Engine: 140 1986cc B20E: B20E timing and idle

[capt jack]

Hi All,

Hope you don't mind me looking in here. I've a question with my 1800ES, but as she has the same B20E engine found in some 140 models I thought I'd try posting here too.

After all sorts of travails due to rusty fuel tank, seized fuel pump and brakes, knackered pressure regulator etc etc etc, Monica, my 1800ES auto, is now running and nearly ready for her MoT. She's a late 72 with the B20E engine (Bosch D-Jetronic)

Getting the timing right is proving interesting! I've a dwell/tachometer - dwell angle is 62 degrees, which is in the middle of the range specified for the engine (59 to 65 degrees), the points are new and set to .035mm. Using a strobe light, I've attempted to set the timing as per the book to 10 degrees BTDC. This is quite easily achieved with the vacuum line off the dissy and plugged, although when I put the line back on to the dissy the idle becomes very lumpy, and the RPM drop, the timing is then retarded. I've read elsewhere on the forum that the vacuum line is best plugged and left off anyway - if that's the general experience I'll happily live with that.

As I've got things set up now, at idle with the vacuum line off, the RPM fluctuate a bit around the 900 mark, and with the benefit of the strobe, I can also see that the timing marks wander about a bit, although really, not very far. For the RPM I'm watching the dwell/tachometer rather than trust the car's rev counter.

As the engine speed is increased, the revs pick up and everything smooths out.

I've also noticed that pumping the brake pedal with the engine idling will cause the RPM to increase to about 1200 rpm, and that then the lumpiness then goes.

At the moment for the purposes of setting things up I'm using unleaded petrol. The fuel pressure regulator is set to 2 bar; the auxiliary air valve appears to be working OK; the coil, points, plugs, leads are all new; the distributor has been stripped and cleaned, with replacement springs fitted.

Am I expecting too much for the idle to be perfectly smooth? My suspicion is otherwise that there's probably a bit of a vacuum leak. I know that getting an engine to idle smoothly can be something of a black art!

If anyone has any experience of setting up a B20E then I'd be really grateful for any tips you can pass on.

Thanks

Cheers

Jack

[Clan]

The ignition timing is doing what it is supposed to , the key here is that when you press the brake pedal hence let air into the inlet manifold , the rpm goes up ., which suggests a rich idle mixture .
Have you have a CO adjuster potentiometer on the side of the ECU above the passengers feet under the dash ? If so twiddle that
Has the Pressure sensor been modified? ( a hole drilled through the sealed adjusting screw in the end? )

[DaveTrees]

Originally Posted by capt jack

This is quite easily achieved with the vacuum line off the dissy and plugged, although when I put the line back on to the dissy the idle becomes very lumpy, and the RPM drop, the timing is then retarded. I've read elsewhere on the forum that the vacuum line is best plugged and left off anyway - if that's the general experience I'll happily live with that.

Are you sure it's a vacuum advance ? Other than some early B18-engined cars, nearly all 140s have a vacuum retard on the distributor ... I assume the P1800 would be the same.

Leave it disconnected - they run better without it. It was just a primitive emission control measure.

[capt jack]

Thanks Guys.

Dave, you're right, it is a vacuum retard on the distributor, and the engine definitely runs better with it disconnected and plugged. I'll make this permanent by blanking off the port on the manifold.

Not sure about the CO pot Clan, I'll have a closer look next weekend.

Can you tell me any more about the pressure sensor mod?

Thanks again for your time and trouble

Cheers

Jack

[Clan]

yes vacuum retard on the B20E the timing is reduced by 10 degrees when there is vacuum in the inlet manifold so the basic timing alters from 10 degrees BTDC to 0 or TCD at idle .
If you disconnect the vacuum system the timing will be 10 degrees higher that it was designed to be especialy under cruising conditions which could result in burnt valves or pistons . Of course under power the timing would be ok because the vacuum disappears anyway then .

When the B20E came out first on the 1800E and later on the 144GL , after a while there was a problem with the fuel mixture weakening off , causing lack of power poor idle and running issues . It was assumed at the time the small filters were blocking in the inlet pipe of the injector . The official quick cure was to alter the pressure sensor to increase the injector opening time to get around the problem . If you drill the big sealed alloy screw in the centre with a 5 mm drill you can adjust the main fuel trim make only tiny adjustments on a CO meter to get the required CO at idle it was 3.5% at the time . After doing this the car will fly , i went off the speedo and rev counter after doing this once in the early 70's :-) in a 1800E

[capt jack]

Thanks for the information. I've got plenty to think about now.

Cheers

Jack