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Author Topic: Engine breaking down on acceleration  (Read 232 times)

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Maystro

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Engine breaking down on acceleration
« on: March 29, 2021, 09:18:13 PM »
Hi Mokers

My engine has been breaking down and miss firing on acceleration.  I thought it was a fuel delivery problem running too lean but after 2 needle changes and 3 sets of spark plugs in a week and also taking my HS4 back to a baseline where I screwed the jet level with base and screwed it 2 full turns then starting again with using the piston lifter as a guide, nothing has changed. 
The best it ever ran was with a new set of plugs with a AAU needle but that lasted about 15 mins and they were totally black and fouled up because I screwed the jet right down using  the carby piston  lift trick which seemed to be right because the engine slightly died then regained composure. 
I put in another set of plugs and tinkered with mixture nut and they are white and breaking down which you would expect if it was running lean.  Moke is running on 2 cylinders at the best.  Again plugs are cactus and never to be used again no matter how much I clean them up.
I noticed though about a week ago when I turned on the heater the engine would misfire.  Since then the engine has been turning over slower and slower.  Today it would hardly start.

I was thinking my alternator may have died and so I have been running on my battery.  Would this cause a week spark and cause my plugs to foul really quickly if they are getting a  weak spark.

Clueless again Brad.
   

Steam

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Re: Engine breaking down on acceleration
« Reply #1 on: March 29, 2021, 09:42:36 PM »
Hey Brad I feel your pain, I went through similar a month or so  back.
My guess would be electrical, coil, points or condenser, leads etc.
Do not overlook the obvious, is the engine earth strap tight, etc.
Cheers, Dave

Drakman

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Re: Engine breaking down on acceleration
« Reply #2 on: March 30, 2021, 06:20:49 AM »
Hi Brad,

Black plugs doesn't sound good.  Take the dashpot off and see where the needle JET is in relation to the top of the venturi bridge, set it about 1 mm down.  Check the float level, is it flooding?

Breaking down/missing under load is usually electrical, plugs, leads including the coil lead, the coil itself.  Is it backfiring, if so out the exhaust? inlet?  Valve clearance?

Run a spanner over the manifold nuts and bolts, is everything tight around the inlet/carby.

Is the car loosing water/ getting hot? I'm thinking head gasket here.   Is it possible the heater cable is contacting something electrical when you use the heater.

Another 2 cents gone, good luck with it, let us know what you find.

Cheers
Dave

Maystro

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Re: Engine breaking down on acceleration
« Reply #3 on: March 30, 2021, 08:53:38 PM »
Hey Dave's

Your not wrong about it being painful, nothing sadder than a grounded Moker. 

I have put in a whole new electronic ignition system about 6 months ago, however I am dubious about the quality since it was purchased on Ebay but it has been running flawlessly till now?  I do still have my old Lucas ballast resistor points type 59D4 dizzy and coil.  Maybe I should try that.  I have been holding off getting one of those 123 dizzys till I work out if my new 1275 build will be a A or A+. 

I can thankfully say it is not the head gasket this time. 

I did notice where a possible air leak could of been in the inlet manifold which was a temp sender port which had a blank screw in.  It was loose so I wrapped it in plumbers tape, but that was after my first set of fouled plugs.  I have since adjusted the mixture and lost 2 more sets of plugs all in a week. 

I did take the jet back to a baseline factory position which is 2 full turns level from the base but using the plunger lifter pin mixture technique that was way to lean and the jet ended up being about 5 mm's down which I thought was extreme and probably why my plugs fouled up so quickly.  But then I have gone the other way and the plugs are white and breaking down on power. 
On this topic of adjusting the mixture with the pin which lifts the plunger/cylinder, has anyone else used this?  Apparently the sweet spot is when the engine slightly dies and recovers, for my carby that means screwing the the jet down about another 3 full turns not flats so no wander why my plugs are fouling?  But if I don't the plugs are white and breaking down. 

I think I have exhausted my avenues with my carby fiddling which was brand new 6 months ago. 

I'm going to Jaycar tomorrow and to buy a multimeter.  Is this useful?  My auto electrics knowledge is less than my mechanical knowledge so is this multimeter going to be useful for testing if my alternator is working and anything else I might need to know.  I'm not looking for some super duper unit. 

https://www.jaycar.com.au/automotive-dmm-with-dwell-and-tacho/p/QM1446

Thanks Brad.


Steam

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Re: Engine breaking down on acceleration
« Reply #4 on: March 30, 2021, 10:20:27 PM »
Hey Brad,
The meter you linked to is fine as far as it goes, it is limited in some areas but has dwell and tacho. Dwell is not much use with electronic ignition tho.
The chinese dissys are prone to all sorts of breakdowns. In your sitution a good plan would be to go back to points and standard coil with a good set of leads and eliminate the ignition as the problem. Chasing ghosts will drive you to insanity.
 The lifting pin is very subjective, it should only be lifted 1/8 of an inch, any more and the test becomes pointless. I have never had any success with it. The mixture should be right within a flat or 2 of two whole turns down from fully up. Any more and the needle is wrong.
If you can tell us your engine specs with which mods you have we can probably give you a ball park needle to try.
However the ignition affects the mixture alot more than you might imagine.
Cheers, Dave

Steam

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Re: Engine breaking down on acceleration
« Reply #5 on: March 30, 2021, 10:22:08 PM »
Hey Brad,
The meter you linked to is fine as far as it goes, it is limited in some areas but has dwell and tacho. Dwell is not much use with electronic ignition tho. Volt range will test for alternator 13.8 to 14v dc when running. Qnd it is a reasomable price.
The chinese dissys are prone to all sorts of breakdowns. In your sitution a good plan would be to go back to points and standard coil with a good set of leads and eliminate the ignition as the problem. Chasing ghosts will drive you to insanity.
 The lifting pin is very subjective, it should only be lifted 1/8 of an inch, any more and the test becomes pointless. I have never had any success with it. The mixture should be right within a flat or 2 of two whole turns down from fully up. Any more and the needle is wrong.
If you can tell us your engine specs with which mods you have we can probably give you a ball park needle to try.
However the ignition affects the mixture alot more than you might imagine.
Cheers, Dave

Maystro

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Re: Engine breaking down on acceleration
« Reply #6 on: April 05, 2021, 02:38:24 PM »
Thanks Dave,

I haven't progressed far.  Partly because I have been working and the other fact that my Moke is broken down at the bottom of my driveway and doesn't have enough power to make it up the hill.  I have charged the battery and using my new multimeter it says it has 12.7 volts.  I tested the alternator and the battery volts went up to 14.2v when I revved it on 2 cylinders.  So I'm guessing my alternator is charging. 
I just put my 4th set of plugs in (NGK BP6ES) hoping that would get me running on all 4 cylinders again just to get it up the driveway so I can work on it but no go, she sounds like it's only running on 2 or 3 cylinders. 
Is their a way I can test the coil with a multi meter to see if it is putting out enough volts? 
Like I said I still have my old dizzy and coil but I don't fancy fitting that on the side of the road? 

I'm thinking it's time for a tilt tray trip to a local mechanic.

Thanks Brad.

Drakman

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Re: Engine breaking down on acceleration
« Reply #7 on: April 05, 2021, 03:31:40 PM »
Hey Brad,

Does it have spark to all plugs?  Do any of the plugs have a wet look when you take them out.  Does it have compression on all 4 cylinders?   Does it make any unusual noises when you crank it over?  Does it turn over too fast, faster than usual when you try to start it?
Is the firing order right? 

Go back to basics, check the compression first, set it on TDC and check the firing order. 

I've got lots of questions but I'm a bit short on answers, sorry.

Dave

Shaun78

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Re: Engine breaking down on acceleration
« Reply #8 on: April 05, 2021, 05:10:37 PM »
Hi just thinking about your misfire,I had a series 2 landrover brought to me a while back,the owner had purchased a electronic dizzy from Ebay that he wanted me to fit,I put it in set the timing it ran sweet until it got warm,then ran on two at best,let it cool back on four until warm,check timinig,valves,plugs,carb settings,nothing,so put old dizzy with points back in and ran fine,so looked at electronic dizzy then I found the fault it had been built using a standard black rotor arm,ordered the correct red rotor arm and away it went,might be worth a look to see if you have the correct rotor arm in your electronic dizzy.

Terry

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Re: Engine breaking down on acceleration
« Reply #9 on: April 05, 2021, 05:33:10 PM »
Hi,

if it is running on two cylinders then the coil is working, your battery is fine etc.

Using a thick glove, i.e. a welding glove, start the engine and remove one plug lead at a time and listen to the engine and then replace the lead and move onto the next lead. If there is no noticeable change then it is most likely that cylinder is not firing correctly, if it does change the engine running and may even stall the engine that that lead/plug is working fine.

Once you have done all four and determined the ones which are not firing correctly, remove the spark plug on the cylinder(s) that is not firing reattach the spark plug lead and rest the plug on any metal surface on the engine and start the engine. Look for a spark crossing the electrode to the tip of the spark plug. Repeat for any others not firing to determine if they spark outside the cylinder.

If you don't get a spark across each plug outside the cylinder for the ones that had no effect when the lead was removed when the plug was screwed in place then you have an issue with either the Plug(but you siad you have replaced them), the lead(swap with another lead and see if you now get a spark) or you have an issue in the cap which could be dirt/oil/crud on the inside or outside(so clean it thoroughly) or a terminal inside the cap that is failed or oxidised.

If the spark plug did have a spark when resting on the engine in your test but has no effect on the engine when fitted and the lead is removed then I would say that you probably have two cylinders that are not firing and they will be next to each other suggesting you probably have a blown head gasket between either #1 & #2 or #3 & #4. If the two non firing cylinders are not next to each other then the head gasket is likely not the problem and you should update this post.

Terry
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Maystro

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Re: Engine breaking down on acceleration
« Reply #10 on: April 05, 2021, 06:23:25 PM »
Thanks guys I really appreciate the time you have put in to respond to my problem. 

Shaun I think the rotor arm should be right because the motor has been running great for 6 months when I installed the new electronic ignition and new HS4. Although the dizzy was an Ebay purchase so anything is possible? 

Dave it certainly doesn't turn over any quicker, if not a bit slower but I think that is from me trying to start it on 2/3 cylinders.  The firing order is right 1342 which is stamped into my brain for some obscure reason.  The rotor button does go anti clock wise I hope?  I have a compression guage but I'm limited what I can do on the side of the road. 

Terry I think my problem is definitely spark  because I don't need any welding gloves when I pull off the leads when the engine is running?   I tried this with my third set of 5 min old fouled plugs and their was only a notable difference when I pulled off number 1 plug.  She was running bad. 
I have run out of light today.  I will run through your very thorough procedure tomorrow if time permits. 
I did notice my spark has never been very bright in previous tests   since I have installed this cheap electronic ignition set up. 

Thanks Brad

Shaun78

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Re: Engine breaking down on acceleration
« Reply #11 on: April 05, 2021, 06:33:01 PM »
The arm could be the fault they breakdown and let the spark earth down the shaft,check out this website he is UK based but it might give you some info.www.distributordoctor.com.

moke

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Re: Engine breaking down on acceleration
« Reply #12 on: April 06, 2021, 09:52:14 AM »
You mention that the carb is 6 months old. Did you replace the carb gaskets as well?
I had similar symptoms with my Moke (fine when idling but undrivable under load) that were eventually fixed when I replaced them (after trying all the other things you've tried here). A quick and cheap thing to try.
Dean
It's hard to leave when you can't find the door - Joe Walsh

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Re: Engine breaking down on acceleration
« Reply #13 on: April 06, 2021, 01:55:05 PM »
I don't think the problem will be from the coil as you say it's just on one or 2 cyls, it could be your plug leads are getting old, you can measure their resistance with your new fangled multimeter, they should have below 20,000 ohms resistance, anything between 15k to 20k is suspect and should be replaced, the lower resistance the better.

It could also be a headgasket problem so check for bubbles in the radiator or browny sludge in the rocker cover cap, you can check gasket problem with a compression tester.
1976 Moke 1275cc (Dynky),
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1975 Moke rust bucket,
1967 Moke rust bucket

Maystro

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Re: Engine breaking down on acceleration
« Reply #14 on: April 06, 2021, 08:06:09 PM »
OK not much of an update, well at least not a very optimistic outcome I don't expect from my findings.

Pulled the plug wires of number 1 and 2 plugs and no notable difference.  If I take either 3 or 4 plug wires off, the engine dies so it is obviously only running on 3 and 4 cylinders. 

Pulled the plug out on number 1 and 2 cylinder separately and I get a good spark on the block.  I didn't bother testing 3 and 4 because they are obviously getting spark and the cylinders firing.  (2 of 4)

It sounds like a blown head gasket but I am getting no milky sludge in my tappet cover or bubbles in my radiator. 

Like Dave suggested I'll have to do a compression test tomorrow.  I get home late from work and run out of light working on the road.  I actually drove down the road today on 2 cylinders and  came back to my driveway with a big run up as fast as I could go on 2 cylinders and nearly made it to top of my garage but didn't quite make it. 

Either way I have to call a tilt tray and send it to garage for someone else to work on it now.....gotta luv living on a hill ;-( 

I was kinda expecting this since I glued that cylinder sleeve back in the bore about 6 months ago and that was number 1 cylinder.  Although I think it was my engine running rough that may have been the cause of my possible blown head gasket.

Anyone know of a 1275 for sale? 

Thanks Brad