Catalytic converters?

[fletchusmc]

Had one of those duh moments this morning, hooked up a timing light and no fire on number 1, all other 7 were working just fine.

[Paul Workman]

Originally Posted by fletchusmc

Got in the garage this morning and this is where I'm at.

Fuel pressure, cold, key on engine off 48 psi.
Idle 44 psi, stayed there as it warmed up.
Remove regulator vacuum line 53 psi.
2000 RPM 43 psi.

After shut down stayed at 48 for 10 minutes, disconnected pressure gage after that.

Took some catalytic temp readings

Driver's side
Front of cat 380F
Rear of cat 650F

Passenger side
Front 350F
Rear 460

Still making me think a problem with the cats. OR is it running way too rich on the driver's side and causing the cat to work harder and causing the higher temps?

The fuel pressure raises a flag; sounds like one of the pumps is not working - or at least the symptoms are the same (as mine were).

With the ignition OFF, an ammeter connected between the positive battery post and the fuel pump diagnostic connector (the short red pigtail jutting out of the wire harness next to the diagnostic connector which is toward the middle, near the ECM).

Configuring the meter to read amperes...



Connecting the meter to the fuel pump test jumper: RED LEAD TO POSITIVE POST, BLACK LEAD TO THE TEST PIGTAIL.



BOTH pumps are powered ON and you can measure the current. Each pump will draw about 4 to 5 amperes ea, for a total of 8-10 amperes.




While the pumps are running, you should measure about 53 psi (again w/ ignition switch OFF). If your current is about half of what it should be, and/or the pressure is not up to par, then pulling fuses (as Jerry suggested) will isolate which fuel pump is not working (NO pressure with the ignition ON).

As for injectors...anything is possible, but the 93+ cars had injectors that were alcohol tolerant, and less likely the issue...BUT never assume.

BTW, you should always check electrical coils (ignition and injectors too) when they are at operating temperature. A bad coil will often read normal resistance until they are heated up.

[fletchusmc]

The original readings I got through the wires and coils were with the engine cold. The car had sat long enough that all the plugs looked the same when I checked them. Yesterday I had started the car long enough to connect the timing light to each wire and found the number one was not firing. Turned the car off and pulled number one plug, could definitely tell it wasn't firing as it was really wet with fuel.

Will run the fuel pressure test again with pulling fuses, maybe have a fuel pump issue as well as no spark on number one. After the fuel pressure test I'll check the resistance through the wires and coils again as the car will be warmed up.

Emailed the former owner yesterday, he's going to look for the coils he removed when he replaced them with the Screamin' Demons. He had already given me the original plug wires and exhaust not too long after I bought this car. Figured I'd pull the plenum, go ahead and do the throttle body coolant bypass (to make it easier if the coil doesn't fix the number 1 no fire as well as when I follow Steve's repaint like he did to his recently, just want to fix this problem before I repaint to lower the chances of messing up new paint by multiple plenum pulls) and put the original coils back in it. Will check all the secondary vacuum stuff while I'm at it.

Of course as most of the people who know me can attest the hardest part for me will be to not let this coil replacement snowball into a "while you're in there" type of thing, especially since Lee just posted up ported injector housing and plenum!

[gbrtng]

A timing light? how 1950s ... Anyhow, you found the problem - the coil is a common part that NAPA should have.

[Paul Workman]

Originally Posted by fletchusmc

Of course as most of the people who know me can attest the hardest part for me will be to not let this coil replacement snowball into a "while you're in there" type of thing, especially since Lee just posted up ported injector housing and plenum!

Yeah, it was an epidemic, up here in FBI land. Most of the Zs up here have caught a dose of it.



However, when it comes to racin', the Zs have taken home the bacon (team trophy) against all comers, 3 of the last 4 contests!

[fletchusmc]

Good news, definitely bad coil. Replaced all 4, started great, idles great, drives great, sounds great. Until you get close to 5k RPM, then no more and a brief check engine light. Chalking it up to first time plenum pull and didn't get something with the secondaries back together correctly.

From what I understand to get codes they show on the heater/AC display? If so that sucks because that's the only part of the car that wasn't working right as it just shows jibberish.

[fletchusmc]

All is well again. Pulled the plenum this morning and found one of the brittle plastic vacuum pieces had broken right at the barbs. Fixed that and drove her, rev limiter in 1st and 2nd so I'm happy again. I didn't realize how weak the coils were getting before the one finally quit as this drives and sounds like a different car now.

[A26B]

Great! I know that feeling well. Chased a bad coil for some time after I first got my Zee.