Electrical gremlins...

[beaky]

My long-suffering 1990 Mustang "Lil' Bandit" has had her problems over the last four years, but all were pretty straightforward to fix, and never a big problem because I don't need to drive every day. I've done a lot of tinkering with it with great success, and rarely paid someone else to do even the bigger jobs. The engine and drivetrain are very strong, with almost 160K on the clock.
But when it started sputtering and dying randomly over a couple of days (when, of course, I had to take her on the highway to get to/from work), I knew I was in trouble. Electrics... I used to have a '76 Fiat Spider, and seriously- as arcane and bizarre (and just plain shoddy) as that electrical system was, it was simple and easy to troubleshoot, and I dread poking around anything fuel-injected, with power everything, and made after the advent of airbags. Terrifying. I fixed a cut wire to the power windows a while back, in the area between the door and chassis, and that almost cost me my sanity. Ford did not make these things to be worked on by owners... oh no.

I'd already had a fuel pump failure, so I thought I knew the circuit involved pretty well... boy, was I wrong. Seemed to respond to wiggling of wires here and there, but finally she just refused to fire up, leaving me stuck and forcing me to have her towed home.
Verified the pump would run with 12V right on it (good thing, as the pump is inside the fuel tank), and adequate pressure on the rail. The starter (which i replaced not long ago) cranked the big V8 relentlessly. So it was a wiring thing. Somewhere.

Sooo many possible points of failure... and all over the car. Fusible links under the hood, ignition switch, fuel pump relay under the driver's seat, inertia switch in the back, the pump harness and ground, another relay on the passenger's side for the computer, and the damn computer itself. I initially suspected the fuel pump relay, and smugly laid out $20 for a new one. Very foolish of me.
It still cranked and cranked, but no fuel pump, and thus no ignition. All the computer does for this is ground the pump relay, so I grounded the wire right where it comes out of the computer, and the pump ran. This proved all the wiring back from there... but the damn thing still wouldn't start.
Took a step back and checked to make sure I was getting a spark- no problem there (good thing, as I'd replaced the ignition wires, the coil, and the ICM a while back). Pulled the MAF connector, etc, etc... still no joy.
Also checked the computer power relay- working fine.
So maybe it was the computer. Hmmm. I don't have a code scanner, but I know how to pull codes without one... didn't care about the codes anyway; I just wanted to see if "Hal" was responsive.

He wasn't.
Pulled the box and opened it up- looked OK, but a 23-yr-old circuit board may have problems that are not so obvious. And testing out the board itself is beyond my resources. So I looked online for a re-man, and saw a wide variance in prices... and of course, no match for my unit.

My "go to" guys at the nearest NAPA store tried every source they knew, threw up their hands, and finally advised me to look on eBay...

Amazingly, the first one listed there was a match! Rather expensive, and it might be a dud, but I am over a barrel- something that just happens sometimes when you drive cars that are over 20 years old.

So I'm using public transportation to get to work this weekend, and praying that the new brain arrives early next week, and it works.
Also hoping that a new brain is really the solution to the problem... if not, I may call it a day and put it on the market as-is. I have a backup, sort of... the '87 Chevy truck is sitting in the garage... but it still needs a new windshield... and a title.

Wish me luck...

[Hagar]

Best of luck. I gave up trying to maintain my own vehicles many years ago. I wouldn't know where to start now.

[beaky]

IT'S ALIVE!!! IT'S ALIIIIVE!!!




The new brain arrived today, secondhand from an Arizona state highway patrol notchback. Installed it and heard that wonderful sound of a 5.0 V8 (with a leaky exhaust) roaring to life. What a relief!!
Haven't road-tested it yet, but let it idle until the thermostat opened, and revved it a bit. Runs fine, and it even cleared the AIR BAG light, which has been worrying me for a long time.
Maybe Lil' Bandit will think she's a police interceptor now...

[expat]

Sean, my experience with car electronics (admittedly only BMW since 1993) is that if you don't clear a code, then the computer may ignore any repair or component that has thrown up a fault code (real or spurious) that has been made until the computer fault codes are reset. It may well be the computer you replaced is possibly serviceable. If you know someone who can reset the fault codes you may well have a serviceable spare in your hand, thus indicating that maybe your fuel pump is slowly giving up the ghost. Of course this could be confirmed if you get the same problem again further down the road.....?

Matt

[beaky]

All true, Matt... but the trouble with the old brain was that it not only seemed to not be controlling things anymore, I couldn't get any codes from it at all. Ground was good, it was getting power, etc etc... but it seemed dead. No functions, no codes, nada.
But I will keep it handy, you never know.

[expat]

To be honest, outside of what I put, that is my sole knowledge of modern cars. My wife's old Diahatsu Charade was the last car I could work on and that was traded ten years ago. It had a 1ltr three cylinder engine with a carburettor Until I bought my MGB roadster last year, I was clueless. I am now back to a double set of SU Hif4's......floats, needles, butterflies......back to the roots

Matt

[beaky]

To be honest, outside of what I put, that is my sole knowledge of modern cars. My wife's old Diahatsu Charade was the last car I could work on and that was traded ten years ago. It had a 1ltr three cylinder engine with a carburettor Until I bought my MGB roadster last year, I was clueless. I am now back to a double set of SU Hif4's......floats, needles, butterflies......back to the roots

Matt

I'm also at a loss with computer-controlled, fuel-injected jobs... and nowadays there's so much junk crammed under the hood!! Just cleaning and gapping the spark plugs can take all day, and require major disassembly.

I miss that old Spider, the first car I dared to tinker with to any extent. Everything was relatively simple and easy to get at, even in that small engine bay.
I'm looking forward to keeping the old truck alive (title is MIA, but she finally found the registration, so that can be replaced, which means it will be on the road this winter)... very roomy engine bay, rock solid V8 with a TBI setup. No power windows, mirrors or door locks, no air conditioning, no air bag. The headliner is steel, lol!! It's a battle wagon that refuses to die. It's fun to drive, especially in snow (3-spd 4WD with manually-locking hubs).

Other than the windshield, one headlight and one tail light, and the exhaust, the only major projects in the immediate future are pulling the bed so I can inspect and clean the fuel pump and filter (and maybe cut an access door in the bed for future service) , and looking into what appears to be a bad front seal on the rear differential. It'll also probably need a new radiator next year... but I don't anticipate being unable to do any of that work myself.

The automatic transmission is the only thing that could eventually be a serious problem (although it's hanging in there just fine for now), but I intend to start looking very soon for a decent manual unit to replace it with.