Hard starting when hot

robsad

robsad

True Classic
Hi all,
I'm in the break in phase of my newly rebuilt 1980 1500 FI engine converted to carb installed in my 74. Specs are: Block bored to 87 MM, Wiseco forged pistons from MWB, performance head from MWB, 34 DMTR jetted according to Steve C recommendation. I have the return line in place from the carb back to the tank. The plugs all show no signs of soot with a tan color on the electrodes. Not sure of the comp ratio but Matt said it's probably somewhere around 10.5 to one. I installed an adjustable cam gear and advanced the cam 10 degrees according to recommendations due to the head saved .075. Facet Cube electric pump, mech pump eliminated. I've put about 100 miles on it so far. Timing set at 12 degrees advanced at 1200 RPM. Idles very smoothly at this setting. This engine starts instantly when cold with choke. However when hot after a run it's hard to restart. It will turn over a few times then starts to bog down a bit but starts eventually with some difficulty. Should add I'm using Klotz octane booster. There is no pinging at all. I must say even with the fact that it has only a few miles on it the engine runs strong with no hesitation. I'll come just short of saying the car now will put you back in your seat in first and second gear. I was told that maybe the timing is too far advanced hence the hard starting when hot. I tried different settings but it runs best where it is. Any ideas ? Thanks in advance,

Bob
 
Unplug the coil and see if it cranks easier. If so then your timing is too far advanced. If it still struggles then it may be a weak starter that can’t handle the heat.
 
Huey said:
Unplug the coil and see if it cranks easier. If so then your timing is too far advanced. If it still struggles then it may be a weak starter that can’t handle the heat.
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Huey,
I'll try that, thanks. BTW this is a new starter, not rebuilt.
 
How is your fuel pressure regulator? Make sure it is not leaking into the intake manifold as this will give you hard starting when hot. Just check it by removing the vacuum tube to see if there if any fuel present. Just thought I would mention this because my 1986 had a hard start when hot when I purchased the car and this was my problem.

Good luck tracking down the problem.
 
As I understand the problem, the motor turns normally, but does not fire off when hot. If so, then this is a fairly common problem with a carbureted X and it is one reason the carb cooling fan is a handy device. It helps reduce boiling of the gas in the float bowl and overflowing into, and corresponding flooding of, the intake.

But sometimes, even the cooling fan is not enough on really warm days. The solution that works is the one that was specified on the driver’s instructions that came on driver’s side visor. Unfortunately, the art and science of using carburetors is passing into history and so the little trick is becoming lost. When the engine is hot, just push the accelerator pedal down about half way very slowly, and hold it there when you crank the engine. This has worked for me for many years. Sometimes it was on the verge of not starting. But with this technique it fires off every time.

And I had forgotten that trick for a while and was having a heck of time cranking the engine on hot days. Then I came across the old visor instructions and it all came back.
 
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robsad said:
Huey,
I'll try that, thanks. BTW this is a new starter, not rebuilt.
Click to expand...

If it is slow crank, and not carb related excessive crank time, most likely the starter heat soaking. I still had that with a new old style starter. Solution was to get the gear reduction starter.
 
LarryC said:
But sometimes, even the cooling fan is not enough on really warm days. The solution that works is the one that was specified on the driver’s instructions that came on driver’s side visor. Unfortunately, the art and science of using carburetors is passing into history and so the little trick is becoming lost. When the engine is hot, just push the accelerator pedal down about half way very slowly, and hold it there when you crank the engine. This has worked for me for many years. Sometimes it was on the verge of not starting. But with this technique it fires off every time.

And I had forgotten that trick for a while and was having a heck of time cranking the engine on hot days. Then I came across the old visor instructions and it all came back.
Click to expand...

^^^ This, I was going to chip in and ask if you are depressing the accelerator about a 1/3 down before cranking the engine...
 
NEG said:
^^^ This, I was going to chip in and ask if you are depressing the accelerator about a 1/3 down before cranking the engine...
Click to expand...
Funny, I've owned this 74 from new and I don't remember this tip but will try this at next run. Now to track down an oil leak on this fresh rebuild. Thanks all !!
 
Just to complete that thought, here is the actual as-delivered card from the visor, in English, and the native language in case that is more comfortable to read.
IMG_1866.jpg
IMG_1867.jpg
 
Sorry, totally didn't realize that your car was converted to carb. I guess I should have read your thread more thoroughly before I replied (or paid attention to what I read?).
 
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