Intermittent Hesitation

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AndyO

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Happy Summer All,

Got a bit of a head scratcher, she's running well in the most part but I have this very annoying intermittent hesitation. I can't seem to force it by high revs, low revs, fast / slow, hot / cold, it's random. If pushed, one hot, I would say after slowing down, second gear and pull off it's more likely to happen.

TYPE 4 Engine 1800 twin Dellorto DRLA 40's

In the last 18 months:

Plugs, Leads, Fuel Pump (rotary correct pressure) new elec ignition, float heights, timing, valve gaps.

I've got a coupe of coils / dissy caps and rotors as spares, I checked the resistance on both coils last year and they seem good. Fresh fuel (Shell premium) after a lay up - also tried an additive to rid the ethanol makes no difference.

I had a good go at balancing and setting the mixtures on the carbs last year and plan on doing that again when time allows, but am unsure if rich / lean or unbalanced condition would cause this.....help!
 
I just took the bus for a tip run, last week started great after re-setting the timing after trying for a little while to start up. Today it was hard going starting again, but started up. After parking up for 15min to loading up the van it started first try but noticed that I got an intermittent hesitation while driving. Parked up to unload and it took a few tries to start up and didn’t feel like it ran perfectly. Parked up at family for 20min and it just wouldn’t start again. I checked the timing and it had moved again! Set it up and tried again nothing, checked timing again and it had moved again though the bolt was really tight. Tried several times again after re-setting the timing but it just wouldn’t spark up, the carb got fuel and the electronic points got spark. So I tested the coil by looking at the spark colour and it was a bit orange with light blue at the ends. This is a silver Beru with roughly 2k km. Got a lift home to pick up an old 15-20yr old blue Bosch swapped it over and it fired up instantly!!
Might just be worth changing the coil for a blue one, especially if you notice a slow start up.
Cheers
 
Thanks both, will swap the coil today and see if that makes a difference.

I’ve got a silver beru fitted and a blue bosh as a spare. She has been difficult to start but I put that down to me flooding her (if i don’t touch the accelerator she starts)

Distributer: aftermarket svda with electronic ignition.
 
Are the original Blue Bosch coils made in Germany still for sale?
The silver Beru doesn’t seem to be good or last for long. If it’s been starting hard I’d defo switch if for a good blue.
Good luck and keep us updated please.
 
By way of update, new coil no hesitation! However.....

Purchased a Bosch 0 221 119 027 coil as it is epoxy filled (apparently oil filled do not like being mounted horizontally) and its getting quite hot. She was down on power after a good run yesterday.....but good today, coil still hot though......

Voltage at the coil:
  • Ignition on: 13.50V
  • Engine Running: 13.98V
Leads:

  1. 1.025K ohms
  2. 1.032K ohms
  3. 1.012K ohms
  4. 0.995K ohms
Sparks all gapped to 0.7mm

Coil resistance:
  • 2.9 ohms primary
  • 7.56k ohms secondary
 
Ah Ok - yes can touch for a couple of seconds. Seems normal then.

Leads and Plugs new last year, not driven much since.
 
I have used Bosch red coils with ballast before now , much better spark on start up.
 
Happy Summer All,

Got a bit of a head scratcher, she's running well in the most part but I have this very annoying intermittent hesitation. I can't seem to force it by high revs, low revs, fast / slow, hot / cold, it's random. If pushed, one hot, I would say after slowing down, second gear and pull off it's more likely to happen.

TYPE 4 Engine 1800 twin Dellorto DRLA 40

I had a good go at balancing and setting the mixtures on the carbs last year and plan on doing that again when time allows, but am unsure if rich / lean or unbalanced condition would cause this.....help!
Have the carbs ever been jetted for your motor? or did you stick them on and it ran so you used them?

putting an O2 sensor on it and logging your air/fuel mixture would tell you if you are rich or lean in all areas or the rpm range and engine loads. I had a buddy that set his up and we put the LM2 on it to see how close he was, he was running at 10 AFR and thought it was good, when it eventually got jetted to the 12.5-13 range it was like a different motor ,
 
I had two coils fail on me within a year, one left me stranded on the M5, the other saved its demise until it was safely tucked up in the garage. The latest one has lasted a few years and I keep a spare in the van too. All were Bosch. The symptoms is a misfire and it gets worse
 
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