2.25 hesitation from idle

[series3]

Hello everyone,

As the title suggests, my 2.25 has a noticable hesitation from idle. If I roughly plant my foot down from idle the motor will either conk out or almost conk out. I think the car may be a little down one power, however I cannot really confirm this.

As long as I am smooth and slow with acceleration, the mid and top range are fine. I have found myself riding the clutch on hills to get it going when cold.

I have checked the idle, mixture, tappets, points gap, sprayed wd40 looking for leaks but nothing has eliminated the problem. Tappets helped a little, though. I also tried to backfire the carb by swapping over leads, but it didn't help.

Its a newish 2.25 with a Zenith, diesel pistons, extractors and a 2.25 inch exhaust. Would the new exhaust system require the carb to be re-jetted or the timing to be advanced/retarded? Or is it something like a warped top cover?

ps. I just wound in my mixture screw and the car slowed down to a stop. Warped top cover eliminated?

Thanks,

Sam

[bee utey]

Check for operation of the accelerator pump. Lift the air intake with the engine off, operate throttle and look for a jet of fuel squirting down the throat. You may have too much or too little.

[Rainer]

Hi,

¿ Have you checked the distributor timing ? If you also have vacuum advance that should work correctly too.

I remember when I got mine 8 years ago just by rotating the distributor it improved a lot.

regards Rainer

[JDNSW]

Guessing, partly blocked idling jet, or possibly incorrect assembly of the link to the accelerator pump. Not the usual symptom, but make sure the heads of the screws holding the emulsion block to the top cover are not bottoming on the body of the carby. Another possibility is that a faulty thermostat is preventing it from warming up properly.

John

[cheerychops]

mine was doing that and it was partial block in hard fuel line in the carby just before the needle float

[series3]

thanks everyone, ill start investigating.

I found this article which helped me getting my bearing on the 36IV, it may help others.

http://www.legionlandrover.com/manuales/zenith-carburetter.pdf

[Walrover]

Recently had similar issues with my 2A Zenith. Recommend you grab the throttle spindle (the bottom one) and give it a yank and see if it moves as mine had worn out the main body of the carby and was sucking in air causing the running problems. A new carby body fixed the problem.

Glen

[isuzutoo-eh]

I heard that retarded timing could cause just such a problem ;)
BobsLandies' timing light shone the way :)

[series3]

Thanks Mark, and Bobslandies for borrowing the timing light. I checked the operation of the accelerator pump, and everything was in order. So I had a look at the timing.

The timing on my car turned out to be super-retarded, something like 10 degrees i think. With that fixed, the flat spot was gone. All that power i thought was missing has returned too.

Isn't it great when you get a nice, easy fix?

[bee utey]

If you are still running points you can do static timing very easily. Just rotate the engine forwards so that the points open (producing a spark with the ignition on, cap off!) as you pass the timing position. You should check points adjustment and timing every 1500 miles at least.

[peterg1001]

Thanks Mark, and Bobslandies for borrowing the timing light. I checked the operation of the accelerator pump, and everything was in order. So I had a look at the timing.

The timing on my car turned out to be super-retarded, something like 10 degrees i think. With that fixed, the flat spot was gone. All that power i thought was missing has returned too.

What did you set the timing to? I've got exactly the same symptoms, with brand new everything in the fuel and ignition line. Timing on mine is set to 6 deg BTDC.

Thanks, Peter

[series3]

Hi Peter.

6 or 7 BTDC sounds about right, I cannot remember exactly though I am sorry. I took it to the recommended setting for 91 octane, and just advanced it a tad more. Maybe Mark (isuzutoo-eh) will remember better.

My flat spot is still there (just); it has taught me to have a nice, slow and steady right foot. I drove on and off a fairly choppy Samurai beach today and didn't have any hindrances. At high revs, such a problem does not exist.

My problem began immediately after the new exhaust system was fitted, and have been told by a few people now (not idiots) that a carb will need rejetting if a more efficient exhaust system is installed. I am wagering on that, but haven't found someone around here I want to take it to yet. Other than that, it's probably keeping my fuel consumption in check.

Sam

[jasonk]

Hi Sam,

When I fitted extractors to the 2.25P in my 2A, I also experienced the engine hesitation on acceleration. Mine was mostly while the engine was cold. I had to run the engine with the choke out for much longer than when I had the standard exhaust manifold.

This was because the inlet manifold was no longer getting heated by the exhaust gases as it did with the standard exhaust manifold. I had an aluminium plate made up with hose fittings attached. It bolts to the underside of the inlet manifold. It is plumbed into the heater hose fittings on the engine to allow coolant to circulate where the exhaust gases used to. (I don't have a heater plumbed into my 2A.) It solved my problem. I have had this fitted for 5 years now.

I'm not sure that this is the same issue as you have, but thought I'd share my experience.

Best of luck,
Jason

[Aaron IIA]

I have seen ice forming on the outside of a 2.25P carburetor when extracters have been fitted. You need some method of getting heat into the inlet manifold.

Aaron.

[peterg1001]

6 or 7 BTDC sounds about right, I cannot remember exactly though I am sorry. I took it to the recommended setting for 91 octane, and just advanced it a tad more. Maybe Mark (isuzutoo-eh) will remember better.

I retarded the ignition a bit, at least I think I did, I turned the distributor a bit anti-clockwise, and it sounds a bit better now.

I haven't had it on the road (I did it yesterday afternoon), but I'll give it a go next weekend and see how it pulls.

I can't see what else it might be, everything else is new and the advance is about the only thing left to adjust.

Peter

[jakeslouw]

Idle circuit is too lean.

Go up a size on the idle jet, or enrich the idle circuit mixture.

I have no idea how the Zenith works, I'm just addressing the symptoms.

Once you install a less restrictive exhaust, you MUST re-jet and set your mixtures as you WILL be running much leaner across the rev range.

I can see none of you owned & played with 4-stroke single-cylinder bikes in your youth.... ;)

[series3]

I have seen ice forming on the outside of a 2.25P carburetor when extracters have been fitted. You need some method of getting heat into the inlet manifold.

Aaron.

Where were you when you saw it? I don't think I should have any issues with a cold inlet at my location, but time will tell...

[Aaron IIA]

Pine forest, Adelaide Hills, June long weekend, 2006. I can't remember if it was the Sunday or Monday, but it would have been between 0900 and 1200. Ambient temperature would have probable been about 10degC, +/- 4degC.

Aaron.

[isuzutoo-eh]

Going by memory Sam's spot on with the timing-closer to 7 degrees than 6. We did adjust the carby to clear the exhaust as well. We didn't mess around much since it was already a huge improvement.

[peterg1001]

I retarded the ignition a bit, at least I think I did, I turned the distributor a bit anti-clockwise, and it sounds a bit better now.

I haven't had it on the road (I did it yesterday afternoon), but I'll give it a go next weekend and see how it pulls.

I can't see what else it might be, everything else is new and the advance is about the only thing left to adjust.

Peter

It turned out to be crap, chugging like a deficient steam engine.

I fixed it today - I pulled off the brand new Zenith 36IV, and put the ex-Holden Stromberg BXOV back on. Went around the block like a beauty. Next weekend I'll try Lapstone Hill, and see how she goes.

Peter