Club 80-90 Forums

Hi wondering if anyone can help with this one, i'm sure its been covered before.
My 1990 Caravelle was running perfectly up until Sunday night, when I noticed a misfire and hesitation under load. When I stopped it cut out and although it starts then it will idle only very slowly and lumpy and will cut out if I open the throttle at all.
Eventually I got it going again with much revving and got home.
Since then it starts fine and idles ok but as soon as I go to drive away it will cut out and idle slow again.
Last year I rebuilt the carb with a kit from Brickwerks.
In the last 6 months its had a new fuel pump (Pierburg one) and push rod and I have checked pump delivers a healthy dose of fuel if I pull the pipe off the carb, complete fuel line kit including filter, distributor and cap, coil, leads, ignition module and I've renewed all the vacuum lines. To me it sounded like an air leak, not ignition, but spraying Plusgas round the carb, inlet manifold joins, servo hose etc makes no difference if its idling slow.
Pulling of the vacuum advance line to dizzy makes it worse and vacuum advance unit works fine.
I'm a bit stumped to be honest, any wise words gratefully received as always!
Thanks in advance.

Will

Just had a similar problem.
After renewing vac pipes and testing the choke pull down/vac unit etc, it turned out to be a[slight] air leak from the gasket on the air intake manifold. With the accelerator pressed to lift the revs a quick spray of carb' cleaner on the offside gasket and the engine ran smooth and picked up revs. It wasn't noticeable until I gave it some revs though. Just a thought.
Had plenty of help from other members
https://club8090.co.uk/forum/viewtopic.php?f=37&t=147654" onclick="window.open(this.href);return false;
David

Great thanks haven't tried spraying the plus gas with the revs up a bit, will try tomorrow

Also, how long were you driving it before it started cutting out? If it was after the engine had gotten up to temp it could be the coil failing. Once cooled down it will run fine again until it gets back up to temp. I bought a new non- Bosch one and it failed about a month after purchase.

Take it for a drive locally and if symptoms starts again have a feel of the coil - if it's uncomfortably hot, could need replacing.

In addition have a check of the vac hose from the vacuum advance to carb make sure it's a tight fit. Also lightly 'move' the fuel hose from the pump to the carb whilst ticking over - if there's even the slightest bit of air in there it will cut out. If it does, might need tightening at either end or need replacing (was it ethanol proof fuel pipe you used).

Coil can be easily tested with a multimeter and a spare 30 seconds. There's a write up in the blog section (I think) on Brickwerks. Good luck.

Thanks for the replies.
Yes it seems ok when cold and I had driven about 20 miles when the problem started.
Will check out the coil too and the HT leads as per the Brickwerks blog.

https://www.brickwerks.co.uk/index.php/ ... arch/Coil/" onclick="window.open(this.href);return false;?

drillmaster wrote:Thanks for the replies.
Yes it seems ok when cold and I had driven about 20 miles when the problem started.
Will check out the coil too and the HT leads as per the Brickwerks blog.

Let us know how you get on

Make sure cone filter is not clogged as that will starve engine of fuel at wide throttle openings. It can be found tucked inside brass fuel inlet pipe on carb (needs a self tapper to ease it out).

Update

Cone filter all clear
HT leads ok
Coil (green sticker) resistance primary 1.2ohms secondary 3.6ohms
Choke pull down unit moves on vacuum, but doesn't hold vacuum like vacuum advance on dizzy and the other vacuum unit on the front of the carb do.

Should it?
Haven't run it and check for air leaks ground inlet manifold again yet and weather up here in Scotlandshire a bit wild not conducive to a test run again…
Coil resistance is a bit out of spec, could this be the problem?

Will

Now diagnosed, thanks for all the help as usual.
Air leak at the front of carb at gasket/spacer and choke pull down unit also letting in air, new one ordered.


Will

Don't jump the gun. You've found faults but there may be more......

I'm renowned for my eternal optimism as you can tell!! At least you're on to something.

Bet that's not it. Might affect the idle but doesn't really explain the hesitation under load.
Just a thought, but have you been through any heavy rain/puddles recently? I'm thinking fuel tank breather or filler neck letting in water. If so, try a bottle of Wynn's Dry Fuel. It's done the trick for several customer's vans (after fixing their water ingress, of course!).

Actually come to think of it yes when I drove back (from the airport) that night the rain was torrential, and the problem started after about 20 miles of motorway with lots of spray and surface water.When I parked it up a week earlier it had been running perfect.
I 'd had the tank out a few weeks ago to change the coolant pipes and theres a new filler neck on it - will check if the clamp is secure but now I remember that the breather pipe onto the filler neck was a bit of a loose fit…… also when I came to put on the (petrol) webasto heater then it cut out which it has never done before, and it took two attempts to restart it, so water in the fuel makes sense!
Re the coil its a Bosch green, doesn't get hot, and I have the original also Bosch as a spare, primary resistance on it is also 1.2 ohms, so probably my meter reading a bit high.

drillmaster wrote: Re the coil........ primary resistance on it is also 1.2 ohms, so probably my meter reading a bit high.

Most domestic digital meters are far from accurate when reading Ohms readings that are down into single figures. It's to do with slight extra resistance creeping in from the leads and connections. Try just shorting the meter probes together whilst on the minimum setting. You will likely get a reading of around point three of an Ohm, just subtract that from the reading you get when measuring the coil and you will then be roughly in the right ball park.