Jump to content

Wierd Sputter and backfire.


Recommended Posts

Hi there.

Been having some issues of when i shut the truck down.

It sputters and backfires and spins backwards sometimes.

its completely stumping me as to how that happens. 

Any info or advice to negate this affect would be much appreciated.

my rig is a 75 long bed 620.

l20b with w53 head.

Weber dgv5a carb

3 speed auto transmission


Thanks Guys

Link to comment
  • Replies 26
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Weber? bet it doesn't have an idle cut solenoid on it. Well nothing you can do about that.


Is the idle speed too high?


The easy fix is to leave in drive when you turn the ignition off, then place in park. The load will cause it to stall faster.

Link to comment

Timing is set to 12°. The carb is a weber dgv5a, no cut off solenoid :/

When in park and no choke idle is reasonable. If I put it in gear and try and accelerate without the choke on. It instantly putters out and dies. If I pull the choke 1/4 closed. It runs really well in gear but idles at almost 3k in park. I've reset the idle a couple times. As directed by redline/weber. I try openeing the choke all the way before I shut it off. But it still idles a lot higher than before I closed the choke. Maybe a linkage is getting stuck somewhere?

Link to comment

I'm gonna try and set it again in the morning. Without choke after completely warmed up and in gear. Hope it helps. If not. I'll just start shutting betty down in gear haha. Btw my trucks name is betty white. Old bitch with a temper and an attitude lol. Thanks for the help guys. Will update if anything changes or figure something out

Link to comment

This is the problem I would focus on. All the other symptoms may be side effects of your "adjustments" to get around this problem.


If I put it in gear and try and accelerate without the choke on. It instantly putters out and dies.

If the engine is fully warm it should drive well with choke off. The fact that it runs better with choke on indicates a severely lean carb problem. To some extent the idle mixture can be adjusted rich to compensate, but doesn't fix the off-idle mixture.


Lean carb could be a bad carb, or there could be vacuum leaks. Are you running a two-piece Weber adapter? If do I'd start there. Remove the top piece and tighten the bolts. Don't over tighten.

Link to comment

Im very skeptical of the jetting if the carb. Everywhere I've looked the combo doesn't seem right. And the aux venturies loose and rattle in the body of the carb.

Jetting is


Primary secondary

Main. 137 135

Air correct 165 160

Venturies 27 26

Aux. Vents 3.5 3.5

Idle jets ? ? (Could not find ant marking on the idle jets.

Acc. Pump 50


As far as the accel pump. It is pumping a good supply of fuel into the butterfly.


Dizzy is in the middle of the adjustment plate. I adjust points every other week to stay on top of them.


I have tuned the carb both ways for a stick and an auto. No change.


As far as vacuum leeks. The person I bought the truck from. Had started an emissions delete. But didn't finish. I am in the process of fabbing a plate to bolt on the end of the intake where the egr is currently bolted up still.


I've plugged all open vacuum lines with tubing, bolts and hose clamps.


It does have the 2 piece weber adaptor. And it's a hunk of junk. It's rtved together on the bottom one. So as soon as I can afford/find another. I'll be replacing it.

Link to comment



Is the vacuum adv ing to the carb?



take a photo of the coil area .


Your 75 should be point ignition. if still so you should have a ballast resisitor and a point 1975 coil. If you have points and no ballast maybe your buring up your points and it arching.

But it this runs good at speed then its highly UNLIKELY its the proplem,

Link to comment

Readjusted the idle and mixture today. Without the choke on I put it in gear and dies as soon as I try to accelerate. My buddy has a weber 32/36 with electric choke. He might not be using it so I'm gonna try and out that on and see if it does any better

Link to comment


New distributor electronic ignition


conversion kit.


Reset the timing to 14°.


Readjusted the carburetor.


I still can't drive without the choke on.


When I try and accelerate it cuts out as if it doesn't have enough fuel.


I put the mixture screw at 6 turns out and it will somewhat run and drive with out the choke.


But that is really too far out.


Any suggestions?

Link to comment
  • 2 years later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.