My 85' XJ has the 2.5lt. 4 cyl. engine. Every time I want to start it, I have to pump gas peddle atleast20-25 times before it will begin to start.


Would changing to a electric fuel pump end this anoyance or do I have another problem I need to address?


It has a stock single bbl motorcraft carb on it.

 

Two things. One fuel delivering circuit in the carb is the accelerator pump. Really it's just like a squirt gun. Idling, fuel is drawn in through the idle jet via manifold vacuum. Running, with air speed, fuel is drawn in through the main jet via ventury vacuum.

So if you are idling and crack open the throttle, suddenly you have neither manifold vacuum or ventury vacuum. The main purpose of the accelerator pump is to provide a squirt right there to fill in, until there is air-speeed/ventury vacuum.

Starting, you can also use that to prime it to start. First crank it for 5 seconds. Then look down in the carb and work the throttle and see if you see it squirting. If not check that both the screws on-top around the bowl, as well as...(some lower stuff IIRC), are tight. (the pump might be working, but all needs to be tight to get that fuel to squirt out where it should.) The accelerator pump is about the first thing to wear out in a carb, you might even still be able to buy one separate, (instead of a whole kit). It's just a cylindrical piston, sort of like a bicycle pump.

The other thing is the choke. It might start OK even with a weak accelerator pump if the choke is doing it's thing.

 

Thanks DFlinstone. So I guess if the pump is wore out then that's why I have to pump so many times to get to start. Also I don't have a choke on it At present. Part of the electric choke is missing and I can't seem to source a replacement. I was thinking putting a manual one on would help?

 

Put a choke of some kind on it!

Do you have to pump it a lot when it's warm?

 

My guess is the fuel is draining back in to the tank and it's taking the fuel x amount of time to get back up in to the carb. Maybe try installing a residual pressure valve or an inline check valve in the fuel line to keep it from draining back.

Miles

 

Before "getting creative" I'd just fix it. No it's not "draining back", it can't. Yes, a manual choke is a fine idea.

 

That doesn't surprise me with no choke. Is it that way warm too?

 

I've had that happen with vintage SBC's, the check valve in the fuel pump fails and the bowl siphons dry. Couldn't hurt to make sure gas is staying in the bowl after shutdown.

 

Howdy Chuck! IIRC the needle valve/fuel supply is high on the bowl. I trust you to correct me if I'm wrong.

Now the check ball on the accelerator pump....but that shouldn't drain it I'm thinking. Waz thinking even if it boiled dry after parking, the acc. pump should squirt after cranking 5 seconds.

I deal with the same cridder, with my choke wired open. (My 84). I keep a dish soap bottle there to prime it to start. It's non-opped, I don't start it often. I always put the air cleaner back on after priming it. (Fewer fires)

 

Thanks everyone!
I will get a manual choke today and install it.

Kingfisher - no it starts right up when warm no problem.

 

Ive gotten hard to find parts here .....if ya wanna upgrade search webber carbs....http://www.carbkitsource.com/carbs/c...eep/index.html

 

No, I'm sure you are right. I've never taken one of those apart. Just taking a shot at it based on similar trouble with quadrajets. The bowl drains through leaky wellplugs, the fuel lines siphon themselves dry when the fuel pump checkvalve fails. Lots of cranking to get it started after it sits.
He's OK once the engine is warm so I'm putting my monopoly money on no choke causing it.

 

I found the problem. I am missing the arm that opens and closes to choke! any one have any ideas on how to find a replacement for it?

 

I think it's about 3" tall, with about a 7/8" bend at the top. I'll keep my eyes open around here, I might have a carb that was in a fire. I prefer a manual choke anyway myself, I'm not sure if that would pass smog or not. Did you check if your accelerator pump is working?

EDIT. Nope, I don't have one. Just a melted alternator.

 

accelerator pump works good. I crossed the starter relay and closed the choke and it fired right up!


I wish I would have noticed the arm missing before.


I am guessing installing a manual choke would be easier than finding the missing part for my carb.