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> Best carbed warm start procedure
bbrock
post Aug 18 2022, 04:15 PM
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Apologies if this is addressed somewhere, but couldn't find anything with google search.

I'm wondering if there is a "proper technique" for warm starting a 914/4 with 40 IDFs. To be clear, I'm only interested in what to do with my right foot when starting after the car sat with a hot engine for 15-30 minutes. I'm hoping to megasquirt the engine over the winter so will happily just live with what is a minor annoyance before spending time or money chasing a fuel boiling issue or similar.

Here's some background on my stock 2L with 40IDFs and mild Elgin carb cam. Timing is set at ~32deg BTDC. Fuel pump is relocated to the front 75-76 location. I run a fuel return line, and I have phenolic spacers between the intakes and heads.

I spent a lot of "quality time" with my carbs and a wide band earlier this summer and they are dialed in and running SWEET. I was running the stock dizzy with injector contacts blocked off and the car ran well, fired instantly when hot or cold, and idled steady.

My old dizzy started acting erratic so I swapped it for a new Pertronix SVDA with Ignitor III replacing the points. That is when the warm start issue showed up. Car fires nearly instantaneous on cold starts, but when the engine is fully warmed up and then left to sit 15-30 minutes, I have to crank too long to fire it up again. Seems like holding the accelerator for WOT works best to get it to catch but I haven't played with different combos too much. Once it catches, it coughs back to life and runs a bit rough for about a minute while it spits out the extra gas.

I suppose the E85 might still be boiling in the carb bowls despite the return line and phenolic spacers. If so, I'll just live with it for now, but wonder what folks think is the best throttle position for starting a warm set of carbs. Also open to suggestions for holding my tongue or mouth a certain way if that will help. And for sure a magic combination of swear words would be welcome as I"m a huge fan of those. (IMG:style_emoticons/default/happy11.gif)
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ssstikircr
post Aug 18 2022, 04:36 PM
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Are you sure it’s boiling the fuel in the bowls…. Or might it be vaporizing the fuel in the fuel line? An old school very complicated hack was to run a couple of the old school wooden clothes pins on the fuel line to dissipate the heat. Old Datsun race car hack for those really hot track days. Don’t laugh but it works. Otherwise you would have to make heat shield to run between the carb and head. Had to do that on a drag/ street bug with 48IDAs.
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bbrock
post Aug 18 2022, 04:50 PM
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QUOTE(ssstikircr @ Aug 18 2022, 04:36 PM) *

Are you sure it’s boiling the fuel in the bowls…. Or might it be vaporizing the fuel in the fuel line? An old school very complicated hack was to run a couple of the old school wooden clothes pins on the fuel line to dissipate the heat. Old Datsun race car hack for those really hat track days. Don’t laugh but it works. Otherwise you would have to make heat shield to run between the carb and head. Had to do that on a drag/ street bug with 48IDAs.


Love that hack! My first 914 had horrible vapor lock problems and there was a hack published in one of the old Mid-Engine Views newsletters to drill a hole in the top of the fuel relay housing and insert the tip of a ballpoint pin in to create a push button to manually run the fuel pump when the ignition switch was on to circulate fuel to cool and clear the bubbles. It worked a treat!

In this case, I'm not sure it is a fuel issue at all. I'm more just trying to rule out operator error and was curious if folks adjust throttle position between cold and hot starts. I'm actually wondering if the Pertronix module might be heat soaking. The only things that changed before this started was switching from points to pertronix, and no longer running vacuum retard. So seems like spark or timing (so spark) might be the issue.
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stownsen914
post Aug 19 2022, 07:41 AM
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When I had a street 914 with dual IDFs and fuel pump relo like you have, it would fire right up when it had been recently running. Cold start was a few jabs on the gas pedal to actuate the accelerator pump and fire right up. You might be right that E85 is part of the issue.
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TheCabinetmaker
post Aug 19 2022, 07:53 AM
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I would suspect the new diz since that's when it changed. You can get a diz rebushed and rebuilt like new.
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bbrock
post Aug 19 2022, 08:26 AM
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QUOTE(stownsen914 @ Aug 19 2022, 07:41 AM) *

When I had a street 914 with dual IDFs and fuel pump relo like you have, it would fire right up when it had been recently running. Cold start was a few jabs on the gas pedal to actuate the accelerator pump and fire right up. You might be right that E85 is part of the issue.


That describes perfectly what I'm seeing now. Then there is the in between when the engine cools down a little from operating temps.

QUOTE(TheCabinetmaker @ Aug 19 2022, 07:53 AM) *

I would suspect the new diz since that's when it changed. You can get a diz rebushed and rebuilt like new.


I don't think it is the dizzy itself as it is brand new and these SVDAs have a good track record on carbed Type 4s. The dizzy is going away anyway because I'll convert to COP ignition when I do the megasquirt.

However, I do suspect the Pertronix module inside the dizzy - possibly heat soaking - which I think could explain things.

Also, I'm wondering about timing. I'm running extra advance for the carbs and E85, but the old dizzy had vacuum retard which should have been pulling the advance back during startup and idle. I wonder if pulling the advance back a degree or two would help. That's about the extent of what I'm will to do at this point.
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stownsen914
post Aug 19 2022, 08:47 AM
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When I had a street 914 with dual IDFs and fuel pump relo like you have, it would fire right up when it had been recently running. Cold start was a few jabs on the gas pedal to actuate the accelerator pump and fire right up. You might be right that E85 is part of the issue.
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FJ1200
post Aug 19 2022, 10:49 AM
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Two things.

The older Pertronix definitely heat soak and will lose spark, a new ignitor is fairly inexpensive. I have had to dump a 5 gal bucket of water on my distributor twice to cool it down enough to get spark back. Both hot days, long low speed driving and then parked to have lunch.

Second, add a switch to over ride the fuel pump relay. My fathers 190SL will boil the bowls dry in 5 min after a hot run. We added a small Facet pump and tied it into the fan switch (warm weather car no heat required). This refills the float bowls and she fires right up.

And I guess a third thing. Talk a little more about the COP ignition. My plan is similar and I would love to use COP. I have not yet done the homework as to what coils will fit the best. I think it needs to be one that uses a mechanical fastener (bolt) and add threaded standoffs to the tins to support them.

Have a great day!

Dan
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bbrock
post Aug 19 2022, 01:03 PM
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QUOTE(FJ1200 @ Aug 19 2022, 10:49 AM) *

Two things.

The older Pertronix definitely heat soak and will lose spark, a new ignitor is fairly inexpensive. I have had to dump a 5 gal bucket of water on my distributor twice to cool it down enough to get spark back. Both hot days, long low speed driving and then parked to have lunch.

Second, add a switch to over ride the fuel pump relay. My fathers 190SL will boil the bowls dry in 5 min after a hot run. We added a small Facet pump and tied it into the fan switch (warm weather car no heat required). This refills the float bowls and she fires right up.

And I guess a third thing. Talk a little more about the COP ignition. My plan is similar and I would love to use COP. I have not yet done the homework as to what coils will fit the best. I think it needs to be one that uses a mechanical fastener (bolt) and add threaded standoffs to the tins to support them.

Have a great day!

Dan


Thanks Dan. Good info! I've read similar about the older Pertronix. I'm running their newest model that I bought just before they jacked their prices way up. I don't see why it would be any more resistant to heat soak than the older ones though, so still suspicious.

I wondered about letting the pump circulate longer before trying to start the engine. I'm running through the stock relay but without the ECU, the pump runs whenever the key is on regardless of whether the engine is running. I'll try just turning on the key without starting the car for a half minute and see if that helps.

For COP, I'm planning to just buy from The Dub Shop since he has several options that he's already worked out for running on a Type 4. I'm going to go the LS2 route to run full sequential because I have a need to go the most complicated route for questionable benefit. (IMG:style_emoticons/default/lol-2.gif)
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MarkV
post Aug 19 2022, 03:05 PM
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I am running Delorto carbs and had a hot start problem for a long time. I switched from a 050 Bosch Distributor with a Pertronix II to a Malory with a Pertronix II and that fixed the problem. I don't remember the exact settings but with the 050 it didn't like the initial timing and would be really hard to hot start. The Mallory is set up at 32 degrees total and it starts hot no problem with just a little throttle.
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R Dub
post Aug 19 2022, 08:44 PM
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I just put the gas pedal to the floor as I crank it and it starts fairly easily when hot.
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Superhawk996
post Aug 19 2022, 09:00 PM
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QUOTE(bbrock @ Aug 18 2022, 06:15 PM) *


I suppose the E85 might still …



Hey buddy! I’m going to troll for a minute.

Your supposed to be running the car on GASOLINE.

E85 is 85% Ethanol

So I’m going to assume you mean your running E15 which is 15% ethanol 85% gasoline

Even so - I’d be trying to avoid alcoholism and would try to find a gas station that uses no more than 10% ethanol (E10).

But in all seriousness if it started with the Pertronix install . . . I’d bet that is your problem. At the risk of offending those that love them. I think Pertronix is rubbish based on their previous products lack of reverse polarity protection and lack of key on thermal protection. I know those are supposed to be solved with Perteonix III but god only knows what the new bugs are and or what new thermal issues it may have leading to extended cranking.

You’ll sort it out !
@bbrock
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bbrock
post Aug 19 2022, 11:40 PM
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QUOTE(Superhawk996 @ Aug 19 2022, 09:00 PM) *

QUOTE(bbrock @ Aug 18 2022, 06:15 PM) *


I suppose the E85 might still …



Hey buddy! I’m going to troll for a minute.

Your supposed to be running the car on GASOLINE.

E85 is 85% Ethanol

So I’m going to assume you mean your running E15 which is 15% ethanol 85% gasoline

Even so - I’d be trying to avoid alcoholism and would try to find a gas station that uses no more than 10% ethanol (E10).

But in all seriousness if it started with the Pertronix install . . . I’d bet that is your problem. At the risk of offending those that love them. I think Pertronix is rubbish based on their previous products lack of reverse polarity protection and lack of key on thermal protection. I know those are supposed to be solved with Perteonix III but god only knows what the new bugs are and or what new thermal issues it may have leading to extended cranking.

You’ll sort it out !
@bbrock


Yeah, you got me. E10 is what I'm using. I didn't think E85 sounded right. They actually don't use that much ethanol around here. Pure gasoline is pretty easy to find but $$$.

Agree about Pertronix. The only thing worse is a set of points. Gawd I hate those things. (IMG:style_emoticons/default/poke.gif) (IMG:style_emoticons/default/happy11.gif)

I'm actually leaning toward timing. Maybe just a tad too much advance when trying to start warm. Don't assume I'll get it sorted though. My motivation is very low. As long as it takes $0 and less than an hour of time, I'm willing to fiddle. Beyond that is just not worth it.

I did fiddle around with different throttle positions when running errands tonight. Foot to the floor is definitely the best.
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Front yard mechanic
post Aug 20 2022, 06:42 AM
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E85 is what we call it here it has up to 15% alcohol and is rated at 85 octane
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VaccaRabite
post Aug 20 2022, 06:50 AM
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QUOTE(Front yard mechanic @ Aug 20 2022, 08:42 AM) *

E85 is what we call it here it has up to 15% alcohol and is rated at 85 octane

err..... no.

E85 has between 50%and 83% ethanol and is over 100 octane. Unless you are buying race gas its hard to find fuel with a higher octane rating. That is why all the turbo guys love it.

Zach
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