Engine Cutout - 1982 Spider - ? Faulty Temperature Warning Sensor

[spidysmo]

Hi gurus,
My 82 fuel injected 2L spider played up for the first time in 12 years of having it. Been about 4 months since I last drove it. Started first kick. Battery and fuel are fine. "Ex. Gas Sensor" comes on as the engine faulters and cuts out - 1st happened after driving about 2Klms. Started and ran for 100 metres then cut out again and starter motor seemed disabled. Tried an hour later and started and ran fine for about 1 KLM so I filled tank (was still quarter full), then soon after, sensor came on again and engine cut out again.
So, car starts fine but unreliable. I spoke with a specialist who has seen this before and he was certain it would the Black, front most temperature sensor (warning light). I found the wire unplugged and hovering over the connector so pushed it on again - thinking that this would surely be the problem. But no, it is worse now.
Could the sensor be faulty?
Is there a work around to test like earth the sensor wire perhaps?
Can I test the sensor resistance when cold perhaps (what value should I expect)?

Note: the Tacho has been going a bit crazy too, since this issue has occured.

Any guidance on how to further troubleshoot so I can drive over the Christmas Holidays would be very much appreciated.
Seasons Greetings to all

[spidysmo]

Update:
I have tested O2 sensor and coil - both seem fine.
Found the 2 temp sender units were wired back to front - now correct, but same issue.
Car starts, idles and revs when staionary BUT total engine cut-out when I accelerate on road - only get about 50m down the road.
Any helpful ideas?

[18Fiatsandcounting]

Any helpful ideas?

From your description, it kinda sounds like the engine is running out of fuel when demand is high. Possible causes could be a plugged fuel filter, a plugged up fuel pickup in the gas tank, vacuum building up in the tank, etc.

Try running the car with the gas cap opened (cracked), which would eliminate a vacuum issue as one of the causes.

-Bryan

[spidysmo]

Thanks Bryan, will do

[Nut124]

When this "total engine cut out" happens, does the engine still idle ok? Can you drive home at low speed or need a tow?

If it continues to run at idle, low speed then it sounds like fuel delivery, like Bryan suggests. If it stops completely, then could more likely be ignition, distributor pickup or the GM HEI ICM.

[spidysmo]

It is a total engine cutout. Won't start while rolling/coasting. Have to stop car, turn off the ignition completely, then I can start it again.
Feels like an electrical cutout to me as instantaneous when it happens rather than chugging along due to poor fuel delivery.

[spidysmo]

I tested the coil and it has 1.3 Ohms on Primary winding (Expected is 0.75 to 0.81) – so not sure if that is significantly high? Secondary circuit tested as 10,750 Ohms (expected 10-11K) so that looks good.

Any ideas on how to test the ignition, distributor pickup or the GM HEI ICM?

[18Fiatsandcounting]

I agree that if the cutout is "instantaneous" then it's more likely an electrical issue. As you note, fuel delivery issues will usually result in a sputtering and cutting out under high demand, but then "recover" once the fuel demands drops (such as at idle).

How about an issue with your ignition switch, in terms of the internal electrical contacts losing connection? These ignition switches are notorious for eventually failing, and this is one way that they fail. You could "test" this by putting a jumper wire between +12V and the B+ terminal on the coil, once the engine is started, and then see if the engine still cuts out.

-Bryan

[18Fiatsandcounting]

PS: Measurements of very low ohms are quite difficult unless you have really high quality equipment. One common issue is that the meter doesn't zero when you short the leads together, so you have to take that into account. For example, if you short the leads, and the meter reads 0.4 ohms, and then you test your primary and get 1.3 ohms, the resistance of the primary is actually 0.9 ohms.

[Nut124]

...You could "test" this by putting a jumper wire between +12V and the B+ terminal on the coil, once the engine is started, and then see if the engine still cuts out.

-Bryan

^^^ This is a good idea. You get the 12+ from the alternator post.

[spidysmo]

If it stops completely, then could more likely be ignition, distributor pickup or the GM HEI ICM.

PROBLEM SOLVED:
You hit the nail on the head Nut124!

It wasthe Ignition Control Module (HEI ICM) that sits under the coil on the heat sink.
Got a compatible unit for $55 locally after much sleuthing of compatible part numbers and it works great. Tacho miraculously working perfectly again too.
See https://www.goss.com.au/catalogue/ IM113. Note, used thermal paste under the ICM.
I also found many loose and grotty connections as well as a broken rubber exhaust hanger. All cleaned and rectified now, as well as the 2 temp sender units on the top of the engine are now both connected and wired the right way round. Amazing what you find when you look, but none of these stopped the car.

Thanks for all the interest and suggestions!
So glad to back on the road again

[spidysmo]

Spoke too soon.
Car ran beautiful over several days/test runs. Only did about 5 Klms overall but up to 100K/ph.
Then, car kept cutting out but seemed a little more like fuel.
Realised fuel pump wasn't running when it wouldn't start.
Eventually, after ignition off and on again a few times, the pump cuts in and engine starts, then stops very soon after.
Not sure if FI system is causing it. Definitely a fuel pump cutout issue now.
I'll do more research on the Bosch L-Jetronic FI system and might try to hotwire fuel pump to see if that helps to keep it running.
I read the pump is controlled by a combi-relay. This relay is in turn switched on and off by a microswitch attached to the air flap inside of the airflow meter. So a few things to troubleshoot next.

Good news is the new ICM definitely fixed the sporadic tacho isse - tacho is perfect again now!

[rlux4]

Have you checked the FI fuse under the dash? Symptoms similar to yours is sometimes a faulty fuse holder. It's on a brown with white stripe wire up behind the fuse panel. The factory fuse holder will loose contact and stop power to the fuel pump. I replaced my holder with a standard AGC type holder and never had the issue again.
Ron

[spidysmo]

Sorted it out today and did an extended test drive.
Someone has run a new wire to the fuel pump with a dodgy round type connector under the floor carpet (back seat foot well). Found the connector was pulled apart, which happened just after I had 2 kiddies in the back seat. Replaced the connector and taped it up. Problem solved. Yay!