Mark 1 carburettor

[JohnCB]

My mark 1 fiesta will not start after resting in a garage for 10 years. I have changed plugs and points, there is fuel to the carb and a good spark at the plugs. I have been told the Weber carb as fitted “wears out” ? Is this likely and how can I fix it?

[Marineboy]

If you take a plug out and turn it over, can you smell/see that you're getting petrol to the cylinder?  Obvs use caution if you do that as there is then an air/fuel mix in the enviroment (hopefully) and a spark close by.  If you have comression and ignition, most ICs will run if you squirt Quickstart or petrol down the carb intake just for testing (again use caution).

[DaveT70]

Have you flushed and put in fresh petrol?

Petrol goes off after a while.

The carb will need cleaning

[anon]

It won't wear out if it has not been used.. Take it off and submerge it in clean petrol for a couple of hours to wet it up, remove, clean and replace the jets you can get to then spray carb cleaner into every hole you can find. With the coil disconnected, ensure the pump is pumping fuel and drain off what you can. It will be useless by now. Add a gallon of fresh fuel  and reassemble.

[Marineboy]

I think Anon is bang on.  Just thinking, unless you get the carb to play nicely, when you MOT it the emissions might be a bit horrid.

[JohnCB]

Thanks everybody, I used a 1/4 full gallon can of fresh petrol gravity fed into the carb fuel intake so it’s not the petrol. I’ll try cleaning the carb as Anon suggests.

[anon]

If you put two full pints into the carb with no effect, That is a helluva lot and should have flooded the engine to hydraulic lock! check for a good spark, not at the caps, take the plugs out. If you' ve soaked them they won't work so you need to know.. with a good spark, I would have somebody turn it over as you spray fuel down the air intake with a trigger spray. That should get it firing and help any leaky valves to seal which might be the reason it won't catch.

 

[anon]

Try palm of the hand over the air intake for three revs on the starter to pull a bit of fuel through.

[isetta]

If you have changed points have you reset the ignition timing properly using a lightbulb on a wire from the battery, and looking at timing mark on crankshaft pulley for correct btdc setting. Did you take distributor off engine?  Did you turn engine over whilst distributor off? If so, it’s possible to have the distributor on the wrong stroke so spark is on exhaust stroke instead of compression stroke (as I found on non-starting cortina I once bought). Have you checked air filter is clear in case a rodent has filled it with nuts or made a nest in it etc. Yes these things do happen

[isetta]

As far as I recall mk1 had a good simple carb with not much to go wrong, but did any mk1 cars, later ones, have that horrible vv type carb with the rubber diaphragm in it? Like my 1984 mk2 had. 

[JohnCB]

No isetta, I didn’t take the distributor off, just the cap to replace the points and then reset them with a 12v bulb. I’ll have another go at it after the weekend. With fuel, air and spark you’ll think it would go!! I’ll also try spraying fuel into carb air intake. And yes, the air filter is clean. Will this engine start/run without the air filter? It’s easier to manage without it until I get it to run and then replace it.

[anon]

Yes, it will and it is far easier to get it started without . You might have sticking valves. Fuel, a correctly timed spark and cranking speed you already have but you also need compression. If an exhaust valve had stuck open, the cylinder would have no compression and it would also have no suction to pull fuel in so the plug would be dry.

I would check the spark at the plugs with them out of the engine, confirm the firing order, check to see if they are wet or carrying soot as evidence of firing, then if good, replace. 

I would then check timing again and ensure the vacuum advance pipe if fitted was good and connected at both ends.

If I could not get a good pull on my hand over the carb, I would check the valve clearances.

[Marineboy]

9 hours ago, anon said:

If an exhaust valve had stuck open

Everything that anon says, but without a new set of plugs, I'd be tempted to clean them with a wire brush and gap them first.  Zorst valve stuck? Could be, but how unlucky would you be for all four pots not to fire or at least try to.  It would pay to get a compression tester just to exclude comp as an issue as testers can be cheap.  This would show any issue that's compression (or lack of it) related.  Weird s*** can happen even when a car is parked up.  I've had a couple of front springs break overnight and an RD250 that had the crank counterbalance weight literally fall out while parked overnight, let alone for 10 years.

[JohnCB]

I appreciate all your comments. I have a compression tester on order and I’ll pass on what I find when I do the test and let you know what happens next.

[isetta]

Compression. I can’t remember how deep the spark plug holes are. On some old cars you could press your thumb over the hole and get someone to turn the key. This could give a sense of if there was plenty of compression.      My wife had a 1.1L 1977 mk1 fiesta when I first knew her. It had a problem with stalling and failing to start. I traced this to an intermittent fault with the anti run on valve screwed into side of carb(sometimes also known as antideiselling solenoid). I removed it and blanked it with a short bolt. Car was ok for years after that.  Does yours have that? Does it click open when you turn ignition on? Does it stay energised when starter motor operating (if it closes due to voltage drop caused by demand of starter motor current then that’s a problem)

[isetta]

also, iirc, these cars have a 6 volt ignition coil. the power supply to it has a ballast resistor in it somewhere to step the voltage down from 12 to 6 volt.

You might say why would they do that. Well the reason is due to voltage drop when operating starter motor as starter motor uses tons of power and causing weaker spark.

When you operate the starter motor a connection on the starter relay / solenoid causes power of 12 volts to go to the coil bypassing the ballast resistor, so it's over supplying the coil with extra voltage to compensate for the voltage drop whilst operating the starter motor.  This extra power cuts off when you release the key and starter motor not operating, otherwise coil would burn out due to overvoltage for too long a period.  (if the car had a 12 volt coil then there would be no way you could overvoltage it to help starting)

Does yours have an old style inertia starter or a newer style pre-engaged starter.   Inertia starter only has one wire to it, a thick cable like the ones on the battery.  If inertia starter then the relay/solenoid will be on the wall of the engine bay somewhere - follow thick live battery cable to it. The relay/solenoid should have two thin wires, one from the ignition switch and the other for providing power to bypass the ballast resistor to coil.    If you have pre-engaged starter motor then these two thin wires will be on the solenoid forming part of the starter motor.  iirc correctly these cars did have problem with corrosion of connectors on pre-engaged starters as they are at front of engine and there is no undertray so they get full exposure to the weather .  Also the loom was on the car body with wires reaching across to starter motor and the rocking of the engine on the rubber mounts sometimes caused the connectors to work their way off. (they pushed on). 

Hope some of this might help eg. it would be brilliant if you just found it was a bad connection on the anti run on valve and cleaned that up and the car sprung into life. 

this age of car is my era when i was doing a lot of work on old 70s cars in the 80s. Cars are too complicated now (but I admit that modern cars can do tons more miles without maintenance and use tons less fuel, and are quieter and smoother, but when they go wrong it can be a nightmare). 

 

 

 

[isetta]

if you were close by I'd come and have a look and see if i could help just for something to do and bring back memories.

[isetta]

if anyone is wondering what an anti run on valve is - in my experience not many car models had them - on some cars when you turned the ignition off the engine would run on very roughly for a couple of seconds. Even though there was no spark at the plug as the igntion system was off, hot glowing carbon around the combustion chamber (on the underside of head and on top of pistons) could ignite the fuel/air mixture to keep the engine running for a few seconds, very roughly.  The anti run valve open and closed a passage in the carb. with ignition off, the electric valve blocked off a passageway in the carb so it did not supply fuel so car could not run on due to hot glowing carbon. I don't know of all fiestas had it, or if ford had to fit it to this model as maybe it was particularly prone to running on. 

[Marineboy]

17 hours ago, isetta said:

thumb over the hole

I was going to suggest this but thought the advice might be a bit risky, however now you’ve said it, maybe not.  I did it on a 2 stroke once, slowly, out of interest, but that’s my problem.  Having said that, I’d rather do it on the compression stroke in case I was sucked in like a genie into a bottle 🤣  I used to have the MK 1, 950, beige with a blue stripe.  My dad had it before me and I recall that he had issues with the anti-run-on valve, so I think it was a thing with these and worth checking out, as you say.  Interesting what you say about the ballast resistor and the 12v/6v stuff.  I knew of their existence but thanks for explaining the ins and outs, you're an education man.  I never had an issue with it so didn’t cross it’s path.  It would be great to know what’s up with John’s car as it’s not a complicated one and it’s odd that not so much as a splutter has come out of it so far.   PS, read your bit about the Allegro 😁