type 4 dropping a valve?

[njv]

hello
well it looks like my engine is dropping a valve on the number one cylinder .

2110cc t4 engine and the bus sqr port heads i used checked out just fine looked ok to go till i got the money toghether for bigger valve heads this year.

well idle has gone to pot cleaned my dells and the mixture screw closes the cylinder down completely so fuel is still getting thru.

compression test gave me 11 bar 159psi on 2 3 4 i had 10bar 145 psi on 1 it was set at 9.3-1 so its good .

did the dirty running the engine off with the valve cover removed and the valve on 1 looks to be opening and closing ok rocker gear is a little worn but should be ok! very messy job mind.

need to make a screw in fitting to do a leak down with my compresor after getting it to lets say 50 psi how long would a good cylinder take to get down to 10 psi anybody any good figures for doing leakdown testing?

pushrods are cromoly and have been set cold so they can be just turned between fingers lash hot seems about right .15mm .

still need to check the lifter and check the lifter and cam brand new web 163 matching lifters broke in properly.

oil pressure is superb .

o yea spark be good tryed new plugs anyway just to make sure.

after running at speed static will idle properly for a while then the cylinder dies pulling the plug lead makes no difference spark is still there.

what else can i check before i tear it down and look at the head internals.

sticking valve or dropped seat?

[njv]

hello.
bad hall sender control unit!!!!

you know how rather than let the engine die when you pull a plug lead and conect it to that spare plug on your engine you keep ye oldie revs up a bit . well this is how i was checking for spark at my plugs .

yesterday i let it idle it was just getting dark when i let the thing idle the spark died !!! when i kept it just over 1000 the spark returned.

well i have a 205 dizzy from a vanagon and a long time ago when i owned mk 1 golf gti s i had a similar problem that turned out to be my hall sender in the dizzy .

so off to the local boneyard today got a different hall unit grabbed the control unit and coil too while i was there got three contol units actually .

fitted the control unit first (1 plug 2 screws heatsink paste between it and the ally heatsink)

fired it up and voila solid 950 rpm no drop no diddley movement sounds better too.

i was going to do the hall then the coil then the control unit but i did this first and its rock solid.

and the one thats fitted is from a mk2 golf same part no apart from a letter at the end .

havent got the foggiest what that tiny lttle black box does or why it would cut my spark at idle on only cylinder no1 but its fixed now .

this explains why when i did a wet compression test with a sqirt of oil in each cylinder they all read 11.5 bar.

o well back to trying to break it again.

[Farmer]

Better than tearing it apart (!)
Often the smaller problems are the most difficult to find out.

About a year ago, I was haunted one full afternoon by a new plug that suddenly decided to go south on me. It worked in the morning. Then after lunch when I was supposed to do a trim, it didnt work anymore. Naturally the plugs was one of the last things I cecked, right.

[njv]

hi
yep im happy not tearing it up just yet!!!

ive done about 500 miles on this engine i think the rings are seating nicely now im going to push out a thousand now before i change the oil .

and so long as shes not leaking ive got to be good to it and stick some synth in there.

i am so baffled by this hall ignition control unit thing i just spent a few hours doing some net searching and well it turns out they do go bad quite regular and with all sorts of odd things going on .

by what ive looked at im quite lucky it didnt do the old will start wont start thing on me !!

even though it is an excellent system and gives a good spark i think i may carry a spare hall sender and control unit on any long journeys i undertake.

all that serching led me to thinking about a bit of cdi any nice cheap kits available in europe i wonder.

thanks for looking.