Technical Uno FIRE 999cc Startup and running problems

[AliBarnett]

Hi,

I'm having trouble with my engine. Its the standard Uno FIRE 999cc with bosch mono-jetronic fuel injection system.
Problem first comes with startup when done for the first time, at first it sounds like it fire normally, but then just goes straight to not firing properly and just being ticked over by the starter motor, this goes on until eventually it builds up enough to run on its own very slowly and builds up to a normal idle. Alternatively, if the accelerator is depressed during this it will start up properly, but then higher than idle revs must be maintain to keep the engine running. When revved up there is an obvious misfire/backfire in one or two of the cylinders, not sure which yet.
The engine runs fine when higher revs are maintained, and idles and runs fine when warmed up, also there is no loss of power.
Sound like its not getting enough fuel when cold or too much air, so i have tried the obvious and the not so obvious, heres a list of things that have been checked and changed:
Fuel tank
Fuel pump
throttle housing including most sensors
coolant temperature sensor
lambda/oxygen sensor
distributer + distributer ECU
spark plugs
thermostat
ignition ECU
coil
all the electronics have been diagnostically checked as well and show no problems.
Timing has been checked and is correct,
Although the vacuum advance is broken the pipe has been plugged to stop extra air getting in to the system.
The head gasket was renewed not long ago and there is no sign it has gone again.

I have one idea left and was hoping someone else had some ideas as to what else could be causing my problem.

Cheers,
Al

 

[Chas Uno]

Timing has been checked and is correct,
Although the vacuum advance is broken the pipe has been plugged to stop extra air getting in to the system.

That could be part of the problem! The timing is set with the vacuum advance pipe disconnected (and plugged), but the settings will change at idle quite dramatically when the vacuum pipe is reconnected. This is supposed to happen, but what this means is that in your case the timing is incorrect at idle because of the non functioning vacuum advance.

Being an SPI there must be some kind of cold start device to adjust the fueling, and it's possible that this is also affected by the vacuum advance being disconnected.

First thing I'd do would be to get the vacuum advance working properly again. Maybe find another distributor to swap over from a scrapyard?

 

[alexGS]

1986Uno45S (Chas) raises a good point and personally I'd rather have that vacuum advance working before trying anything else.

However, to me it also sounds a little like the over-fuelling that Monty Mort refers to in his post about the throttle position switch-plunger on the thread https://www.fiatforum.com/uno-technical/74160-uno-idling-running-problems.html

Good luck with it, and are you another new forum member?
-Alex

 

[AliBarnett]

Although yes the vacuum advance will make a minor difference to the timing, it really doesn't make enough to cause this much problem, this is my third uno with same engine (should probably have learned by now!), but i have the distributers off both old engines and vacuum advances were shot on both, with no running problems.

The cold running/fuel adjustment is done by the ECU which gets its info from a variety of sensors, all of which have been tested, changed and retested, so i don't think it is an electrical/control problem. That includes the throttle switch, not sure what he's going on about in that thread, as far as i'm concerned the fuel injection is fully electronic and has no hybrid with a carb. However, i will have a look just incase. Anyway, if anything its not getting enough fuel, because it starts just fine with a little extra throttle.

I'm thinking more mechanical problems, the guy at my local garage has suggested that the cam loadings may not be correct, so my next task is to check the clearance between the cams and valves, also need to do some compression testing, because the guy also said that the third cylinder was lower than the others reading 120, while the other were 175 (i think, wanna clarify this for myself). If it is need to find out whats causing this, may solve my problem.

I'm thinking more hardcore problems rather than the obvious, as i have already said i've covered the majority of things.

Cheers,

P.S. I'm not new new, but haven't posted anything since about january, busy time being a student.

 

[Morty Mort]

When you changed the distributor, did you change the cap and rotor as well, or did you replace these from the old one? I've had two non-Fiat distributor caps fail on the Uno, causing backfire, and an ignition of an uncompressed fuel-mixture. It run fine (but not very fast, and an incredible loss of torque) on three cylinders though, as the distributor delivered current to two cylinders at the same time. I found this fault by removing one HT lead by another until the engine suddenly went fine on 3 cylinders.

M.

 

[Morty Mort]

I'm thinking more mechanical problems, the guy at my local garage has suggested that the cam loadings may not be correct, so my next task is to check the clearance between the cams and valves, also need to do some compression testing, because the guy also said that the third cylinder was lower than the others reading 120, while the other were 175 (i think, wanna clarify this for myself). If it is need to find out whats causing this, may solve my problem.

Hei.

Some thing like this has also happened one time, when the head gasket blew for no particular reason. The car was idling, when I was picking up my wife and kid for a doctors appointment at the local hospital. The car decided to die there and then - propably it thought it was a great place to become ill.

The visual and audible symptoms actually was similiar to the distributor cap fault, except when reading the cylinder compression. Low compression on two cylinders and high on two - the gasket had blown between the two with low compression.

Luckily it was a straight forward job to change it... without having any engine knowledge.

But as suggested before in my previous post - remove one HT lead from one spark plug at a time to locate the faulty cylinder / HT lead / cap fault (rotor?).

M.

M.

 

[Chas Uno]

Well, the golden rule of tuning an engine to make it run correctly is to ensure that all parts crucial to the correct running of the engine are working and correctly set.

Otherwise you don't know for sure if one faulty component is actually causing problems elsewhere...

If it were mine, first thing I'd do is replace the vacuum advance diaphragm and set the timing. The vacuum diaphragm isn't that expensive and is quick and easy to replace once you know how. I'd also replace the distributor cap and rotor arm (they're fairly cheap), and if the problem still exists then possibly the HT leads and spark plugs. In effect making sure the ignition system is in fully working condition. After that I'd also do a compression and valve clearance check, though a FIRE engine has to be seriously neglected for substantial wear to occur in these parts.

Only after that would I start looking into sensors and other parts of the engine.

Don't forget that the SPI system IS a hybrid carburetor type assembly, and as such is fairly simple with not a lot to go wrong. However, I've only worked on carb'ed Unos so can't offer any more help.

But again, my advice would be to make the vacuum advance diaphragm work correctly, and also ensure that all vacuum pipes are correctly connected and not leaking. Once that has been eliminated from the equation then other areas can be looked at.

That's my advice, so it's up to you if you wish to follow it

 

[alexGS]

The cold running/fuel adjustment is done by the ECU which gets its info from a variety of sensors, all of which have been tested, changed and retested, so i don't think it is an electrical/control problem. That includes the throttle switch, not sure what he's going on about in that thread, as far as i'm concerned the fuel injection is fully electronic and has no hybrid with a carb. However, i will have a look just incase. Anyway, if anything its not getting enough fuel, because it starts just fine with a little extra throttle.

Hmmm... "he" (meaning Monty Mort, presumably) was referring to the throttle switch as reducing the injector duty cycle for when the engine is idling (or starting). To me, it seems quite relevant. I wonder if your engine actually has too much fuel at idle or when starting, and the 'little extra throttle' is in fact adding extra air to dilute the surplus fuel.

Or, if you still think it has not enough fuel rather than too much, have you checked the fuel system pressure or had it checked? Also the fuel filter seems to be absent from your list of checks/replacements?

The reference to a 'hybrid' is probably because it is a single-point injection system that distributes the mixture in a similar way to how a carburettor does, e.g. with the fuel injected and atomised above a throttle plate.

I'm thinking more mechanical problems, the guy at my local garage has suggested that the cam loadings may not be correct, so my next task is to check the clearance between the cams and valves, also need to do some compression testing, because the guy also said that the third cylinder was lower than the others reading 120, while the other were 175 (i think, wanna clarify this for myself). If it is need to find out whats causing this, may solve my problem.

Not sure what the last sentence means, but you're right about the compressions being a possible contribution. Valve clearances make a little difference as well to the idling smoothness. I haven't heard the term 'cam loadings' before?

I'm thinking more hardcore problems rather than the obvious, as i have already said i've covered the majority of things.

Hardcore!

This is always a dangerous assumption to make. :nono: The fact remains that the most common problems have the simplest of causes. I also agree with Chas in that it's always best to eliminate the obvious before looking for the obscure. Anyway, good luck with finding the problems and let us know how you go?

Cheers,
-Alex

 

[AliBarnett]

Cheers for all the suggestions,

a few things however:

Distributor cap has been changed, and the HT leads and spark plugs have all been checked, all are in working order (sparkies are new and working). Whole ignition system working fine.

The vacuum advance really doesn't make that much of a problem on the SPI.

If the system was getting too much fuel at idle, i would have idle problems more at high temperatures than low, not the case here.

Throttle position switch has been changed and tested, no problem there or with any of the sensors.

Fuel system has all been changed and checked (apart from fuel lines tho plan to check them if no luck elsewhere), fuel filter is a part of the pump, secondary filter has been checked.

I have checked the valve clearances today, and wow they are really bad, had no clearance on inlet valves for cylinders 2 and 4, no clearance on some of the exhaust valves, time to sort them out methinks.

As for the term cam loadings, i assume it refers to how the valves and therefore cams (when in contact) are loaded by a spring, if clearances are too big or too small the loadings on the cams won't be right at the right times.

As for the term hardcore, i was really refering to things that were beyond my ability to put right as i have pretty much done all the obvious things. I wish it was 'simple' but i have run out of 'simple' things to do

Oh and i understand why it keeps being refered to as a hybrid now cheers.

I'm still gonna check the compression when i eventually get a socket that fits the spark plugs (tomorrow), but thats gonna be effected by the valve clearances, so think its time to get it to the garage again and get that sort by a pro, will let you know how it goes, cheers for all the help.

Ali

 

[alexGS]

Sounds good!
Remember to update us so we know for the next time

Thanks,
-Alex

 

[Morty Mort]

The vacuum advance really doesn't make that much of a problem on the SPI.

You can't be more right. You can drive around forever with a broken unit. Doesn't affect anything else than some fuel consumption maybe, which is minimal anyway.

M.

 

[AliBarnett]

Well, i got the vlave clearances sorted, which made it run smoother, but didn't solve the problem, so i changed the secondary fuel filter at the same time as fiddling with the accelerator cable and the push button thing at the side of the throttle housing, did funny things when i mucked with it, but i started the car this morning and it worked first time! Yeah baby!
If it starts happening again, gonna look at that little button thing see what its doing when its cold, but hopefully i won't have a problem, ha who am i kidding!

Cheers for all the input you all gave!

Al

 

[Rob-mint-mk1-uno]

Sounds to me like that thing you pushed is to do with the automatic choke, that would be why it's worse in the mornings when it's coldest.
Try cleaning the carb and all the other chambers on it aswell.
Could be some dirt in there or summit.
Let us know if the problem has gone

 

[AliBarnett]

Still not working properly, but i think i've foundish the culprit. It is to do with the little button, whether its the automatic choke or not i don't know, but its fully electronic, so i doubt its dirt that causing it. What i thinks happening is that the button is fully out when i try to start it, but as i do this, it goes in, which is stops the engine from getting enough fuel. If i push the button further in, then it automatically comes out, increasing the amount of fuel, making it run fine again.

I've attached some photos (sorry their blurred, used my phone!) to try help u understand what i'm going on about, first picture is the setup with the accelerator bushel etc. 2nd is the inside of this thing, and third is how its connected to the outside. Basically something controls the motor which makes the thing with the springy bit on go in and out. That iny outy bit has a potentiometer or something in it i think which goes towards contolling the amount of fuel let through the injector.

Well, now i know the problem, but no idea how to fix it.
Any thoughts are very welcome!

Cheers
Ali

 

[pong07]

hi!

i was browsing the site when i came accross this thread...

i have almost the same problem, but in my case, the engines starts good, but after maybe in use for 30 mins or more, the idling goes down all of a sudden and engines just stops, then you can start it with no problem at all.. then after you start it it would work fine then maybe i'll do that for 2x-3x max, then all would be well...

my dad installed a tchometer for him to be able to adjust the idling easily, sometimes you would see an erractic movement on the idling, this we experience i think when the car heats up..

the engine has alreayd been overhauled, replaced pistons rings and gaskets.. but we can't seem to solve thwe problem...

any suggestions... thanks!!