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Another embarrassing break down

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bigjones

bigjones

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This time the police cruiser stops. I thought he was going to tell me to move along but instead he offers to help! Turns out he had an MG years ago.

This got even better when a hot chick drives past, stops and says "Hey, I love your car!"

Anyways, the car would sometimes start up but then stall out. Sometimes it just wouldn't start. We managed to get it running again so I could limp home and thus spare me the tow truck. Phew!

I had gone to the store and it was running fine. Coming home, it back-fired out the ehaust when I changed up from 3rd to 4th. That must mean something.

At home, I looked in the fuel bowl (single HS4 in a 1500) and it was half full (or is that half empty?? Is that normal?) Turned on the auxillary electric fuel pump and let it run a while then took another look - still just half full. Float seems to operate fine ( 7/32" gap between float and lid).

Plug color is a nice tan on the porcelain.

Any ideas - I'm seriously thinking now of putting in an electric pump to replace the mechanical.

Cheers!
 
Are you still running points Adrian? If so, I would start with a basic electrical tune up, paying attention to the points gap. When the points start to wear and close it can be very difficult to start the engine. I don't know if that could eventually lead to backfires between shifts, but I always start by looking for ignition problems.

I'm not sure about the float level. Half full sounds a little low, but you have to consider what the level might be with the float sitting in it. Hopefully others would know for sure.
 
Hi Doug!

Forgot to mention - it has the early Pertronix.

Fortunately, it won't start up so I have a good chance of figuring this out.

Cheers!
 
If it had points i would say that they closed. On a pertronix who knows.
 
bigjones said:
Hi Doug!

Forgot to mention - it has the early Pertronix.

Fortunately, it won't start up so I have a good chance of figuring this out.

Cheers!
Click to expand...

I thought you had the stock Opus unit in there. Did you convert it or did it come like that?
 
Adrian, I might pull the fuel line at the carb and see if fuel is being pumped (run it into a bucket) there might be a clue in your comments about the fuel bowl, but, even so, you can eliminate it as a variable quickly. remember, one variable at a time - fuel, spark, air - at the right time and you're good to go.
 
Oops and what I would be looking for if no flow is a plugged line or sludge in the tank.
 
Do you think this has anything to do with it?

DSCI0068.jpg


Yes, the carb piston is wedged at the top of it's travel. I couldn't push it down. Took the dome off and it fell down OK. The only sign of any grit which may have gotten in there is this ring that I never noticed before.

DSCI0069.jpg


Anyways, cleaned things up and the car started first time and seems to run fine now.

Cheers!

Kellysguy, yes it is the Opus dizzie but I put a Pertronix in there many years ago.
 
nice when it's the easy stuff - glad you checked before you went crazy.
 
Adrian, is that a later HS4 with the spring loaded needle or an early one with a fixed needle?
 
Doug,
Thanks for the question.
I'm not quite sure - the needle feels spring-loaded and I've never gone through any kind of centering procedure.
Let me look up the model and get back to you.
Cheers!
PS. The NCMGCC is off to Wilmington this coming weekend - we set off in a convoy - stay the night(s) and head back to Raleigh, again in a convoy.
 
It occurs to me that the backfire caused the piston to jam up. Often that is caused by lean mixture, often caused by an intake leak. I suggest you keep investigating. The piston rarely, or never goes up that high while driving. It can jam when slammed to the top.

Peter C
 
except that the backfire was out the exhaust was it not?
 
Chicken or egg? Did a lean mixture cause a backfire in the intake and jam the piston up, or did the piston get jammed up and cause over rich condition and backfire through the exhaust?

...or was there an intake backfire before the exhaust backfire?

The plot thickens...
 
Ha!

Thanks for all the comments.

Here's what I think hppened:

I have the jet lowered way down, about as far as it will go. This is to try and richen up the mixture. Remember this is a single HS4 (AUD 135R) feeding a 1500.

Coming back from the store, I could feel the engine still not getting enough fuel (sort of a slight miss - nothing serious just doesn't feel right). So I had this great idea - I pulled the choke way to see if it would make a difference. Didn't seem to but this was at full throttle and I'm betting at this stage the needle actually came out of the jet. When I pushed the choke home, the needle for some reason didn't go back into the jet but got wedged.

I drove about a mile like until it conked out at the Stop sign. Like I say, I had a terrible time trying to get it started (no wonder!) but when it eventually fired up I could drive another mile back home where it died in the driveway.

Think I need to investigate a richer needle.

Cheers!
 
Trevor - the piston being stuck in the Up position would cause a lean condition, not a rich one. The airspeed through the venturi would be very low with the piston up.

Bigjones, your jet being way down is disturbing, suggesting something's wrong somewhere that won't be cured by a rich needle. I'd suggest you first look for an air leak inboard of the throttle. The old trick of spraying around with brake cleaner, starting fluid or similar can pinpoint one of those.

Bear in mind that a richer needle won't affect your low speed running or ease of starting to any extent you'll ever notice. The root diameter of needles, that is, the bit that's doing the work at low speeds, doesn't vary much. Are you sure your present needle is correctly located in the piston? The photo of yuor piston cuts off at just the wrong place to tell, thoug hit does look like there's a fatter protrusion than there ought to be. You really do need to understand what kind of needle you have (see Doug's question above) and make sure it's at the right height and properly centred, if necessary.
 
True Roger. My mistake.
 
Roger,

Thanks for the input - sorry about the poor picture.

Here are some better pictures of the carb piston and needle:

DSCI0070.jpg


IMG_1803.jpg


IMG_1804.jpg


Looks to me that the needle is at the correct position and that it is of the spring-loaded type.

I had lowered the jet to about the lowest position (something like 24 flats down) to enrichen the mixture. At "12 flats down", the spark plugs showed no color on the porcelain - that with the very slight rough running (when cruising) got me thinking that the carb is running too lean - to be expected given that it has to provide enough fuel fo a 1500 engine.

Cheers!
 
DSCI0047.jpg


My helper and I have sort of confirmed what happened to cause the break-down.

With the choke pulled out (jet lowered) and with the air cleaner out of the way, I pushed the piston up with my finger. Sure 'nuf, the needle came out the jet. Being spring-loaded, it moved to the rear and away from the jet opening, thus jamming the piston in the fully open position.

With a hooked wire, I carefully pulled the needle forward and it went back down into the jet. I closed the choke (jet in the up position) and repeatedly lifted up the piston - couldn't get it to come out the jet.

So......I think I'm alright so long as I don't go yanking on the choke at full throttle (ha!)

Roger, I'm still a bit unsure why you don't recommend a richer needle.

Cheers!
 
well who's the peacock now? strutting because he found a solution. please, some modesty.... :jester:
 
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