Fuel delivery woes

[wre805]

I have been enjoying my '62 D200, my first Sweptline.

A couple weeks ago I idled for too long while talking to a neighbor. Truck died while I was sitting in it, and wouldn't start back up.

I left it overnight, the next day it started up fine. Started driving home, engine got up to running temp -- and started stumbling any time I'd give it a touch of throttle. Barely limped it home at low speed.

Seemed like vapor lock / fuel delivery issues / air in the fuel so I did a few minor things:
* Pulled air cleaner and verified i'm getting two nice jets of fuel when i pull the throttle
* swapped out the inline fuel filter
* replaced some of the old crusty rubber fuel lines between tank and fuel pump
* pulled & check my fuel sending unit
* replaced a crusty vacuum hose from carb to timing advance
* replaced a cracked rubber cap on one of the unused carb ports
* checked the heater riser on manifold to make sure it wasn't stuck shut (butterfly flaps were in fact long gone, so that wasn't it)
* poor man's carb cleaning with a bottle of spray
* spray started fluid around the base of the carb to see if it is sucking air at the manifold, no sign of a leak

After each of these I did a test drive - the stumbling was always present.

Truck now cold starts and idles. maybe better than ever before! but still is stumbling under throttle, and if the weather is hot, having trouble with hot starts like the fuel is vaporizing or ???

is it Carb rebuild time? New distributor time? Anything else I should try before I get more drastic?

The only thing I can think of is this... the vacuum timing advance hose was pretty bad, like crumbling and melting. Maybe some crud got sucked into the diapraghm on the distributor, or the port on the carb, and the timing advance is jacked up?

I've nearly exhausted my amateur weekend warrior mechanic skills lol.

[Wildergarten]

Which engine?

If it's a big block there is a potential for one problem that is relatively serious. The fuel pump on a big block is driven by a pin riding in a bore that itself is driven directly off the camshaft. If you or the previous owner was not maintaining ZDDP in the oil, that cam lobe and pin can quickly be worn, thus instigating a low rate of fuel delivery. There is no other stock fix for that other than replacing the cam and pin. The alternative is an electric fuel pump which requires control by installation of an oil-pressure-actuated switch. Most electric fuel pumps are noisy too.

[wre805]

Wildergarten ,Thanks for the reply and the knowledge. It has the 318 poly.

[Wildergarten]

Wildergarten ,Thanks for the reply and the knowledge. It has the 318 poly.

If your engine is a Poly, then the fuel pump is NOT driven by a pin on the camshaft; it apparently works the same way as does the LA-318. But with flat tappets, you do need to be hip to adding a ZDDP additive to your oil anyway.

[swptln]

If it starts and runs fine cold and you're getting the symptom of vapor lock, only when hot...start with your carburetor settings, ie float setting, fuel pressure, choke pull off, accelerator pump, etc. Then check fuel lines, filter, sending unit sock, etc. eliminate as much rubber hose as possible. Then check your timing, make sure your getting mechanical advance as well as vacuum advance.
If it starts like it's flooded when hot, then I'd say you have fuel line/carburetor issue.

[martincom]

Check for vacuum leaks. If you have power brakes, pinch off the hose to the vacuum booster with a pair of needle nose pliers. Is there a change in idle speed? If so, you have a leak.

Check the PCV valve in the same manner. With a properly functioning PCV system, the idle speed should drop approximately 50 RPM when the hose is pinched off.

Monitor the fuel pressure by teeing in a pressure gauge (a quality vacuum gauge will double as a fuel pressure gauge and they're affordable). Fuel pressure should be 3.5 to 7 psi at idle, depending on the pump. Pressure should remain fairly constant when the engine is first turned off and then slowly decay to zero.

[nutz]

i was thinking it was flooding out ,maybe float is sinking or float valve leaking
but hard to say when it stalls will it start with a little carb cleaner

[wre805]

Thank you swptln, martincom, nutz for your pro advice.

I was going to start checking PCV valve, fuel pressure, timing, float valves as recommend. But had already decided on Sunday to pull and clean the gas tank. nuts bolts & chain, Evaporust, etc etc. It was not the worst condition ever, but it definitely needed the cleaning.

I reinstalled the tank last night and tightened the hose clamps all along the fuel lines. Put the most $$$ gas I could find in it, I had to drive one town over and get some top-tier, our closest station is a little sketchy.

So... with the clean tank and tightened fuel lines and fancy gas it is running very well. I think I had a combo of bad gas, dirty tank, and old rubber hoses. If I really stomp it there is a little "burble" but not a full on stumble and nothing like before. I never "floored it" in the past so I am probably being a little overly critical now. I need to drive it further today and make sure it starts OK when hot.

I have added ZDDP, thank you for that tip martincom.

It still needs a carb clean or rebuild, but I like the truck to be drivable, and I know it will take me awhile as a novice, so I ordered one a reproduction 2bbd off Amazon. I'm going to swap them and then go through the Carter that was on it, which is not original and has a lot of unused ports, it must be off a later engine.

[nutz]

good start
could have been crap getting sucked up in the screen
or bad gas
time to drive it

[martincom]

The ZDDP suggestion was from Wildergarden. I use Mobil 1 0w-40, which has the required amount of ZDDP. It is pretty reasonable on Amazon, about $27 for a 5 quart jug.

If the Carter is 1973 or newer, it maybe lean for your truck. They started leaning mixtures quite a bit for emissions then. The factory service manual will have the main jet and power enrichment rods listed. You might be able to source them from Mike's Carburetor and swap them out.

If you don't have a factory service manual, it will be the best investment you can make in your truck. Quality reprints are available from Bishko, https://www.bishauto.com/, and Faxon, https://www.faxonautoliterature.com/

[wre805]

Problems are all solved now. Caused by... Pertronix