Starts and idles beautifully but no acceleration

[JPP]

My b2b 218 starts and idle well.  It revs ok, when I manually turn throttle, when I use foot pedal, I get popping and hesitations. I starting to think carb linkage or springs are causing the issue.  Stumped..

[Mike36]

Visually inspect your linkage from  foot pedal to the carburetor. Then put a brick on it to hold it down, and inspect again. It may possibly be rubbing on a bare wire. Also make sure there is a ground strap from your engine to the body, and it is clean and making contact on both ends.

[Fernando Mendes]

Check all its pump circuit.

[JPP]

Springs matter. I start playing with carb spring and accelerator pedal spring. What a difference. Suddenly I have power and acceleration. But still intermittent.  Does the two spring have to be the same. 

[HotRodTractor]

What about the advance for the distributor? The mechanical and vacuum advance still functioning correctly?

[Fernando Mendes]

23 hours ago, JPP said:

Springs matter. I start playing with carb spring and accelerator pedal spring. What a difference. Suddenly I have power and acceleration. But still intermittent.  Does the two spring have to be the same. 

 

[Don Coatney]

23 hours ago, JPP said:

Springs matter. I start playing with carb spring and accelerator pedal spring. What a difference. Suddenly I have power and acceleration. But still intermittent.  Does the two spring have to be the same. 

I have repeated this story many times on this forum. Back in the day many of the unscrupulous repair shops along the highway would charge customers for a complete tune up but simply replace the throttle spring with one of lesser value. When done the customer would test drive the vehicle and comment how much better the vehicle accelerated because it took less pressure on the foot feed to get up to speed.  

[JPP]

Don, sure saw your post before.what about the spring above rod 14-14-3?  I do think vacuum advance could be an issue, but for now need the throttle body spring.   I got 14-06-1 from classic dodge but no mention of throttle body spring, is it the same?

[torqczar]

symptoms of  an accelerator pump problem . will truck rev better w/ half choke.  next  remove air cleaner ..engine off.. look down carb.  push linkage to full throttle. is there fuel squirt..yes/no.  no/ you need to  check accel. pump cup..  old stuff doesn't like  2017 gas.. take the top of carb. off to see pump cup  ,pump well and check ball and look at fuel level   and trash in bowl.. yes/  it squirts fuel  I'd head to compression next , static and running . if ok, look for a runs  lean problem .  

at low rpm , timing doesn't  change  much until higher rpm.  as long as the basics  are covered : point gap,dwell  base  timing..  was this truck running  for a while ,or just got started after pulling from barn? not enough info for diagnosis. or you got a wet dist. cap.

[JPP]

Torqczar,  great questions.  After warm up choke all in no need for choke.  If I pull out choke after warm up engine splitters.  Air cleaner has been off for two months.  Plenty of fuel squirt as I move throttle.  Compression checked cold 85-90 psi for all 6 cylinders. New plugs.  Starts up fine, as I rev engine loses power and splitters, even a backfire or two.  If I accelerate slowly revs up but if I punch it, she dies down. Wish I could post a video.

[Young Ed]

1 hour ago, JPP said:

Torqczar,  great questions.  After warm up choke all in no need for choke.  If I pull out choke after warm up engine splitters.  Air cleaner has been off for two months.  Plenty of fuel squirt as I move throttle.  Compression checked cold 85-90 psi for all 6 cylinders. New plugs.  Starts up fine, as I rev engine loses power and splitters, even a backfire or two.  If I accelerate slowly revs up but if I punch it, she dies down. Wish I could post a video.

Upload the video to photobucket or similar and then you can post a link

[Merle Coggins]

I had a similar problem once, after a points replacement. It would start and run nice. I could even blip the throttle from under the hood and all was good. When I reved it higher, or tried to drive it above 2500 RPM it would sputter, back fire, and loose a great deal of power. As it turns out I didnt' get the spring connected right for the points and they would start to bounce, or float, at higher speeds. I reinstalled the points correctly and all was well. 

Merle

[torqczar]

 backfire as exhaust  pop,  then the point breaker plate might be  losing ground or  points /condenser problem.   did you check coil output ?,  lift coil  wire up 1/2 in  start motor, will it arc a spark to wire..  with coil wire  raised, rev motor to point of problem.is spark  consistent.   if it passes test ,than problem is carb  and/  or fuel level.  when you rev motor  and release throttle does it stall or just return to idle? sure  acts like a wet dist.  ,   the cap comes off ez,, I would look.while the cap is off check for loose /broke wires. your down to a couple things for a  motor  to run. all thats left is spark and fuel.

[JPP]

Torqczar,  Coil Out put, I did remove coil wire and put it near head and got blue spark at turn over.  You say lift the coil wire up 1/2" from coil?  so still in coil socket just not bottomed out?  When I release rev'd throttle goes back to idle.  Will idle all day long.  As I go through gears 1st is ok, 2nd is dogged and 3rd if I baby it will get up some speed.  Run great in reverse.  I think this is due to gear ratio is lower for reverse than 1st, so doesnt require as many rpm.  Is this true?

[torqczar]

just raise wire up out of coil socket,  so you can see it spark   but I don't think its a spark issue ..  Runs great in reverse.  As I go through gears 1st is ok.    ,    almost every trans I've seen 1st and rev. are the same.. there a few that a different . but not on an old dodge

" When I release rev'd throttle goes back to idle   ,As I go through gears 1st is ok, 2nd is dogged and 3rd if I baby it will get up some speed."...  this   is a classic fuel volume issue.  as we go along  more info comes out.  to diag  ,pull gas line from  fuel pump output to carb  input,  add a short piece of hose to a catch can .. spin motor.   is fuel pump  volume   there,    3 or 4 strokes of fuel pump should output  1/4 cup of fuel + / - .  if it does  carb jets are  clogged/ or float stuck up Like t..ihis

if there is low volume   need to check fuel line to to tank/ fuel  pump check ball .  if fuel pump diaphragm goes bad it fills crankcase with fuel. wish  vehicle  was in front of  me ..

 Like t hope this helps

[JPP]

Here is a video link. 

 

[Don Coatney]

Suggest you do a further inspection of the distributor. Sounds as if there may be a possible short circuit when the mechanical advance plate moves. Looks like a good squirt in the throat of the carburetor so the accelerator pump is working well. I would rule out a fuel issue. Check the wires inside the distributor.

On a side note you are running a skinny fan belt on fat pulleys. Get the correct belt.

[John Rogers]

Just a thought but there is a possibility that the condenser could be bad. Years ago I was having a similar issue with my '69 Charger R/T. The 440 that ran fine at idle but as soon as I tried to rev it it spit and cut out something fierce. I put another condenser in it and it ran like a top. I also had this happen a time or two with my vintage race bikes as well . If you have another condenser laying around possibly try swapping it and see if it helps. It's worth a try.

           John

Edited July 8, 2017 by John Rogers
I cant type (and at times spell) to save my life :(

[JPP]

John, I like the idea, everything else I can confirm performance on, condenser not so much. Thanks

[Jeff Balazs]

I wouldn't rule out carb issues so quickly. If you can't find anything obvious with the ignition take a close look at the step up circuit components including the jet. I ended up having to change this jet in order to get things working correctly. Made a huge difference to how well the truck ran.

Jeff

[John Rogers]

I completely forgot about this until a minute ago but back in '89 or '90 I traded a bunch of basically junk to a guy I worked with for his 1972 Dodge 1/2 ton with a 318. The guy was beyond disgusted with it because it would idle but as soon as you cracked the throttle it would stumble baaad ! He just wanted it out of his sight and out from under it.  I towed it home and tinkered with it and I noticed that when I would open the throttle lots of black smoke came out of the tail pipe. I took off the top of the carb peered inside and low and behold the main jet had actually backed out and was laying in the bottom of the bowl with the fiber gasket laying right there beside it. I screwed it back in and fired it up and it ran great. That night I thought and thought about it and finally decided to tell the guy about it and gave him the option to trade back because I actually felt a bit bad about the whole thing but he said he was so PO'd at it didn't want it back so I just kept it and drove it. These kind of problems can be so irritating but Ive found that a lot of the time the cause of the problem is so small and basic that its easily overlooked. I sure hope that you get it figured out soon so you can enjoy driving it.

                 John