Help… engine skips after driving 30 minutes.
 

I’m new to this site. My father just gave me his 40 Ford Coupe. He has had it over 40 years and never put it on the road. I have finished it and trying to work the kinks out of this fresh rebuilt flathead. After driving around for 20-30 minutes it wants to skip or something. Runs fine up to that point. Not running hot. It is 59AB block with offenhauser intake and heads. Bored 30 over with an Isky cam. Electric fuel pump and electronic ignition. Running 2 stromberg 97s rebuilt by uncle max. I have fuel pressure set on 2. Any ideas?

Re: Help… engine skips after driving 30 minutes.
 

Nice car . Its a lot to go over . Possible wrong fuel cap , blocked exhaust , crap in the gas tank , loosing fuel volume or pressure, coil , etc . Lets start , your fuel filter doesn’t catch enough , the fuel pressure regulator has been known to not be precise. Have you actually checked the fuel pressure with a gauge ?
When you say miss , are there any circumstances where it doesnt miss ? Does it ever stall and not restart until cool ?
What temp does it run at ? Are the spark plugs wires on tightly, a good check is to open the hood and run the car at night with no flashlight and look at the motor , look for spark .
Are there any noises , hiss from the exhaust? If you remove and reinstall the gas cap doe it make any noise or difference in its running ?
Any white smoke out ofthe exhaust ? Have you retorqued the cyl heads ? Should do 3 hot - cold cycles retorquing after normal running temp , let cool then retorque . Do this 3 times .
Check plugs for water . Any loss of radiator coolant ?
Is it still 6 volt pos earth ? I see the unilite and coil but I dont know if the coil is 6 volt ? Could be any .

Re: Help… engine skips after driving 30 minutes.
 

https://www.fordbarn.com/forum/attac...3&d=1685230368

https://www.fordbarn.com/forum/attac...0&d=1685230368

https://www.fordbarn.com/forum/attac...1&d=1685230368

https://www.fordbarn.com/forum/attac...2&d=1685230368

Re: Help… engine skips after driving 30 minutes.
 

Thanks Petehoovie , now I see the 12 volt battery !

Re: Help… engine skips after driving 30 minutes.
 

Could be ignition coil.

Re: Help… engine skips after driving 30 minutes.
 

Thanks for replying. I know it’s like looking for a needle in a haystack. To answer what I know, it’s not losing anti-freeze. Not smoking. Runs about 170 degrees. I have not checked the fuel cap or fuel pressure with a gauge. Wires are tight. I haven’t noticed any hissing or noises from exhaust. It runs fine for about 20 to 30 minutes and then starts to act up. I don’t know if it’s skipping or not getting gas. Just frustrating trying to figure it out. I’ll check your other suggestions tomorrow. Thanks again!

Re: Help… engine skips after driving 30 minutes.
 

Ken, I wondered the same thing.

Re: Help… engine skips after driving 30 minutes.
 

Tank venting - gas cap???

Re: Help… engine skips after driving 30 minutes.
 

“Skipping” could be intermittent spark. Both coil and condenser will often work fine when cold, then fail when warm from operating. I would start by replacing the condenser. Don’t see it in your pics. Under the coil?

Re: Help… engine skips after driving 30 minutes.
 

He has electronic ignition. (Which can be flakier than points in many cases.)

It stll could be the coil, though.

Re: Help… engine skips after driving 30 minutes.
 

The style fuel pressure regulator you have installed are known to not keep a consistent pressure. That could be contributing to your issues.

What is the condition of your fuel tank? Has it been refurbished or replaced? It could be clogging the pickup with trash and killing the fuel supply after running a while if it is not clean inside.

Re: Help… engine skips after driving 30 minutes.
 

Replace the Coil

Re: Help… engine skips after driving 30 minutes.
 

from past experience i would change the coil and move it from the engine to the inner guard dont know where you are higher or lower states but im guessing it could be cooking the coil had very similar problems moved the coil and all good coil was that hot you couldn't touch it

Re: Help… engine skips after driving 30 minutes.
 

JC, welcome to the Ford Barn, very nice car! Not only old or in ur case rebuilt Ford Flatty’s but all carss issues! Some times things r obvious others you chase the gremlins & get overwhelmed. As said there are a few more several issues that could be ur problem. My suggestion when chasing gremlins is the same on all cars! To reduce stress & becoming overwhelmed make a check list of the potential issues provided & any u might have. Starting w the easiest ( in this case change the coil). If no make note & check off & move on. Having said that does the engine do the same if sitting in neutral idling after 30 min’s, increase the rpm & hold to see as well, if it happens while not under load If no probably means only happens under load. make note check off move on to the next easiest on the list probably fuel cap if no check off & move on. Continue w this process, it works 95% of the time & u know where u r in the process! Keep track, don’t randomly try things & you’ll get there without throwing wrenches around, lol!
BOL!!!

Re: Help… engine skips after driving 30 minutes.
 

Add a ballast resistor to the coil .Ted

Re: Help… engine skips after driving 30 minutes.
 

I have one installed.

Re: Help… engine skips after driving 30 minutes.
 

try a Flame thrower coil ,with a BR ,

Re: Help… engine skips after driving 30 minutes.
 

Those type of pressure regulators have been known to have problems. Take it off and see how it runs. I used one of those regulators once and I emphasize once. I switched to a Holley one and had no more problems.

Re: Help… engine skips after driving 30 minutes.
 

Thanks for all the input. I’ll try some of these suggestions this week starting with the coil. I’m pretty sure the gas cap is not vented. Not sure about the tank. I’ll have to ask dad about that. Been raining all weekend so I haven’t got it out. I’ll post when I get to the bottom of it.

Re: Help… engine skips after driving 30 minutes.
 

Regarding the vented gas cap.Here is an original '40 gas cap,back side.You see the hole for the vent.There also might be a vent tube in the filler neck.

Re: Help… engine skips after driving 30 minutes.
 

Re: Help… engine skips after driving 30 minutes.
 

I have had the identical trouble with the coil mounted on the engine. Moved coil to a cool location - problem solved

Re: Help… engine skips after driving 30 minutes.
 

Doil doil doil doil low resistance mellory coil over loads the module and causes shut down miss fire coi coil

Re: Help… engine skips after driving 30 minutes.
 

Great looking car! You've come to the right place. It's not quite as bad as a needle in a haystack. You've probably heard before, it's likely either fuel or spark. Sounds like a majority are leaning towards a spark problem. Looking forward to hearing how a different coil works out.

Re: Help… engine skips after driving 30 minutes.
 

JC, welcome to the Ford Barn, and as TJ & Zax40 mention in their posts just above,
that those adjustable fuel pressure regulator's do NOT have a good reputation at all.

As well as Not regulating pressure very good, they also are known to have the
diaphragm spring a leak inside the regulator and they spray fuel all over heck,
out from under the dial. Ask me how I know, it happened to me, and I was
lucky to have had quick access to my fire extinguisher. Scarred crap outta me.

Get yourself a Holley fuel regulator (pic below) as they have a small weep hole
incase the diaphragm does leak, it DON'T spray fuel all over the place. And the
diaphragm in the Holley 12-804 is also replaceable, and 1-4 lb. ;););)

Re: Help… engine skips after driving 30 minutes.
 

Re: Help… engine skips after driving 30 minutes.
 

Sorry it’s been a while but I haven’t had time to mess with the car until yesterday. The more I read, the more I’m confused. I want to replace my coil. I have a Mallory Unilite distributor and a ballast resistor. What coil should I switch to and do I need to leave the BR or not?

Re: Help… engine skips after driving 30 minutes.
 

I have always wondered what happens in the coil or condenser when it gets hot and shuts down. Then when cool it will start again. Is there something that disconnects when hot that re-connects after cooling down?

Re: Help… engine skips after driving 30 minutes.
 

question ? i see a generator ? electronics don't like gennys and mechanical regs [they micro spike and will eventually destroy them] is the unilite a genuine mallory [old type] or a msd mallory.? If you dig into the background paperwork from mallory they list 2 filters [ 1 at the coil and 1 inline at the distributor]that they say are mandatory for generators and recommended for alternators , as for which coil follow mallorys recomendation [no warranty dramas ] and recheck the wiring instalation is critical [i have run my ignition directly from the battery via a relay in an attempt to get the smoothest voltage i can AGAIN Electronics dont like spikes .

Re: Help… engine skips after driving 30 minutes.
 

Would you diagram that?

Re: Help… engine skips after driving 30 minutes.
 

I offer advice not to guarantee a fix, just tests you can pefrom that are free to help keep from buying unnecessary parts.

It all depends on what "skips" means. I did this for a living and had to look at repair tickets written by other people that left out a lot of the details. I worked nights and the driver's days, so I rarely got to talk to them. "If" I could duplicate the problem. I could almost always feel if it was ignition or fuel. The two problems feel completely different.

If you step on the gas further during the problem, does it fall of its face and run out of gas unless you back off the pedal. Does it backfire through the carburetor at all when you give it more throttle. Both of those are signs it's running out of gas. Does the misfire get worse with more throttle than it's probably ignition but if the engine acts like it running out of gas and not misfiring its fuel. When the issue is happening will it idle without the misfire and then when you raise the idle the problem starts again. Once the problem starts does it gradually get worse in a short driving distance or does it stay the same the further you drive. How much fuel is in the tank when it happens. What's the temperature outside. What happens if you give it a little choke when the problem happens. Does it have the neoprene tipped needle and seats on the carb floats or all metal ones. The new neoprene ones are sticking shut after driving them for a while, at least it did on my friend's roadster. You can lightly tap on top of the carb above the needle and seat and see if the open up. Those twist fuel regulators are junk. I had one on a 1966 Mini Cooper S and after a while of driving it would shut the fuel off completely. I would get out twist the regulator and reset it and I was good again for a while. I tried a couple brand new ones and they both did it. Try resetting the regulator when the problem happens. Regardless of it is the problem or not I would get rid of it and get the pump with the correct pressure as checked with a gauge at the carbs. That fuel filter belongs before the pump, back by the tank. It is not protecting the fuel pump from getting junk into it. It's not large enough either. Those were used on Volkswagens and small engines. These old Fords usually have a lot of junk in the gas tanks and will plug those filters up in a hurry. What if that glass filter breaks in the engine compartment or the hose comes off with the electric fuel pump still pumping, the car will burn to the ground. You want the least number of things that can leak fuel near that hot engine and plug wires.

Do you think it's just one Cylinder misfiring or are they all doing it. If it misfires at idle and you have a timing mark, can you put a timing light on it to see if the timing mark is jumping around. That would be a sign of a bad coil or ignition module. How bad is this misfire, is it a little annoying or do you fear you won't make it a block. You can try jumping a wire directly to the coils external resistor (these chrome Mallory's do use them) and bypass the ignition switch. That's probably not a very old Mallory coil on there so it should be good, but you never can tell. The resistors are either good or burned out, I've never seen one have an intermittent problem. We had the same type on the Dodges at work. When they did fail the engine would start while the engine was still cranking bypassing the resistor and then die when the switch returned to the run position You could check the resistance of the coil hot when it's not having the problem and then when it is. Honestly, I hear so many problems with these aftermarket electronic ignitions on flatheads that I don't trust them. I'll just stick to points. I never saw a set of points keep my dad or me from getting where we were going and back home during the points era. You carried spare ignition parts just in case and the tools to install them on the daily drivers like the Mustangs. On the Early Fords my dad always had a spare distributer with him he could swap out, but he never had to.

I have extra electric fuel pumps and I will stick a five gallon can of fuel on the passenger floor with another fuel pump and go for a ride, If the problem goes away, I know it's in the tank, filter, pump or lines. I also have a ignition scope so I can look at the ignition to spot a bad coil or condenser, module, wires... You are at a disadvantage without a scope.

Re: Help… engine skips after driving 30 minutes.
 

agree with all of the comments on moving the coil. bad location.


also, drive the car 30 minutes and remove the gas cap. what does the car say then?

Re: Help… engine skips after driving 30 minutes.
 

I've had the same problem on several cars over the years. Two had defective coils, another was bad condenser.

Re: Help… engine skips after driving 30 minutes.
 

Probly a good time to reiterate, as I said in my earlier reply. Don’t randomly think or act on all u’ve read in this great thread. It is easy to get confused. U must look @ the suggestions, try to make a list of all in order of simplest to do first. Go thru the list trying each & making notes like changed or not, better, same, worse. Take ur time don’t get discouraged or overwhelmed, this should eliminate the confusion! One or more of these suggestions will lead to resolve.

Re: Help… engine skips after driving 30 minutes.
 

With respect: I would have thought that to be a good place for the coil in that it is in front of the engine with fresh air from the fan blowing on it. Nearly the same place as the original Ford coil. Just a bit higher.
Also, I thought Bubba indicated that the Mallory coil was not right for his system. His advice is like little "gold nuggets".

Re: Help… engine skips after driving 30 minutes.
 

Thanks for all of the suggestions and help so far. It has finally got to where it won’t even start now. I have put a new flamethrower coil on. I’m getting plenty of fuel and fire on all cylinders. Im thinking it’s this electronic ignition. I’m about ready to snatch this distributor off and go back to the original one.

Re: Help… engine skips after driving 30 minutes.
 

I think this is a good idea.

"aussie merc" asked if this is a generator (it sure looks like one). I don't see an answer. As he stated "electronics don't like gennys and mechanical regs" and I agree.

Let's get back to basics.

Re: Help… engine skips after driving 30 minutes.
 

I ran Pertronix electronic ignition on my '41 for several years with no problems, except for the darned 7mm spiral wound ignition wires that pertronix requires gave me fits, particularly is wet humid conditions. The more recent 9mm wires are probably okay, but will not go through the flathead wire looms. So I went back to a points distributor and Packard 440 solid core ignition wires (except for a one foot length of spiral wound from the coil to distributor to suppress ignition interference with the radio). Been running fine with points ever since, but with a Tubman condenser to counter the famously unreliable condensers being sold. And, I keep a spare distributor and coil in the trunk as insurance.

Re: Help… engine skips after driving 30 minutes.
 

cant argue with the original dissy but if you want electronics then you must upgrade the electrics to suit and its all about a smooth constant supply and absolutely as near as perfect earths .Your cars wiring system was designed 30years before transistors and now you want to enter the space age . It can be done and is often quite successful ; Dig deep into all the installation paperwork you can find, for whatever system you choose [IE not listed with but required by mallory a 611 power cell and the inline power filter ]. Most failures can be traced to ether wear in a related component [dissy cam lobes] or incorrect install .Even something as simple as connecting an earth or power in the wrong spot can reek havoc ,read the directions 3 times/ think and then reread then if any doubts contact the manufacturer most are more than willing to help