52 cdv, vapor lock, or fuel filter? Maybe timing?

[Omarine]

Hello all,

I hope everyone is well. I spent some time getting ignition working right, and now it is. I admit, i advanced the timing slightly. Ive got all 8 cylinders firing now.

Well coincidentally, i now have stalled out a few times for fuel issues. First i thought it was out of gas. Then it happened again. So i changed the plastic fuel filter. It seemed dirty but not too bad.

Well today it happened again. This time whole family in the car. I topped off tank, car idled while i filled it. Drove off and then did the stalling thing again. Took a bit of time, but i poured some fuel straight into the carb to get it going again.

When this happens, fuel pump shows fuel in it. But the filter which is next to drivers fender shows empty.

Could this be vapor lock? Water temp was showing only 190*.

I didn't have these issues when two cylinders were missing and timing was at the timing mark. Is this coincidence?

Just how related is timing advance and fuel issues on these cars?

Or maybe gas cap not venting enough?

Have a hard time believing it could vapor lock so easily. Fl was about 85* today.

Might try putting timing back. Any insight?


Thanks
Oscar

[wrench]

Could be vapor lock. I don’t know what you mean that’  the fuel pump shows fuel in it’...

Do you mean the glass bowl at the fuel pump shows fuel?

I don’t think a filter on the driver’s fender is stock. Do you know if this was added? I don’t know why there would be an extra filter and I think this would be a bad location and application for extra filtration and could aggravate a vapor lock situation.

Either way, if a filter shows air, then likely vapor lock.

I live in a cold climate. And I store my ‘51 in an air conditioned garage with a full tank. So on an 85 degree day, I have 65 degree fuel and I can drive most of the day without vapor lock.

If I leave the car in a hot garage in 85 degree weather and I start out with 85+ degree fuel, it will vapor lock pretty quick.

I don’t have a primer pump or anything yet as it is on my ‘to do’ list but the way I drive the car and the cold climate vapor lock is not a major issue. If I lived in a warm climate , I would have jumped on the primer pump mod a long time ago.

If you read and search the forum and talk to anyone who remembers these cars from back in the day, they will tell you vapor lock is an issue.

As for timing and vapor lock, you could adjust the timing to the point that it will affect operating temp which would aggravate vapor lock and adjusting the timing could contribute to hard starting (restarting) even if vapor lock did not come in to play.

As for not happening with the misfire, well if you had basically two dead cylinders it would have been running cooler. Theoretically...

[Omarine]

Thanks Jim, yes i meant fuel is visible in the glass bowl, almost to the top.

The timing  has barley moved the needle on the water temp, if that tells us anything.

Hot cranking and starts are strong except when the fuel issue hits (cranking remains strong) which has happened while driving after being shut off, or idling..

Yes that fuel filter was added at driver side fender by previous owner

Oh and I've only put 90 octane ethanol free fuel available here in FL...

Thanks again
Oscar

[Jeff Rosansky CLC #28373]

There are going to be many others that jump on here far more knowledgeable than I. But just a couple of quick observations if I may.
Put the fuel system back to stock. Not for the stock debate but for the routing. The fuel is vulnerable when exposed to the heat of the engine compartment. The more fuel line you have, the more the fuel is allowed to heat. Just because your water temp is relatively low, the engine compartment isn't.
When that happens again just pop the fuel cap and listen for a hiss in case the cap vent is bad.
This is for debate but I run a little Marvels in the fuel to raise.the boiling point.
Original metal fuel line? Look at/under the clips to check for rust. A small pinhole may allow it to run ok normally but adding to the heat issue may just be enough to cause a problem.
Lastly, despite the problem, congratulations on somehow finding a way to get the whole family in the car.
Please keep us updated.
Jeff

[James Landi]

Sometimes you have a fuel pump with mechanical linkage that is oh so slightly worn that it does not have sufficient "revs" with the starter motor engaged to pump fuel into the carburetor to fill it up to the necessary level.  In my experiences, the fulcrum and diaphragm can be just fine, but the pivot point on the fulcrum can be worn down, so there's insufficient push until the engine is revving high enough to make up the difference. I've often wondered when some of our members have added an electric pump in series with their original mechanical pump, if my diagnosis could have solved the problem.  I don't know where your fuel pump is located, but on many Cadillacs, the pump is located above the engine, and on original equipment, there was a zerk grease fitting that would push grease into the vulnerable pivot point to keep it lubricated, simply because no lubrication gets thrown up to that pivot point.  I also have run some Marvel oil mix on fill up as was noted above.  Gasoline does boil in a hot carburetor, and as mentioned above, adding some Marvel oil always helped me to start a super hot engine.
Hope this helps,   James

[Omarine]

Thanks James, my fuel pump is stock, appears to have been rebuilt at least externally it does. Trans, engine and starter all came to me rebuilt just dont know how long ago.

So i might just grease a zerk fitting on the fuel pump? That sounds simple enough. Looking to go the electric fuel pump route...

[James Landi]

Oscar, so you have a Zerk on the pump, and so it's likely very old!  Frankly, if my diagnosis is correct, new grease won't be much good if the pivot on the fulcrum  is already worn out. It might be possible for a clever machine shop person to take the pump apart and add a bushing or a larger pivot rod to take up the slack, and in doing so, provide the pump the maximum performance you need when the cranking motor (which turns at appriox. 150 rpm) is trying to get you started.  YOu might connect up a fuel pressure gauge to the pump, and find out for certain what kind of pressure the pump offers during cold cranking. That would assure you that a weak fuel pump is the problem or not.    Hope this helps,   James

[Omarine]

Thanks again James, i looked again. No zerk. Pump failed 2 of 3 tests: psi and volume. Passed the hold pressure with engine off test. Rebuild is next before any electrical anything.

Had only 3 psi. Book calls for 3.5-5.25 psi. And after more than 12 probably 18 squirts, it still barely got 1/4 pint , let alone 1/2 pint.

The coincidence is probably not the timing, it’s that now that all 8 cylinders are firing for the first time since I've had the car, it revealed that the fuel pump cannot keep up....

As for fuel line, its new rubber from the drivers fender, under the ps pump and over to the pump.... would steel braided or a section of steel line keep the fuel any cooler than straight black rubber?

Thanks again!
Oscar

[TJ Hopland]

Does this car have a rubber line back at the tank too?  If so don't forget about that one.

[Omarine]

Coming out of the tank is steel, will have to follow whole line to know.

The more i think about it, the more i think i need to repeat the tests again. This time without the plastic modern filter the po installed next to the fender.

Seems odd that the pump will hold pressure with engine off but was weak and had poor volume. Im growing suspect of that additional filter.

This car already had me changing whole ignition system when all the problem was wrong point gap...


Cheers

[Daryl Chesterman]

If, after replacing the fuel pump, you still have the symptoms of vapor lock, you might try a product like this heat shield that is shown on this website, for fuel lines and wiring.  There are many other kinds on the internet, but this is an example and you can order by diameter and length.

https://www.heatshieldproducts.com/hot-rod-sleeve

Daryl Chesterman

[Omarine]

Thanks Daryl, that’ very helpful, been looking for this for a long time...

[James Landi]

Oscar,

The fact that the pump holds pressure has to do with its internal check valve. the potential issue that may be the problem, has to do with a worn fulcrum that does not provide sufficient pumping action against the diaphragm, and that problem would be revealed in your pressure/volume reading.  The prior post regarding your fuel line would also cause problems,so my suggestion is to set up a small alternative tank and hose, similar to an outboard motor, so, for diagnosis purposes, you can check that off the list of potential issues.  Hope this helps, James

[Omarine]

Thanks James, it does help. and will definitely look for more rubber sections all the way back to the tank.  Had a fuel starvation issue although less pronounced on an Impala and it turned out to be the 3 sections of rubber hose from the tank to the pump that were old and clogging.  I had forgotten about that lesson.

this is my first old caddy, and the book helps but some things are omitted and though everything looks rebuilt, there are some other things I have found wrong.

So another thing - the vacuum line coming off the pump only goes to a single fitting on the intake manifold in front of the carb (but the carb has its own line going to the distributor vacuum advance).

the wiper motor has no vacuum line going to it (another thing the PO omitted). 

should't that be a TEE fitting on the manifold? this would provide a vacuum line to the disconnected Wiper motor...or is it a direct vacuum line from fuel pump to wiper motor?

thanks again

[James Landi]

Yes, there should be some vacuum connection to the wiper motor...but one can only imagine the condition of the vacuum wiper motor.  Most times these "motors" get stuck for lack of lubrication, thus eventually, vacuum leaks become dramatic, so if you're hemorrhaging vacuum, your distributor  advance doesn't work, and your carburetor idle doesn't work, so a previous owner simply gave up on it.. I owned a couple of '56 Cadillacs during the late 60's and 70's and used them as daily drivers, so I absolutely needed working wipers...   In a fit of frustration, because the wiper motor was failing, I sprayed WD40 into the input "atmosphere" port of the wiper motor while it was oh so slowly running... it came to life almost instantly...I suspect the light lubricant on the major moving vane-like pumping arm did the trick.  I'd ask others about getting your wipers going again.  There's likely many practical ideas..   James

[Omarine]

thanks again James,

so i guess the question really is - does the fuel pump vacuum need to be connected to engine vacuum (manifold) in order to work properly?  (wiper motor aside, will deal with that later)

[Omarine]

Well, here to report some progress. When i realized by fuel pump was weak, i went ahead and replaced everything.

New tank, all new line, new rubber hoses, fuel pump and i even wrapped fuel lines in engine compartment to insulate them from heat transfer.

Also dipped filler neck in apple cider vinegar over night. Was atrocious inside.

One thing i noticed was pump I took off was loose, maybe it was letting in air there. Who knows. New pump puts out the 5.5 psi i was after.

Installed an electric back up pump on a momentary toggle too. Have yet to use it, hope i don't need it, but it’s better than being stuck...

Check out the gunk that came out of filler neck - that was one round of apple cider vinegar...

Thanks to all who commented

Cheers
Oscar