Cosworth Problems

In news: snipped-for-privacy@posting.google.com, Tappner decided to enlighten our sheltered souls with a rant as follows

Without seeing the car, it's hard to diagnose, but I narrowed it down to one of the following.

A: Contamination of the fuel supply due the the rust, try blasting some redex through it. B: Turbo boost set too high, causing detonation (unlikely, but possible) C: Spark plugs gapped incorrectly, Cosworths are *very* plug gap sensitive. D: Pipe off somewhere.

HTH

Hi

This is a very VERY long shot but its worth mentioning i reckon.

The car that I race doesnt have electronic ignition, just has a bog standard setup with dizzy. After we had an engine fire, and melted all the electrics, we re-wired the car and one of the guys incorrectly wired up the dizzy. When the ignition was turned on, a spring loaded peice of metal (inside the dizzy, dont know what its called but as the lobe of the dizzy came around, it pulls this spring loaded piece away and the spark is created) heated up red hot. As a result, it lost its "springyness".

The car ran very rough but ran. We changed the timing to help it run but it didnt solve the problem. When revved past a certain number of revs (circa

Like I said, a long shot, but worth bearing in mind. It took us best part of a day, to-ing and fro-ing from halfords replacing bits that we thought could be the culprit!

HTH

Max

First place to start would be to check all of the basics, such as fuel pressure, condition of ignition system. Then a test of the injection system will need to be carried out. From your description, there could be a problem with a coolant temperature sensor, causing too much fuel to be injected into the engine. This can also cause the backfiring you mention.

I am not sure if a fault code reader can be utilised to test the ECU on your car. It may be a case of having to test through the system manually. The Haynes Automotive Engine Management Manual gives information on how to do this.

HTH

Anthony Remove eight from email to reply.

The most common fault on these that causes the running problems you have is a faulty / failed / poor connection to the phase sensor in the dizzy. Very carefully check the wiring to it, the multiplug and the connections from the plug to the Hall sensor inside. They often break. Its easiest to remove the dizzy to do this.

If you have problems getting a new one- ask the parts guy to cross reference it with one from a Lancia Thema turbo- they use the same one.

Tim..

Blocked fuel filter from the rust in the tank. Symptoms will be if you leave it sat for a while the rust will fall to the bottom of the filter and it'll run ok for a bit. The longer you drive the more the rust shakes back up until the filter element is blocked and everything stops for tea. That'll be £35 please. Address is on the website :)

Dave Baker - Puma Race Engines

The spring loaded piece of metal thing is called the points. All cars had points until the 1980s and all cars since the 1990s have not, more or less. They used to need adjusting every few months and replacing every year or so. A Sapphire Cosworth is pretty unlikely to have had points, so if it has, someone has seriously messed it up. Basic electronic ignition uses a sensor in the distributor to trigger a transistorised ignition module.

We thought we had the problem with the rusty tank, for the same reasons as Dave points out but the 1st garage changed the filter, and it still wasn't running right. The problem seems to be too much fuel (or not enough air!) Does the Haynes Manual show you how to read the codes without specialist equipment like you can do with Vauxhalls?

Thanks Jim

Too much fuel will not cause backfiring.

The only things that will cause backfiring is 1) incorrect spark timing, 2) excessively lean mixture 3) intermittent spark.

Tim..

That sounds more like a rev limiting device, may be built into the rotor arm.

MrCheerful

If it is the chain drive engine then I have known them jump a tooth on the chain and slightly mistime the cams, they still run, but very badly. However this would not usually get worse the longer the journey. Might be worth a look though.

MrCheerful

Almost certainly this won't be the root cause of your woes, but it may be a contributary factor: are you using super unleaded or the cheap stuff? May be that the timing is set up for the higher RON fuel.

Regards, Jim.

failed actuator

ask here for more information (or join the RSOC)

Checked all pipe, plugs, etc. today and went for a run. Car appeared to be running a bit better, but still lack of power above 3000 rpm. After around 20 miles started to lose power and misfiring eventually made it home and booked an appointment with a local specialist in "high performance vehicle tuning" who is confident in being able to diagnose the problem. Will report later with the results

thanks for all suggestions

Jim

Belated update:

The garage had problems tracing the fault as it didn't show up on the diagnosis equipment, but after a process of elimination the phase sensor along with the temp sensor were replaced. problem almost cured! there is still a slight hesitation under full load, and I am waiting for a new set of Magnegor plug leads, which should solve this. Starting to enjoy the car now - was longing for my elderly (but very reliable) Calibra.

Thanks for all suggestions

Jim

Did I not tell you to look at the phase sensor FIRST?!

Tim..