Hi,
After a great three hour drive in my 79 auto (all stock), I suddenly started having hesitation.
But only above 2500, it would run just fine if you baby it, which is what I did the last 5 miles home.
At a stand in neutral, it will rev up to 5000 with no problem. The hesitation is only under load.
And its real hesitation, not transmission slip, the RPMs drop way down.
It almost feels like the secondary is flooding it when it opens.
I researched it, and this guy had exactly the same problem: http://archive.mirafiori.com/show.php?fid=2&msg=163472
I checked the cap, and no hissing when I opened it (but it almost always hisses when I open it to refill when low).
What order should I follow to diagnois this?
Change fuel filter?, fuel pump?, open up the carb? (god help me), pull over and have a beer and let it cool off?
I know carbs can be tricky when good and hot.
It has been running fine, and the carb seem really clean (I am a new owner), and it idles and accelerates with almost none of the usual carb funny business.
I have rebuilt carbs on two different 60s era Honda motorcycles, but this thing looks like an entirely different beast.
Thanks for any leads.
Hesitation above 2,500 under load
-
onejohny
Re: Hesitation above 2,500 under load
It sounds like you are starving for fuel. The fuel pump is in your trunk.
Check and or replace the the fuel filter and strainer. (one filter under hood, one in trunk)
If it is plugged with rust your tank may need to be drained and cleaned.
If rust got past the filters you may want to use an air compressor to blow out the lines (disconnected of course).
Check fuel pump functionality with a multimeter for voltage and for fuel flow. Replace as necessary. Universal fuel pumps can be found locally at auto parts stores for $50-60.
I had a similar problem. Kinked fuel line on the fuel pump the previous owner replaced. I also had a semi shorted wire that wasn't getting 12V reliably to the pump. And the filters were pretty plugged up.
The federally mandated 10% ethanol has high water content and causes rust issues on old cars.
Check and or replace the the fuel filter and strainer. (one filter under hood, one in trunk)
If it is plugged with rust your tank may need to be drained and cleaned.
If rust got past the filters you may want to use an air compressor to blow out the lines (disconnected of course).
Check fuel pump functionality with a multimeter for voltage and for fuel flow. Replace as necessary. Universal fuel pumps can be found locally at auto parts stores for $50-60.
I had a similar problem. Kinked fuel line on the fuel pump the previous owner replaced. I also had a semi shorted wire that wasn't getting 12V reliably to the pump. And the filters were pretty plugged up.
The federally mandated 10% ethanol has high water content and causes rust issues on old cars.
-
Jrlovvorn
Re: Hesitation above 2,500 under load
Thanks so much.
Running with the gas cap a little loose and replacing the inline fuel filter under the hood seems to have solved the problem, at least for now.
I am goint to look into the pump and the lines when I have time.
Really appreciate the guidance.
Running with the gas cap a little loose and replacing the inline fuel filter under the hood seems to have solved the problem, at least for now.
I am goint to look into the pump and the lines when I have time.
Really appreciate the guidance.