Hesitation woes continue

[p24-1953]

Hesitation continues..

So I have been fighting the hesitation for a month now. In the last month i have rebuilt the carb, installed a vacuum guage( runs 18hg at idle), replaced the mech fuel pump and installed a pressure guage (hold steady at 4-5). Bumped the timing up to 10.

Even after all of this the truck will start to surge when it gets above 45 in third or 25 in second. It will pull strong up to this point and then starts bucking. The vacuum will slowly drop from 18 to 5... When you let off the throttle the vacuum shoots back to 20+.. the fuel pressure never drops 

In neutral you can run the rpm high and it never stumbles and the vacuum idle hold mostly steady.

I'm now wondering if the carb is at fault, it has a d6g1 carb and it is a 1948 dodge 230 engine. Is the carb wrong for the block? What else could it be? Weak springs would show up while racing in neutral, right? The needle may flutter 1/2 hg in each direction when it is racing but that is all.

I'm at a loss? So are my local car guys.... any thoughts?

Edited October 14, 2017 by p24-1953

[NiftyFifty]

Silly question...is your gas cap vented/not plugged??  Or lines pulling air somewhere??

[p24-1953]

New cap, new 3/8 lines, new tank.  The lack of fuel pressure drop makes me think it is not a fuel issue.

[maok]

Is it surging or hesitating?

 

[JPP]

I had a similar issue, and as you did chased everything, fuel pump, vacuum, carb, plugs, plug wires and while this never  improved anything it was worth getting everything right. So what I did was chase the electrical aspects. Look at your voltage getting to points, should be 6.4 volts for 6V system. Turned out I had a loose ignition wire under dash. No more hesitation. Good luck. 

[Merle Coggins]

Sounds like a points bounce issue to me. What RPM are you 'racing' the engine when siting in neutral. I would venture to guess that it's not as high as  as you reach at 25/45 when driving. I had this happen to me once after replacing a set of points. I didn't get the spring hooked right. It ran great in the driveway, but once I took it for a spin it wouldn't go over 40 MPH and would loose a great deal of power. I got it home and started tracking down what I had done wrong. I found that if I reved it higher enough in neutral I could replicate the issue. With my timing light on  it I found that the timing would retard a great deal and the light flashes would be very erratic. A closer inspection of the points revealed my error. Once the spring was connected properly, and all was reset, it ran like a champ. 

[Brent B3B]

please post your solution p24-1953. I am having the similar issues this summer. although I haven't gone to the extent of trouble shooting you have , yet,   my bucking seems to smooth out when I pull the choke....

edit= removed video, don't want troubleshooting misdiagnosed for OP

Edited October 15, 2017 by Brent B3B
don't want to take focus off OP thread

[p24-1953]

Brent mine isn't that rough.   And  it is not effected by the choke.    It just runs out of steam.  I changed points condensor and coil today.  I also checked the compression and it was good.  We will see tommorow how the changes help.

Edited October 15, 2017 by p24-1953

[pflaming]

So you replaced the . With an electric fuel pump or another mechanical pump? Last April I rode with a forum member to the BBQ in his 47 Plymouth, with a 218. It would nearly die out then suddenly run like a champ. Seems the five fuel bowl bolts were just loose enough to allow gas sepage through the bowl gasket which evaporated before noticeable. He tightened those screws and drove home. STML can't recall his name, from Acton CA. He drove around 55mph , I was in the back seat, perfect seat at a perfect speed. TKS ! 

Edited October 15, 2017 by pflaming

[Mike B]

I just fixed a similar problem. For me, it turned out to be a bad condenser in the distributor.

Mike B

North Idaho

[p24-1953]

Changed out the coil, condensor and points (all of which were less than 3 months old) and it works great.  Was able to cruise at 55 and it still was pulling.

Don't know which one of the 3 it was, but on don't care as long as it runs..  

[Veemoney]

I had similar issue with my 47 running great all these years then one day it started to stutter in any gear when it was getting high in the RPM range. If you backed off it was good again. Went on for about a week

I rebuilt the carburetor and still had the issue. Then decided to check the glass gas filter I had installed inline with the 6V pump.. It always showed gas but when I pulled it, it ended up It had restricted flow. I just blew threw it and could tell. I serviced it and put it back in and no more issues. Not sure where you are checking for pressure on your system but make sure you have no restrictions in the gas line. The pump will give you pressure but it doesn't take much to slow it down. 

Making sure the point spring or springs are installed correctly will lend the same result as mentioned by others.

Good luck