Works fine at idle, or a steady speed...
If I do a real slow acceleration I don't notice anything. If I do a normal acceleration she she sputters and jerks but eventually gets there. If I really give it some gas it struggles more and occasionally backfires.
Just changed the fuel filter and same deal.
Any ideas?
Check - vac advance on the distributor, then a visual check on the counterweights and springs inside of it (they could be gummed up/broken spring etc). Next is secondary vac servo/solenoid on the carb. If it's split it will create an air leak into the carb + disable the secondary throttle butterfly (no mid range to top end power). Other possible problems - fuel cut solenoid on the carb (not likely but still possible) disconnect the wire running to it and run power straight from the battery+ to check function (it should have an audible click when the circuit is connected/broken). Ignition coil - they break down after 10 years and this will cause power loss, poor fuel economy and misfires under hard throttle. Blocked jets - try purging the carb. Engine running, cover the throats of the carb with one hand while opening the throttle. This will force the carb to pull excessive amounts of fuel through the jets and sometimes this is enough to unblock them.
Tune - check base timing with a timing light and maybe try to dynamically tune it (no timing light required). Loosen off the distributor retaining nut, start the engine and hold the throttle open @ about 2,000 rpm. Gently swing the distributor between advance/retard until you find a sweet spot and the engine rpm increases by itself and lock the retaining nut up and test drive it, listening for engine rattle or feel for power loss or something amiss. I slightly under gap my spark plugs to allow for a more aggressive engine tune and use premium fuel instead of regular. Physically look at the spark plug electrodes for a sign that there is an issue (fouled plug, plug too clean - anything that indicates one or more of the plugs aren't doing their thing) Look at the engine running in darkness to see if you can spot any arcing from spark plug leads or the coil, visually inspect the inside of the distributor cap and rotor for tracking or burnt terminals.
Last thing - vacuum leaks. They are tricky to hunt down. Check the manifold gaskets and spacers, vacuum lines, brake booster line and check valve. This should keep you busy for a whole weekendGood hunting, hope you find the glitch.
Hi haruman -- With an already repaired & good ignition system, new fuel filter; Vernon, a local neighborhood DIY mechanic, advanced my trucks timing & installed a new fuel pump... I put in a can of Seafoam into the gas tank & now run 92 octane gas -- most of your problems are no longer happening to my truck...
Driving with Aloha
Which carburetor do you have? The OE Mikuni or a Weber? Also, when idling and in neutral, if you quickly open the throttle, does it rev okay or sputter and stumble?
I have the Weber, and mechanical fuel pump. Weber's been installed for about 4 years.
I'll go check the idling in neutral in a few minutes.
OK. Using a Weber changes diagnosis - my bad for not remembering you've done the swap. Are you using the mechanical pump with a regulator?
No regulator.Originally Posted by geezer101
Check fuel flow. The mechanical pump might be on it's way out and can't supply the Weber with enough flow to keep up demand. I'm surprised it's held up this long without issues. Time to think about a HVLP electric pump
So I tried it at idle in neutral and it still sputters and stumbles.
So what's a good way to check the fuel flow?Check fuel flow. The mechanical pump might be on it's way out and can't supply the Weber with enough flow to keep up demand. I'm surprised it's held up this long without issues. Time to think about a HVLP electric pump
I'm thinking that the accelerator pump or nozzle has failed. With the engine off and the air cleaner removed, if you look down into the carb while opening the throttle, do you see a stream of gas from the accelerator nozzle? If not, the nozzle is clogged or the pump has failed.
I see a dribble...
I think that's the issue. A dribble isn't sufficient so it's starving for fuel when you try to accelerate. I'm not familiar with the Weber's internals, but another member or an internet search should tell you how to access and fix the accelerator pump circuit.
Just ordered the part, looks pretty easy to swap. 4 screws and it's easily accessible, shouldn't take but like 10 minutes...
Yeah I had to do this with a weber 38 38 installed on a ford pickup (1978 f150) and it is literally take the top half off and change it throw it back on check your floats and ride on.
Now if your timing is pig rich it will blow accelerator pumps and power valves like no other, I literally got a pop from the engine when the accelerator pump went out.
Sounds great. If the Weber is only four years old, chances are the nozzle is clogged. Compressed air may clear it, but often only temporarily because any foreign material still inside can replug it since the end opening is typically quite small. When you take it apart, look for crud on the old part and in places where it can collect inside the carb. Clean out any you find and consider installing a small filter between the fuel pump and the carb as extra insurance. When its back together and any lost fuel replaced, opening the throttle quickly should send a strong, steady stream from the nozzle.
Last edited by FMS88; 02-01-2020 at 05:54 PM.
Are there two nozzles? One on each side? I can see a stream from one but not the other...
So to date:
New accelerator pump
New fuel filter
Can of HEET in the gas (in case there was water)
New gas cap (old one seal was crumbling)
Still doing it, I can see a stream on one side but not the other, leading me to think that jet is clogged?
yes there are 2 jets. so yes you do need to clean it. this is probably your whole problem if its on the primary butterfly
Try purging it. It might clear it out (if you haven't already attempted to do so...)
Here's where you can find diagrams of the various Webers that fit:
https://www.carburetion.com/Weber/weberdiagrams.asp
For the DGEV/DGAV the accelerator pump jet/nozzle is #96. It looks the same although numbered differently for the other models. It's on the primary barrel and appears to have two nozzles. (I don't have a Weber so I have to rely on the diagram.) If one side is plugged, you may be able to clear it with compressed air, but you might have to remove the top of the carb to get to it the screw that holds the jet/nozzles.
How to purge?
compressed air and some carb cleaner is my best guess, idk lol.
Blocked jets - try purging the carb. Engine running, cover the throats of the carb with one hand while opening the throttle. This will force the carb to pull excessive amounts of fuel through the jets and sometimes this is enough to unblock them.
Suggested it on an earlier post on this thread.
Oops I missed that, will give that a shot! Thanks!Blocked jets - try purging the carb. Engine running, cover the throats of the carb with one hand while opening the throttle. This will force the carb to pull excessive amounts of fuel through the jets and sometimes this is enough to unblock them.
Suggested it on an earlier post on this thread.
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