'80 Fi Won't start when Hot

[courtenay]

It did it again. Drove for about an hour, stopped and tried to restart. No go. Cranks well, sounds like it wants to start - it coughs and splutters, diesel like smell from the exhaust. Let it cool for a couple of hours and starts right up and runs strong.
Be interested in ideas as to where to start to figure this out.

[narfire]

Bruce, check all the connections to the sensors.
Check the cold start injector is working then shuts off.
If you stop on a hill and having a crank start issue, will it start/run if you bump start?
My guess is that somehow the car flooded, perhaps pull a couple of plugs the next time it happens and see if they are soaked.

[courtenay]

Thanks, Chris. I'm not sure how to check the cold start injector, but I did disconnect it yesterday when the car wouldn't start and it didn't make any difference. The strange thing is that the car runs well when it is hot (ie normal operating temp) and it starts well when cool - it just doesn't want to start when it's hot.

[rlux4]

Ah, the old conundrum; spark or fuel?
If it's fuel I'd suspect the fuel pump which is cooled by flowing fuel. Without the flow it could be heating up enough to loose internal contact from the expansion of metal. If it's spark I'd check the condition of the rotor and contact points in the distributor. I'd guess it's unlikely ECU/injectors part of the equation, they aren't usually affected by the condition you're experiencing.
Hope I'm not too late responding, I'm away a lot lately for work.
Ron

[courtenay]

Thanks, Ron. Not too late. Took the car for a long run yesterday so I could get home and do some real diagnostics - fuel, spark etc. Got home, shut it off and it started right up. I did unplug and replug all of the sensors as well as the coil wire and took the cap off the distributor and checked those two little wires before I set off, so maybe I "fixed" something. It's raining here today so won't get a chance to try it again, but will next sunny day.

[So Cal Mark]

I'd start by tee'ing a fuel pressure gauge into the pressure line to see if you're holding pressure with the engine off, and creating pressure when cranking. I'll bet you have to leave it shut off for about 15 minutes to experience the no start issue. If the pump check valve isn't holding pressure or if you have an injector leaking, you could be getting vapor lock in the injection rail

[76was124]

I know I am resurrecting a 9 month old thread but was curious Bruce, what did you find to be the problem? Was it vapor lock as Mark mentioned?

The exact same thing happened to me tonight with my 82....drove great for an hour, parked it for and 15 minutes, then when I tried to start it, it would crank, but not start. Only had a single sputter on the first crank attempt, then nothing. No fuel smell either and unplugging the cold start injector didn't make a difference.

I let it sit 20 minutes, then 40 minutes, still wouldn't start, same after 60 minutes. 1 hour 40 minutes later she started on first attempt. (10 minutes before the tow truck arrived of course )

Bringing the tools on the next trip, and maybe a can of freeze mist, to gently cool the fuel rail, fuel pump or a sensor/connector

[YVRSpider]

I'm having the exact same issue with my '82. Did you manage to figure this out and if so, what was the issue? Would love to get this sorted out, thank you.

[76was124]

It's been so long and so many updates to the car since then, I am not sure I remember what exactly it was on mine.

Definitely wasn't vapor lock. It might have been a bad connector I had on the temp sensor at the manifold coolant T.

[micbrody]

I think it's a sticky AAV. The AAV provides more intake air to match the extra fuel from the CSI and ECU modulated early engine start fuel requirements as modulated by coolant temperature signal from T-piece coolant temperature probe to ECU.
I had poor starting problems; one of the things I did was clean and adjust the opening on AAV. Turns out my starting issue was a failing fuel pump (that's another story). When I replaced fuel pump, car started great; but I noticed that I would have re-start problems if car had been warm from recent trip. Another interesting thing I observed was when I did get car started when warm, it would idle between 500-600; but when warmed up after a minute, it would go to the tuned idle of 900. So my conclusion was that I had adjusted AAV to be too closed at a given temperature, not providing enough air to the startup fuel mixture sequence ( the extra fuel injected is controlled by CSI, and starting temperature of coolant from T piece thermometer signal to ECU).

The AAV opening is controlled in two ways: direct heat of engine conducted to AAV and heats up bimetallic strip in AAV that starts to close shutter. The other source of heat is the electrical connection that provides heat via internal resistor to bimetallic strip. This is energized anytime car is running.
So in my situation, shutter was open when cold; car started; and electrical connection fully closed shutter after a minute. When car stopped and then restarted 10 minutes later, the shutter was still too closed, starving the enriched fuel mixture of air. Eventually, as engine heated up, the ECU decreased the idle fuel administration, making air fuel mixture match better; idle became normal. I readjusted AAV to be more open at a give temperature (tiny nut on AAV).
For people in this thread : I think your problem is a gummed up AAV that is sticking too closed when hot; but when bone cold, does eventually open. So I would :
1) DO NOT adjust nut
2) remove AAV , spray carb cleaner and shake cover both holes with fingers. Repeat a few times
3) repeat cleaning, but with dilute dishwashing soap
4) reinstall and pray to the Fiat Gods

[76was124]

I don't believe the AAV would prevent a cranking engine from starting, only from idling badly when cold or poor performance when warm.

Have you confirmed its no fuel, or no spark? I usually check no fuel first by spraying carb cleaner or stater fluid in the intake (Remove the boot at throttle plate, with throttle plate open a couple squirts, reattach the boot and crank). If it runs momentarily then it's not a spark, or timing problem, it's no fuel.

No spark will give you a series of items to check from the ignition switch, wiring, coil, distributor to the plugs.

If you have fuel and spark during a no start, then I would check your static timing marks and distributor timing, and ignition pick up adjustment. This is assuming you have proper cylinder compression of course, which I would think you do if the engine eventually starts and run okay.

[micbrody]

I thought the same thing; however when problem would happen in this situation (hot car), I would eventually get it started by cranking and hitting gas peddle (throttle plate allowing more intake air); and when I adjusted AAV to be more open, everything works now.
It could be flakey t-piece temp probe; but very easy to clean AAV and see what happens

[76was124]

Likely a coincidence. The AAV should be closed on a warm engine ( no air bypassing the throttle plate)

[micbrody]

I agree; however even now, when I start the car when warm, it idles at 1000-1100 and then after a minute goes down to 900. My interpretation is that heat from engine does change the shutter; however, the continuous 12 volts speeds up and completely seals the AAV .
So in my situation, it was completely sealed when it still should have allowed a tiny amount of air to match the tiny increase in fuel (even in warm engine) that is programmed on engine start from ECU.

So the question is: does an engine that is warm but as been off for 10-20 minutes) still need the "extra" heat from the 12 volt connection.
This can be easy experiment:
1) I will run engine for normal commute.
2) shut off
3) wait 10-20 minutes. Engine still very hot
3) restart without electrical connection: If it starts and idle after a minute goes down to 900, then you are correct; Electrical heating connection is redundant for hot engine. If it remains at 1000-1100 for many minutes (gradually going down to 900 after 5 -10 minutes), then electrical connection must fully seal AAV (hence why it is always energized whether at start-up or when car has been running for an hour). Honestly, I don't really know the answer to the experiment.

For people that are having problems starting their car, I was suggesting that the AAV is being stuck open. Symptoms would be slightly higher idle than normal in warmed up car; but difficult start for warmed up car because of too much air in startup mixture.

[courtenay]

I know I am resurrecting a 9 month old thread but was curious Bruce, what did you find to be the problem? Was it vapor lock as Mark mentioned?

The exact same thing happened to me tonight with my 82....drove great for an hour, parked it for and 15 minutes, then when I tried to start it, it would crank, but not start. Only had a single sputter on the first crank attempt, then nothing. No fuel smell either and unplugging the cold start injector didn't make a difference.

I let it sit 20 minutes, then 40 minutes, still wouldn't start, same after 60 minutes. 1 hour 40 minutes later she started on first attempt. (10 minutes before the tow truck arrived of course )

Bringing the tools on the next trip, and maybe a can of freeze mist, to gently cool the fuel rail, fuel pump or a sensor/connector

It was the fuel pump. It would work fine when the engine was cold but not when hot. Replaced the pump and problem solved.
I figured it out by turning the ignition to the on position and moving the arm to open the AFM - then listening for the fuel pump to come on. It would come on when the engine was cold but not when hot. I have no idea why, and frankly I'm not sure I care. The car runs fine now.