cold start 1980 FI help!

[sigkadetm]

I need a little help. When starting the engine cold the cold start injector sprays fuel and the aux air valve is open allowing air to enter. Shouldn't the RPMS rev up? My 1980 FI Spider starts up fine when cold but the high speed idle is low until the engine warms up. Is this normal?

[76was124]

No, it should idle high when cold. Have you gone through the FI setting procedure in one of Brad Artigue's maintenance manuals? Link is:http://www.artigue.com/fiat/

[vandor]

Well, not too high tho, maybe around 1000 rpm?
The AAV is supposed to close as the engine warms, keeping the idle speed fairly constant.

[ORFORD2004]

It happen to mine when he was cold the idle was very slow and want to stall at corner. It was the AFM.

[sigkadetm]

Everything seems to be working unless I overlooked something but the engine RPM's stay the same or go lower. Fine after the engine warms up.

[RRoller123]

Pull the two hoses at the AAV and look through it when the engine is cold and make sure you can see daylight, in the form of a triangular opening. This opening will be closed when the engine is warmed up.

Also check the connections to the thermal sensor at the coolant "T" at the front of the engine. They are frequently damaged due to their location.

2 Possible candidates for this fault.

Pete

[76was124]

Everything seems to be working unless I overlooked something but the engine RPM's stay the same or go lower. Fine after the engine warms up.

Sorry, I am having trouble understanding the situation...so a couple questions to get clarification:
1. When you say everything seems to be working, what specifically is included in 'everything'
2. The ' Low idle' when cold is what RPM?
3. What is the RPM when warm?
4.How ( what procedure) did you use to set the timing and idle/ throttle plate screw?

[vandor]

> Also check the connections to the thermal sensor at the coolant "T" at the front of the engine.

If that connector breaks, falls off, or loses contact with the temp sender in any way, the FI will think that the coolant temp is extremely cold and use a super-rich mixture that usually flods the engine where it stalls and won't restart.

[RRoller123]

True, unless it actually IS really cold outside. In that case the sensor just happens to be ~ correct when disconnected, and the operating problems will show up as the engine warms.

For those interested in studying the Bosch L-Jetronic system, there is an amazing amount of quality material available on the web.

This link from the BMW folks has a very good PowerPoint type presentation on the components, etc.

http://www.firstfives.org/faq/ljet/jetronic.pdf

This one, from the VW folks, has a good component description too, but also a good trouble shooting manual:

https://www.type4.org/manuals/ljet/

But here is Bosch's own manual, a long, detailed slog through the swamp for sure. Probably best printed out for studying:

http://foxed.ca/rx7manual/manuals/BOSCH ... Manual.pdf

[RRoller123]

I need a little help. When starting the engine cold the cold start injector sprays fuel and the aux air valve is open allowing air to enter. Shouldn't the RPMS rev up? My 1980 FI Spider starts up fine when cold but the high speed idle is low until the engine warms up. Is this normal?

Your problem is directly addressed on pages 23 and 24 of the Bosch manual. May not be the actual cause, but sounds like a good match to the issue.

[sigkadetm]

Thanks everyone. I'm going to recheck everything again this weekend and I'll post the results.

[sida555]

I am having the same exact issue. I have checked the aux air valve and its working correctly. according to the Bosch L-Jetronics manual the cold start revs handle by the aux air valve + engine temp sensor on the coolant T + the ECU ? If the cold start valve works what would be my next step to check the low idle issues when on a cold start ?

[rridge]

Check the FI temp sensor on the coolant tee for proper resistance and inspect for possible FI harness wiring and connector damage as suggested six years ago above.

The sensor is not a precision instrument. With a cool engine at 68F the resistance between the two contacts on the sensor should fall between 2100-2900 ohm. As the thermostat approaches opening temp, at 180F, the resistance should be 270-390. When in doubt, replace it. They are both cheap and temperamental.

[sida555]

Check the FI temp sensor on the coolant tee for proper resistance and inspect for possible FI harness wiring and connector damage as suggested six years ago above.

The sensor is not a precision instrument. With a cool engine at 68F the resistance between the two contacts on the sensor should fall between 2100-2900 ohm. As the thermostat approaches opening temp, at 180F, the resistance should be 270-390. When in doubt, replace it. They are both cheap and temperamental.

Thank you I will check the resistance. I do have a couple of good working aux valves in hand too. Aux valve resistance I did check and verify the functionality. Any other possibilities besides the coolant temp sensor ? If fuel injector harness damages wouldn't it effect running when it's up to operating temps as well ? The car drives fine when it's up to operating temps.

[sida555]

It happen to mine when he was cold the idle was very slow and want to stall at corner. It was the AFM.

My AMF had been messed with by someone prior to me. I am planning to send it out to FIC to get it refurbished and calibrated to the factory settings as a base line.