Did a nice drive around town, about 30 minutes, car is running great.
Pull into Safeway for groceries, gone about half an hour. Go to start my 88 XJS, no start! Not even a slight catch. Humiliatingly popped the hood on my Jaguar in a parking lot. All looked good (I thought my previous work maybe knocked a wire loose?). Felt ignition amp, it was hot. The dreaded heat sink? Car was only running at 180F, and ambient temp is 50F. Car was down to 160F when I tried to start it.
Long story long, the Accel module I put in a month ago is caput? Luckily, I recently bought a mobile tool kit and kept the old GM module with heat grease in the car. So 15 minutes later, I was on my way.
That will teach me… the GM module I bought new has been working flawlessly for 7 months, and I decide to replace it like an idiot. It’s now back in.
I am going to buy another GM module as backup, and never sway away again!
HUGE coincidence, today I switched from 91 US octane to 89 US octane. No pinging, same performance. Doesn’t make the engine run hotter, does it???
Just tested after sitting in my garage 30 minutes with GM module back in. Started right up. Coolant temp was 160F.
Using infrared temp, intake manifold was 130F, ignition amp was 200F. Is this right?
Do the modules create that much heat? I know some have relocated theres to cooler areas, and there’s been tons of talk about this helping or not.
that happened to me , module was very hot poured some cold water over and car started and got me home!
but after trying to find out what problem was , it happened after i changed to a HI output coil!
changed to a standard coil , been yrs since any problems!! go figure?
ron
Glad you got home easy, I thought about that too, but had only beer no water…
I am running new OEM single coil. I just started car again, after 10 mins idling to get warmed up (180F coolant), ignition amp was 180F, intake manifold was 100F. As soon as I shut down, ignition amp fell to 150F.
I guess I’m curious what others run at. Is this normal? Hopefully it is, and only the GM module can take that heat? Or do I have something causing it to run too hot? I bought the entire amp from SNG, and remember noticing no big resistor looking thing like the original. If this previously reliable GM module suddenly goes out too, I guess I have a new problem.
One thing I found reading out there, the aftermarket module makers like Accel and Pertronix recommend running their coil/modules together. I did not, still have my single ducelir coil. Perhaps this was an issue.
That’s kind of what I’m wondering. Many of those modules can pass high current to the coils, and although I think they “also” take low Ohm coils… maybe the single Jag coils just drew too much amperage? Or it could have been that amp just was part of a bad run. Nothing wrong with a GM amp but there can be crappy ones too… some supposedly w/ amperage limits that start affecting spark within RPM ranges the V12 is capable of.
Dunno… what Accel amp module? (so it can be avoided - or at least compared to those who’ve had better luck with it).
Greg I had these cars new…They would cut out even driving back in the day until the GM diode was created.
They are better and even all these years later the best.
TIP
Move the amplifier to the fire wall or somewhere else AWAY from the top of the engine cooking the box!
ONE PROBLEM, You cant move it TOO far , there will be a slight voltage drop if the run is too long and then the heat will bring you back to square one.
Some guys relocated near the radiator, I think our last HE version was on the firewall.
GOOD LUCK
Drive on…
GTJOEY1314
One time Motorola made an I.C.( MC3334 family ) that was the front end for anybody wanting to make a constant energy ignition unit. This provided the trigger input, logic, timing and output signal functions.
You needed to add a case for it, a high current power device, heatsink and a few protection devices.
I would guess GM use this I.C. and add the rest of the components to suit. Perhaps GM use a better output device than the rest, or better heatsink. From reports of non GM units being iffy, best to spend the extra for the GM type.
With my engine idling in garage with hood open, the ignition amp seems to be about 70F hotter than intake manifold. 100F intake manifold, amp was about 170F. After sitting to create heatsink, the intake manifold warmed up to 130F. Started car, and at idle the amp now rose to 200F.
So relocating is simply reducing that initial base temp? If I can relocate to ambient temp area, then the amp should be ambient + 70F?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
12
I’ve never measured the temps as you’re doing, but your numbers don’t surprise me. I believe you’ll find the ign amp gets hottest at idle, runs cooler at higher RPM. At idle is where it’s absorbing the most energy keeping the coil from overheating.
I think your numbers clearly indicate the fallacy of relocating that amp. It’s sitting on a massive aluminum heat sink 70 degrees cooler, and it still gets that hot. Unless you bolt it down to an even better heat sink, it’s gonna cook for sure.
And AFAIK nobody’s ever made an improvement over the basic GM module. Lots of places offer something fancy-schmancy, but I think they’re all snake oil – and, as you’ve experienced, probably unreliable.
i was thinking of buying a simple aluminum heat sink (for CPUs), drilling out two holes, and using the two bolts to mount atop ignition amp (if there’s enough clearance with hood).
could help a little bit?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
14
Probably couldn’t hurt. The intake manifold should be plenty of heat sink, and it has cool air flowing through it, more at speed. But the way the ign amp bolts to it probably leaves something to be desired in heat conduction; it’s really only two small heat paths surrounding the bolts. A finned block on top, perhaps with some of that conductive paste under it, would presumably help keep the ign amp temp closer to engine compartment temp, which is hopefully a bunch less than 200 degrees.
Yes, although its not the GM style amp. And that location was a bad idea, at least on the eTypes. A later mod, quite common, relocated the amp up front where it would receive better airflow.
I don’t know much about the Lucas XJSs, but what about putting the amp and a heat sink where they are on the Marelli cars? Marelli ignition amps
-Bob
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
17
As long as you provide that nice thick aluminum heat sink they’re mounted on!
I’m not sure I see any benefit to moving an amp to the top of the radiator; that radiator runs about 200 degrees, doesn’t it? Now, out front of the radiator would be cooler! Or, as someone suggested, inside one of the air filter housings. Or perhaps inside the wiper housing in front of the windshield. A cool spot would be nice, but remember that it must be mounted on a heat sink of some sort.
The heat sink is stock on the Marelli cars. The radiator top plate or bracket or whatever it’s called doesn’t touch the rad, so it should not be as hot as the rad itself. There should be quite a bit of air swirling around in there, gotta be better than right on top of the engine. You could always drill a couple of holes in the vertical part of the bracket, under the hood seal, to let of bit of air in. Heck, you could make a 2’ long heat sink that would go clear across the rad bracket…
This setup is totally stock on my car, and the amps are the originals, but given that it’s a totally different ignition and there are two of them (halving the workload, I presume) it’s just a guess that this mounting location would improve the longevity of the Lucas component.
Bob
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
19
See, this is where I get lost. Why does it gotta be better than right on top of the engine? The radiator is hot, the intake manifold is cool. Why is moving it from above something cool to above something hot “gotta be better”?
Maybe it’s not. Just seems that getting it to a place where there is airflow, and having a heat sink, would be better than sitting right on top of things where the ambient air temp is much higher.
Having said that, is this whole thing really a problem? Do the GM amps regularly fail when in the stock location?
Correction to my first post above - my memory was backwards. Scratch the “drilling holes” comment. The front of the car and the grill are to the right in that picture, the amps are directly in the flow of the outside air coming thru the grill. The rad bracket does not directly touch the rad, it sits on a piece of foam.
