Headlights Killing Engine

DMECMAnderson · Post by **DMECMAnderson** » Thu Sep 20, 2007 9:43 pm

I'm having a very strange problem with my '81 Fiat Spyder 2000 that I hope the collective forum can help me out!!! The problem is (of course) electrical.

The car starts and runs fine when cold. After running and being driven for about 15 to 20 minutes, when I turn on an electrical device that demands energy (like the head-lights or the fans), the engine cuts out. I've also noticed that this only happens when the RPMs are below 2000. I've replaced the regulator, which fixed another problem. The car has a new blue BOSCH coil (again fixed another problem). I've recently replaced the temperature sensors (NOT the Fuel Injection Sensors, that one is on order), and have determined that the temperature readings are correct as displayed at the gauges.

What's really strange is once the car has reached the state of this problem, I can turn on the lights kill the engine and if I turn them off quickly the engine restarts (still spinning) and continues to run. It is literally like the spark is being turned off to the engine. Again if the car is driven with no lights or no fans running, never has a problem no matter how long I drive the car.

At first I thought it was a bad ground, but all of these together do not add up to a bad ground. Then I thought it was an over temperature issue, but my gauges appear to be correct. I've ordered the fuel injection temperature sensor (temp sensor II), but I'm beginning to be concerned that the problem is in the Fuel Injection ECU.

Anyone have any good ideas?

racydave · Post by **racydave** » Thu Sep 20, 2007 10:06 pm

First Id check the charging voltage, eng runnin, at the battery. It should show you about 14 volts. Secondly, check clean connections at battery, then starter. Also go over the grounds esp engine to chassis. We tend to overcomplicate things, stay with the basics first...

mbouse · Post by **mbouse** » Fri Sep 21, 2007 9:47 am

i'm thinking both the engine and headlights are controlled by the ignition switch. that big white connector behind the ignition switch may be at fault.

clean and tighten all connections in that connector block.

DMECMAnderson · Post by **DMECMAnderson** » Sat Sep 22, 2007 1:54 pm

Hunting the grounding idea. Noticed that I have about a 0.5 ohm restitance to chassis from the engine block. Also noticed that there is a small current running (0.5mA) from the engine to ground when the engine is running. Looks like I have an inadequate ground between the engine and chassis. There looks to be a small ground wire added (14 gauge) from the engine to the chassis, but I can't believe this is the only ground.

Any place for me to start looking?

DMECMAnderson · Post by **DMECMAnderson** » Sat Sep 22, 2007 2:22 pm

Checked the ground wire from the transmission bell housing to the chassis. Appears to be solid with no marked corrosion.

So Cal Mark · Post by **So Cal Mark** » Sat Sep 22, 2007 4:19 pm

I'd check for a voltage drop under load rather than checking resistances, I think it shows more real-world problems. Start at the positive batt cable connection

DMECMAnderson · Post by **DMECMAnderson** » Tue Sep 25, 2007 7:55 pm

The problem has progressed (at least today). Drove a little more today than normal. The engine now will cut off with no electrical accessories turned on after about 40 minutes of driving. If I simply pull over wait about 2-3 minutes, I can restart the car and drive about another 10 min before it dies again.

Given that the Tach is dropping immediately to zero, I'm sure the spark is being prohibited some how. The electrical is strong even after then engine has cut out so the battery is likely to be OK. The coil is new, the only other spark control that I can think of is the distributor. Is it possible that there is something expanding with heat in there that could cause this kind if problem.

Note the battery measures 13.5 volts when the engine is idling.

I guess the good news is that the problem is getting more persistant, that makes it easier to find...

racydave · Post by **racydave** » Tue Sep 25, 2007 8:37 pm

the more things go dead, the closer to the batt connections I would look. since all the wires then go to the starter and branch out from there, if something stays powered up, then id be at the starter, then to ign switch. What Mark said about the voltage drop test is true! Ohm meters can be liars, you need a load across to find the voltage drop. Alot of owners install a seperate ground strap engine to chassis because similar problems. Keep us posted!!!

manoa matt · Post by **manoa matt** » Tue Sep 25, 2007 9:36 pm

The symptoms you describe sound like the coil is overheating and shorting out.

The bosch blue coil is a replacement for the points type coil. If you have a 1981 then you have an electronic breakerless system. The two coils have different resistances. This Accel coil has the correct resistances for the electronic breakerless system. This is the coil that I'm currently running with an electronic breakerless system with no problems.

http://store.summitracing.com/partdetai ... toview=sku

Besides the one offerd by IAP ($198)I have not found another coil that has the correct resistances for the electronic system.

Make shure you have a good engine ground. Also check to make shure the coil body is grounded to the body of the car. DO NOT GROUND THE COIL VIA THE TERMINALS.

Do you have a control module? Make shure the bare metal on the back of the module is clean and touching clean metal on the coil heat sink.

Also check the wires of the pickup unit inside the distributor. They get brittle from the heat and the insulation cracks and falls off, after that they will short out.

So Cal Mark · Post by **So Cal Mark** » Tue Sep 25, 2007 10:21 pm

your latest post sounds like your ignition module is breaking down. It mounts under the coil, and is available at any parts store for about $30. The module is the same as GM used in the 1980s, so it's a common unit

DMECMAnderson · Post by **DMECMAnderson** » Tue Sep 25, 2007 10:48 pm

I made an error in my original post. It's not a BLUE Bosch coil, but it is a Bosch Coil with an Orange (Red) sticker...

I ordered from IAP based on model and year. The new coil came with a new control module as well as the heat sink. I've already double checked all of the connections and made sure that the coil heat sink was tight against the chassis.

You all are great for providing the inputs to date. I really appreciate the help.

I'll start hunting inside the distributor.. Let you know if I find anything obvious.

Thanks again for the help!

So Cal Mark · Post by **So Cal Mark** » Wed Sep 26, 2007 12:51 am

your problem doesn't sound like a dist pickup problem, but sometimes the situation doesn't translate very well to the forum. Your latest description sounds like a voltage drop to the coil. Can you attach a voltmeter lead to the coil and simulate the trouble by turning the lights on?

Early on Mike Bouse suggested checking the ign switch connection. At this point I'd second that suggestion. Also try wiggling the connections on the back of the ign switch

mbouse · Post by **mbouse** » Wed Sep 26, 2007 10:42 am

when i encountered this issue, it would happen once per season. drive all day long, then BAM! on the side of the road dead for about 4 minutes. Re-start and go for the resto the season.

Gradually, it became twice per season, then once/month, then once/week.

i eventually found that it was the CONNECTOR on the positive feed wire to the coil. i cut that connector off, and replaced it with another connector, May 2006.

I have not had the issue since, and used the vehicle as a daily driver at least three months this year.

DMECMAnderson · Post by **DMECMAnderson** » Wed Sep 26, 2007 7:48 pm

Sometimes I feel like this is a running diary... I'm probably not being a good poster here. To try to provide you all of the things that I've tried, including all that you've suggested so far....

I already took a good look at the ignition switch, rattled the cables, the keys, the connectors to check all the connections. This was one of the areas that they guys at work suggested too. Nothing seemed to be at issue here.

I've measured the voltage to the input of the coil before then when I turn on the lights killing the engine, I've noticed no change in voltage. Of course the tach output voltage goes from a AC signal to ground immediately when the problem occurs.

Probably because I'm paying closer attention to the car as I'm driving, I noticed that just before the car dies, that the engine misfires above 2000 RPM but continues to run. If I immediately turn one or more of the electrical devices, the misfiring stops and the car will idle OK. A few more minutes of driving ANY electrical load will kill the car when < 2000 RPM. A few minutes after that it dies no matter what even though any electrical device I turn on immediately after the problem turns back on with no problem, indicating the battery has full charge.

I've studied the electrical diagrams and can find no common theme to indicate why just the radio running would interact with the ignition or why this would be RPM related.

One more thing I noticed, when the problem is occurring, I can kill the car by turning on the lights, if the car is moving, I push in the clutch allow the RPMs to fall < 2000, I can "jump" the car back to life by turning off the lights IF AND ONLY IF the "jump" causes the RPMs to be > 2000 RPMS, that is to say that I have to go fast enough or be in a low enough gear to achieve 2000 RPMs before the ignition starts firing.

Now if I'm reading the manuals, diagrams, etc. correctly the only thing that could possible know the engine is turning > 2000 RPM is the mechanical pickup from the distributor. Why this would have any bearing on the problem is beyond me a degreed Mechanical and Electrical Engineer. (Perhaps that's my problem too darn much education causing me to overlook the simple problem

)

I'm sure that the problem will resolve down to some $0.15 part. Perhaps it is the connector that Mike is referring to. I think I have one to swap with, guess I have nothing to loose!!

racydave · Post by **racydave** » Wed Sep 26, 2007 8:23 pm

Dave, Once upon a time, on a old Nova I had a no start one morn, but when I jumpered 12V to the coil, it started. I replaced the coil, never had another problem. Also, my wires on my Fiat ign switch connector had been hot, and the wires werent very healthy because the poor connection at the terminals in the connector. I butt connectored them to repair it.. A volt drop test on the colum side and to the battery neg term would show a problem. We do a drag test with the opposite terminal to chech for tightness in the connector terminals. If it is male side, drag test with a female. Also ck for exessive corrosion.

PS, nice ride!