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 Posted: 07-21-2018 01:11 am
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jomac
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my Jensen after a half hour drive, started off from stop light it started sputtering ( loss of power ) then stalled, i looked under the hood and noticed nothing unusual, got back into the car and it started and i drove home without any problems. it was warm and humid , temp about 80 degrees.
half tank of fuel and engine a normal temp. any thoughts on where to start to troubleshoot? first time this happened.
flame thrower coil is 4 years old.

more info, i have a pertronix distributor 176628 and a 40k flamethrower coil (40511), it stalled again after driving 5 mins, and it was 65 degrees outside. this time it did not sputter just lost power i pump the throttle no effect. then it stalled. but i waited 30 sec. and it started right up.i drove home about a mile. i checked the carb diaphragms, are good, oil in carbs, checked the full pump relay, and pump., i have a fuel check valve installed , will bypass it.removed fuel line to carb filter and check valve- plenty of fuel in line. but removing check valve anyway.also, i have a low oil pressure shut off valve on engine due to the electric fuel pump, it seems to be in good working order. i checked the ohms on the coil there within specs.but that's only static measurement. checked fuse block all are good and tight. my bet its the coil, the ignitor I: if it failed i don't think it would restart so quickly.?

latest update 7/23 talk with pertronix tech support they said that it's most likely the ignitor is failing, but a lose connection of the two leads to the coil could cause it. well my connections a sound. i order a new ignitor. also, they ruled out a failing coil, because i could restart the engine so quickly. coils overheat and take time to cool. FYI whom ever encounters the problem.

Last edited on 07-23-2018 11:54 pm by jomac

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 Posted: 07-21-2018 04:52 am
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Tim Murphy
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I would start by changing fuel filters. Just curious, when was the last time you changed the fuel filter by the gas tank?. Could be an intermittent fuel pump problem if you have the original. You can check that when you change fuel filter in engine compartment. Also make sure you have about an inch of oil in the carb dampers. Good luck and tell us how everything went. Take care.

Last edited on 07-21-2018 04:56 am by Tim Murphy

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 Posted: 07-21-2018 01:25 pm
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Brett Gibson JH5 20497
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Ignition system always verify before attempting to play with the carbs, Tim's correct that you should also do the easy stuff on the carbs as well.

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 Posted: 07-21-2018 05:03 pm
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dwalls1
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Yes, check the easy stuff, first. If you have the stock fuse box as I do, I start there. not that the fuses are blown, but subject to losing contact.

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 Posted: 07-21-2018 09:28 pm
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Esprit2
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jomac wrote:
flame thrower coil is 4 years old.Is the rest of the ignition system stock, or has it been upgraded to some aftermarket electronic ignition? If so, which one. If Pertronix, is it the basic Ignitor, or the Ignitor II / III?

The basic Ignitor doesn't have a thermal overload protection. When it over-heats, it dies, and stays dead. Replace it. Since your engine started running again, that doesn't sound like the basic Ignitor.

The Ignitor II & III both have thermal overload protection. When they over-heat, they shut down. But once they cool back down below the threshold temp, they start working again.

Hotter than stock coils are not appropriate for breaker points. For points, coils should be restricted to 24k volts or less. Hot coils can draw enough current to burn the points.

Hotter coils draw more current, which causes the points/ ignition amp to run hotter. If over-heating seems to be a problem with the Flamethrower coil, try installing a lower voltage output coil... one with a higher internal resistance, Re (R sub e).

*~*~*~*~
Carry a bottle of water with you. Next time the engine dies in that way, try slowly pouring the water over the carbs, cooling them down. If that solves the problem, then the carbs may be percolating in the heat.

That's easier said than done with the 907, since the distributor and starter are directly under the carbs. The point is to McGyver some way of cooling the carbs and see if that gets the engine running again (ie, cures the 'percolation').

*~*~*~*~
80F isn't exactly "hot", but the engine bay temps can be much hotter. What temperature thermostat is installed? A cooler T-stat rating is better during the hot Summer months. Thermostats are available in 165ºF, 185ºF, 192ºF & 195ºF.

*~*~*~*~
The stock water pump's impeller is pretty lame, and doesn't move much coolant. It's also prone to cavitation at higher rpm, which leads to overheating.

The impeller from the Turbo 910 is a dramatic improvement and moves a lot more coolant. The 910 impeller's nose is longer, so it won't fit into the JH pump's housing. Take it and the original impeller to a machine shop, and ask them to shorten the long nose to match the original impeller's. After that, the rest of the rebuild is by the book, and cooling is greatly improved.

Of course, make certain the radiator core is clean and working efficiently.

I'm just clutching at straws, and not presenting any of this as the 'fix' you seek. Just some things to try.

Regards,
Tim Engel

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