3 Month Long Tuning Saga

[e21paddy]

Hey all,

I dropped my car (81 320/6 e21) in to the mechanic in May. I still haven't got my car back due to an issue that is being chased over and over. Below is a transcript of a report I received from the mechanic. This mechanic is well received in the BMW community here, so I am giving him the benefit of the doubt that he is doing all he can to get my car back to me.

Has anyone any ideas?

I write to update you on the situation with your car.

It has been a real mind-bender to date. When the car came in it was running poorly, as most of the components had been replaced, it appeared the carburetor was the issue
We replaced the Carburettor and the car ran better. After driving it, I was happy to let it out after a final tune up.
When I went to check the timing, the car cut out. Since then it has refused to run properly and I have gone through every related/connected component since to find a fault. I am working on it in my spare time so that you do not incur any costs on it.
So far I have gone through and replaced everything from another car to try to get it running right.

Here is the list so far:-

Refitted old Carburettor
Distributor, Rotor, Cap, Leads, Plugs
Re-set timing, both Valve and Ignition
Replaced Earth Lead
Replaced Coil and Lead
Replaced Crank Sensor
Compression test on each cylinder
Fuel System - Cleaned out tank and lines, fresh fuel put into vehicle
Disconnected exhaust and checked back flow
Replaced Ignition Module

All these components are linked to the starting and running of the car, and the donor car is running perfectly.
So it has been a bit of a brain teaser!

I also had a retired Carburettor guy look at it but no Joy.
It has to be something simple as every connected component on it is new at this stage.

[Jeroen]

I guess we all ran into something smilar at some point and it can be very simmple but very annoying indeed! A few thoughts from my side.

First of all, I always try to get down to the basics, you need fuel and a spark. Fuel pressure and volume sufficient? Do you have a spark at the plug? At least these simple things may help narrow things down.

A few thoughts on individual items listed:
Refitted old Carburettor - why replace it in the first place and not overhaul it, but ok. Base gasket and intake manifold gaskets ok?
Re-set timing, both Valve and Ignition - ignition static ok, and after that the right vacuum hoses for advance were fitted?
Replaced Crank Sensor - car does not use a crank sensor, only goes to diagnistic terminal near the thermostat housing. A sensor that does make a difference is the impulse sender on the ignition dizzy, but if the entire dizzy was swapped against another one of the correct type (!!) that probably also means a swap of the pulse sender?

Last one for now: apart from ignition timing, did you also check if the timing marks on the crank and cam line up?

Hope this helps, good luck and keep us posted!

[e21paddy]

Hi Jeroen,

Yes we have fuel and spark, the reason it was sent in for a final tune was that it was running very rich, and was poorly performing as a result.

Before getting to this mechanic, I had a local mechanic change timing belt, re-time the car etc. He had the same issues where it wasn't perfect. I reckon he got sick of it as he works on more modern vehicles, and then sent it on his way.

I then moved it to a more specific mechanic who deals with these cars, and now we run into these issues. Twice I have been very close to picking up the car, only to have overnight gremlins jump in and mess up the plans.

We replaced the carb with a 38 DGES weber, as he reckoned it was the carburetor that was giving the trouble. I have passed on the information to him and hopefully, I'll get some word back soon.

[Jeroen]

Could it be you have a dodgy electrical connection somewhere? A regular E21 check is the fuse box for corroded contacts or fuses. In case of electrical issues, always roll your fuses for starters.

[e21paddy]

The earth was replaced, and i believe he said he checked all earths.

The fuses are in pretty good condition, as i was doing my own troubleshooting before going into the new mechanic! I drove it 40 minutes to this garage without any real issues!

[uwbuurman]

Distribution belt sprung one tooth over??

[e21paddy]

The timing belt? I’m nearly sure that was checked but I’ll add it to the list!

[uwbuurman]

Well, it that has spung one tooth over, than it is undoable to get it timed correctly. And, no offence, it wouldn't be the first one to encounter this.

[Jeroen]

Yup, suggested that one as well (did you also check if the timing marks on the crank and cam line up?), realistic option!

[shadyracer01]

Has the fuel pump been swapped yet? Possible worn pump pushrod or diaphragm issue? Also, any signs of vacuum pressure in tanks when removing fuel cap, ie, blocked breather? As the fault occurred upon checking dynamic timing, then the vacuum pipes at dizzy would be disconnected for this, I would be checking for air or inlet manifold leaks, sometimes you can hear a slight whistle noise if this is the case.
Good luck, totally understand how frustrating it can be!