Today I was driving the truck and it did it this morning once and once when going to lunch I stepped on the throttle and the truck just laid down just accelerated a little stopped paused for a minute then started accelerating again. To me it felt like the accelerator pump was not working and it took the moment for the jets to take over. I checked the accelerator pump just now and isn't leaking and if you step down on it after it did it the first time it just a slight hesitation as the converter slips a little.


I am curious could a coil going bad cause this?


I saw in another post that a jumping tach is a sign of a coil problem and I haven't had it happened recently but earlier this yea the tach would jump some but the engine didn't feel like it was missing and accelerated fine.


Just looking for some opinions as I will be doing a lot of work to the truck this weekend.


Or is this going to be a accelerator pump problem? Its not leaking but the last time I took it off to move the accelerator pump rod to the next opening I noticed the diaphragm was cracked.

Look down the carb throat with the engine off. Just the sliightest movement of the throttle should send some fuel squirting down into the throat of the carb. If there is any delay, I would suspect something wrong with the pump. This new ethanol fuel is hard on the pump diaphragms.

I know about that I already replaced the pump once before.


Thing is though old timer at work he told me carbs really should be rebuilt every 5 years or so. Well this carb was never rebuilt we took the old one off and bought a reman and installed this reman back I '97 or so.


Thing that is confusing me is it is so random. Some times it lays down some times it doesn't. Lately yesterday and today the truck went into a shake mode tach I didn't look to see if it was bouncing around but I bet it was and I could hear coughing in the exhaust pipe which tells me most likey a lean condition.


I was thinking maybe replace the fuel filter but hate to go to the trouble if the carb needs to be rebuilt.


But I figured since this is so random but it has done it only once for each start up cycle I am wondering if maybe it is a fuel filter. I know lately Ive been having a hot restart problem like the engine is flooding out and just today I had a problem where the truck started up then stalled out but restarted fine and stayed running.


Seems more like a fuel issue than an electrical issue.


Might need to dig out the two carbs that came off this truck find out which one has more CFM and rebuild that one and throw it on the truck.

With my problem being so intermittent I have decided my current plan of action is to run a can of fuel system cleaner in the truck, replace the fuel filter, and replace the accelerator pump.


I also will be pulling all 8 plugs to clean and reinstall. been just over a year since I did that and I have a hot miss that is here and there which is from the carbon fouled plugs in four of the eight cylinders.


The accelerator pump the front cover is wet but not dripping, I recalled last summer when I pulled the accelerator pump to adjust the linkage up one hole the diagphram was cracked all over the place. I also noticed when I looked at it today the push pin sticking through was not touching the accelerator pump arm so I figured replace it Just as a precaution.


I would pull the carb to rebuild it but I don't have the time with work and I cant let the truck sit as I still haven't gotten my carb rebuilt on my Mercury. I will try to check the other carbs I have put up from this truck see if any are duplicates of this one CFM wise and rebuild that.

If you don't know when the fuel filter was replaced I would just do it. It is not a high dollar item and it should be replaced if not each year at the least every other year.


If the little metal plunger is not hitting the pump arm there is something wrong.
The gas today with ethanol into causes all kind of strange things. Remember when our trucks were new and any old parts in parts stores (carb kits?) were not meant to have ethanol touch them.
So you may have bought a carb kit or just the pump if it was NOS it could fail in short order.


Also don't forget the rubber fuel lines. They may look good on the out side but be junk on the inside.
Dave ----

That's why I purchased a new filter its a wix which I cringe over as every filter problem at work I had was a Wix.


But I will be replacing it. I don't honestly think its a fuel delivery problem as I can floor the throttle and the engine will wind up to 4,000 rpm with out laying down its just at normal driving every now and then theres a pause or a lay down. It is so random it just makes me want to pull my hair out as I cant find anything common to have an idea of where to start my looking at.


I have even been thinking of buying a new dist, coil, and ignition module and replacing all of it just to put my mind at ease.


The accelerator pump is weird as it has a stand alone peg that you slide in place I am thinking it might be worn or it might have been two lengths and I installed the shorter one which was fine at the neutral pump linkage hook up.

While this is true for the mid-1970s and older engines, it's not true for ours. The auto manufacturers have been building their vehicles to handle up to 10% ethanol since the late 1970s as a result of the 1973 Arab oil embargo and the later "energy crisis" in 1979.

Timeline of alcohol fuel - Wikipedia, the free encyclopedia

Ethanol fuel in the United States - Wikipedia, the free encyclopedia

History And Other Information On E85

http://www.iea-etsap.org/web/E-TechD...0_GS_OK_NH.pdf


Additionally, Page 8 of my 1981 Owner's Manual says:

"Gasohol, if used, should contain no more than 10% ethanol...."

Wait, OIC, I'm sorry - you're talking about OLD rebuild kits perhaps being available from the parts stores back then... I guess this is possible but I don't know how compatible they would be with the then-newer carburetors....

I think there were difference between the 2100 and the 2150. I have a 2100 if I remember right on my '56 and that thing has a choke pull off built into the top choke horn where as on m 2150 it has a pod mounted on the side.

If it was the excellerator pump I think you would also hesitate off the line.

What you describe makes me wonder if the EGR is hanging open.

There is a hesitation off line as well but its never consistant. If you press harder on throttle it tends to not happen and with the gap between the arm and plunger it has me curious. I know i adjusted the linkage up to give more fuel which fixed 90% of my off the line hesitation. But i never noticed the freeplay I have now. For the cost of the accelerator pump i just rather replace it and make sure the plunger to arm has no play even if i have to find a longer rod and cut it down to custom fit it.

The egr i blocked off last year with a piece of aluminum plate. Unless the plate has burned through but i doubt it though.

I will have to see but yesterday I installed a new walker brand accelerator pump. The one I had was a dorman and the pump was a two piece design a diaphragm and a push rod. But the Walker one was a one piece and it was actually longer after installing the Walker one I had absolutely no slack between the arm and the accelerator pump.


I drove the truck afterwards to get some parts for another car I am working on. Had zero hesitations and zero bogs that time.


Time will only tell how ever. I doubt my warm restarts will improve and I doubt my just dropping dead after starting up some times will be fixed but hopefully the shaking and wanting to drop dead when accelerating has been eliminated.