sticky floats?

[TomFromStLouis]

If this is laughable, please enjoy. I have never been inside the carbs since I consider them sort of the deep end to an inexperienced wader. Anyway, a fellow who identified the year of my BJ8 as he approached me with my bonnet raised (dad also had a '65) suggested a diagnosis to my problem I wanted to run past you.

My problem is that after a spirited bit, especially on warmer days when my water temp is up at 180-190 or so, the car dies at idle. It happened twice this weekend, once after accepting compliments on the car, the light changes, car dies. I laughed. No effort at restarting is rewarded until the temp cools down to ~160. Battery and starter are all performing fine. As it cools, occasionally it turns a few cranks, but in general it acts like it is not getting fuel. I have suspected the carbs based on the above and the fact that they are a black box to me. My random adviser suggested that perhaps the floats were sticking as they warm and expand and need lubricating.

Since almost any logic will convince an idiot, I like his idea. Any other explanations? I'll let you guys speculate.

 

[Dave Russell]

There is nothing to stick due to lack of lubrication. The float, needle, pivots, are all "lubricated" by the fuel.

Hot soak starting problems are often caused by improper float bowl venting, leaking float valves, or or improperly set float levels.
D

 

[zblu]

Or by vaporising in a high spot in the delivery line causing fuel vapor lock

 

[healeynut]

Tom -

Also if your throttle bushes are worn, this can happen when too much air leans out the mixture when the car is hot.

You should rebuild your carbs - its actually a pretty simple job for a BJ8 as long as you have the parts.

 

[GregW]

You should rebuild your carbs -

I think it's a little early in the Q & A to say that. It is not unheard of that a failing ignition coil would have similar symtoms.

 

[Ed Kaler]

..................... totally, Greg!!

Ed

 

[TomFromStLouis]

Okay, I have heard that my symptoms suggest vapor lock, but the only solution to vapor lock that I have heard is insulating the fuel line to keep the fuel from vaporising. I presume the line to insulate is the flexible pipe in the engine bay (Moss 376-830). And maybe flexible pipe carb to carb 376-870? Any more? Insulate how? Any other vapor lock solutions? It bothers me that I have this problem regularly after 20 minutes in 70 degree weather. I want to drive in the summer too!

If not vapor lock, then Dave's ideas come into play. Somehow, I think he has the right diagnosis, and not just because he is the man (you are Dave). But also because regular vapor locking suggests to me some kind of design flaw - everyone would have it - or I have an unusual coincidence of some kind. So it should be the floats; I will address them with a visit to my mechanic to learn float adjustment. Should be fun and enlightening.

I am open to quick and easy vapor lock preventitives.

Oh, and healeynut, if my throttle bushes were worn, then wouldn't manual throttle manipulation from the engine bay override that? Choke on, choke off, throttle down from inside the engine bay, none of that changes the start. And I guess you could be right about rebuilding if vapor lock and float adjustment fails, but lets hope it does not come to that.

 

[Bob McElwee]

Tom,
Don't rule out the electrical system yet. Mine use to be very hard to start when it was warm. After I put a Crane unit in, I've had no problem starting hot or cold.

 

[Dave Russell]

Hi Tom,

A couple of comments.

The fuel pump is located pretty much at the rear of the car at a cooler location. Pressurized fuel coming out of the pump does not flash to vapor easily.

If vapor does form in the lines, during shut down, it should be pushed down the line (flushed out) when the pump starts pushing liquid, & the vapor should be vented via the carb float bowl vents.

The next time this happens, loosen one of the fuel supply pipes where it joins the carb. See if air or fuel comes out. (Ignition on). If air comes out, the carb float chamber is not venting properly. If it shows a mixture of air & fuel see next paragraph.

The other thing that could cause air/vapor in the lines would be a tiny air leak on the suction side of the fuel pump, between pump & tank. The leak could be so small that it doesn't show external leakage but still allows the pump to suck enough air in to cause fuel starvation. This "could" mimic vapor lock & has many times. A very rare condition might be an air leak in the delivery pipe inside of the tank. Doubtful.

When you have the hot start problem, does the pump tick rapidly as it would if vapor were continually present? Or does it tick rapidly for a short time & then pretty much slow down?

It's always possible that a bad ignition coil could fail during a hot soak & restore itself when it cools a bit, as Greg suggested. I don't think it would do this very many times before it failed completely though.

This all takes longer to explain than to do.
D

 

[TomFromStLouis]

After some rest, the first start attempt causes the pump to tickity tick and then it slows down and stops. A second attempt immediately after start failure causes very little pump action.

Since you mention the fuel pump, I should mention I recently replaced the older one with an electronic SU. There are no visible leaks at this installation and the problems preceeded the change.

I have wondered why the pump does not push the air out (maybe that's why they call it "lock"?). The float bowl vents you refer to are the little holes on top of the float chamber right? One of the two chambers has some old oil splatter around outside; it is conceivable that the vent on that one at least is gunked up a bit.

 

[GregW]

Hi Tom,
FYI the fuel pump vapor lock I think was more problematic in the earlier cars where the pump was located over the exhaust system. It was moved over to the right side of the car at some point, Pretty sure before your car was built.

 

[TomFromStLouis]

Oh yeah, my pump is near the right rear and the exhaust passes down the left.

 

[Dave Russell]

I mentioned that a tiny air leak in the pump suction line could cause similar problems.

The strict definition of vapor lock is the pump itself or the suction line getting so hot that the liquid in it vaporizes. Much less a problem when the pump is not mounted in the engine compartment or near the exhaust system.

If vapor in the line is not vented via the float bowl, the pump will still stop pumping when it's set pressure is reached. Pressure is pressure - Doesn't matter if it is vapor pressure or liquid pressure. No venting or wrong float levels would be most likely.

Look here:
https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28867
For the BJ8, Item 38 is the vent banjo. It may have a plastic extension tube which has been known to melt closed.

Item 41 is an inside scalloped washer which allows air flow between the cap nut shank & the bowl lid, via the scallops so that it can reach the vent banjo. It has happened often that someone put non scalloped washers in this location & inadvertently blocked the bowl vents. The top washers, item 37 are not scalloped.

If you feel inclined, replace the coil with another that has around three ohms primary resistance, but check the venting first.

Good luck,
D

PS - I have no idea what "little holes on top" are. If your car doesn't have the vent banjos & correct sealing washers, I suggest you get them.

 

[TomFromStLouis]

I will check the venting when daylight returns as you suggest. Meanwhile I shot a picture of my float chambers. The little hole I referred to is just south of the true banjo vent and washers in the picture (right side chamber) also just below the philips head screw on the clamp; the hole is surrounded by a nipple of some kind - part of the chamber casting - and looked to me like a dirt collector. I'll ignore it.

 

[GregW]

Maybe it's just the angle of the photo, but your fuel line looks weird. Like it has a kink in it.

 

[TomFromStLouis]

I noticed that too. In a larger picture it looks less kinked and more like the outer black rubber is split in two, part under the clamp and part not. The outer woven sleeve does not look like it goes all the way under the clamped part. May need a new hose? I will look at the real thing in daylight.

 

[BUNDYRUM]

Hello Tom,

Don't worry about "the little hole" it doesn't go anywhere.
I see nobody has mentioned the needle valve assembly in the top of the float lid.
If you look at the link that Dave provided it is item # 31, part # 371-055.
If the valve is worn it could stick closed.
Item # 31a part # 386-390 is what I would highly recommend to replace your original valves. They are much more reliable.
You said you would look at the float level, please read/look at the manual first and really understand about checking the float level and how it is changed as it is important. This is something you can do yourself it's not difficult.
The float level is set by bending the lever that is attached to the inside of the float lid but you have to bend it in the correct place.
Yes there could be a problem with the fuel hose but then you would have the same problem when the engine was cold.
keep at it you will get there eventually and be happy you did.

bundyrum.

 

[healeynut]

Tom - If you aren't hearing anything from the fuel pump, it's not vapor lock.

 

[healeynut]

Tom -

Your float chambers are very dirty indicating that there is alot of fuel overflow in your float chambers. This suggests that either:

1) Your float chamber needles are sticking open (that usually happens when they are very worn or if there is alot of dirt/rust sloshing around your fuel system, and the dirt/rust is clogging up the float chamber valves keeping them open.

2) Your brass floats themselves are starting to fail an have fuel in them, meaning they don't float high enough allowing the float chambers to overflow with gas.

Either way you have to fix these things, you are wasting lots of fuel if you allow your float chambers to get this dirty.

Also, if you are opening the throttles when hot and getting no response, that does suggest you have an ignition problem - either bad coil or bad condensor.

Alan

 

[TomFromStLouis]

I truly appreciate all the time and effort in these responses. You all have given me several specific talking points to discuss with my buddy who has all the tools. I will let you know what we learn when we dig in.