BJ8 Sputtering at High Engine Speed and in Overdrive

[SteveHall64Healey]

Gents, My BJ8 is sputtering - loud spitting from carb area, with hesitation - at engine speeds of 3700 RPM or higher under acceleration, with the Overdrive engaged,Mitch the engine at full operating temperature. Oddly if I run the engine under acceleration at similar engine speeds, but not in OD, it is perfectly smooth with no sputtering or hesitation.

The fuel pump was quite old, so as I had a new in box SU pump, I replaced it. Problem actually got slightly worse. I have also replaced the jets with new Grose type, although the problem pre-dates this changeout.

Any ideas on root cause?

thanks
steve

 

[Bob_Spidell]

My money's on ignition; sounds like intermittent miss. What kind of distributor cap, wires, etc. are you running?

 

[Keith_M]

If it's really only happening when the OD is engaged, then I think it has to be electrical. The ignition system and the overdrive system seem completely separate to me, so it's hard to see how one would affect the other. I'd be looking for something that's miswired or for a short. Try tracing the overdrive wires and checking continuity.

Keith

 

[RAC68]

Hi Steve,

I would suspect that if the OD is involved and contributing to your issue, it is because of a loose connector at the fuse box or ignition switch. However, I would suspect the OD is not involved in the cause of engine sputtering. Have you checked your fuel. Has it been in the car all winter and could it be sour (turned bad or collected water)?

I understand you replaced the SU pump and the problem became a little worse. Did you adjust the pump's diaphragm? If you are funning a filter, did you change is as well? One thing I would suggest is that you consider pulling a few plugs to check on the burn color after running a short while under the sputter RPM and then checking them after running over the sputter RPM? I believe this would give some if fuel or its delivery is involved.

Good Luck,
Ray (64BJ8P1)

 

[SteveHall64Healey]

My money's on ignition; sounds like intermittent miss. What kind of distributor cap, wires, etc. are you running?

The car is running a Pertronix ignition that is at least 5 years old. The cap is NOS Lucas and the wires are less than one year old. I had the same issue last year on the old cap and wires set.

 

[Bob_Spidell]

Are the wires copper stranded? I had a high-speed miss under load when I tried 'modern' wound-wire noise suppression secondary wires; they don't play well with the original style caps.

As others mentioned, it could be electrical with the OD or other circuit; or it could be that the OD on increases the load on the engine and marginal ignition starts to fail. Do you get the problem 'lugging' uphill in fourth?

 

[bdcvg]

I had a very similar problem and it was a bad rotor

 

[RAC68]

Hi Steve,

How are you progressing on resolving your issue. Most of the responses, as always, are directed to clarifying the conditions, environment, and unique circumstance the issue appears in and some have offered suggestions based upon past experiences with similar simptoms. However, knowing what you have done and what you have learned since your last posting is critical to maintaining a continuing progressive participation toward finding a resolution, or have you resolved the problem and if so, what caused the sputtering?

Based upon your last response, I am leaning toward your problem centering around fuel and its delivery. You mentioned the situation happened a year prior when bringing your Healey out of hibernation. Have you used a fuel stabilizer in your fuel. Is this condition taking place when burning fuel in the tank during its Winter sleep or on fresh fuel?

You indicated the sputtering happened during acceleration at 3700+ RPM under O/D and not at the same RPM without O/D. Since, when accelerating, at a specific RPM the overall O/D gearing is higher and require the engine to overcome greater drag. This condition will require additional fuel to generate this added power and, if too lean, could cause the engine to sputter.

The causes of running lean at mid to high RPMs are many and could be the result of a weak pump (as you have already addressed) to an undersized fuel filter. Assuming that your pump is performing properly and lines are clear, have you done a carburetor adjustment and balance recently? Have you checked the float bowls are filling with your new Grose jets?

Good luck,
Ray (64BJ8P1)

 

[Healey 100]

Acts like it has insufficient dwell, giving a weak spark at higher RPM. This always gets worse when the engine is under load, as with the OD engaged.

Since you changed the cap and wires and fixed the problem before, that merely improved the spark enough to get by. But the underlying condition was still there.

I would ditch the Pertronix and try points again, I'll bet that fixes it. If that's too radical for you, try changing the coil and rotor first, just to eliminate that possibility.

It sure sounds like an ignition problem to me.

 

[Bob_Spidell]

Acts like it has insufficient dwell, giving a weak spark at higher RPM. This always gets worse when the engine is under load, as with the OD engaged.

...

I would ditch the Pertronix and try points again, I'll bet that fixes it. If that's too radical for you, try changing the coil and rotor first, just to eliminate that possibility.

It sure sounds like an ignition problem to me.

Don't follow the logic here. It's with points that the dwell--in time value--becomes less when engine speed increases. I believe with a Pertronix--at least with the Pertronix 'I' suitable for Healeys--the dwell is fixed (I believe the later Pertronix units--'II,' 'III,' etc.--can vary dwell with speed).

FWIW, we have Pertonix in a BJ8, a BN2, a '46 Chevy 2-ton truck, a '55 Thunderbird and a '65 Mustang. All perform flawlessly.

 

[HEALEYJAG]

Its a fuel issue...the overdrive statement is a red herring..........check all fuel lines for blockage and check how fast fuel is pumping throught the lines....also check carbs for blockage etc..


Doc

 

[Healey 100]

Bob:

The Pertronix uses a conventional coil. It is probably an electronic set of points that applies voltage to load the coil for a dwell interval and suddenly interrupts the current to produce a spark. I am suggesting that if the dwell interval is too short, a weak or no spark results. This could be caused by a defective or improperly installed Pertronix pickup in the distributor.

Reverting to points is just a way to diagnose the problem. If changing to points has no effect, there isn't much reason to look at the ignition, it leaves only the coil that hasn't been eliminated.

BTW my Healey 100 has been running for 40 years on Lucas points and an ancient coil. I have had few problems with them. I do change them every 10 or 15K miles. For the amount I drive this car, that's not very often.

 

[Bob_Spidell]

Bob:

The Pertronix uses a conventional coil. It is probably an electronic set of points that applies voltage to load the coil for a dwell interval and suddenly interrupts the current to produce a spark. I am suggesting that if the dwell interval is too short, a weak or no spark results. This could be caused by a defective or improperly installed Pertronix pickup in the distributor. ...

Yup. It's most likely a power transistor with a timing circuit driven by a Hall Effect switch. The reported failure mode for Pertronix--that I've heard of--is outright failure; I can't imagine a circumstance where the electronically-controlled timing circuit would change, but anything's possible.

 

[SteveHall64Healey]

Thanks for the ideas everyone.

I checked an article off-line at: https://www.calverst.com/articles/EL-Ignition-Pertronix_Ignitor_issues.htm
which confirms what I had always understood: when Pertronix ignition fails, it fails completely. I also checked coil operating temperature and it is normal - warm from ambient engine heat, but easily held in your hand. I also checked connectivity between the backing plate of the ignition and the block and there is zero resistance.

I measured fuel flow and it is 1.63 l/min versus the spec of max flow rate of 1.13 l/min in the shop manual. The pump that this new one replaced ran at 0.51 l/min and was quite anemic to listen to, and yet the sputtering got worse with the new pump. Fuel lines are new and clear, carbs are clean and clear. The car runs and starts well and the plugs have the correct colour - tan. Fuel to air ratio confirmed last night using Colortune, but it's very hard to know if there's enough fuel in the mix to meet higher revs under OD load.

Next, I will check the solenoid electricals, although I suspect it's engine load caused by the use of OD. When It sputters and I take the OD off and run it through the rev range of 3000 to 5000 for 15-20 seconds, no sputtering.

If the electricals are ok, I will try adding a bit more fuel to the mix. Over the winter, I set and balanced the carbs. The fuel I've been using is fresh Sunoco 94 with no stabilizer.

steve

 

[Keith_M]

Here's an off-the-wall idea. Let's assume for the moment that the OD issue is NOT a red herring. The fuel pump and the OD system both come off the same point on the fusebox. If you have a bad connection there, it might be possible that the OD unit uses enough juice to rob the fuel pump, starving the carbs.

I know it's far-fetched, but we've hit all the obvious stuff.

 

[SteveHall64Healey]

Not crazy at all - I'm going to give it a look.
steve

 

[Patrick67BJ8]

Not crazy at all - I'm going to give it a look.
steve

I had carb backfiring several years ago and it was a cracked Intake Manifold.

 

[Keith_M]

Not crazy at all - I'm going to give it a look.
steve

Steve,
It occurred to me that the best way to test this would be to check the fuel flow to the carbs with and without the OD engaged.
keith

 

[SteveHall64Healey]

Steve,
It occurred to me that the best way to test this would be to check the fuel flow to the carbs with and without the OD engaged.
keith

Brilliant Keith! I think you've just saved me a ton of effort here. Will check this over the weekend.
steve

 

[RAC68]

Steve,

A very good review and information summary. For my education, how have you measured fuel flow and how will you measuring it during your drive?

Good luck,
Ray (64BJ8P1)