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Sun Jun 22, 2025 3:48 pm

In.

Tomorrow I will finish assembling it and see if she will fire. She hasn't run since 2019 when I pulled her out of the sunroof car. I thing she will go

Don

Tue Jun 24, 2025 7:06 pm

OK that went well.

I need some shims for my pulley or a longer belt, it is too tight.

Don

Sun Jun 29, 2025 9:51 pm

A little update:

The engine that could is doing it again. I forgot what a wonderful little mill this one is. It is now powering car #6 beautifully. I now realize how poor the original engine was. It must be badly out of balance. I could really feel it working against itself.

Taking it apart now and haven't found anything to suggest what went wrong with it. Other than being super oily it all seems fine so far. I will think of a way to pull the wrist pins out without taking the pistons out of the cylinders so I don't have to disturb the rings.

Don

Mon Jul 21, 2025 4:04 pm

For the past week the car has been making lean running condition problems. Bucking during acceleration and down in power. Today I hooked up my fuel pressure meter today and both fuel pumps were making less than 1 PSI.

This was a surprise as the '54 fuel pump was rebuilt 2 years ago with a new spring and the pressure tested to 3 PSI. I measured the push rod and the two I had were both the same length. I measured the stroke length and it was exactly as specced in the manual, 29 mm to 34 mm so all that was correct leaving me with stretching the spring as recommended in the manual. I carefully stretched it 1/4" and reassembled the pump and mounted it to the car. It now make 1.5 PSI which is within the spec of 1.3 to 1.85 PSI. we'll see if this solves the issue. Strange that both pumps make exactly the same pressure.

Don

Mon Jul 21, 2025 10:15 pm

Let’s hope that gets it! That would be a very simple fix!

Thu Jul 24, 2025 5:40 pm

So for a couple of weeks now I have been dealing with a lean running issue. Anything more than half throttle and it bogs and runs on one or two cylinders.

To address this issue I have made sure of the ignition first, from British cars I know that 90% of carb problems are ignition. I dismantled both distributors I have, made sure the advance mechanism was working freely and put them back together. In investigating the ignition I discovered one of the vacuum advance units was not working and removed it from service.

I then turned to fueling. I dismantled the fuel tap and made sure it was all clear as well as the soft line from the tap to the chassis. I then ran the engine until it stalled clearing all the gas out of the line. I filled the line with carb cleaner and let it sit for a couple of hours and then blew the line out with compressed air. I replaced the fuel filter and the soft lines from the chassis to the fuel tap and to the engine.

I installed both fuel pumps I have and they both made 0.75 PSI. Very suspicious. I stretched one of the springs to get 1.5 PSI which is in spec for these pumps. I rebuilt and carefully cleaned both carbs I have.

All of this has had no effect on the lean running issue. The car is very hard to start from cold, will run on one cylinder for a few minutes before the rest catch and will buck at anything more than half throttle. Over half throttle it will run on one cylinder catching intermittently and run on all four for a half a second then back to one. The car has become almost undriveable. I am at the end of ideas. The last thing I will try is replacing the intake manifold. If this doesn't work then I am completely out of ideas. I will also try a tank of premium gas but at a compression ratio of 6.7:1 this is a silly idea.

Is there a way to test the intake while it is on the car?

Don

Thu Jul 24, 2025 8:28 pm

A little more data: If it idles for a minute or two that is when the bucking and stumbling is worst. If I'm stopped at a light, when the light turns green she absolutely does not want to go. Cruising along she is fine, no problem.

I stretched the fuel pump spring another 1/4" and it made no dofference to output pressure.

Don

Thu Jul 24, 2025 10:21 pm

Is the accelerator pump squirting?

Fri Jul 25, 2025 7:07 am

Quote:
Is the accelerator pump squirting?

Yes, both carbs behave the same way.

Don

Fri Jul 25, 2025 9:03 am

On the intake manifold. What testing are you thinking about? For flow or cross over to the exhaust? I am starting to think there is a cross over of exhaust gas being sucked into the intake stream. It may be only one cylinder. I bet that if you take another look at the plugs, thinking that is a possibility, something may stand out.

To test the manifold, I would pull it off the car. Fabricate 4 block off plates. 2 large and 2 small, then add an air injection Schrader valve to the intake tube and the preheat tube. Then pump up each one and listen.

Fri Jul 25, 2025 10:18 am

I will assume that the pump rebuilds included the 35mm preload on the activating rocker during assembly. Were the check valves inside replaced? They must be dead flat, so also the valve seats, or pressure will be lost. If you operate a rebuilt pump by pushing the rocker by hand, you should hear the check valves making wheezing noises if they are sealing correctly. Some check valve springs are better than others, some rebuild kits have iffy parts.

Does it run fine (temporarily) with the float bowl filled?

Best O' Luck!

Fri Jul 25, 2025 5:26 pm

OMG now WTF!

Oil light stays on bright at idle. It is a new switch so I'm thinking it is out of spec. There is no reason for the oil pressure to be low.

Anyways went on a road trip, about 360 Km

There is a geocache at the North gate to Whiteshell Provincial park that I always leave a note and a little gift

Moving South through the park

2.3 billion year old rocks

Destination West Hawk Lake

So the running issue is as bad as ever, nothing I have done has had the slightest effect. Pulling away from a stop I can get about 1/4 throttle or it just bogs and wont accelerate. If I hold the throttle down it does not improve. Letting up to 1/4 throttle will make it accelerate normally albeit slowly. I can manage it for driving but it is a nuisance for sure.

DOn

Fri Jul 25, 2025 5:31 pm

Quote: I will assume that the pump rebuilds included the 35mm preload on the activating rocker during assembly. Were the check valves inside replaced? They must be dead flat, so also the valve seats, or pressure will be lost. If you operate a rebuilt pump by pushing the rocker by hand, you should hear the check valves making wheezing noises if they are sealing correctly. Some check valve springs are better than others, some rebuild kits have iffy parts.

Both pumps were carefully rebuilt and working perfectly. The whole issue happened suddenly, one minute the engine was working flawlessly and the next it wasn't.

Don

Fri Jul 25, 2025 5:35 pm

This was interesting, three different fuel pump springs

All three of them make about 3/4 of a PSI

Don

Sat Jul 26, 2025 10:11 am

Also: the thing I was most worried about during the drive was the fan belt tension. I set it up according to the manual but at some point yesterday I thought it looked tight. Sure enough it was tight as hell. I never heard of that before a belt becoming tighter. Anyways this AM I checked and it was again the correct tension so I guess things expand and tighten up when they get hot. BTW it was +30C yesterday so pretty hot for the old girl.

Don

Sat Jul 26, 2025 1:02 pm

I had similar problems with my 1977 Mazda a while ago. At first, I thought it was a carburetor or fuel pump issue. However, it turned out to be a malfunctioning ignition coil during operation. The resistances of the primary and secondary windings were correct, though.
Are you sure the (new) ignition coil is functioning properly?
Measuring the resistance of the primary and secondary windings is a static test and provides limited information about the coil's condition because this test cannot measure the coil under load/in operation. For that, you would need to perform a dynamic test with an oscilloscope or a special coil tester.
Or try another ignition coil.

Regards.

Sat Jul 26, 2025 6:47 pm

OOO, easy to do. I will try that. New parts have been known to fail.

Don

Wed Jul 30, 2025 8:23 pm

Quote: I had similar problems with my 1977 Mazda a while ago. At first, I thought it was a carburetor or fuel pump issue. However, it turned out to be a malfunctioning ignition coil during operation. The resistances of the primary and secondary windings were correct, though.

I ordered a 6 volt coil from Amazon on Monday and got it today. No matter what you think of Jeff B and his cohort you can't argue with the results.

Anyways I bolted it up to the car and went for a drive. No sign of bogging or hesitation at all. Ran like it should the whole time. By jove I think I've got it.

Lesson learned. Yet another shit part from CIP.

Don

Sat Aug 02, 2025 12:05 am

:thumbsup:

Sat Aug 02, 2025 12:49 am

sunroof wrote: Quote: I had similar problems with my 1977 Mazda a while ago. At first, I thought it was a carburetor or fuel pump issue. However, it turned out to be a malfunctioning ignition coil during operation. The resistances of the primary and secondary windings were correct, though.

I ordered a 6 volt coil from Amazon on Monday and got it today. No matter what you think of Jeff B and his cohort you can't argue with the results.

Anyways I bolted it up to the car and went for a drive. No sign of bogging or hesitation at all. Ran like it should the whole time. By jove I think I've got it.

Lesson learned. Yet another shit part from CIP.

Don

It looks like the issue has been solved.
Which brand of coil did you buy from Amazon?
And which brand did you buy from CIP?

Regards.