1931 V8 starts idles & revs good in neutral, won't rev in gear, dies in a block

[cookcrete]

My 1931 Lasalle V8 Sport Coupe unfortunately has never been able to leave my neighborhood under her own power.  I start her every couple of months, and when I do she starts right up, idles well and revs while in neutral.  Every time I try to take her for a spin it seems she tops out at about 10 mph (won't accelerate or rev beyond that, almost like there is a governor) then in a block or so starts to miss, and dies, like as if someone just shut off the gas supply.   She won't start again until cooled down.  The previous owner removed the vacuum tank and installed an electric fuel pump & pressure regulator, which is providing about 2 psi fuel, if the inline gauge is accurate, and I can see fuel in the clear aftermarket fuel filter I installed to confirm fuel is actually getting to the carb.   The Cadillac-Johnson carb had been professionally rebuilt according to the previous owner.  Maybe the float is messed up and not allowing the carb a supply? It is still connected to the exhaust heater tubes, and I wonder if the modern gas + a lot of heat is the problem. The stalling happens so fast after being on the road the heat idea seems unlikely to me.  I thought maybe the fuel pump was faulty, but when I disconnect the line it pushes plenty of gas out.  I checked the compression and all cyl are 100-110.  Any ideas or suggestions would be greatly appreciated. Lew

[Chris Cummings]

Maybe under load, the carb is getting flooded?  It's tricky to mate an electric fuel pump to what is essentially designed as a gravity feed system.

And how is your coil?  I had coil trouble, and my car (Johnson carbs) behaved anemically similarly to what you describe.

Chris

[cookcrete]

Thank you Chris.  I was wondering about both the flooding and the coil.  The plugs indicate a severely rich mixture, and black soot spits out the tailpipe.  Maybe I'll try toggling the electric pump on & off while driving just for lack of another idea.  I'm not sure I have any way to test the coil.  I'll do some research on testing the coil or possibly replacing, if such a thing exists.  One thing that always puzzles me is why, even though I'm only a block or two from home (which doesn't seem very far/long to me to get really hot), it won't restart until it cools down.  Maybe the Johnson being connected to the exhaust heater tubes boils the gas that fast?
Lew

[Chris Cummings]

If you are flooded, it takes some time for the excess fuel to evaporate.

What does your temperature gauge say when this is going on (is the engine really hot)?

Is the butterfly valve in your exhaust manifold free or stuck?

Replacing the coil is easy -- NAPA/Echlin IC-7.

But my eye is still on that electric fuel pump.

[wheikkila]

I would check the carb. It sounds like the main jet is plugged.
Thanks Wayne

[novetti]

Lift the rear wheels and put the car in stands at your home garage. Rev in gear and see if the same happens.

Is everything at the gearbox/drivetrain/wheels spinning free? No bind?

[cookcrete]

Thanks you guys, for all the excellent feedback.

I've ordered a new coil (big help with the right part Chris...thank you!)  Hopefully that will help or solve once I get it installed.

The engine temp gauge does not indicate high temp, but not sure how well it is working.  For what its worth, I recently flushed the radiator & block and was pleased at how much flow I saw, plus I've rebuilt the water pump and can see action in the radiator.

The carb flooding scenario seems very probable to me based on numerous factors. The wait time for flooded gas to evaporate reinforces this in my mind.  Great thoughts Chris.  I'm going to install a "better" fuel pressure regulator and try to turn it all the way down to the minimum 1 psi setting, VS the current one that seems to only reduce to 2.5 psi.

I wonder if it is normal that when I shut off the engine the gas disappears from the glass filter in the supply line?  Apparently it is siphoning back to the gas tank, which I would not expect with an electric fuel pump in the line.

Great point about the main jet being plugged Wayne.  I wonder if there is anyplace on the Johnson I could spray some carb cleaner as a lazy man's 1st attempt to free it before I yank it apart?  I'm still puzzled by what version of the Johnson carb is on my engine.  All the diagrams I have show a "counterweight" on the bottom side like in attached drawing... Mine has nothing there.  Also, I do not see a butterfly valve in the exhaust manifold on this particular setup I have.  Maybe it is not visible?

Thanks for the generous sharing of knowledge!
Lew

[Chris Cummings]

Here's the extent of illustrations of the carburetor in the 1929 Shop Manual.  The entire Shop Manual can be downloaded from gmheritagecenter dot com among the vehicle information kits on that web site.

Chris

[pmhowe]

I will bet you a cold beer that you have a partially plugged fuel line. I had a similar problem with an XK 120 Jaguar and a 1948 MK IV Jaguar some years ago. The symptoms you describe are consistent with gas starvation. My solution was as follows: I disconnected the gas line between the fuel pump and the gas tank. I then turned on my air compressor and blew air down the line. On old Jaguars, there is a copper fuel filter in the bottom of the gas tank. It was full of crud. Obviously, my solution was temporary. It identified the problem and fixed it until I could clean the fuel system. In your case, I recommend you disconnect the fuel line behind the vacuum tank, and force air back into the gas tank.  Be gentle; I didn't use more than 10 psi of air.

Phil

[Johan Boltendal #158]

Hi, it may not sound friendly or helpfull, it is well intended, find some one that works and knows the '30 Cadillac, bring him or her you car and have it repaired. It could as easily be an electrical  fault, as it is a fuel related one.
An electrical fuel pump is a NO GO on a 31 Cadillac, this is a heading towards a disaster .Have a proper working vacuum system installed to start with .
All the help you can get is of course from exp and also well intended, it wont help if you are not in the know. There is no magic involved. As said, may sound harse, but it's the only way.
Good luck and hopefully you will drive your car, more then around the block in time to come.   Johan

[wheikkila]

I have to disagree with Johan on some of this. I do agree the system should be fixed to work like it should. But on these old cars. If you want to drive them. You need to know how to do minor repairs. When you are sitting on the side of the road. You need to know how to clean a fuel line, clean or change points. And the only way you learn is by fixing and maintaining your car.  I hope you find the problem and are out on the road driving.
                        Thanks Wayne

[fishnjim]

Certainly demonstrating patience won't fix this.

Pre-war, a little out of my direct experience/interest, but it just sounds like a fuel delivery/starvation issue.   The low pressure seems to confirm that.   
Probably from improper installation of the accessory delivery system. 
You should monitor fuel pressure from start and see what happens to it over time.
Try it without the gas cap on.
Or something very close to this without knowing the '31 specifics. 

From what i recall, those early vacuum "pumps" don't vent at the tank.   They vent at the vacuum "pump", so if you eliminate/by-pass that part, there's no air coming in to the tank to balance the pressure.   So it slowly starves itself of NPSH.   It takes a while for air to flow back in, so it can start.   Under idle you're probably getting sufficient flow, but as soon as you accelerate, it's deficit in gas for the mixture and stalls out.  Mixture has to be in a narrow range of fuel concentration to burn. 

You can coil, battery, and wire, but if fuel issue, those won't help.

[cookcrete]

I appreciate all the helpful ideas and input.  I'll keep investigating/tinkering.  I bought two prewar cars, partly because I love non-computerized mechanical stuff, partly in anticipation that I could work on their inevitable problems with a chance (small apparently in my case) that I might succeed in fixing them, and partly because I like conversing with/ learning from other guys that know way more about this stuff than I do..  Fuel under-supply (at least up to the carb inlet) is not the issue, oversupply could be I suppose.  Exhaust is not restricted, but the carb & manifold above the carb is getting very hot quickly, so I am in the process of eliminating the exhaust tubes that shoot hot exhaust gas into carb manifold.  I suspect timing is off too, so I need to decipher the timing process from my old books.  4 distributor lobes, 2 sets of points, hold your mouth just right....If I find a place near me that can bench test it that probably makes a lot of sense for a person like me.
Thanks again.
Lew

[Chris Cummings]

Lew,

Just relax and be methodical about it.  The mechanism worked well, and yours can work well again.  Look for members near you who own cars in the 1928-1931 and see what they know (and who they turn to for help).  Not everyone follows the message forum.

Good luck and have fun.

Chris

[cookcrete]

Thanks Chris....great advice!
Lew