1968 Chrysler 20 hp don't want to run unless fuel line is disconnected.

[c-dubb]

I have a friend that has a 1968 20hp Chrysler that just recently started giving him issues. It will start on the 3rd pull and idles well, but it will bog when you give it throttle. We just discovered that if you disconnect the fuel line at the quick connect fitting, after a second or two it will run great until all the gas is gone from the line.I thought it may be getting too much fuel so we pulled the carb to clean it and adjust the float. No Change. Hopefully one of you have seen this before and can point us in the right direction. Thanks for any input.

 

[RCO]

If you are confident that the carb needle and seat is good, you most likely have a ruptured fuel pump diaphragm. It will leak fuel into the pulse port and flood out the motor. For testing purposes, you could bypass the pump and hook a fuel line directly to the carb and keep pumping the bulb to see if it solves the problem. If it starts running bad when you pump the bulb with the line connected directly to the carb, the carb still needs attention.

 

[las]

Try looking at the fuel pump! Mine was bad and only by removing the fuel line I was able to get it to run decently...
​It turned out to be a torn rubber diaphragm.

 

[c-dubb]

I called and had him check the fuel pump (not very old) and he said there were no punctures and that it all looked good. I suggested he replace the needle and seat (which he recently replaced) because I can't see too much else that will cause this. If you guys think of anything else, let us know. Thanks.

 

[jerryjerry05]

Sounds like the connector might be bad??
​Try hooking direct to the tank without the connector.
The connector has a rubber seal that goes bad and can suck air.

 

[c-dubb]

Ok, he just put a kit in his carb and no change. He has also just chewed up another impeller, I think this makes 3 in just a few months and hasn't even been in the water yet. Can running on muffs while troubleshooting cause it to chew up impellers?

 

[wickware]

Please post a pic of the impeller. I feel the housing has to be bad for the impeller to go that quick. Running deep in a 55 plastic barrel has always worked good to get instant cooling water. Without instant cooling water you are taking a chance on ruining your impeller. I would start and instantly kill w/o water on all dist trips 1984-2012 vs learning of a problem 100 miles from home.

I have always heard change every 2-3 years. I went 1984 -09 w/o changing on my 1970 35 HP Chrysler. It looked as strong as my new impeller with good flexible rubber and no cracks. My points looked just as good from 1984 -2009 but I changed them anyway.

Afterwards I did need to clean my points due to adding too much oil to the point?s rubbing blocks oil wics (1-2 drops vs more). There were no burns just oil vapor in dists and on points contacts (causing hesitation) at WOT and instant WOT.

 

[c-dubb]

No Title

This pic is of the last one, about a month old never on the water just in a barrel. The one before this one, the rubber part just came off of the brass part.

 

[las]

Is he using the correct size impeller? I would think that with a destruction like that something is way wrong!

It's hard to tell from the photo, but it looks like the impeller is actually taller than the housing.

 

[jerryjerry05]

No Title

The wrong muffs can do that.
​The one in the pic is the right one.

IF?? the impeller was too tall?
The housing wouldn't go all the way down.
The brass insert would stop it.

How cheap were the impellers? Chinese?

Those older outboards used an impeller with 10 vanes. Maybe the wrong one??

 

[c-dubb]

Just want to point out that he is running in a drum while troubleshooting, not muffs. Not sure where the impellers are made, but since it is a 1968 motor maybe they are just old?!? Anyways it still wouldn't take any throttle before he determined impeller was bad. Any more ideas?

 

[jerryjerry05]

IF??? the motors not in the drum deep enough??
​The cavitation plate needs to be 3-4in under the water level.

These pumps aren't self priming.
Once they start they are usually deep enough to pick up water and continue to draw water.

Run the fuel line straight from the tank to the pump then to the carb and see if it helps.

 

[c-dubb]

He should have his new impeller later this week, We will try bypassing his quick connect fitting and see. I've already mentioned about how deep the lower unit was in the drum. I'll post the results, thanks.