Which ECU?

[Roppa440]

My second FBO ECU went faulty last night. That is two in six months.

The first was faulty from the start and was replaced buy the supplier.
I also fitted the FBO coil and ballast resistor at this point just in case there was something about my set-up that the FBO unit didn't like.

The second has only lasted 500 miles. I switched the ignition on to test my fuel gauge without starting the engine. It was only on for a minute. When I came to start the car later there was no spark except one as I switched off which would be the field collapsing in the coil as the primary voltage was cut. So the ECU is not switching.

Where do I go from here? Should I just go back to using a Chrysler Orange box? I don't want to use a multiple spark type unit. This is a street/occasional strip car that revs to 6500rpm and runs high 11s.

Is there any make of ECU that is more reliable?

[MEK-Dangerfield]

I've had my FBO ECU for years without any problems. Given the facts here, maybe your ballast resistor overheated. Did you check that with an ohm meter. I think the FBO setup uses a .8 ohm ballast resistor.

  Mike

[UKcuda]

Hi Dave (and everyone as I've been "off-line" for a while)

I can totally recommend the HEI conversion I did as a brilliant alternative to the branded or OEM set ups.  It gives a hell of a spark and I've been using my 'cuda as my daily right through the winter and it has not missed a beat

Here's the thread:

http://www.cuda-challenger.com/cc/index.php?topic=62561

[Roppa440]

I've had my FBO ECU for years without any problems. Given the facts here, maybe your ballast resistor overheated. Did you check that with an ohm meter. I think the FBO setup uses a .8 ohm ballast resistor.

  Mike

Resistor is fine. Voltages are all at what they should be and where they should be. Resistances (grounds, distributor etc.) are within spec.

The ECU is not switching. Which is what happens when they go. I wonder if my supplier had a bad batch or something?
The first one used to start when cold but fail when hot. This one just suddenly will not switch at all.

[Roppa440]

Hi Dave (and everyone as I've been "off-line" for a while)

I can totally recommend the HEI conversion I did as a brilliant alternative to the branded or OEM set ups.  It gives a hell of a spark and I've been using my 'cuda as my daily right through the winter and it has not missed a beat

Here's the thread:

http://www.cuda-challenger.com/cc/index.php?topic=62561

That looks very tempting.....

Have you got a wiring diagram? Good UK source?

[Roppa440]

Bought a HEI module on ebay. Going to give it a try. They have been fitted to many millions of cars since the mid-70s so should be pretty reliable I would have thought.

[UKcuda]

If you're doing something like mine give me a call if you like ('phone No PM'd)

[Chryco Psycho]

I have repeatedly had problems with FBO parts so I quit using them
I have been using the Mopar Chrome box on everything with no issues

[Roppa440]

Don't you just hate it when your car calls you a liar?

I came home tonight and went through everything again. Tried bypassing the resistor first. I figured even if the resistor metered OK there might be a chance there was something up once it had current going through it.

So without the resistor I got a spark!
So I put the resistor back in series to prove the point. STILL had spark?

Tried the coil I had in there to start with. Still had a spark.

Put everything back as it was. Car fired up straight away!

Not sure what to do now. I have looked for any bad or loose connections and found none. All the wiring is new. Good ground connections where needed etc.

I guess all I can do now is see if it happens again?

Just bought a HEI module as well. Damn.

[wally426ci]

I had good luck with the stock black boxes....  I wonder which one to get also, need to convert my truck.

[UKcuda]

Still could be the ECU going yeah/no yeah/no.

As you have now got the HEI module I would strongy advise chuck it on there and "say goodbye to ignition wierdness"

[Chryco Psycho]

the resister can change resistance as it heats up , I have seen them work cold & fail warm

[ShelbyDogg]

If it was the resistor, you would have had spark while cranking.  Many of those new boxes are made cheaply in China? and don't last long. All my working ECUs are old units from other cars or old Chrome boxes that I've had for years. The new ones don't last so carry spares just like ballast resistors at all times.  First thing I do when I don't have spark is pull the dist. cap off, then rotate the rotor back and forth so that the rotor point is passing the pickup point, with the coil wire close to ground. I also plug in another distributor and spin it, to check the pickup.

[Roppa440]

the resister can change resistance as it heats up , I have seen them work cold & fail warm

The FBO module this one replaced was doing that. It would just stop switching as soon as the engine warmed up. I will have to get this one hot to check it is not the same. But the weather has turned a bit nasty for now. Maybe at the weekend.

I might fit that HEI thing anyway. I liked the idea of fitting one in a Chrysler ECU box (which I am starting to suspect is what FBO have done anyway) so that I could carry a stock ECU as a spare. But the FBO unit that failed on me the first time seems to have vanished. I think I threw it in the trash a couple of weeks ago. Double blast! So I don't have one to use as an empty core.

[Roppa440]

If I fit the HEI module my only concern is the coil. Use a ballast resistor or not?

I have two coils at my disposal.
One is the FBO coil with a primary winding of 0.8 ohms and came with a balast resistor of 1.7 ohms cold.

The other is my old Jacobs coil which has a primary resistance of 1.6 ohms and which I used to use in conjunction with an old resistor that came with the MP electronic conversion kit I fitted back in 1990. That was about 1.5 ohms cold if I remember?

Obviously with the lower primary resistance the FBO coil will work better. More current in, more current out. But will the HEI stop it getting too hot if I used it without the resistor I wonder?