427/425 Engine Problem
My engine runs great on start up and for a period of time on the road. After 5-10 minutes driving and you bring the car to an idle the engine starts to sputter and after a short period it will cut off. You can restart but the same thing will occur. If you rev engine it continues to run rough with some backfiring. After engine is off for about an hour it runs fine again. All new harnesses on car with complete TI ignition parts from TIS with the exception of distributor which he rebuilt. When this first occurred I thought it was the carb so I sent spare 4150 to Dated Components for restoration. I put that carb on with same results. New fuel filter and fuel pressure good. While running I have 2.6 volts going to coil and 8.5 at pink wire going to distributor. I checked volts when the engine was running bad and volts were the same.
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Re: 427/425 Engine Problem
Walter,
What you describe mimics what a defective coil pick-up in the distributor does when it gets hot.
Doug -
Re: 427/425 Engine Problem
Similar issues for me not that long ago on a 427. It had multiple faults, both fuel and ignition. Intermittent/heat related faults are tricky to nail down.
Is it Fuel or Ignition? You have to definitively eliminate one.
FUEL: (What fuel are you using? Has something changed since this problem began or is it all new?)
When it dies, with air cleaner off, check for fuel flow from the accelerator pump by flipping the throttle linkage. If none, and since you say Fuel Pump is good(how did you verify?) then you have Vapor Lock. Check fuel line near exhaust manifold with IR gun. If it's over 150* F it's likely VL. Rest a hour and it's good is a sign. If you have side exhaust, this adds even more heat to the fuel line under the door sills.
If fuel is good at the accelerator pump, then it's ignition.
IGNITION: Which TI Module Circuit Board did Dave supply in the restoration/rebuild?
Your 2.6v at coil+ and 8.5v at the distributor Pink input are in range. With just key on, you should get 2.5v to 4.5v at the coil+. The Pink to the distributor comes from IGN RUN 12v, but through a dropping resistor in the TI harness so 8.5 is about right IIRC.
Remove your ignition shield from over the coil and check coil body temp with IR gun. Which Coil are you using? Coils are difficult to diagnose hot so a swap may help eliminate the fault. You can use a Standard Napa/etc type Points Coil to diagnose.
Distributor pickup coil. Did Dave install a new PU coil? Test when hot by unplugging the 2 terminal plug from TI harness and connect 2 leads of the dist connector to a ohm meter. Should read 500-700 ohms. Also check to be sure the 2 terminals are connected properly as polarity is important.
Distributor connector:
Dist White(input) to Pink(Power)
Dist White/Green(output) to Gray(dist pulse to TI Module input trigger)
Also check TI Module case ground at the case and radiator support. Use toothed washers at grounds.
RichComment
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Re: 427/425 Engine Problem
Walter, Could be a result of restricted fuel flow? If the rubber hoses on the fuel line start to collapse you will get a condition like you describe. Good luck.Comment
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Re: 427/425 Engine Problem
Thanks to all for suggestions. I will try and report back.Comment
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Re: 427/425 Engine Problem
What is the difference in coils for TI ignition and a standard points coil?Comment
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Re: 427/425 Engine Problem
GM Standard points coils typically range between 1.2 to 1.4 ohms in the Primary winding.
GM TI coils have a larger diameter wire in the Primary winding compared to the Standard coil, therefore less number of turns which yields a lower Primary winding resistance, on the order of 0.4 to 0.5 ohms.
RichComment
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Re: 427/425 Engine Problem
Is there anyone reproducing a true TI coil?1969 Riverside Gold Coupe, L71, 14,000 miles. Top Flight, 2 Star Bowtie.Comment
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Re: 427/425 Engine Problem
sounds like a bad power valveComment
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Re: 427/425 Engine Problem
No one makes a "true" exact GM coil of any type that I am aware of. However, "close" reproductions do exist. I am not certain if their physical, electrical and temperature rated specifications exactly match the GM coils.
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Re: 427/425 Engine Problem
John, Wouldn't that cause a problem 100% of the time when running? He also stated he had another carburetor rebuilt and it exhibits the same problem after about 5-10 minute run time.
Over the last year there have been many cars with problems similar to Walters, both BB and SB. It seem like there's a virus going on. I had the same problem over the summer on a TI BB and it was a bear to diagnose. That one had both fuel and ignition issues, all intermittent. That was a blast to figure out.
RichComment
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Re: 427/425 Engine Problem
I ask about a repro TI coil because I've been involved with more that one TI car that ran poorly only to find it had a repro TI coil that was really just a points coil that had a TI coil part number embossed on it and a TI tag. Once an actual GM TI coil was installed the cars ran great. Seems to me it would be an easy task for a repro points coil producer to produce a true TI coil.1969 Riverside Gold Coupe, L71, 14,000 miles. Top Flight, 2 Star Bowtie.Comment
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Re: 427/425 Engine Problem
Chris, Interesting.
Which TI amplifiers were in them? I have not had the opportunity to run a points coil in a TI based car with original Delco amp, and this may be a configuration that causes poor running.
I have run a points coil when using the new amp and it ran satisfactorily at various speeds and high ambient temperatures. Before doing this, I've had discussions with Dave Fiedler about it and he said the only difference is that the spark voltage will be less due to the lower currents in the points type coils. Maybe noticeable only at high performance driving. I have driven a L71 many miles with this arrangement and I could not tell the difference. Only one example though. Dave knew I had a new type TI amp in the car, but we didn't discuss use of the original Delco type amps and their compatibility with points coils.
I see that there is a "replacement" TI coil listed in that link I posted. Maybe someone has done what you asked about but I have no information of its specifications. I'll try to get more info on that one. Allegedy it's made here in the US.
RichComment
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Re: 427/425 Engine Problem
Richard, my first experience with this problem was with my old L78. Ran fine at full throttle until 4000 rpm, then would start breaking down. As soon as a I removed what turned out to be a points coil and put a GM TI coil in, car screamed to 6500 rpm. If memory serves, that was with the original TI amp.
Most recently I was helping a friend with his 69 L89. Car ran fine under gentle driving, but once he started getting on it, it started stumbling. We pulled out his repro 263 TI coil (ohm measurements same as 207 points coil) and I swapped in my original 263 TI coil from my L71 in it and it ran great. His car has a new solid state TI amp.1969 Riverside Gold Coupe, L71, 14,000 miles. Top Flight, 2 Star Bowtie.Comment
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Re: 427/425 Engine Problem
Chris, Interesting......When his L89 began stumbling was the engine normalized/hot and the coil inside ignition shielding?
One note. Maybe a typo?.....The 207 is a TI coil and is a GM service replacement for the 263. The 207 and 263 both have the same Primary resistance. I understand that the 263 was the coil that shipped from St Louis but never available as a service replacement.
RichComment
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