Power loss

[Doug&Deb]

Okay I’m really stumped. This is a continuation of my fuel problem thread. I originally traced the problem to the float sticking. I cleaned the carb twice, no joy. Tonight I installed my spare carb. Slightly better but still no power up hill. Seems to be breaking up slightly. Coil was hot after 1st test drive so swapped it, still no joy. Both carbs are rebuilt. Distributor is rebuilt. Timing is correct as is dwell. Plugs read good and are almost new. Compression is 90 on all cylinders. The problem seems to show up after the engine is fully warmed up. Engine was rebuilt 10,000 miles ago and this started quite recently. Help!!

[maok]

What is the coil resistance on the primary connections?

Is it 6v or 12v?

[DJ194950]

Can you temp. add in a pressure gauge for fuel that can be seen when driving to see if you are having a lack of fuel after warm up and driving?

 

May have fuel starvation issue and that would show it for sure and then the diagnosis which is more complicated, but it's a starting place.

 

Just 1 opinion/ guess/.

 

DJ

[Doug&Deb]

6 volt system. I’m not sure how to add a fuel pressure gauge. I do have an electric pump near the tank for priming. Turning it on doesn’t have any effect.

[Sniper]

Is the exhaust flapper working properly?

[DJK]

How about the pick screen in the tank?

[Bryan]

If it were a modern car I'd say check the catalytic converter.  No power going up a hill.   Maybe a rat crawled into your muffler?   Fuel filter okay?   Condenser & points?

[Jerry Roberts]

Is your replacement coil getting hot too ?  Is it an old coil that should have been thrown out ? Those symptoms are the same problems that I had when my coil went bad . 

[Doug&Deb]

Not sure about the tank. Fuel filter is new. Sediment bowl on the pump is clean. Points and condenser are new as well as plugs and wires. The coil that I swapped is old and I didn’t check if it was hot. By then the frustration level was off the chart so walking away was the best option. I’m wondering if I’m looking in the wrong direction. The car is hard to start once hot and the idle sometimes gets slow and sort of lumpy for lack of a better term. Blipping the throttle sometimes clears it up and it’s normal. 

[Dan Hiebert]

Is the Sisson choke still used in 1952?  Just a theory here since none of your fuel or ignition remedies have seemed to work.  I had the same power problem with our D24 many years ago.  The hard start and rough idle when hot (cleared up with the throttle "blip") led me to R&R the choke.  The choke didn't have the gasket under it, and the bi-metal was toasted.  Didn't know diddly about the Sisson choke at the time, so I replaced the choke with a manual unit, and haven't had that problem since.

[busycoupe]

Just a thought, is your electric pump in line with the fuel line?  Could the check valves in the electric pump be offering resistance to flow going to the mechanical pump?

 

 

 

[Kilgore47]

It could be a vacuum leak.  The base of these old carbs can warp and create an air leak.  Check with a straight edge.  It can be fixed by filing or sanding it flat again.

 

The 47 P15 had a similar idling issue.  It would idle smooth and then get lumpy.  Lumpy is a good description.  Blip the throttle and after a minute it would get lumpy again.  Turned out to be a valve adjustment problem. Got the valves adjusted and now it idles very smooth and has more power.  At 10000 miles on your rebuilt engine may need the valves adjusted.

 

 

[Doug&Deb]

I’m planning on a valve adjustment. I wondered about that also. The Sisson choke is good and properly adjusted. I’ve had the carb off so many times it’s possible there’s a leak. The electric pump is a flow through and one that many members of the forum use. Also turning it on has no effect.

[kencombs]

Still 6v but coil hot.  Assuming the dwell/gap is ok and the replacement was a known good unit, my first thought is a bad condenser.  If you have a known good one, not new out of the box, I'd try that.. 

 

Also, check the primary resistance of the coil.  Compare to stock spec, just in case.

 

A hot coil would indicate higher than normal current draw for some reason.

[Sniper]

Did you check the exhaust flapper valve?  It's easy to do, if the engine is cold.  Does is turn freely by hand?  Is there a spring resistance to it?

 

If it's stuck closed you are going to have issues when the engine is warmed up.

[Bryan]

3 hours ago, Dan Hiebert said:

Is the Sisson choke still used in 1952?  Just a theory here since none of your fuel or ignition remedies have seemed to work.  I had the same power problem with our D24 many years ago.  The hard start and rough idle when hot (cleared up with the throttle "blip") led me to R&R the choke.  The choke didn't have the gasket under it, and the bi-metal was toasted.  Didn't know diddly about the Sisson choke at the time, so I replaced the choke with a manual unit, and haven't had that problem since.

That's what my father had done on the 48 I have now. Sisson unhooked and manual choke installed.

[Doug&Deb]

Exhaust valve works freely. Choke is good. Will check coil resistance. I’ve tried both new and old condensers. No difference. 

[Bryan]

3 hours ago, Doug&Deb said:

Exhaust valve works freely. Choke is good. Will check coil resistance. I’ve tried both new and old condensers. No difference. 

If the valve adjustment doesn't work, try something crazy. Take the muffler off, but leave pipe to it on.  On my 92 Dodge Dakota recently had the muffler just all of a sudden get loud. I thought the joint to the exhaust manifold broke loose, nope that was fine.  Maybe something stopped the muffler up.  Last resort.

 

It isn't like these things have 10 different sensors and a computer.  Enough fuel, no air leaks -> proper mixture at throttle (up a hill).   Spark, at proper time (vacuum & mechanical advance) under load.   Compression.   Exhaust.      Power to wheels -> Nothing dragging like slipping clutch or sticking brakes.

[Sniper]

18 minutes ago, Bryan said:

sticking brakes.

 

Hmm, that reminds me, the parking brake isn't on, is it?  Don't ask me how I know, lol.

[Doug&Deb]

Lol no parking brake on. This all started when I decided to replace the fuel line. A previous owner had run rubber line from the tank to the fuel pump. Ever since I’ve had problems. I’ve cleaned the sediment bowl and carb repeatedly. I even replaced the carb with a spare ( both rebuilt). I’ve checked for vacuum leaks but I’ll check again. The electric pump is an Airtex E-8902  which others use. I’m running out of checks. A valve adjustment is next.

[Sam Buchanan]

 

Quote

This all started when I decided to replace the fuel line.

 

OK, last change is usually the culprit. Make sure there are no minute leaks in the fuel line (crack, loose/faulty fitting, etc) where air could be sucked into the fuel. Check again for any obstructions in the line. If still unresolved remove the electric pump in case it is introducing air. Simplify, simplify, simplify. ?

Edited May 21, 2022 by Sam Buchanan

[DJ194950]

To add a temporary  fuel pressure gauge you will need to add a t- to the fuel line just before the carb with the extra line leading to a gauge where it can be read by you ( under dash., on on hood,?, etc.) to show fuel pressure when the issue shows up . And compared with the number before the issue happens-Same day, temp, driving, etc. type of thing-

 

Just one check?

DJ

[Loren]

Have you changed the gas cap?

Most you can buy now days are not vented and are so labeled (at least they used to be).

Your car should have a vented cap.

A quick check would be to loosen it and take a drive.

[Doug&Deb]

No I still have the original cap. I went through that with an aftermarket cap. I have a suspicion where I may have an air leak. That’s the next thing to check. Thanks Sam. I hadn’t thought of that.

[Sniper]

When I bought my 51 I could hear the gas tank oil canning as it heated up and cooled down, so I bought a new "vented" cap for my 51.  It is nothing like the original vented cap, it has some spring loaded valve in there to do who knows what, venting the pressure isn't one of those things though.  Anyway I found the solution here and it fixed the issue.

 

https://p15-d24.com/topic/53341-gas-tank-leak-on-angle/#comment-568776