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Old 07-21-2011, 03:33 AM
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Ignition Problems

Sbc in a hobbystock dirt track car 360 ci 9.0 compression with 2 barrel carb and hei distributor. The problem is in the feature when the engine temp rises to 200 or higher the engine will cut out and sputter especially on restarts. I always start in 2nd gear and shift to 3rd the car revs and sounds good coming to the green and when i drop the hammer and go it sputters and after i fall to the tail it will clear up and run and be ok. I have changed carbs, fuel filter, fuel cell vent, petronix coil module cap rotor. The car still sputters. I just changed the pickup coil and will try it out tonight. Car runs great early in the night for the shorter heat race. It definately seems to be heat related, hopefully the pickup coil will fix it.

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Old 07-21-2011, 04:27 AM
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Is a fuel line close to a heat source (exhaust ect)?
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Old 07-21-2011, 04:44 AM
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The fuel line has been re routed further away from the exhaust manifolds. It does have a steel fuel filter b/t the pump and carb.
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Old 07-21-2011, 05:02 AM
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Heat related problem.

A year or so ago my sister had a daily driver with a similar problem. When the engine reached temperature after 3 0r 4 km it would cout out after a splutter. All the service dept. efforts were in vain. They went through and pulled the tank, lines, filters etc.
In the end it was found to be an electronic component in the ignition module, in the distributor. A second hand distributor was sourced from the wreckers and problem solved. The last option was going to involve pulling the muffler to check for collapsed baffles but this was not needed in the end.
I recently replaced an ignition module in a Mazda only to have it fail 3 months later. Had to go for an ignition module with 2yr. warranty.The symptoms of the Mazda were similar to your problem. All earth connections were thoroughly cleaned and rebolted.
Cheers
Al.
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Old 07-21-2011, 06:02 AM
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You are using heat sink compound on the bottom of the module?
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Old 07-25-2011, 07:53 PM
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A little update on the engine. I replaced the pickup coil before i went to the track and it fell flat on its face in the heat race. I started the feature and quickly started having issues. I was at the back so i had time to troubleshoot, i watched the fuel pressure gauge and when it cuts out the fuel pressure drops down to 3 psi or lower. It is now getting worse and completely dieing, but when you let the clutch out to roll the engine over while coasting the engine fires when the fuel pressure comes up. I had a 110 gph carter fuel pump that was about 6 yrs old and the fuel pressure was fluctuating with rpm it would go from 7 down to 6. So i replaced the fuel pump with a holley 110 gph and emptied the fuel cell to check and replace the fuel pickup. The car seems to run ok at the shop like usual is there anything else i need to look at, it will be 2 weeks before i can race again.
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Old 07-25-2011, 09:06 PM
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I tracked a faulty ignition module down which missed when it became warm by using an inductive timing light with the pickup clipped to the high voltage coil lead (not the plug leads) and when it starts to miss you can look at the strobe light to see if it has gone out and comes back on. You will need to duct tape the light to somewhere visible so you can glance at the light while powering up the engine on the track. Sometines its hard to tell between a fuel misfire and an electrical misfire but the timing light will still keep on strobing if the ignition system is up to scratch and the 3 psi fuel is starving your engine.
Cheers.
Al.
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Old 07-26-2011, 12:17 AM
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Quote:
Originally Posted by hobby28
I had a 110 gph carter fuel pump that was about 6 yrs old and the fuel pressure was fluctuating with rpm it would go from 7 down to 6.
Were you having this same "cutout/sputter" issue with the Carter pump?

Quote:
petronix coil
Do you have the correct ballast resister feeding voltage to that coil?
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Old 07-26-2011, 12:36 AM
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Is there any rubber connecting hose on the feed side of the fuel pump.
It may be collapsing and or kinking with heat. Age.
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Old 06-10-2012, 07:03 PM
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Guys my problem is back again, last night was the first hot night at the race track and the same sputter was back on restarts. The car ran awesome after it stumbled and it went the back of the pack. It sputters and almost dies, then it will fire just a little, then it clears itself and runs great until the next caution and restart. I changed the engine late season last year and the problem went away and i am still running that engine, so i am stumped. The fuel pressure gauge fluctuates alot under load, it will go from 8psi clear down to 3psi sometimes. Do you think i could be sucking air in the fuel line somewhere, and how would you test it. Or am i boiling the fuel in the line and once fresh fuel gets pumped up there it takes off?
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Old 06-10-2012, 08:30 PM
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Quote:
Originally Posted by hobby28
Guys my problem is back again, last night was the first hot night at the race track and the same sputter was back on restarts. The car ran awesome after it stumbled and it went the back of the pack. It sputters and almost dies, then it will fire just a little, then it clears itself and runs great until the next caution and restart. I changed the engine late season last year and the problem went away and i am still running that engine, so i am stumped. The fuel pressure gauge fluctuates alot under load, it will go from 8psi clear down to 3psi sometimes. Do you think i could be sucking air in the fuel line somewhere, and how would you test it. Or am i boiling the fuel in the line and once fresh fuel gets pumped up there it takes off?
1. Are you running any type of fuel pressure regulator? The regulator may not be working correctly letting too much fuel back to the tank and dropping your fuel pressure.
2. Check the vent @ the fuel cell.
3. Have you checked the float level on the carb?
4. Do you have a heat isolator between the intake & carb?
5. Check the needle & seat in the carb, it may be sticking.

Last edited by S10 Racer; 06-10-2012 at 08:36 PM.
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Old 06-10-2012, 09:29 PM
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I am not running a fuel pressure regulator and have raced for 10 years without one. The vent at the fuel cell is clear. The float level is good and the needle and seat appear free and in good shape. I don't have an isolator on the intake we a forced to run an aluminum carb adaptor from a performer eps intake to a 2 barrel rochester.
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Old 06-11-2012, 02:34 AM
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Quote:
Originally Posted by hobby28
I am not running a fuel pressure regulator and have raced for 10 years without one. The vent at the fuel cell is clear. The float level is good and the needle and seat appear free and in good shape. I don't have an isolator on the intake we a forced to run an aluminum carb adaptor from a performer eps intake to a 2 barrel rochester.
You should consider running a bypass regulator that will constantly circulate the fuel from the tank to the regulator. If the regulator is placed near the carb, there should be no problem w/fuel percolation.

I'm going to guess you are already using an insulator between the carb and intake. You could also try blocking the heat crossover under the plenum. Use a good quality mechanical fuel pump.
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Old 06-11-2012, 10:20 AM
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You have two previous post mentioning insulators between the manifold and carb and that's what I was thinking. I had the same problem with a BBC years ago. I installed the insulator and also a sheet of aluminum painted flat black on the top side. Heat was directed away from the carb. Worked like a champ. Something else to try.
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Old 06-11-2012, 10:01 PM
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I called Sean Murphy with SMI carbs today and the first thing he asked was how much fuel pressure I have. I told him 8lbs and he told me to drop it to 5lbs and the problem would go away, and I was flooding the engine out by blowing by the needle and seat. It makes sense so I will install a regulator and see what happens, I am also going to try and keep some heat off the carb. Thanks for all the input.
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