Technical hot starting trouble

[AGT]

I have a few problems with the starting of my car when hot.

The car runs fine when moving but after about an hour of slow moving
or if the engine is switched off it will not start again for about 5 mins and
will occasionally backfire.

I will list a few details: The car has new braided fuel lines- there is plenty of
fuel in the float chamber when it wont start- the temp gauge never goes
over 90 degrees-Fuel is being squirted in when it won't start (i can see it when i open the throttle)-the car has new leads (although much longer than they should be)- it does not have a carb fan fitted-there is a spark at the coil when it won't start-all cooling sytem components are new-once it has restarted it will miss through the rev range. I origanlly thought it could be
fuel vapourisation but I am now wondering if it could be the weak ht due to
the length of the ht leads. Any ideas? cheers

 

[jimbro1000]

Can you be more specific about the "not-starting"? Is the car acting like the battery has gone flat or does it turn over cleanly but refuses to fire?

There are a couple of things you can try - first of all ditch the air filter in favor of a high performance filter and housing. The original pancake housing soaks up a fair bit of heat and causes problems that way. Make sure the insulation plate is still fitted between the carburettor and the manifold too!

The other thing to try is re-running the main power cable to the engine bay (from battery to starter motor) - these degrade over time and any increase in resistance will result in starting problems. There is another wiring mod that helps with general usage to replace the brown wire to the fuse box as this too suffers the same problem and causes most of the wiring grief in the car.

The HT leads are very unlikely to be the problem *but* after 30 years the originals could be rather the worse for wear. A set of good leads (nothing fancy) will do the job there if there is any degradation.

 

[AGT]

The car spins over fine. I dont know if it is relevent but this all
started after the car got very hot in a traffic queue due to the fan
not working.As I said, as long as the car is moving-fine-if I should stop
it wont restart for another five minutes. I am thinking that rising
heat in the engine bay is playing a part. I have taken the filter off whilst I await my k&n this have made a slight improvement.

 

[jimbro1000]

You might want to consider running a compression test when the engine is cold and when the engine is hot. There is a distinct possibility that this isn't just a hot starting problem and you have a leaky head gasket. Short of stripping everything down and doing some proper tests a compression test is probably the best you can do as a precaution.

The normal hot start problems on an x1/9 are vapor lock (fuel refuses to come out of the carb) and poor earthing/power feed to the starter motor in which case the engine just won't turn over.

In some cases the engine starts but stalls after a few seconds and it takes a bit of churning before the fuel supply builds up again and it runs properly. This just be fuel vaporisation from the float chamber and there isn't much you can do about that one.

The problem you describe does not fit any of the above faults, so dig a bit deeper and see what the compression test results are. I would expect to see good cold compression on all four but one or two of the cylinders dropping pressure when hot. If it comes up good hot as well then the problem is elsewhere and it will take some more delving to find.

 

[AGT]

I don't know if this is relevent but last night when I took
of the top off the carb I saw two very small streams of bubbles
coming up from the bottom of the float chamber?!

 

[jimbro1000]

Now that is weird - was the engine hot at the time or cold?

 

[AGT]

It was hot. This was during one of it's playing up periods. I took
the top off to prove that the float chamber was still full of fuel and that
is when i saw it. Think pan of boiling water on a tiny scale and that's
what it looked like but just two streams.

 

[jimbro1000]

Sounds like the fuel is getting all the volatiles boiled off and there isn't much you can do about that but just leaving it to cool off wouldn't help the situation - infact it would just make it worse since even more of the fuel would be boiled off (or rather the volatile part of it).

If you've got fuel in the carb (and can verify it is going down the barrel when you turn the engine over) then I seriously doubt this is the problem. The fuel would have to be really seriously boiled up and leaving it wouldn't help.

You need three things to get the engine to run - fuel/air charge, compression and a spark. You can easily check that you have fuel going in and likewise for a spark which just leaves compression.

 

[AGT]

I don't want to tempt fate but after fitting a new coil, I took it
out last night without incident Perhaps the coil was breaking down when hot? Fingers crossed. Cheers jimbro

 

[jimbro1000]

You might want to consider getting a set of plug lead testers. They are just transparent caps that fit between the plug and the lead that flash when there is a spark - makes it much easier to see if things are going wrong.

Keep in mind that just replacing the coil could be a temporary fix if anything else in the ignition system is failing.

I swapped to an electronic ignition system on my last car and coupled with fixes to the other likely candidates for hot start problems it make the car pretty much bulletproof (right up until I cracked the block).

 

[Jefflun]

Hi
I occasionally have the very same problem on my X1/9.
It has no carby fan, but insulator is still in tact, it has electronic ignition with new dizzy cap and leads, compression is ok and carby is good.
Brown wire has been done, extra earths added to body and engine and a new Odyssey High crank battery. I'm convinced its largely related to the carby and has been a thorn in Xies sides for ever.
I have found that if you press the accelerator pedal hard to the floor and dont pump it while you are trying to start the car when it is hot, it will restart after a small amount of cranking every time.
According to a Fiat Mechanic friend, this doesn't seem to happen on fuel injected models and he has suggested that I fit a fuel injection system to the car anyway.
Regards Jeff

 

[AGT]

:bang:

I swapped to an electronic ignition system on my last car and coupled with fixes to the other likely candidates for hot start problems it make the car pretty much bulletproof (right up until I cracked the block).[/quote]

After my latest spate of vehiculer aggro I am thinking of going this
route along with a facet pump.I still haven't had any hot start probs
but now it decices that after half an hour it wants to miss under load.
took it out this morning for an hour-30 miles-not a problem, took it
out this afternoon-15 minutes-missing like a pig under load,it is really intermittant.If I convert ignition and pump then EVERYTHING will be uprated
and the car will either be cured or featured on the news at ten FALLING FROM THE SEVERN BRIDGE!!!!!lol. Do luminition do a kit for the x19? I know
I can go the uno route but the old 'oh no's' are getting a bit thin on the ground now