Engine Running Woes

[NickJ]

Got the camper MOT'ed week before BusTypes (been off the road for 12 months) but hadn't been able to give it a decent run before, runs ok when on the choke but as it warms up it starts not to run as well. When going along at a steady 50-55 no problem but as it slows down and ease off the accelerator then put my foot down its as if it wants to cut out if I pump the pedal it seems to cough and then catches, but if going very slowly unless keeping over 2k revs it will stall.
Coming home from the show nearly home and stalled at some traffic lights in the middle of town, front of the queue, 2 cycles of the lights before I could get it to start I was popular :lol:
It is a stock 1600, stock carb, vacuum dizzy, carb has had a refurb using one of the kits available and was able to set it to idle ok. replaced coil,points, condenser,cap, leads & rotor.
Any ideas please :?:

 

[easy]

Could be some sort of air leak in the carb somewhere or maybe the fuel pump is on its way out? how old is the fuel pump? 8)

 

[NickJ]

It has got an electric pump fitted, that was on it when I bought the van doesn't look too old though, it does seem to be working I can hear it clicking on and off.

 

[easy]

hmmm that rules that out then, must be some sort of air leak when you put your foot down, something opens up to much :?:

 

[NickJ]

I was wondering if it could be a problem with the dizzy :?:

 

[Araon]

Hmmm is the auto choke deffinately set up and opening fully?

What are your plugs looking like?

and yes it could well be the dizzy have a look at the vac can is it pulling ok

Where you taking the vac from

 

[NickJ]

I'll have a look after work tomorrow and post an update cheers so far

 

[pete nice]

Could be just a blocked idle jet. Start with the easy stuff. Check the fuel cut of valve is working on the carb too.

If they are fine, check the points gap, then start looking for air leaks. It's not a bad idea to set the valve clearances before you start any fault finding work. Go through everything in a logical order.

 

[NickJ]

Cheers, not really had a proper look yet but I did set the valve clearences on Sunday so I have got to a starting point

 

[noddy]

As pete said check the fuel cut off valve on the carb, Ive had two problems with mine that cause a similar problem, First carb I had some one had over tighten the cut off valve and stripped the tread so it kept working loose and causing the engine to run badly at low revs and made it hard to get started.
The second problem I had that cause a similar affect was a loose electrical connection at the coil causing the fuel cut off solenoid to open and close intermittently.

 

[Jimbly]

I don't know if it's any help but I gather (and please, someone correct me if I'm wrong) that the throttle butterfly shaft bushes wear and leak air in. There's a guy on eBay selling replacement bushes. Also, could it be the accel pump diaphragm thingie split?

 

[Hilly_70]

... if you check and need some carb spindle bush's let us know as i have some spare and you can have em for cost ..

Hilly

 

[NickJ]

Thanks for all the info and possible causes, this is where I have got to so far,
reset valve clearances, checked plugs-clean light brown colour, changed dizzy for 009 with new points,
started up ok, while warming up would rev fine using the throttle lever on carb. but when it had warmed up and the choke was off it would idle fine but if the throttle was opened it would try to stall if I closed the throttle it would idle ok again. :x could it be the main jet blocked ? ran out of time last night as it was getting dark and didn't think the neighbours would appreciate me reving up the van all evening.

 

[Araon]

any moisture gathering at the base below spindle or at worst case any visable bubbling?

try spraying something like wd40 around the spindle see what happens at idle then when you open the throttle

 

[noddy]

sounds like the accelerator jet circuit has a blockage.

Take the air filter hose off the carb, open the choke, pump the throttle linkage and see if your getting a squirt of fuel from the small tube with the down pointing jet.
This is supposed to enrich the mixture as you move from tick over to running speed, when the main jet takes over, poor transition from tick over to running speed would indicate it this jet that's the problem.

Another reason the accelerator jet does'nt work correctly is the small ball bearing valve in the float chamber sticking, or you may just need to adjust it to deliver more fuel, this is done on the linkage on the generator side, take the small split pin out and move along one hole on the linkage bar.

Was it ok before you rebuilt the carb?

If you up for a run over I will give you a hand setting it up.

 

[NickJ]

Hi Ian,
I never actually drove it before I worked on the carb :roll: but Dave the PO said that it never liked driving around town so I think it maybe something that has gradually got worse, I had the carb off last night and cleaned the idle jet , from what you have said I don't think it was quirting down that little tube, should petrol come out when the throttle is pumped even with the engine off ? There isn't much of a petrol smell when it is pumped with the engine off.
I'm getting a dab hand at getting the carb off now :lol: so I think Ill have to strip it again.
I don't think my nerves could take the drive over until it's running a bit better too many trafic lights :lol: but I may take you up on that if I can get it somewhere near, cheers mate.

 

[noddy]

Hi Nick

If you have fuel in the float bowl and you pull the throttle arm it should squirt fuel from the small tube (accelerator jet) strait down the carb.

I would get yourself a can of card cleaner and strip the carb again, it is possible to take the jet out of the body and back flush it and the drilling to the jet in the carb body. If you have a compressor blow all the drilling through.

Did you replace all the diaphragms when you rebuilt it?, including the small square accelerator diaphragm (I only ask because it it split this could be adding to your problem)

 

[rev-al]

Crud in the carb is my 2 penneth. I'd strip it down and clean it right out - and put a rebuild kit on it while you're in there - can't hurt and doesn't cost much. (do keep all the old parts you swap if you do the kit tho - just in case.)

 

[NickJ]

I did replace the pump diaphram, but as this was the first time I'd stripped a carb I was a bit wary of doing something wrong and bu@@ering it up, so only swapped over new for old and cleaned what I could see. So as it looks like this is the problem I'll get the carb off tomorrow and try to give it a thorough clean.
Thanks again for the advice. 8)

 

[noddy]

Nick

When you take the pump diaphragm out again you should see a small drilling in the casting that goes to the float bowl and has the small ball bearing valve, this can get stuck give it a good blast with carb cleaner from both sides float bowl and diaphragm side.

I would refill the float bowl and pump the throttle linkage to check its squirting fuel before you refit.

Just a point to remember carbs can be a bitch to clean. One thing I have done in the past to loosen up stubborn varnish is, put the carb part in a zip lock plastic bag spray **** loads of carb cleaner into the bag, zip bag closed and leave overnight.

Another couple of areas that I missed the first couple of time I cleaned a carb are, behind the edge of throttal butterfly when it closed there are some small drillings, and one last thing make sure the gasket between the top and bottom half's doesn't cover any of the holes.

Good luck, if you can get it sorted send me the carb, and I will get it sonically cleaned at work.