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Distributor or carburetor???

After reading this thread, what direction should I go?

  • New Distributor or new pickup and HEI Module

    Votes: 3 100.0%

  • just new pickup and HEI Module

    Votes: 0 0.0%

  • Carburetor kit and clean the jets

    Votes: 0 0.0%
  • Total voters
    3
  • Poll closed .
Chief Brody

Chief Brody

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Rochester 4 barrel, 350

I took the Blazer out today, beautiful day...BUT

It idled great but sputter upon acceleration all the way through...not just in one spot. I don't notice it when I am parked and floor it. Just when in drive.

Where do I start looking first?
 
Water in the fuel can make it idle ok but crap out under a load..weak spark can do the same too..

I once had a distributor rotor do this too,it had a fault or crack that let the spark jump to distributor shaft and ground out when I put the car in drive and tried to accelerate ,it would idle fine but as soon as you gave it any throttle it sputtered and stalled..ran perfect in neutral at all
speeds !..:screwy:
 
One of the most easiest things to check is the PCV valve or hose. Either one can cause this issue.
 
My first thought is fuel supply.

Two things, check filter (obvious) and then ensure that the rubber sections of fuel line between the tank and pump are ok. I had a cracked line pre mechanical pump that would draw air in, but not leak fuel (at least noticeably).
 
Probably unrelated but suddenly the fuel meter is crazy...I filled it up and it show 1/4 tank...so the float is funky or something...maybe ground wire?

Someone ask how long it has sit..about 5 months since I last got it out. I will check the fuel filter.

I noticed that nobody said timing.

I will check the rotor too.

Don't know how to check for weak spark.
 
Given who it belongs to, first thing you need to do is examine it carefully top and bottom for Remora........

After that, I'd start looking at fuel supply. Could easily be bad fuel or fuel pump. Also, the very first thing is pull the dipstick and check the oil level. If its even a little over full, stop everything and replace the fuel pump.
if the diaphragm in the pump develops a pinhole, it can very quickly put lots of gas in the oil which will total an engine.
Otherwise, you need to do a fuel flow and pressure check. If the filters are good and the pump passes the tests, then it sounds like clogged jets in the carb like ktmoutfront said.
 
Given who it belongs to, first thing you need to do is examine it carefully top and bottom for Remora........

After that, I'd start looking at fuel supply. Could easily be bad fuel or fuel pump. Also, the very first thing is pull the dipstick and check the oil level. If its even a little over full, stop everything and replace the fuel pump.
if the diaphragm in the pump develops a pinhole, it can very quickly put lots of gas in the oil which will total an engine.
Otherwise, you need to do a fuel flow and pressure check. If the filters are good and the pump passes the tests, then it sounds like clogged jets in the carb like ktmoutfront said.
 
Water can mess with the rheostat on the sending unit for the fuel gauge ,make it read wrong,ethanol can too,as well as a bad ground..
I'd do a test sample of the fuel in a glass jar..see if its cloudy or water layers on the bottom after it settles awhile..

If you have the original "in the carb" fuel filter,I have seen those plug with insects that only God knows how they got in there..some years had the rubber "roll over check valve" that liked to plug up,I used to yank them out or use the older version filter that didn't have them..most of my GM's I "deleted" the in carb filter and put a external one on in the fuel line..

My friends that buy auction cars often get some that will only idle and they sat for months ,they put gas treatment like Chevron Techron or octane booster ,then fill the tank with the highest octane fuel available locally ,like 93 octane,to dilute any water in the tank and many of them start running much better after letting them run awhile..
 
I'll check the fuel filter and accelerator pump today.
 
The accelerator pump checks out ok. I crank the accelerator mechanism full and it quirts gas into both front "venturies" or barrels

I replaced the fuel filter and also added some Star Tron Enzyme additive and then drove it.

It is better, but not completely gone. I think it was more intermittent. I'll know more when I can drive for a couple hours or so and maybe drive out some this gas (or water) if that is what it is.

The old filter didn't look bad to me. but I don't know.

20190324_160459-2.jpg 20190324_160504-2.jpg
 
It actually looks bad, but I would have to see a new one to be sure. I have seen brand new ones look worse than used ones.
 
I'd toss that filter,water wont go thru the paper and though it may look clean,it wont let enough gas flow thru it..

I ditched those OEM filters and put an in line filter on instead,I had one carb crack and another one strip its threads and I was boned...never liked that setup--if the filter plugs up,the spring lets it get pushed aside and allow dirt & crud to flow right past it too..

I would suspect water too,if you used ethanol gas,and it is sometimes hard to tell if water is in that kind of gas,because the alcohol acts as a "dry gas" in ways--the water stays in suspension instead of sinking or settling to the bottom like it did in old leaded gas--the ethanol starts to break down after 3 months and the alcohol separates,then gets to eat away at things that dont like alcohol..like hoses,foam carb floats,gaskets,etc..

Any original hoses or ones not made after the 1990's can fail from ethanol,they can turn to a gummy substance inside,or harden up and get brittle and crack or split..the hose joining the electric fuel pump to the sending unit often fails that way--it splits and the engine starves for fuel once the level of gas in the tank drops enough to expose the split to air...

I think most car fires on an older vehicle are due to the ethanol eating thru old hoses not rated for it..

I remember rebuilding a carb with an old kit I bought at a swap meet--a good "Filko" brand one,but a day or so after I drove the truck,the accelerator pump was non existant!--it didn't squirt at all...I pulled the carb back apart and found the material the "cup" used was in pieces in the bottom of the float bowl--all there was on the cup was that coil spring,and it started to scratch up the bore where it rode!...it looked like leather..
Had to buy an accelerator pump the next day (was surprised they listed them separately..that one had a neoprene rubber looking cup on it..
 
It is a pain in the butt to get that filter out. I have the metal fuel line all the way to the filter housing.
 
If you have the OEM steel line and do not want to cut it to install an in line filter there,you could add one to the feed line from the gas tank to the fuel pump instead..on the suction side of the fuel pump instead of the pressure side..

GM relied mostly on the fine mesh "sock" filter in the fuel tank to screen out most of the water and crud,their in-carb fuel filters were not the greatest idea really..

Some claim the fuel pump may not pull enough fuel thru a gas filter on the suction side,but I have done this on many of my GM vehicles and never noticed any starvation issues..heck,the quart sized spin on diesel fuel filter on my pickup is on the suction side of the mechanical fuel pump factory,which is the same pressure output and GPH rating as a small block V8 ..if it works on that it will on a gas engine..
 
Well changing the filter didn't solve the whole problem...so there's more going on than just a dirty filter.

I think it is sluggish too..lacks the power it once had.
 
Pull the rope of the carb off and look for water in the bowl. Wont be much, just drops. Pull the jets and clean them.
 
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