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Healey BJ7 Stumbling Engine

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Brian Hughey

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Car runs like it is on three cylinders.

This car has been rebuilt from the ground up. Car ran fine for a couple of months. Then it began to stumble, I thought it was the fuel pump and I replaced it with an after market one while mine was being rebuilt. Ran fine for a couple of months.
It began to stumble again and I replaced the fuel pump again with the original one that was rebuilt. It ran for about a hour and began to stumble again.

I then began to believe it was something else and took the carburetors bowls apart and checked to see if the needles were tight and they were. Emptied the fuel tank to ensure it was clean. Checked the output of the pump, 1.3 l/min (No air in the fuel) Parked the car for a couple of hours came out and it ran fine again for an hour.

Signed

Puzzled!

Comments please
 
Check you spark plugs their color may give you an indication as where to look?
 
The short running periods may indicate a coil problem. Every time you've changed a part/serviced something the engine runs for a while because the coil is "cold" at that point but heats up until it stops working altogether.
 
Went for a drive tonight and the car ran fine, until I stopped for coffee. Came back out and it ran terrible. I drove a mile and stopped, turned the car off for a minute and then restarted and the car ran fine. I wonder if it could be the ignition switch?
 
Brian Hughey said:
Went for a drive tonight and the car ran fine, until I stopped for coffee. Came back out and it ran terrible. I drove a mile and stopped, turned the car off for a minute and then restarted and the car ran fine. I wonder if it could be the ignition switch?
Click to expand...

You'll get those symptoms if one of the carb needles is not secure and is dropping into the jet, then when the vacuum piston settles it'll pick up its needle and the car will run normally (temporarily).
 
Bob_Spidell said:
You'll get those symptoms if one of the carb needles is not secure and is dropping into the jet, then when the vacuum piston settles it'll pick up its needle and the car will run normally (temporarily).
Click to expand...

I had that last fall. The car would run at slow speed on one carb. It never actually died. Drove it 100 miles back from an event and it got 25mpg in the right lane on the freeway.
 
The ignition and trunk switches aren't that selective; it will either run or it won't, it's not going to half run.

I'd be leaning towards the coil and or condenser myself too, as already mentioned. Either of these items can be changed in a matter of minutes, even on a hot engine by the side of the road. For conclusive results, change one (1) part at a time until the fault is rectified.

Good excuse to take a couple more drives.

Something else: I once lost a few placings at an autocross event from doing too much preparation the night before. I applied a few drops of oil to the center of the distributor, like you're supposed to do to keep the mechanical advance free, but must've used a drop or two too many. I had also recently installed a fuel pressure regulator, so all my focus as to why the engine was misfiring at high RPM was on that. Once the car was home and I was going through everything from scratch, I found the inside of the distributor cap and points covered in a film of oil. So simple, all I had to do was wipe off the inside of the cap and clean off the points, and it ran like a champion again!

Lesson learned: don't overlook the small and simple things. People always tend to jump to the conclusion that their issue is a worst case scenario (a guy with a Z3 wanted to replace his head gasket because the coolant was a little low__he'd been repeatedly topping it off above the COLD FULL mark on the reservoir__when we collectively convinced him to stop doing that, he quit losing coolant...).
 
What about the ignition wires? Those modern carbon resistance wires can go funky when warm, then recover when they cool off. Your problem sounds like ignition to me. Try changing the cheap stuff like wires, points, condenser, distributor cap, rotor...
 
steveg said:
99% of fuel problems are electrical! Condensers & coils are the main culprits these days.

Also the trunk cutoff switch.
Click to expand...

Mentioned the trunk switch because I have a friend with a BN2 who would drive it a mile or two, then the switch would become worse and worse, then cut out entirely. The battery connection worked OK; the ignition part would cut out. Just saying...
 
I had that problem develop many years ago after an engine rebuild. Found that it was a stickey exhaust valve due to one of the bronze valve guides grabbing the valve stem when too hot. When it cooled down the valve spring would pull it closed. I believe bronze can compress slightly when reamed and reduce the clearance. Ok when cold but sticks when too hot. It was cyl #3 and the first three cyl plugs indicated they were running lean compared to 4 thru 6. I adjusted the front carb and the problem dissappeared.

Another odd one I found on a friends tr3 was a piece of rag in the gas tank floating around and stumbling or stopping the engine when it blocked the tank intake screen. Stop the car and the rag would drop off until it found its way back to the screen again.

Check the easy stuff already suggested then search for the unusual. You'll eventually find the gremlin.
 
Tproject posted:

"Another odd one I found on a friends tr3 was a piece of rag in the gas tank floating around and stumbling or stopping the engine when it blocked the tank intake screen. Stop the car and the rag would drop off until it found its way back to the screen again."

I had precisely the same problem (and keep in mind that the filler on a 100 is inside the boot) except is was a poplar leaf that had somehow gotten into the tank--the issue ended after I pulled the sending unit and managed to fish out the leaf.

That said, I doubt your issue is a fuel blockage and vote with the majority that it is ignition related. Stick with it, change one component at a time and eventually you will find it or it will go away on its own....
 
I checked the plugs and all is good, trunk switch looks to be in good condition as well. Fuel tank is clean and flow output is good. 1.3 l/min I found wear to the rotar and cap but believe they are still working well. IMG_0133.jpgIMG_0132.jpg
Any suggestions on how to prevent this wear? I have ordered an new coil and I hope this solves my problem.

Thanks all for your imputs.

Brian
 
It looks like an electronic ignition in there. There is sometimes a clearance issue that raises the rotor on the shaft. It also looks like the carbon center electrode is odd ( almost like it went in upside down, since the concentric circle on the end resembles the way the spring attaches ).
 
Drive it, when it stumbles, touch the coil. If, overly hot, replace. If not, check wiring at coil. It is temperature related, could be a clogging exhaust. Something simple, think what is temperature related and go from there. Switches and electrical either work or don't work and only if the wiring terminals are solid. Ignition main feed could be loose. Small things can make life miserable. Check the rotor and make sure it is seated and the carbon tip in cap is set.
 
I had a similar problem. Turned out to be the coil. Thanks to some smart folks on this forum who correctly identified the problem. I replaced the coil and problem solved.
 
#1: I had a similar problem on my TR4A. We had installed a Pertronix ignition and a Lucas "Blue"(?) coil (it's been a while, but I think hat was what their hot coil was called). Update: the synapses are working again! I think it was a Bosch Blue coil, and a Lucas Flamethrower. We had the Lucas. My Fiat/Alfa and VW buddies all wanted the Bosch.

My brother wanted to make darn sure that the coil never fell off, and really tightened the clamp around it. It eventually started to fail hot (miss and no power). I found the coil's clamp had slightly crushed coil's can. A new coil, gently clamped this time, solved the problem. Wasn't even the Prince of Darkness' fault, but due to a couple of American gorillas!

#2: My brother has an Alpine with a Ford V6. He had installed a MSD electronic ignition that he had been given to him by a friend, who could never get it to work right. Turns out the the dist. was never properly set up, and the car would cut out at higher revs, during spark advance. The problem turned out to be "rotor phasing". After searching on-line, I found the procedure on the MSD page:


  1. Check Rotor Phase while engine is running for best accuracy. Ideally get the rotor tip leading edge right on the front side of the terminal in the cap while watching it with a timing light. To do this, you need a 3/8 or 1/2" hole in your distributor cap right behind the lug on the #1 plug wire position, with the timing light hooked to #1 wire. While the engine is running, point the light down on top of the cap so you can observe the alignment. It helps to paint a white mark on the rotor so it will show up better with the timing light. White typewriter correction fluid works well for marking the rotor.
  2. Rotor Phasing - Alternative Method - Many racers simply bring the engine up on it's compression stroke and rotate it over to the fully retarded timing value as indicated on the balancer. Then, just adjust the rotor tip till it is pointed directly at the #1 plug wire terminal. While this method may not be quite as accurate as done with the timing light method, it can be very close and can also be used in conjunction with method #9 for verification.

Here's a brief video to help visualize what's going on: https://www.youtube.com/watch?v=aWMlNwGW0tM

This cured a lot of problems. I remember adjusting the position of the magnetic pick-up below the rotor; it had been installed maxed in one direction. I ended up with it almost maxed the other way! Car ran great when we finished. Hope this helps. Jim
 
Just have a look at the low tension wire from the coil to the dizzy, check both ends - I found that the wire had broken inside the insulation at one end and was actually stopping the car from running when things got hot. Another thing - check the floating plate under the fixed plate in the dizzy - the two plates are clamped together with a three pointed (star) spring steel washer and circlip. Sometimes a leg of the washer breaks off and drops down into the body of the dizzy and that can affect the running - but generally all the time.

Best of luck

:cheers:

Bob
 
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