I'm having a problem I can't figure out with my EA81 BRAT. If I stomp the go pedal, it seems to 'miss' for about a second, causing an almost complete loss of power and rapid drop in RPM, then it 'catches' and revs fine. If I'm less aggressive with the throttle it revs without complaint, only when I suddenly give it a larger amount of throttle does it hesitate. It does it from all RPM, e.g. if I slowly rev it up to ~4000 then stomp it, it still hesitates, but at higher RPM it doesn't hesitate for quite as long as it does at low RPM. It feels like, at a guess, it takes a moment for the fuel supply to catch up with the throttle. I recently replaced the fuel filter, but could the fuel pump cause this?

What carb are you running? Your guess is probably not far off. Sounds like an accelerator pump dive adjustment issue or a bad accel pump. Float level may be set too low, or you may have a supply problem (like a weak pump). Did you replace the rear fuel filter?

Check your timing and vacuum advance, a ruptured diaphragm or broken hose and retarded timing might cause this.

can also sound electrical problem like a component suddenly not liking your instant big demand - crud in coil tower ? along to dizzy cap or acc pump in carb is worn, blockage ...

Let us know the setup you have.  What carb?   Definitely check for vacuum leaks.

The carb is a cruddy old thing of some kind. I bought the car a few months ago and as far as I know the engine is stock, I don't actually know what to look for to identify the carb. It has a single 'hole' opening to the airbox, so 1 barrel? Do I have that terminology correct? I've never owned a carbureted car before, is there a walkthrough on how to adjust it?

 

Distributor cap was replaced along with the fuel filter soon after I bought it. Rear fuel filter? I didn't know there was more than one... I replaced the one under the car, just behind the drivers seat. New plugs and wires too, but old coil. New gaskets and vacuum lines everywhere, but it's possible I have one in the wrong place or just not making a good connection.

Edited August 22, 201510 yr by musubk

Update: I replaced the front fuel filter, reseated a few vacuum lines, and sprayed carb cleaner all over the inside of the carb, and it's behaving much better now. Still does it for 30 seconds or so after startup but drives fine after that. Thanks for all the suggestions.

Quick question... after replacing fuel filters do you need to prime or bleed the lines in any way? And if so, how?

Thx!

I just got over this issue, for me it was timing. Killed my cat (alytic converter) trying to figure it out

 

 

Quick question... after replacing fuel filters do you need to prime or bleed the lines in any way? And if so, how?
Thx!

Nope, that's a diesel thing. Just crank it a few times while flooring it and you should eventually get gas up there. Mine's hardwired and it takes about 7 seconds for it to go through both filters after filling an empty tank.

Perfect thank you.

 

As for the brother, he came home with a huge smile saying something along the lines of, 'so thats what it feels like to drive a car and not have to worry about the temperature gauge the whole time.' Lol. Hopefully it stays that way. And hopefully he replaces that rad cap.

 

Cheers all. Thx again.