Issue after starting

hmmm....we I had this problem it was down to fuel pumps...

best of luck Andrew

 

although with mine, the roughness dissappears after about 15 seconds of idle.

I haven't investigated fully yet, but some of the causes I've been "encouraged" to look at are:

1. Fuel Pump - apparently old seals and lines degrade, causing some blockage on a screen in the fuel pump
2. Fuel Filters - time for a new one anyway.
3. Fuel Accumulator - I think I'm going to replace this also.

Other thoughts that I've had are:

1. Leaking/dripping fuel injector
2. Leaking/dripping cold start valve - although, this probably isn't my problem, as I've replaced this recently.


Sid

 

if you could look around the car for a few symptoms other than just the hard start.

you should look for things like a raw fuel odor from a pressurized fuel line leaking or starting to seep, look for anything suspicious that does not fire up in the right order or things that aren't ticking like they should be.

we had a odd rough start on sidtx's 85 mondie for a while. first thing we investigated was the cold start valve (bolted to side of intake mani.) and found a seepage and wetness in the area the day AFTER it had run. we replaced this guy with a reman, and grabbed as many like-units from Volvos and Mercedes as we could find at the pick n pulls to stock our parts warehouse.

after we replaced this doohickey we still noticed a strong raw fuel odor that wasn't just permeating back through the air intakes while the car was off.
on the right rear fender area there are 4 or 5 fuel lines that run between the fuel tank, the accumulator (like we should replace anyways) and the cis unit. we made a day out of it and replaced 3 or 4 of these hoses and instantly the residual fuel odor was gone.
car starts up really nicely now too!

other than this, make sure that all your other connections are good. spark plugs are correct, plug wires are down good, dizzy has a good cap and rotor contacts... the basic stuff.
often times on dizzy cars people overlook the distributor systems as a whole.

 

Check the extension/extenders fitted on your spark plugs. If they have burn spots on the outside. Easy check and it rules out at least one of the dozen things that could be the cause. Recently I had this issue when she started to idle rough at traffic lights.

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Maybe it is obvious, but I will note it sounds like it might just be one bank of cylinders not firing, not all 8. So it can be fuel, or just as likely, electrical issue affecting one bank of cylinders. Fuel demand at idle is minimal.

Regards,
Jerry

 

According the symptoms I don't expect the O2 sensor system is faulty. The O2 system is only used when the sensor is warm, during cold start situations the mixture control system is in open loop state. The symptoms are more pointing towards a failing mixture enrichment in cold situations. Sometimes it's the over-voltage protection relay of the mixture controller which disconnects the power to the mixture controller. There is a fuse on top of the protection relay, it's good to check this fuse. The controller and the relay is located in the trunk nearby the O2 sensor system. If I am correct, US versions does have a frequency valve to control the mixture, this valve should be buzzing. If not this is also pointing towards the over-voltage protection relay and/or the mixture controller.

 

Crank position sensor?

 

If there was fuel starvation due to blockage it would be worse under acceleration which does not seem to be the case.

Try disabling the cold start circuit (there are two ways to do this). See if that helps. If so then the cold start is not working correctly.