robsayers

Last night I was driving around a bit, all of a sudden when I got on the throttle, it would start running really rough and barely want to accelerate. Normal cruising and idling were fine however.

I tried just easing on the throttle all the way to WOT, and once it was open all the way, it would accelerate fine. Only when I would quickly get on it would the problem occur.

It was raining out, not sure of that would be an issue or not.

Any help greatly appreciated, autox is this weekend!

mwatson184

It runs rough right when you punch the throttle? If so I would say your accelerator pump is the culprit. It works like a squirt gun, shoots fuel when you mash the throttle.

-Marques

MosesX605

Sounds like the accelerator pump to me...

Maybe the diaphram has torn. It's fairly easy to check the diaphram with the carb on, it's on the driver's side rear of the carb, just above the baseplate. You can disconnect the linkages and then four bolts later the pump is apart. You'll want to make sure that there are no cracks or tears and that the diaphram moves easily. They can get pretty hard with age.

Good luck.

robsayers

Cool, thanks for the advice, I'll check it out.

robsayers

update on the problem.

I'm led to believe its not the accel pump.

For once, if I mash the gas, the hesitation never stops, If I understand correctly, after the fuel "catches up" with the extra air, power should resume, but this isnt the case.

Also, when this happens, if I back off to about 80% throttle, it behaves just like it should, and from then all I have to do is slowly get back in the gas all the way to wot, and it will do fine. Its only the final 20% or so of throttle thats giving me problems.

The problem doesnt happen all the time either. Yesterday I was driving the 7 around almost all day, and didnt have a problem until around 10 last night. Today it has been coming and going. After long period of working correctly, it seems to screw up again after making moderate to hard right turns.

I screwed around with the carb today making sure nothing looked out of place or stuck or anything, the accel pump was giving a nice squirt of fuel, so I'm once again sorta stuck on this.

mwatson184

I know it's a stretch, but try replacing the fuel filter. It can do wonderful things, and costs around 3 dollars.

-Marques

cdrad51

not a stretch really. My car was exhibiting the same symptoms and it was the fuel filter. Change it, and if the problem persists, do a volume and pressure test of the fuel pump and replace if not within specs.

KehoeAutomotive

If it started while it was raining out side you might want to check the distributor for moisture.

Any amount of water would make it miss and it would appear to be worse under a strong load.

Then look at the fuel system.

robsayers

i'm pretty sure its not rain related, as we've had 2 beautiful days recently. The guy I bought the car from changed the fuel filter about 2000 miles ago, so I doubt thats it. Either its a short/grounding issue... or fuel.

I'm gonna go ahead and order a fuel pump and fpr tomorrow, since I'll need that when I get a weber anyhow, I may as well get it now. Thanks for the advice guys!

cdrad51

Make sure the Nikki and the Webber have compatible cfm and psi when ordering the new pump.

cdrad51

Sorry, I was in a hurry when I posted the above and doesn't make much sense does it. What I meant is make sure the outlet pressure and feeding capacity of the pump you're planning to get can adequately supply your current Nikki carb, and realize if you get a weber carb with different specs, the fuel pump might need to be changed again.

robsayers

The one I'm ordering is 140 gph, I'm also getting a 5-12 psi FPR, should that do it for a stock nikki? Or do I just need to order another stocker for now?

cdrad51

5-12 psi FPR? stock spec is 28.4~37.0 psi for the FPR!

MosesX605

Maybe for the fuel injected GSL-SE. Not for the carbed 12A's though.

MosesX605

edit: double post.

robsayers

Yeah, I guess I forgot to mention, this is on an 83 gs

cdrad51

Oh, in that case it should be more than fine. Stock fuel pump pressure is 2.84~3.55 psi for the 12A.

But wait a second, why are you getting a FPR? that's what made me think you had an SE. 12A engine cars don't have a FPR, afaik.

robsayers

Carb'd cars can use them... I figured it would just be a good idea to keep the pressure stable at all times. Either way, I just ordered a stocker for the time being.