Hot start troubleshooting

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Tucaz520

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Here we go. Another hot start thread lol could use some opinions. 

351c 2V no modifications 

Car starts immediately when cold and runs great. 

Runs good and strong when warm as well. 

The problem comes when i shut it off. 

If i wait less than say 10 seconds after shut off it will fire right back up in an instant.

If i wait longer than that say a couple minutes up to about 15-20 i have to keep the pedall to the floor while cranking.  The starter sounds strong for the first few seconds then slowly gets weaker. I would estimate it takes 5-8 seconds to start. Right before it starts the battery seems to be getting week.

The car does diesel when shut down from time to time.  I rebuilt the carb and am waiting to road test it to see if the dieseling has been solved.

My thoughts

Since the starter sounds strong at first i dont think its a heat sink issue.

I started to think fuel was getting sucked into the combustion chamber and draining the bowl. But it will fire immediately afterit cools.  so i dont think the bowl is getting emptied. 

Still have points ignition and a coil thats probably from 1999 if not older lol.  

Id really like to pinpoint the problem rather than start throwing parts at it. I know it will all have to be replaced anyway but id still like to know what the issues is incase it returns. 

Im down to 2 thoughts 

1 it is sucking fuel after shut down and flooding

2 weak spark because of old components.

 

Canted 393

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Probably boiling fuel, vapor lock. The cure would be to run a carb spacer.

Hard cranking , check cables from the battery and to the starter and also have a good ground connection. Its a good place to start before we start spending your money.

 

Twins

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Tucaz:

You are describing EXACTLY how my car used to behave before I dug into it a bit. As canted noted we believed it was due to vapor lock.

I dreaded letting it sit 15-20 minutes as it was a real PIA to get started again. I cant tell you exactly which of these things cured the problem (or recall if I did more) but it is cured:

1. My timing was way off and needed to be advanced.

2. Carb spacer as already suggested -could solve the problem right there.

3. In my case, I wound up changing the intake manifold for other reasons but this was done at the same time as:

4. Conversion from points to Petronix ignition

5. Proper thermostat.

6. larger row radiator.

My car starts right up now hot or cold although eventually I did put in a new starter. It runs significantly cooler with no needle creep in traffic on hot days. Start with the least expensive thing. Maybe the timing, the carb spacer, thermostat if needed, etc. Petronix ignition at some point if you want to go that way. Determine if the car is running excessively hot as well before throwing parts at the cooling system. Good luck.

 
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Mikes73

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Excellent advice posted above, nothing really to add to that.

 

Tucaz520

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Thanks for the input.

The car does seem to run a little hot even thought the guage doesnt show it.

I do still have the metal fuel line that runs along the front of the engine.

Im going to start there and see if i can get some distance between the block and the fuel line and then check the timing. I miss spoke earlier about no mods i forgot about a rebuild which included a mild cam and because of that the timing may have been changed.

Once i check the timing and fuel line ill look into carb spacer. Anypne have a source for those?

 

Twins

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Excellent advice posted above, nothing really to add to that.

Thanks for that Mike.  After 4 years I finally had something relevant to add.  Felt good!
 

Twins

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Thanks for the input.

The car does seem to run a little hot even thought the guage doesnt show it.  

I do still have the metal fuel line that runs along the front of the engine.

Im going to start there and see if i can get some distance between the block and the fuel line and then check the timing. I miss spoke earlier about no mods i forgot about a rebuild which included a mild cam and because of that the timing may have been changed.

Once i check the timing  and fuel line ill look into carb spacer. Anypne have a source for those?
I tried isolating the line, I think I even wrapped it at one point and relocated the fuel filer but it did nothing.  I thought it would have helped but not much if at all.  With the hot weather coming your issue will probably worsen. Mine did.

It's been about two years since I did the work but I probably got the spacer from Summit Racing.  They are relatively inexpensive and come in a variety of materials - including wood if I recall correctly!  If you are going to install a spacer, make sure you have the clearance between the now elevated carb and the hood - especially if you have a ram air set up or you might have a real issue when you go to close the hood!

 

Don C

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It's actually called fuel percolation, when the fuel in the bowls boils or expands enough to flow into the intake manifold. A high float level will excacerbate the problem.

A weak coil or bad condenser can mimic fuel percolation.

Your battery may have a bad cell, needs to be load tested.

 

Mikes73

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Excellent advice posted above, nothing really to add to that.

Thanks for that Mike.  After 4 years I finally had something relevant to add.  Felt good!
HahaHahaha, no problem at all.

 

Tucaz520

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Ok moved the fuel line and same results.

Next up timing which will be a chore to figure out since the vac advance hasnt been hooked up ever since the rebuild around 1992.

A little history on the car again. My dad owned it since 1976. 1992 ish he took it in for a rebuild on the engine. While apart he had the shop install a mild cam. He then used to to commute from Sierra Vista Az to Douglas Az daily 50 miles each way. I may have exaggerated that distance in an erlier post but hey i was a kid and it felt wayyyyyyyy further lol.

When the car is on the road it does seem to lack power on the lower end but runs and idles strong. When on the highway it absolutely screems. 60mph-100nph makes me grin from ear to ear. Accelerating from a California roll say 20mph-50mph make me wanna hide my face as it seems to take forever to get there.

Im thinking with the long commute the timing was set at the advacnce mark. The vacuum disconnected and plugged. I checked everyrhing out and applied a vacuum and everything works as it should. Stay tuned as i iet it cool, clean an mark the balancer and see what my timing is set at.

 

Tucaz520

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Also snaped this pic after i shut it down. Notice the smoke\vapor coming from inside the carb. Is that solid proof of percolation?

 

Tucaz520

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Ok disclaimer im not experianced in setting timing and the wonderful interwebs here has more info than is usefull and of course contradicts.

So i just got some numbers and hopefully someone with more knowledge than me can chime in.

First thing i did was slide under the car and by luck all the degree marls were right there at the bottom and easy for me to clean and mark.

I did notice they were marked at 0 degrees and16 degrees already.



 
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Tucaz520

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Next i raided the kids sidewalk chalk and filled in the numbers and other degree liines.

Again im not sure of the proper procedure to set timing but this is what i did.

With no vac advance hooked it idled at 1000 RPM and it stayed true to the 16 degree mark that was made when the engine was rebuilt.



 

Tucaz520

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I bumped the rpm up to around 2500 and the timing was at 25 degrees.

Sorry no pic of thst one. Not enough hands.

Next i hooked up the vac advance and the idle speed was 2000 RPM the timing was coming in at above 30 degrees



Obviously bumping the rpm up to 2500 sent it way passed any degree markings.

 

Tucaz520

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With the car up to temp and me playing with the timing light when i shut it down it did diesel both with and without the vac advance hooked up.

Should i leave the vac advance hooked up set the idle at 1000 rpm and adjust the timing to 16 degrees or less?

 

Mikes73

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You wouldn't happen to know the rear axle gear ratio would you? This may have some bearing on the lacking performace in 20 to 50 mph range.

 

Tucaz520

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You wouldn't happen to know the rear axle gear ratio  would you?  This may have  some bearing  on the  lacking performace in 20 to 50 mph range.
Unfortunately i dont. I do know the gears were switched 2 times over the life of the car.  Im sure the last time it was modified to help with the daily commute so possibly it is geared for highway driving.

 

Tucaz520

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Ok went back out and messed with it some more.

Orginal vacuum hoses seem to be all in the wrong places.

I connected vac advance hose and retarted the timing down to 8 Degrees and it so idled rack back down to 1000 rpm.

Tightend the dist and hit the throttle and the timing jumped passed 30 degrees ran rough and backfired.

Thinking the vacuum sorce the advance may be the wrong one.

So down the rabbit hole i went. Turns out im missing a ported vacuum switch the threads into the water pump and has 3 lines attached to it a a speed check valve in line up to the vac advance.

Numbers 1 and 6 in the pic.



 

Don C

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The idle speed is too high, it should be around 650 with a manual transmission and with an automatic transmission in drive. That will contribute to dieseling. You are using the correct procedure to check the timing, just need the idle speed lower.

What you are seeing sounds correct.

 
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