Today after its wintersleep I started my cosworth for the first time in 7 months. It started fine, ran fine at cold idle and I waited untill it ran in closed loop mode.

When ran in closed loop mode I notice a little hassitaton. When giving it some more revs I could hear it began to run on 3 cylinders so I stopped the motor from running.

I then inspected the spark plugs and found number 3 was wet of fuel. Change this spark plug and i ran ok at idle. So I took a short drive through the neighbourhood for about 5 minutes without problems. Than at return at my home it started to smoke badly and again run on 3 cylinders. Right away inspected number 3 and it was wet again!

Clean the spark plug, started it without spark plug and no injection to clear the fuel that was left behind. Than after putting the plug back in it ran ok.

So I took a bit longer run. First minutes all went fine, but after 10 minutes its started to run on 3 cylinders again. Tried to solve it at the hard shoulder but the spark plug on cylinder 3 immediatelly kept being wet after restarting the engine.

So a tow at home it was..

Arriving at home I thought I might just get it started and quickly get on 3 cylinders in my garage. But at that point it started fine so I could get it in without a problem. Left it for 1 minute at idle and also no problem.

So I am very confused where to look for.

I think maybe it could be a bad distributor cap or an injector that is leaking.
It runs L8, 55's and a MSD 380bhp chip.

I hope you guys can give me some useful tips.
Thanks in advance.

 

Get your injectors tested! If you leave it and one is leaking you could end up with bore wash. Could also be a spark problem on that cylinder but will rule it out and peace of mind

 

Swap the suspected injector to another cylinder and see if the issue follows it.

 

Still no luck.. checked the fuel injectors by let them spray seperately. No difference when you look at the spray pattern.

Interchanged the injector from 2 and 3. Still overfuelling at cylinder 3.
Interchanged the ht leads from 2 and 3. Still overfuelling at cylinder 3.

This morning started the engine when cold and again no problems even after about 10 minutes at idle. Then took a small ride. At first no problem but after about 10 minutes it started running on 3 cylinders. After checking spark plug 3 again this was completely wet.

So the problem is not in the injector, spark plug or ht lead from number 3.

I am thinking does it occure that inside the L8 ECU a transistor is failing when getting hot?
Or maybe it could be in the distributor cap that after a few minutes it stops sparking number 3. (checked this cap and cleaned it without any result).

Finally when the engine was hot I measured the resistance of the CTS at 510 Ohms. Is this a good value?

 

I've had this exact fault before. Check the fuel pressure regulator vacuum pipe for fuel which indicates a split diaphragm. The reason for No3 always being the faulty cylinder is it is in line with the lowest part of the inlet manifold so the excess fuel collects there. Original regulators are fetching big money so I replaced mine with an adjustable one with a gauge (ebay special) and all sorted.

Hope this helps as it's easy to check and I'm pretty confident it's your problem. Best of luck.

 

Thanks!
I really thought this could be it so I have just tested this. Engine had cooled off for an hour or so. It started ok and I drove untill this problem started again (again after about 10 minutes). Took of the hose from the fuel pressure regulator but it was dry.. Also disconnected the hose from the inlet side and there is also no sign of fuel.

Disconnected the plug from injector number 3 and started the car. It runs on 3 cylinders not too bad at idle. As soon as I reconnect the plug for number 3 it stalls. When I then try to start the engine you can hear its overfuelling. Disconnect number 3 then start the engine it runs on 3 cylinders at idle.

Last year untill its wintersleep it didnt had a problem at all. Just now that I restarted it it has occured.

Hope someone else has got some good idea for this.

 

id get a scope on the injector connector and see what the waveform looks like from the ecu (compared with another injector) I'd suspect failing output components overdriving no3 injector.

 

I had that problem on my Saph, injector negativ wire, got grounded on fuelrail. When it got contact whit fuelrail, the injector opened

 

Thanks. I checked that but my wiring is ok.

Maybe have to swap the fuel pressure regulator to see if that solves it.

I have this fuel pressure regulator from a '92 Sierra 2.0i DOHC. It looks a little bit different than the cossie one, but it should fit. Can I use this one to see if it solves the problem?

 

The cossie regulator will be rising rate to match the boost pressure but the dohc regulator wont be so it wont be suitable

 

yes only difference is the vac pipe comes out the top. Just keep and eye on fuelling if you have a afr gauge.

 

a bit confusing those 2 latest replies.

So if I connect this DOHC regulator and then drive it while keeping the boost lower than 0 psi it will be ok? I do have a small band AFR gauge in my car to monitor the closed loop function.

That way I can take a short drive and see if it goes overfuelling with another regulator.

 

I suppose the YB uses batch injection, so multiple injectors inject at the same time for the same duration. If that is the case you can swap the injector plugs over (assuming the cables are long enough) to see if the problem then moves to another cylinder. If so, the fault is in the ECU. But I don't know if all 4 injectors inject at the same time on the YB.

..I just checked the YB wiring diagram and all injectors have their own link to the ECU. Actually that has to be if the ECU would be the problem. Though I still believe swapping injector plugs could be an option.

 

Hi Marc,

No they are turned on one after another. Already swapped injectors ofcours and didn't make any difference.

So after cleaning the spark plug of number 3, turning the engine a few times over with no the spark plug fitted to get ride of the excessive fuel, the engine starts ok and I can have a drive in it.
Untill a few minutes later it starts to sputter and its the same story again..

 

Are you sure they are switched open one after the other? Because on full power there is no time to do that, as they need to inject fuel almost constantly. If the problem stays on cylinder 3 when swapping fuel injector plugs over this would rule out the ECU.

 

Yep, the injectors are driven sequentially.

 

it will show if your reg is no good. As for rising rate i dont remember turbo technics changing the fuel reg when they tweeked the dohc 8v.
Also i am sure i used a dohc one on a fez turbo.

 

Ok thanks for this advice. I will first try this then.

 

It doesn't, it has sequential fuel injection (this is what the phase sensor is for) so you cannot swap the connectors over.

In addition what Jamie says below is correct, the FPR is 1:1, that is to say for a bar of boost the fuel pressure will rise in proportion, it's quite likely it is what is causing the fault though, although I would not change it for anything other than the original part.

Martin

 

Still no luck with this problem, spark plug number 3 still very black and running on 3 cylinders when warm.

Ruled out:

Spark plug, injector, HT lead, dizzycap, rotor, fuel pressure regulator and CTS. Why just number 3 suddenly?

 

have you checked your getting a good spark at the problem cylinder ,maybe its too weak to ignite .you could also check that all lugs are intact on your crank pulley incase the one inquestion for number 3 is damaged

 

I changed the rotor cap and HT lead and spark plug for that cylinder, what else can cause a bad ignition to only that cylinder?

Good point about the lugs, I will check them!

 

try substituting a different ecu....assuming phase sensor/pulley etc check out ok along with the wiring to problematic injector.

 

Next you will have to do a leakdown test and a compression test.

 

Thanks guys for the advise. Problem starts when engine is getting warm. When cold it runs fine. Also thinking the lambda sensor could be failing?

 

Just a thought, have you checked the inlet manifold gasket? (between head and manifold)
With engine running spray some carb cleaner around cylinder 3 inlet where it meets the head, if then engine note rises you have an air leak there.

 

Also if you do replace the regulator don't get an 'eBay special' not worth cutting corners as a cheap on will just fail on you.

Can you not get genuine ones anymore then?!!

I know when mine failed the inside of the inlet/throttle body looked like it had oil in it but was actually fuel as has been said above

 

Been searching for this problem again today. Started with the same problem:



Number 3 overfueling..

I then changed the oil, dismantled the ISCV and totally cleaned it. Also checked the timing, ignition amplifier and the CPS when I saw this:



It was totally covered with a thick layer of oil en dirt. You can see I partial whipped it.
So cleaned the whole CPS, reconnected it and checked the gap. It's between 0.6-0.8mm, so perfect.

Than took it for a testdrive without the lambda sensor connected so the closed loop function wouldnt be activated. It ran beautifully!
After reconnecting the lambda sensor it still ran fine. So I think I finally have found the cause of this misfire in the dirty CPS!

Maybe the signal for 3 cylinders was just about ok, but the fourth one was too weak.. Could that be true?

 

Yes i have found that the lugs on the pulley can be at different heights which is why i check the gap on all 4.

Glad thats has sorted your issue.

 

Good that it's solved. And also nice that you posted what the cause was. A lot of times you read about problems, but also a lot of times the root cause and solution is never posted, while I suppose the problems will have been solved in most cases.