BJ8 Sputtering at High Engine Speed and in Overdrive

[Keith_M]

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)

Ray,
If the problem is really that the OD unit is reducing voltage/amperage to the fuel pump, it will reduce flow to the carbs whether the engine is running or not. He should be able to just remove the fuel line from the carbs and watch the flow while someone engages the OD solenoid.

Keith

 

[RAC68]

Hi Keith,

I understand your approach and that is how I would approach evaluating fuel flow. However, Steve presented quite definitive flow values and I was wondering how he got those numbers.

Regards,
Ray (64BJ8P1)

 

[SteveHall64Healey]

As noted above, I measured flow by removing the fuel line from the car, and placing the line into a calibrated measuring cup. I then turned the ignition on for 30 seconds and measured the volume of fuel delivered in that time. Is there are better way to do this?
steve

 

[RAC68]

Steve,

I applaud your presentation. Although, as mentioned to Keith, I would have taken the same approach. However, the numbers, as you presented, gave me the impression that you had some sort of flow meter that could be hooked to the line before entering the carburetors that could be used and read during an actual drive for a true in-operating picture of pump performance. A while back I remember seeing some sort of a gauge that could be used in that manor and was wondering if it was what you had used.

Thanks for your response,
Ray (64BJ8P1)

 

[Gearhead_Garage]

Here's one more thing to test. I just had this exact problem on my bj8. The fuel pump ground wire had broken internally. It would run fine for a while and then start sputtering. The pump was not passing enough current to keep up a decent flow rate.

 

[SteveHall64Healey]

I measured the flow rate with and without the OD engaged. Without OD, fuel flow rate was 1.62 l/min. With OD engaged, the flow rate was 1.61 l/min. The difference is likely due to experimental error. So, it does not appear that the OD is a factor. Also, as I watched the calibrated cup fill with gas, it was apparent that the flow was smooth and regular. I think the pump is probably ok. I also inspected the electrical connections and they look fine.

Earlier this season when I changed the flow valves from Viton to Grose-type, I noted that one of the float bowls sat at a lower level than the other. I changed valves because the old ones had clearly worn out and fuel was periodically being discharged through the discharge tubes. I wonder if the float bowl having the lower level simply runs out of fuel at peak demand? I have had this issue both before and after changing the flow valves.

I will adjust the level of the lower bowl to that of the higher and see if that has any effect.
steve

 

[Bob_Spidell]

...
I will adjust the level of the lower bowl to that of the higher and see if that has any effect.
steve

Float level is critical; why not check/set per the spec instead of just matching them up? AFAIK, all Big Healeys specify 7/16" 'gap' between the top of the lid and (what would be) the bottom of the curled 'spoon' at the end of the float lever. A 7/16" drill bit works a treat. Also, I have a Grose jet that sticks; the little ball seems to become embedded in its recess. It's a new(er) one; I've heard the company changed hands and quality suffered. I've had a pair on my BJ8 for many years with no problems.

FWIW, my dad had a problem with off-idle stumbling on his '55 T-Bird. We tried everything, including replacing the (obvious candidate) accelerator pump, to no avail. Finally, Dad went through the carb one more time and thoroughly cleaned all holes, ports and jets ('American-style' carburettors are ridiculously complex compared to the ingenious SUs). Problem solved. If adjusting the float levels doesn't do the trick, a thorough cleaning of the carbs would be my next step.

 

[SteveHall64Healey]

Thanks Bob. Just to make sure I get it right, do you know of a documented (i.e. step-by-step) procedure for doing this?
thanks
Steve

 

[andrewss]

Steve, I have had a similar issue with a clients BJ7... I have read all the threads and would like to know which model of SU pump do you have and where is it located. I ask because after having exhausted all other avenues I found that the SU pump was a 'push' pump and was positioned approx 1 1/2 inches higher than the old pump causing a 'vacuum' in the fuel line. As it was intermittent it was almost impossible to detect.. On the flat fine, slightly uphill driving sometimes and downhill never and in O/D often and don't ask me why !!.. The pump an AZX 1332 electronic relies upon free flowing fuel from the tank and has to be positioned below the fuel tank... Just in case you run out of other ideas !!! good luck

 

[SteveHall64Healey]

Hi Andrew, the fuel pump I recently installed is the SU fuel pump for late BJ8's, Moss# 377-161. It replaces an identical unit that came with the car, and is mounted in the original factory mounting holes. The problem has not been intermittent for me. At 60 mph I can cruise indefinitely with no problem. If I attempt to accelerate past about 75 mph and hold it there, the sputtering will occur. I was able to trigger the sputtering last night without OD engaged - I just have to hold the throttle a little higher and for a longer period to trigger the issue than if I run the car at 3700 rpm with OD for about 30 seconds.

With the current geometry, the gas tank is higher than the fuel pump and the carbs are higher than both, so I would wonder how an air lock might occur.

thanks
steve

 

[Keith_M]

Thanks Bob. Just to make sure I get it right, do you know of a documented (i.e. step-by-step) procedure for doing this?
thanks
Steve

Steve,
I agree with Bob that float height is critical. Here is the procedure.

View attachment Scanned_20150505-1509.pdf

 

[Bob_Spidell]

Argh ... Got the drill size wrong. Sorry about that.

 

[SteveHall64Healey]

Argh ... Got the drill size wrong. Sorry about that.

No worries Bob - I followed the manual and set them to 5/16" using the drill bit method. They were way off initially at over .5" each. Test drive tomorrow.
steve

 

[Patrick67BJ8]

No worries Bob - I followed the manual and set them to 5/16" using the drill bit method. They were way off initially at over .5" each. Test drive tomorrow.
steve

Make sure that they do not drop down too far or they will lock themselves in a full open position allowing full fuel pressure to bypass the needle/seats and the fuel goes out the overflow pipes. This is often overlooked when setting up the needle/seats of the carbs.

 

[Bob_Spidell]

Make sure that they do not drop down too far or they will lock themselves in a full open position allowing full fuel pressure to bypass the needle/seats and the fuel goes out the overflow pipes. This is often overlooked when setting up the needle/seats of the carbs.

And, you may need to tinker with the mixture setting afterward.

 

[SteveHall64Healey]

I just test drove the car at 3500-4700 RPM in 3rd, 4th, and 4th with OD engaged for periods of several minutes at a time and was unable to reproduce the problem - no sputtering observed. The only change was to correctly set the float level levers. Will monitor over the next couple of days, but it the issue appears to be solved

Fuel mix seems ok without adjusting it. The car started with the first turn of the key. Idle is a little higher than normal, but it is steadier than before at about 1200 rpm. Will dial that down to 900 rpm.

Thanks for the suggestions everyone,
steve

 

[SteveHall64Healey]

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)

Does anyone know if there is a calibration procedure for these pumps?
thanks,
Steve