1988 DG T25 - Intermittant but bloody annoying problem

[ktm200hove]

My lovely T25 has this horrible problem which refuses to go away. It goes something like this.......

1) van starts and runs ok when on auto choke
2) once off choke it commonly (but not all the time) runs like a pig, with either a) no idle or b) no midrange or both. When you press the gas pedal down say to 1/3 to 1/2 the revs go up and down madly, however, when I press the gas pedal beyond a 1/2 it seems to clear itself, but revs like a madman.
3) I'm sure there is a corresponding lack of power when the above happens.....

when this problem occurs, I usually pull to roadside, open the carb and spray copious amounts of carb cleaner into the jets - that seems to sort it, but the problem always seems to come back, either straight away or a few days later.

I have got the tank cleaned and have added a second petrol filter, but these have no solved it. My only other ideas are that the petrol pipes have deteriorated badly and are contaminated the carb or could this be fuel supply problems with the petrol pump struggling to pump fuel through the various filters.

Anybody got any ideas??????????????

[Slackbladder]

sounds just like mine!!

[VWCamperfan]

Sounds like an air leak somewhere between the carb and the engine. Check all seals and joins etc between the two. If you can't find a problem then start engine, run until it starts to falter then spray wd40 on any seals or joins between the carb and engine. Is there is an air leak the engine will speed up and run smoother.
There should only be fuel filter by the way, underneath the van just outside the fuel tank. Any extra filters can cause problems.
I don't think its a fuel starvation problem however as it doesnt do it at high rpm, just low to medium and this points towards a blocked or partly blocked idle jet. What may be a quick fix if to run engine without air inlet pipe from filter attatched to carb, rev up engine to a highish rpm then place hand firmly over top of carb while keeping throttle open. This will create a vaccuum in the carb and may suck a blockage out with any luck. If not then it may be a carb strip down and clean the jets jobbie.

[toomanytoys]

Has the carb been apart and cleaned etc.. spryaing stuff in the top wont clean out the float bowl and jets..

[David Last]

Don't know if you've sorted this problem yet, I've only just spotted the post.
Similar problems on my 1990 T25 turned out to be a rotten HT feed cable connection inside the distributor cap. Ability to deliver HT current variable.
Cheers
Dave

[Mocki]

adding a seconf fuel filter will only make things worse, the pump is only designed to pull the fuel trhough one filter, next to the tank, adding another one will strain the pump diaphram, and cause you problems later in life........ so to speak....... and filtering petrol twice wont solve anything, unless the first filter isnt a filter anymore.......

[HarryMann]

If the mid-range jest are blocked then they are blocked, or intermittently blocked, carb cleaner is not a substitute for cleaning the carb out... not magic , it just removes varnish!

Either manually disassemble and clean but don't go rooting about through the jeys with anything abrasive!

Or try this: Air filter off, engine running, leather glove on hand (Or not!), get it just above adle coming onto main jets and as you whack throttle open, choke the whole intake with hand just as it tries to rev up madly.. , remove palm of hand just before it dies. Repeat. Repeat.
Suction will very often drag dirt through jets or upset them, so if it gets better or worse, noticeably, that'll muck in your carb.. if not fully resolved, disassemble and clean thoroughly...
Worked many times for me with fixed jet carbs prone to blocking intermediate jets (main jet usually large enough to pass fine dirt)

[HarryMann]

If the mid-range/intermediate jets are blocked then they are blocked, or intermittently blocked, carb cleaner is not a substitute for cleaning the carb out... not magic, it just removes varnish!

Either manually disassemble and clean but don't go rooting about through the jets with anything abrasive!

Or try this: Air filter off, engine running, leather glove on hand (Or not!), get it just above idle coming onto main jets and as you whack throttle open, choke the whole intake with hand just as it tries to rev up madly, remove palm of hand just before it dies. Repeat. Repeat.
Suction will very often drag dirt through jets or upset them, so if it gets better or worse, noticeably, that'll muck in your carb.. if not fully resolved, disassemble and clean thoroughly...
IF you can't feel a strong suction on your hand then not doing it right... vary throttle/revs at which you block it to cover as wide a range as possible. Don't worry if you stall it a few times, just clear the flooding and try again.
Worked many times for me with fixed jet carbs prone to blocking intermediate jets (main jet usually large enough to pass fine dirt)

[Mocki]

leather glove....... hehehehe........

[HarryMann]

I don't bother, but years ago since I last needed to do this...

[Mr Bean]

leather glove....... hehehehe........

Don't talk to me about gloves!
Her indoors talked me into wearing latex gloves so as to keep my hands clean for my daughters wedding giving away effort. So I am working outside doing my quick change keyless chuck drill trick and the latex gets caught up round the chuck and I finish up with the drill spinning round with one of my fingers winding up like an elastick band untill the plug pulled out. Some days later and after I had masking taped my finger to a lolly stick the swelling went down and now my end finger joint works sideways as well as normal. It doesn't hert so much now but after four weeks I guess I will get an earfull off the medics if I try for a cure.
Damn and blast!
Ken

[HarryMann]

So I am working outside doing my quick change keyless chuck drill trick and the latex gets caught up round the chuck and I finish up with the drill spinning round with one of my fingers winding up like an elastick band untill the plug pulled out.

Hey, done very same thing, but not got too hurt, in fact it's quiet common as I don't learn quickly, old habits and all that...

Ditto masking tape, in fact ditto anything sticky with latex gloves on... I now use a mix of nitrile from Costco (very thin, pretty good and 300 for about £7) and vinyl ones... Latex ones are hard to put on and remove.

Trick, to turn them back from being inside out and to test for splits and tears at same time - just blow them up like a balloon. Helps get them off in sticky weather too, just blow up the cuff

PS Use them by choice myself, transformed working on motors IMHO, just buy good nitrile or vinyl ones that fit well.

[blackiebest]

For sure I agree with David Last. Exact same symptoms in my bus and went through so much carb related diagnostics before I decided to look elsewhere. Two mechanics only made things worse and cost me money before I started to examine everything again, so

Pull off ht leads from plugs, look closely at the contacts which connect to the plugs, if should all look the same. On mine one was a little green so I carefully took off the metal housing and could see a tiny trace of corossion on rubber, hard wired the lead to plug and yahoo problem solved, £26 set of new leads including plugs from JK and am at 100 % again. Really leave your carb alone untill you are sure your problem is there. Bet you a fiver its the leads!

[Mr Bean]

So I am working outside doing my quick

Trick, to turn them back from being inside out and to test for splits and tears at same time - just blow them up like a balloon. Helps get them off in sticky weather too, just blow up the cuff

Nuvver trick:
Someone I know has one hand missing and was chuffed to pieces when I suggested they turn one glove inside out so as to finish up with two same handed gloves. I guess that would work if you only used one hand say foe holding something when painting for instance.
Cheers
Ken

[Mr Bean]

[quote="HarryMann"][quote] Helps get them off in sticky weather too, just blow up the cuff
Her indoors caught me using that technique in the hallway to remove my latex gloves and rushed out bucket in hand as she thought I was chucking up on the carpet! Last time I chucked up was at the Elisebethan Banquet at Hatfield house about thirty years ago. Lovely wenches serving mead from massive pitchers!
Cheers
Ken