Where to start if your CF is misbehaving and you're not sure where the problem may be.

Re: Engine bogging down during breaking

Post by Ties » Subscribing Member » Fri Mar 30, 2018 11:38 am
Joined: Tue May 27, 2014 12:17 pm
Posts: 53
So today I was trying to get the carb off to change the gaskets anc check the black plastic thingy, but I cant seem to get it off. I undid both the nuts from the studs sticking trough the gaskets and the plastic thingy in to the carb, and I removed the big air intake hose from the top, and while I can wiggle it around a little bit, it seems to be stuck on the right stud (from inside the cab looking forward). Is there some other retaining mechanism I missed? or can I just get the hammer out? I didn't want to bash it to hard yet in case I missed something

Re: Engine bogging down during breaking

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Post by Phil Bradshaw » Club admin » Fri Mar 30, 2018 12:06 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3791
A hammer is a bit drastic: the alloy of the carburettor isn't that tough.

Check for flange deformation around the stud holes, usually due to over-tightening of the nuts, the right hand one being the easier of the two to swing a spanner on and mangle the flange in the process.

If there is nothing else in the way (e.g. a thin washer that's been missed because it has crushed into the flange) then carry on wobbling until the right hand stud lets go.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Engine bogging down during breaking

Post by Ties » Subscribing Member » Fri Mar 30, 2018 2:35 pm
Joined: Tue May 27, 2014 12:17 pm
Posts: 53
Phil Bradshaw wrote:Check for flange deformation around the stud holes, usually due to over-tightening of the nuts, the right hand one being the easier of the two to swing a spanner on and mangle the flange in the process.
Turns out it was quite bad in my case, so bad in fact I had to remove the entire stud from the manifold with a wrench arround the exposed threads. The nuts had been overtightened so much that the top of the flange had been squished right in to the hole and formed right in to the narrower part of the thread on the stud, so that the rest of the stud simply wouldn't fit through the hole anymore.

But after removing the stud from the inlet manifold and filing the hole back to it's original size, the rest all went smoothly for once!

The black plastic pice was fine, had no cracks or anything, but the two gaskets looked very old and worn, they where almost entirely solid. So after scraping them of with a knife I made up two new gaskets from some gasket paper and installed them with a bit of grease on both sides (I didn't have any proper gasket stuff, so hopefully the regular multi-purpose grease will hold up) and it seems to have worked!!

I'm still a bit scared to declare it an all-out victory, since the idle is still quite rough and speeds up and slows down a bit, but it's no longer stalling every time I hit the brakes!

Going to drive it for about a week to see what happens before I call it a full succes, but so far its looking very promising! :thumb: :thumb:

Thanks once again for all the help!! :thumb:

Re: Engine bogging down during breaking

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Post by Phil Bradshaw » Club admin » Fri Mar 30, 2018 3:46 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3791
With a flange hole distorted that much by over-tightening it's a safe bet that the gasket face of the flange isn't flat any more.

A straight edge across the flange face will indicate extent of any bow or other distortion between the stud holes.

Quick fix is to add another gasket between the flange and plastic insulator.

Grease or non-setting sealant (e.g. Hylomar Blue) is ok for carburettor gaskets; setting sealant is better in terms of delaying inevitable leakage when the nuts work loose again (when the gasket/s likely will fail first) but then cleaning off gasket and sealant residue can be a pain.

To true up a face with file and abrasive cloth/paper without dismantling the carburettor, first seal up the throttle spindle with grease, inside the venturi and outside at both ends, to prevent grit and dust from entering the spindle bores and seals.

Finish the face on 150 grit or finer abrasive cloth or paper laid on a clean, flat surface (e.g. sheet of glass). Finished surface does not have to be polished, just flat and smooth enough to seal all round the venturi opening.

Once the sealing grease is cleaned off (scrape/wipe off contaminated layer before washing off residue) check for free movement of the throttle spindle over its full arc of travel - best done with throttle return spring removed and and choke and accelerator pump link rods disconnected.

If the spindle is sticky then use a spray can of carburettor cleaner or WD40 to flush out any residual grit until the spindle moves freely.

Lubricate spindle with engine oil before refitting the carburettor.

Once you're certain that the flange is not leaking adjust the idling volume control and speed screws when the engine is thoroughly warmed up to see whether this will cure hunting at idling speed.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Engine bogging down during breaking

Post by Ties » Subscribing Member » Mon Oct 15, 2018 1:11 pm
Joined: Tue May 27, 2014 12:17 pm
Posts: 53
Time for long-overdue update.

I think I'v managed to fix the vacuum leak at the carb, after filing back the flange and using lots of gasket sealant the engine seems to be ok during breaking for now.

I still noticed the engine idel speed was quite inconsistent for about 20 seconds after taking my foot off the throttle, sometimes it would idle a lot faster than other times, but after a while it would setteled down. This turned out to be a simple fix, the return spring on the throttle wassnt returning the throttle to idle tully, so I just turned the spring 1/3 of a turn extra and this seems to have fixed that.

This was al based on short test drives. The main problem however was discovered today during the first longer drive.

I'd noticed the engine was still running a little rough even after fixing the leak, but didn't think to much of it. But while driving the van today to run some errands, it slowly started running worse and worse, then started backfiring and loosing power. I managed to limp it to a parking spot in 2nd gear, and took the bus for the rest of the way.

On the way back I figured I would try to see if I could get the van running again and limp her home. I realised that the one thing that changed since the last longer drive was the vacuum leak. So I unplugged the vacuum advance hose from the carb to the distributer and just left it dangling lose in the engine bay, creating a new vacuum leak. This seemed to do the trick, and she ran perfectly all the way home!

So my current working theory is that someone has previously messed with the ignition timing to compensate for the lack of vacuum at the distributer, and me fixing the vacuum leak has now messed up the bodged timing.

I'v ordered a timing light online that should hopefully be here in the next few days, will post another update when it arrives.

Re: Engine bogging down during breaking

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Post by Phil Bradshaw » Club admin » Mon Oct 15, 2018 1:44 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3791
Another possibility is broken distributor base plate earth lead. This is the wire with a fork terminal that goes under the condenser securing screw.

Simple test: unhook wire from under screw then tug.

Not so simple: distributor has to be removed and dismantled to replace a broken wire.

Delco D300 Howto is here. :thumb:
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  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Engine bogging down during breaking

Post by Ties » Subscribing Member » Sun Oct 21, 2018 4:16 pm
Joined: Tue May 27, 2014 12:17 pm
Posts: 53
Phil Bradshaw wrote:
Mon Oct 15, 2018 1:44 pm
Another possibility is broken distributor base plate earth lead. This is the wire with a fork terminal that goes under the condenser securing screw.

Simple test: unhook wire from under screw then tug.
Took a look under the distributer cap and the black wire seemed fine

The timing light also arrived and I hooked it up today, and looks like the ignition is set to about 18º before TDC at idle rather then 9º with the vacuum hose disconnected. So seems like its just a mater of putting it back at 9º before TDC and hopefully that's the problem sorted.

Only one stupid question, how do I actually adjust the ignition timing on a CF...?

Re: Engine bogging down during breaking

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Post by VDUB384 » Club admin » Sun Oct 21, 2018 6:25 pm
Joined: Wed Sep 12, 2012 9:01 am
Posts: 1383
Slacken the three bolts at the base of the distributor and you may have enough movement to correct your timing by turning get it slightly if you can’t get enough that way you will have to remove the distributor and move it round a spline. If you have to take the dizzy out make sure you line the timing marks up first before you start.
Dave
Whilst good maintainece is the best prevention"If its not broken don't fix it."
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