Poor running Chrysler 125 - ideas? FIXED with PIC

[steveclv]

Posted on another thread but it got buried..

I have just replaced the fuel pump seals etc and was rather disappointed - the old one was almost perfect and I was hoping to find that it was torn and rotten

If it had been then that may have been the answer to the problem....

It starts easily but will backfire as it starts - runs very smokey.

If I run it on the lake it tops out at 4200 rpm but starts to miss and bog down after 30 seconds or so - if I back off the throttle then it recovers and it seems to run forever at 3000 rpm. I thought fuel starvation but the plugs are sooty and black.

I think that the top carb needle valve may be leaking slightly - and when I tilt the motor forward, fuel pours out of the top carb - but all 4 spark plugs were the same - sooty and black so bottom carb may/must be involved in the problem too.

If I run the engine at idle and then use the throttle advance to rev to 2000 rpm and then back to idle, I can hear a sort of misfire or popping on the overrun - not really loud but it is there.

So I'm thinking that I need to probably rebuild the carbs and reset the float heights and then check the ignition timing.

Any other thoughts? Compression was equal across all cylinders by the way.

 

[steveclv]

Re: Poor running Chrysler 125 - ideas?

Re: Poor running Chrysler 125 - ideas?

One other piece of info...

When I removed the fuel pump and fuel delivery pipe, I tested the primer pump by squirting fuel into a bottle - the squeeze of the primer bulb pushed a lot of fuel into the bottle but it took maybe 5 or 6 seconds for the bulb to reinflate - is that normal?

I know it has to suck fuel from the tank but how quickly should that happen?

If it's not normal for it to take that long then maybe I have a blockage in the tank pickup?

 

[Frank Acampora]

Re: Poor running Chrysler 125 - ideas?

Re: Poor running Chrysler 125 - ideas?

I would be willing to bet that running at 4200 RPM, you would see the primer bulb collapse.

When squeezing the bulb, it should reinflate almost immediately.

SO: You need to check the fuel line from tank to pump. If you have a quick-connect at the tank, remove the male end and check behind the ball check. A lot of junk can collect there and catch in the pressure spring.

You are mixing oil into the gas at a 50-1 ratio so under normal conditions the plugs will look black. As long as there is not a build-up that shorts across the plug gap, that is close to normal.

Dont mess with the carbs until after you correct the fuel delivery problem. Since the carbs have the venturi dip tube (Brass thing you see in the center) exposed, when you tilt the engine while not running and with full carbs, fuel will run out the dip tube and out the front of the carbs.

 

[steveclv]

Re: Poor running Chrysler 125 - ideas?

Re: Poor running Chrysler 125 - ideas?

OK, so took Franks advice and ripped out all the old fuel line from the bulb to the tank - for some reason the previous owner had gone from 3/8 ID at the bulb to 1/4 to the tank. So I replaced it with a single piece of 3/8 from bulb to tank.

While I was at it I decided to pull the pickup from the tank just to check it - I tried blowing through it and it wasn't very easy so I unscrewed the aluminum pipe and found a filter in there.

OMG - the filter was completely caked up with crud - I had to chip it away - that's what caused the problem and probably one of the main reasons for the poor running.

I took pictures cos I know everyone loves a picture

 

[MikeM40]

Re: Poor running Chrysler 125 - ideas? FIXED with PIC

Awesome so you solved your problem.
Yea everyone loves the pics

 

[steveclv]

Re: Poor running Chrysler 125 - ideas? FIXED with PIC

Actually, no - I traded one problem for another

I solved the engine cutting out at high rpm due to low fuel delivery

Now I have some sort of weird ignition related problem