unit? I couldn't find that model, and it seems that the 2-channel scopes of theirs that I *could* find were 200 p ounds sterling, so ~$400-ish.