hesitation blues

[edoh]

driving along - all well - every now and again (4 or 5 minutes - doesnt seem affected by which gear or flat or incline or speed) a momentary hesitation -then engine instantly picks up - and off we go again until the next time -
changed fuel filter
idle stabilisation unit
rotor arm spark plugs and leads
idle speed and mixture screw set -
aa man checked timing -
running out of ideas!

any thoughts people?

keep thinking its a carb fault - but not sure what! tried some carb cleaner and cloth over top of carb whilst revving like a good un - still no joy -

any thoughts or ideas much appreciated -

otherwise - van running really well -

(why is there always an 'otherwise'?!? )

[kevtherev]

clean the carb properly
clean carb filter
check pump delivery.

[edoh]

as always -
thanks for the quick reply and informative comment kev -
if you've got time/patience - could you expand a little?

carb filter - is the little filter situated where the fuel hose goes from the fuel pump to the carb -
take out with a small screw extractror and clean -

clean carb properly - is that a take carb off - bench - and dismantle - soaking each section in carb cleaner and blowing compressed air through all jets jobby?

any hints on how to check pump delivery?

thanks in advance -

edoh

[CovKid]

Assuming its a 1.9, fetch the little cone filter out of the brass carb fuel inlet pipe - its tucked right inside and needs a self-tapper or wood screw to grip it and pull it out. Make sure its clean. Sounds as though carb float level isn't being sustained and if this filter is clogged it'll starve you of fuel at reasonable or full throttle. Don't neglect your air filter either. I recently struggled to isolate a poor idling due to a totally clogged air filter - often overlooked.

[Red Westie]

Ignition misfires are quite pronounced on/off afairs whilst carburretor/fuel system faults tend to be more subtle (like you describe).
I agree with the small gauze filter (blow out)
Don't try to clean the fuel filter! just replace it (they are very cheap) make sure it is fitted the correct way round signified by the arrow.
Air filter needs to be clean
Heres where it gets complicated: fuel line blockage? water in the carb? internally collapsed fuel lines? failing fuel pump? vacuum advance unit failed? air leak on the inlet side? wrong petrol cap fitted? ignition switch fault?
All the above could give similar symptoms.

Martin

[edoh]

thanks all -
a comprehensive list to be working through!

your thoughts and responses are genunely appreciated -

will update as i work through the various items -

many thanks again -

edoh

[edoh]

working through the list like a good un -
- still a slight hesitation -
have done dist cap - rotor arm - spark plugs - plug leads -
replaced coil and idle stabilisation unit with good ones -
cleaned out carb w cleaner and compressed air - (though not taken off and dismantled) -
changed air cleaner - changed fuel hose from fuel tank to filter and from pump to carb and carb back to return pipe -
new fuel filter - fuel pump seems to be running pumping fine - no water in system - little cone filter in carb fuel inlet taken out and cleaned -
no leaks in hoses or pipes -
van starting brill - on the button - and running fine -
tho still w a slight hesitation ?-

or am i imagining a hesitation now?!?! ....


(95mb engine running video too big to post) -


next on list -
double checking ignition timing with a strobe (with a matey ) rechecking idle and fuel mixture screws (again) - and putting in a new vacuuum advance on side of distributor -

these are all jobs that will need to be done somewhere down the line - and will hopefully keep the van running over the years -

pause.......

late E D I T -

having taken the van for a 10 mile drive -
van sounding really fine - and driving amazingly well -
on rechecking fuel lines - notice that the fuel filter is already starting to turn black and look clogged up! after a short run!


is this a crap in the 20 year old fuel tank syndrome thing? to which the only long term solution is a new fuel tank?
maybe what might have been clogging up carb/fuel lines? .........mmnnn.............

keep driving and keep changing fuel filter every few days?

as ever - your thoughts welcome
not sure what i'd do with myself if the repairs/improvements list ever ended!

may have to go deeper into carb (haynes carb book covering 2e pierburgs on top of shopping list)! -
jk out of fuel tanks til october - though they have fuel sender units and filler necks/etc -in stock gsf seemingly have fuel tanks in stock -

[Aidan]

ignition switch

too many keys on the bunch

try with just one key

[edoh]

will do

not sure why - but worth a try -

currently 10 or 11 work and play keys swinging round the corners with me and van!
thanks for the tip!

[edoh]

would the fuel filter clogging up so quickly - indicate an early renewal for the fuel tank?

[Red Westie]

Dropping the fuel tank isn't as bad as it might seem, it will give you the oportunity to swill all the crap out of it and evaluate it's condition. If you are lucky you may get away with a coat of hammerite.
As for the key syndrome...VW's around this era practically all used the same ignition switch. They are a known weakness and one of the things that can exagerate symptoms is the weight of a bunch of keys pulling on the switch whilst driving.
Again no big shakes...as a replacement costs under a tenner from GSF.

Martin

[edoh]

thanks so much for your informative and helpful replies -