Car does not start when hot

Keep it on topic, it will make it easier to find what you need.
zachmac
Posts: 1084
Joined: Sun Aug 24, 2008 9:20 am
Your car is a: 1978 Spider [1979 2 ltr engine]
Location: Aiken, SC

Re: Car does not start when hot

Postby zachmac » Wed Jun 14, 2017 2:19 pm

zachmac wrote:
PAV1980Spider wrote: If I crank the starter the engine will not start when hot even though the starter will be rotating the engine very well. At the same time, if I push the car and engage a gear, then the engine comes to life almost immediately. I have no idea how to explain this. What does (or does not) get engaged differently when the engine is cranked by the starter or rotated by the motion of the wheel? quote]

The only difference in what you describe is the path for current through the ignition switch. You are getting current to the coil and plugs when in the running position but not in the start position. When I get home tonight I'll research this and remember what is different but I am pretty sure you are looking at an electrical issue, most likely in the ignition switch and starting circuit. It could be the air flow switch as I think that plays a role in starting versus running but it's weird that you have the opposite problem most people have, no fire when starting versus in run. That tends to support a worn air meter surface.

This isn't a fuel delivery problem or the car wouldn't start and run so well on the pop the clutch start. Been I while since I messed with the fuel injection (sold my 80 years ago) but I kept all my files from then so I'll dig in tonight.
Jeff Klein, Aiken, SC
1980 FI Spider, Veridian with Tan (sold about a year ago), in the market for another project
2009 R350 Mercedes, family hauler
2005 S600 Mercedes V12, 620 hp, 740 ft lbs torque

CajunMike
Posts: 312
Joined: Sat Dec 27, 2008 12:44 am
Your car is a: 1979 Fiat Spider

Re: Car does not start when hot

Postby CajunMike » Wed Jun 14, 2017 5:17 pm

Check the control module as mentioned. It's a $25 part. Spent a week trying to figure this out, replaced several things before I got to it. I would drive to a store and get back in to leave no start.. Had to wait till engine cooled to start again. This happened several frustrating times. Would crank cold no problem. Good luck.

zachmac
Posts: 1084
Joined: Sun Aug 24, 2008 9:20 am
Your car is a: 1978 Spider [1979 2 ltr engine]
Location: Aiken, SC

Re: Car does not start when hot

Postby zachmac » Sat Jun 17, 2017 11:57 am

I have an excell table I put together years ago on the combi relay. You'll see power is routed differently when cranking versus when in run. Perhaps something temperature related is causing your relay to work initially but not when hot? Send me an off forum email and I'll send you the file. It may help diagnosis?
Jeff Klein, Aiken, SC
1980 FI Spider, Veridian with Tan (sold about a year ago), in the market for another project
2009 R350 Mercedes, family hauler
2005 S600 Mercedes V12, 620 hp, 740 ft lbs torque

zachmac
Posts: 1084
Joined: Sun Aug 24, 2008 9:20 am
Your car is a: 1978 Spider [1979 2 ltr engine]
Location: Aiken, SC

Re: Car does not start when hot

Postby zachmac » Sat Jun 17, 2017 5:01 pm

Couldn't get it to format so here is a photo of my relay table.
Image

If you notice, the power to the fuel pump and FIs is different in the "run" key position versus "cranking". Seems like you are getting it both positions when cold but for some reason only in "run" when hot. I'd warm it up and check for FI firing *(you'll need a node light and a friend) while cranking. I suspect you'll find there are not firing when hot an cranking but have power in run which is why it will start with a rolling clutch pop.
Jeff Klein, Aiken, SC
1980 FI Spider, Veridian with Tan (sold about a year ago), in the market for another project
2009 R350 Mercedes, family hauler
2005 S600 Mercedes V12, 620 hp, 740 ft lbs torque

md88plt
Posts: 47
Joined: Fri Jan 22, 2010 12:57 pm
Your car is a: 1979 Fiat spider
Location: tennessee

Re: Car does not start when hot

Postby md88plt » Sun Jun 18, 2017 8:09 am

Check distributer cap. I installed a new distributer cap (made in China via World Auto Parts brand) that ended up being defective. The defect showed up when the engine temperature rose to normal temps. The heat from the engine/exhaust manifold was heating the distributer cap and changing the internal resistance of the cap so that the car would not start and or lacked power. I finally figured this out with my ohm meter. Hope this helps. BTW I always make sure that my parts are not Chinese made.

PAV1980Spider
Posts: 19
Joined: Fri Mar 25, 2016 2:14 pm
Your car is a: 1980 Fiat 2000
Location: Chesterfield, MO

Re: Car does not start when hot

Postby PAV1980Spider » Mon Jun 19, 2017 3:47 pm

Thanks a lot for your help! I think that next to check will be all related to the ignition key, which has been giving me troubles for awhile. I know there is something loose in it since every now and then I need to wiggle it a bit to turn the engine off.
Need to find a node light and a friend now though.
Sorry for not responding on time.


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