2stroke1971

'85 Fb, 12a, 220,000 miles.

When it is cold out, and especially if it has not run in a day or two, it is a bear to start.
Pull the choke, crank it and nothing. If you pump the heck out of the pedal like 15 times, then crank, you get a bit of a fire. Pump the heck out of it again, and again a little bit. Eventually, it comes to life after about 4 or 5 of these almost fires, and after much pumping of said pedal.

Revs to high heaven with the choke on at first, like 4000 rpms...I try to trim the choke off to settle it down a bit but if i push it back in too much of course, it dies.

Takes a good while to warm up, as soon as the rpms drop low enough I usually start driving before the choke turns itself off, although I am easy on it until it is all the way warmed up.

If I drive it to work in the morning, then at lunch time it starts pretty easy...just pump the pedal like twice and it fires right up, even if it is cold out.

And even on the coldest of mornings, if I spray a bit of starting fluid into the carb, it fires immediately. In fact, it doesnt even take starting fluid, a bit of gas down the throat will do it as well.(not alot either, just a tablespoon or so will do it) So regardless of temperature, or how long its been sitting, if I get some fuel in its throat, then presto starts right up.

It also has a stumble right off idle. I had rebuilt the carb last year and the stumble went away for a while but it is back.

It would seem to me that when I go to start it in the normal fashion, it is not getting enough fuel to fire up readily. Pumping and pumping the pedal dumps some in I suppose, but I dont think I should have to do that. Im thinking an accelerator pump issue....its like it bleeds down or empties out after sitting for a while,...the off idle stumble suggests an accerlator pump issue to me as well...

Or...it has alot of miles, for all i know the motor has never been rebuilt...low compression? Not enough to pull fuel readily when cranking? Once it is running, it runs out really well though...its quick as hell, i could melt the tires off the thing if I wanted to.


any comments or suggestions would be greatly appreciated!

Neil

Hillbillyag

iTrader: (2)

I don't think this will be of any help to you, but mine does something very similar. Cold start is very difficult and warm starts are easy. However, I have never had any luck pumping the gas. I just keep turning it over and eventually it starts and holds idle. I can't get it to start with the choke on at all. Once the engine catches I have to blip the throttle a few times to get it above 1000 rpm and then pull the choke to warm it up. I can usually get the choke to hold right around 1500 rpm. I have been thinking something similar, that maybe fuel is bleeding back and it takes awhile to get fuel to fill the bowl. Hopefully someone with knowledge will have an answer or suggestions for us both.

NCross

iTrader: (18)

Sounds ignition related. First thing id do is check the spark plugs, wires, ohm out the coils, and inspect the ignitors.

It could be a carb issue as well. Mine have always started just fine without a choke. Two pumps of the gas, rev it up to 2000 RPM with the choke ( for fast idle) and set off.

2stroke1971

Thanks for the replies!
I found an old thread from 2001 about cold starting procedures, where everyone was posting theirs. There was one guy who's car sounded just like mine! I laughed out loud...."pump the pedal 10 times, crank it, repeat 15 times, fires, dies, repeat, etc..."
Someone suggested to that guy to check the operation of the choke flap. it was a very detailed explanation about the hows and the whys...essentially, it has to close ALL the way at first, in order to block the primaries completely...this creates enough suction to pull the fuel in that is needed....there is a little vac arm that will crack the shutter open a bit right after starting...

I took the air filter off and pushed the pedal in and pulled the choke. It was NOT closing all the way. I played with the linkage until it did close....then went back in the car and hit the key. It started RIGHT UP, dead cold, without ANY pumping of the pedal. Im sort of relieved...it has 220,000 miles on it, I was thinking it was just in need of a rebuild. (I could do that, Ive rebuilt many motors over the years from boats, cars, motorcycles, etc...I am an industrial mechanic of sorts by trade) but the cost is pretty high for the kits, and this car unfortunately has some rust issues underneath...scary on the drivers side...Ive got to see if I can do anything with that before I would rebuild it...

Im not sure why it was not closing all the way, I didnt get that far yet. The linkage on that Nikki is horrendous. My choke cable is a bit frayed, I think I will start with a new cable, hit all the link pivots with some Kroil and go from there. I think with a new choke cable it might be easier to trim down once it fires...I think the whole mechanism, cable and linkages is a bit sticky.

While I was in there, I noticed that two vacuum caps that I had put on the carb had already rotted to pieces...after only a year. Cheap lousy caps!

I am also gonna try to address the miss off idle...The accelerator pump seems to squirt late in the travel...so the pump arm moves right away when you begin to open the butterflies, but the squirt does not happen until well into its travel...


Oh what have i got myself into?

Jeff20B

iTrader: (13)

Sounds like it just needs an new accel pump diaphragm. Unfortunately Mazdatrix doesn't sell just that part anymore (I think I bought the last one late last year). You will need to get a 30 dollar rebuild kit from your local auto parts store or rockauto.

2stroke1971

I rebuilt the Nikki last year with a kit from Ebay....not to say that the lousy ethanol crap hasnt destroyed my pump diaphragm already! When I first rebuilt the carb, the miss had gone away...then my son drove it for a year, sometime since the miss came back..he never told me about it, but I noticed it when I took the car over last week.

NCross

iTrader: (18)

Have you cleaned and lubed the linkage and throttle plates? It could be binding and then snapping open suddenly causing the stutter.

Jeff20B

iTrader: (13)

It could be the brass screw above the accel pump. If it has a slow leak, it will make a flat spot and feel like a miss whenever you press the go pedal. Sterling recommends using some teflon tape to seal the threads. One of my carbs has this leak and it developed a flat spot so I'll take a look next time the top of the carb comes off (soon for a jet change).