Vague, dreaded ‘sputter’ ‘hesitation’ etc.

[Slow Loris]

Okay so I’ve read the last 10 years of posts on the matter, most of which are never resolved, or are resolved by the blessing of the Pope and a miracle occurring…so I need some direction

 

I have a stumble, sputter, bog, that occurs when I hit the gas on take off in 1st, and in 2nd, not above second though. Have the stock Hitachi on an L18.

 

If I stay on the gas, I “get through” it and drive away.

 

It seems like wisdom dictates this may be related to:

-accel pump

-jet blockage

-vac leak

-distributor?

 

Dunno what else?

 

So I replaced the accel pump recently and have robust stream of fuel for full stroke of pump (old one was floppy and tore up). Passages seem clear by way of carb cleaner squirting through, but this is the one and only carb I’ve ever worked on so what do I know?

 

I opened plugs for main jets and squirted carb cleaner through there (appeared to come out somewhere in the throat—  so, clear not blocked?)

 

One thing I don’t understand about the possible distributor off a tooth as a possible cause is if that’s something you “get through” simply by staying on the gas? Seems like not, but I’m a noob so I don’t understand why this is always suggested as a possible cause. Timing at idle is spot on, at least. Either way, yes I’ve replaced the distributor to go to EI. Could have screwed that up? Would like to understand how that could relat though.

 

So where do I go next? Keep cleaning passages all over again? Take out main jets and clean those directly? Hunt down vacuum leaks? Uhh dare I say get a Weber? (No I’m not ready for that!)

Thanks for any guidance.

 

 

 

 

 

 

 

 

 

 

 

 

Edited May 7 by Slow Loris

[datzenmike]

If the distributor was 'off a tooth' it would have had too have been removed and put back in wrong. The fact that you were able to correctly set the ignition timing means this it's so.

 

 

The next one needs the carburetor removed...

 

I would remove the primary jet. You may need to grind down a suitable screwdriver to make it narrow enough to fit up in there. It's the only way to see if it has any obstruction. The primary jet (closest the valve cover) will be numbered around 100, the secondary around 150-160. They can be interchanged so they may have been and make sure you don't.

 

 

[Slow Loris]

Okay got it. Thank you for clarifying the distributor possibility. Didn’t want to keep barking up the carburetor tree if that wasn’t it.

 

I’ll see what’s up with that jet. 
 

Thanks!

[banzai510(hainz)]

EZ

If doistributot is off you would be able to time it but the dist would be almost maxed out on one side of the slot. If off a tooth your top end usually is killed.

 

I have seem worn dist bushings were the shafts wiggles.

 

You have a old carb it is almost 60years old.  Time for anew one

 

 

adjust timing from around 7 to maybe a better 12deg Before TDC and see how it runs

[Stoffregen Motorsports]

Basic rule of thumb is -

 

Rich = stumble, burble, more of that then take off

Lean = stumble, dead nothing then take off

 

Many reasons it can feel lean. Blocked jet, blocked filter, pump not up to par, even ignition or cam timing is off.

 

Feeling rich can also be clogged jet (air corrector), too high fuel pressure, float bowl too high.

 

How do the spark plugs look?

[Slow Loris]

@Stoffregen Motorsports Plugs look…dark and dull for the most part except for cyl 3 which is not looking great, pretty oily I guess. They are smelling pretty gassy though. Maybe things are pointing to rich? 
 

 

As near as I can tell in my attempts to cut the engine whenever the stumble was happening and pull over real quick the float bowl was dead on the line. But considering it “recovers” perhaps I’m just too slow to catch it?

 

@datzenmikeI got the jet out and sprayed it clear. Couldn’t tell there was any blockage but who knows. It’s a 115, fwiw.

 

I will put this back together, put in some new plugs and run it and see what happens and then what the plugs look like later.

 

@banzai510(hainz) thanks about the distributor. I wasn’t sure cause of the swap to EI needing all the different pedestal, plate, etc. plus the distributor dropped in clocked differently than the original so didn’t know how all that would add up. Plenty of adjustment left for timing though. I’m at 12 BTDC now as that’s what I read for L18. Sounds like that’s prob not my problem though so will keep digging thru carb.

 

 

 

 

[Slow Loris]

Sounds like 115 is a little high on the jet, especially since I’m at 2,700 ft, though not sure if it’d be a significant contributor to the issue? Though, strangely the PO lived at 4,200 ft so…huh?

[datzenmike]

L18 carburetor should be about #100. #115 would be better at sea level. You could try a smaller #100

 

https://www.amazon.ca/Carburetor-25pcs-55‑115-Replacement-Dellorto/dp/B09S2Y9FSX/

 

[Slow Loris]

Ah cool. Yeah will do! 

[banzai510(hainz)]

11 hours ago, Slow Loris said:

at 12 BTDC

Long as you have lots of movement with the timing light. if you can rotate the dist where it goes down to zero or up to 25deg BTDC then your on the money(use a timing light). you dist is correctly installed.  If it was banked all the way to one side then it will be a issue.

 

 

be honest I had my yellow  510 with 44mm it was fucking black on the plugs and sill ran fine

my 38/38 Weber was also over jetted rich for a land Cruiser and was black. ran fine.

meaning is I think your waisting your time on this.

Edited May 8 by banzai510(hainz)

[datzenmike]

It may help, won't hurt. Mileage will go up.

 

11 hours ago, Slow Loris said:

 ...I wasn’t sure cause of the swap to EI

 

 

When you changed to EI distributor did you get the EI matching coil as well?

If you did did you by pass the ballast resister?

What plug gap are you using? With full EI you can open the gap to 0.038"-0.042"

[Stoffregen Motorsports]

Yeah, judging from the pics, I'd say it's rich.

[CharlieWhiskey]

confirming to have sufficient intake manifold vacuum. If the vacuum is not enough to lift the plunger rod up from the power value, or if the vacuum is lower than specified, the plunger under the air horn will press down on the power valve to release more fuel. Make sure the power valve, which is in the bottom of the carburetor body, is tight and secure as well.

[Slow Loris]

9 hours ago, datzenmike said:

It may help, won't hurt. Mileage will go up.

 

 

When you changed to EI distributor did you get the EI matching coil as well?

If you did did you by pass the ballast resister?

What plug gap are you using? With full EI you can open the gap to 0.038"-0.042"

Yes matching coil.

 

Yes bypassed.

 

I think I gapped at 0.042

 

 

6 hours ago, CharlieWhiskey said:

confirming to have sufficient intake manifold vacuum. If the vacuum is not enough to lift the plunger rod up from the power value, or if the vacuum is lower than specified, the plunger under the air horn will press down on the power valve to release more fuel. Make sure the power valve, which is in the bottom of the carburetor body, is tight and secure as well.

 

Interesting, I could be wrong but I think in this DAF model carb (pretty sure that's what I have) I don't have a power valve? Is there an equivalent?

 

10 hours ago, banzai510(hainz) said:

ran fine.

meaning is I think your waisting your time on this.

 

Yes I won't obsess on the condition or my gas mileage but I would like to run more fine than it's running now. 

 

[datzenmike]

How about decreasing the plug gap to below 0.040" and try that.

 

 

[CharlieWhiskey]

8 hours ago, CharlieWhiskey said:

confirming to have sufficient intake manifold vacuum. If the vacuum is not enough to lift the plunger rod up from the power value, or if the vacuum is lower than specified, the plunger under the air horn will press down on the power valve to release more fuel. Make sure the power valve, which is in the bottom of the carburetor body, is tight and secure as well.

my bad, I mistaken it was L20. 

here is the spec. DAF328 L16

main jet #115 ( both Primary and Secondary )

Main Primary air bleed #240, Secondary #120

Slow jet Primary #48   Secondary #180

Slow air bleed Primary #180, Secondary #100

Slow Economizer Primary 1.8mm ( 0.0709")

Economizer bleed Primary 1.8mm  (0.0709")

1 hour ago, datzenmike said:

How about decreasing the plug gap to below 0.040" and try that.

 

 

 

[datzenmike]

115 sounds large.

[Rustbin]

According to the book I used when playing around with the DCH340 model Hitachi carbs the main jet primary jets varied between 97 and 105 depending on year and application. I changed all the jets and air bleeds to match those on a higher horse power engine, and it ran fine, changing just the jets makes it run worse.

[CharlieWhiskey]

2 hours ago, datzenmike said:

115 sounds large.

i copied it off from the service  manual. (Printed service manual from Nissan Motor Company, Tokyo, Japan.)

I wished to send photo but will need to figure out how to do so.

[datzenmike]

What's used in Japan may not be what's allowed in emission sensitive North America. Generally the primary is smaller than the secondary and secondary jets about 50% larger than primary. Close to 100/150. I had a '71 and I did have the carburetor apart but that was almost 50 years ago.

[Slow Loris]

I peeked at the secondary and it’s a 155. Not that my carb is a reliable source of information.

[Slow Loris]

Well I feel a little bit like I just got my first prescription for viagra but…I am back in business.

 

Yep, I put a Weber on it. @banzai510(hainz) claims another victim.

 

Anyway running great. Thanks for the help troubleshooting this problem everyone, feeling a little guilty I took the easy way out. But feeling GREAT that the truck runs pretty well now…

 

…except for the brakes AGAIN and now the horn honks whenever I hit the right turn switch but…those will be fun problems to solve.