90 GT No spark (thanks Rog, I was wishing)
 

Sorry Doc, got to post this because it's got me stumped.

Docs rebuilt engine won't start. The engine is a total rebuild, new everything. Here is what we've done the past few days.

Engine in, wired up, fueled up, cranks. Has fuel pressure at 50psi or so. Fuel delivery is not an issue.

Ignition seemed to be the problem this morning early so we tested his brains since the injectors were not firing. LH was bad as tested in my '88. Rebuilt the brain (as in put in a new JDS unit with the GT chips) Tested good.

New caps/rotors/plugs/wires/coils all ends tested good on ohm meter. We exchanged each unit with known working ones, from the LH/EZK to the rotors. All grounds triple checked. Have an osciliscope testing everything.

Put the hammer on with new brain and Hammer shows all parts working as required. Can't test EZK due to non-running condition, but it does show up as a working component.

I'll jump ahead now to what we have now. Spark only on #4 and #5 cylinders. That tells us that the EZK is not getting a proper signal from the speed sensor, speed sensor is new, compared to the working old one and they are the same. We've tested the final ignition loop, continuity from the EZK to all connected components. Tested all LH loops.

Both of us are lost and I hope someone can give us some advise on where to look.

For the record in case it matters its a 90GT 8>)

Oh yea, it has bags.....

You are abso-friggen-lutely sure about spark on only 4 and 5? No spark on all would be the speed sensor or both amps. No spark on four would be an ignition amplifier, coil etc.

No spark on 6 sounds mechanical in nature.

If it is a speed sensor failure mode it's the weirdest one yet. It should be all or nothing.

Was the engine pulled, fixed, and put back in? Or was work done in place?

Just for completeness sake:

The Hammer will allow you to test the speed sensor when talking to the EZK

Swap-in a known-good set of the ignition amplifiers.


Dumb-ass questions:
You put spark plugs in right?
Are all four coil wires connected for each? The two little ones, the big one and the ground strap?
Battery charged?
Battery ground strap tight?
Engine ground cable tight?

Was the LH bad before the engine job? If not what happenend to it?

Think I recall the EZK needing a signal from the LH but if its not then no plugs would be firing.

After seeing speed signal EZK sends signal to LH to turn on fuel.

One more dumb-ass question:

New plug wire sets come with two different sets of coil wires. You use one set or the other depending upon the 'nose' of the coil. If you use the wrong set you'll have very poor spark to the cap.

This is why we are so stumped.

Only spark on 4 and 5. We pulled the plug wires, used a jumper to check on each attached to the spark plug, grounded against the block. Only spark on any of them is 4 and 5.

No spark on 6. Mechanicals are all new, tested with known good.

I on wierd speed sensor failure, it's a bitch to pull that w/ engine in the car, that's why I insisted on installing a new one before the engine went in the car. All new stuff was done with the engine out of the car, should have been plug and play.

Can't talk to the speed sensor since all test with the EZK involve engine running.

We did not put in new ignition amps, when we thought there was a problem with one side, we swapped from one bank to the other with no change in the pattern. Swapped back, same issue.

Plugs are in, new copper WR7Dc's, coils are installed correctly #15 black, other brown, triple checked with 3 different coils. 2 known good, 1 new each side.

All grounds repulled, recleaned, mounted. Chassis to block, each coil to heads. Battery is good, pulled twice and tested, new battery installed as a base test.

See why this is so damn weird and we are stumped? I've tried 2 different EZK's, 3 if you count the one tested in my car.

Used a couple of different sets of coil wires. The wires that are on the car were in use when the 2/6 bearing went. Went ahead and tested each wire, each cap and all have either 3k or 1k ohm resistance depending.

No, that was what we started with when the injectors were not firing so we swapped it in to my car and nothing. So then came the brain rebuild, which fixed the LH. EZK was fine, but would not send the spark signal on any of the known good EZK's we used.

I put in a new beru coil wire when we thought it was that, or the coil on one side, when tested it didn't make any difference when we tried 3 different coil wires. We get the spike for charge on the coil, the coil wire ignites one time on each one. (tested with a spark plug in the coil wire grounded.)

One of the Hammer tests involves cranking the starter while the EZK looks for the signal. It's there.

Ok. Fine. I'll go find it. Can't sleep anyway...

We'll try ign amps tomorrow or Fri. I did swap the connectors from L to R on the amp, and it reacts the same. The only things leading me to the crank sensor are the fact that 4 and 5 are adjacent firing in rotation, and that the CPS was swapped out. The old one was working when the engine siezed. We've run my EZK in a 88, and run a known good EZK in my car, and the failure mode stays the same, although we need to reverify with a working car again to double check.

When we very first tried to start it, I got it to run on a squirt of carb cleaner. It sounded like all 8 fired for a second or two, then I let it run out of fuel. AFter that, we lost ignition pulses gradually until now we have only 4 and 5. Note that these are on the left and right bank of ignition. I would not expect the amps to fail the same way unless I damaged them when swapping cables.

This is a weird one. If I don't get it soon, I'm parting the damn thing out.

I'll take the running gear

Well !@#^%$^%!@#

Yup. The Hammer won't check the speed signal. The "unmentionable" tester will. The FM says the 9288 will and the Spanner will.

I usually get good deals on inoperative 928s, keep me in mind :jumper: :icon107: