1800: P1800ES fuel injection

[142 Guy]

Originally Posted by VolvoRoyS

The car had no hose linking the vacuum retard to the inlet manifold (it was blanked off at the manifold), the inlet air hose was ripped apart and the air filter very dirty. So far I have fitted a new air filter, inlet air hose but when I fitted the vacuum advance hose there was a very noticeable drop in engine revs so don't why that would be.

However, idling is quite rough so now plan to focus on the fuel injection starting with the throttle valve, throttle valve switch and idle adjustment. Any suggestions as to why the idle would be rough especially when cold would be welcome.

The drop in idle speed is normal if you reconnect the vacuum retard function. At idle, increasing ignition advance from a base point tends to increase engine torque which tends to increase engine speed (up to a point). Retarding the ignition reduces torque which tends to drop engine speed. More modern cars with ECU controlled ignition timing use this characteristic to help stabilize idle speed (engine speed goes up - retard ignition slightly to bring it back down and vice versa).

If you set your static ignition timing at 10 BTDC and set idle speed with the vac retard disconnected, attaching the vacuum line will then cause the distributor to retard about 5 deg which causes the idle speed to drop. In the service manual you will find that basic ignition timing is checked with the vacuum line blocked off; but, idle speed is set with the vacuum line attached. The engine will operate satisfactorily without the vac retard connected. The retarded ignition at idle helped to control nitrous oxides by slightly reducing combustion temperatures. With the vac retard disconnected you will likely notice that at idle the exhaust has a more acrid / eye watering characteristic.

What is the nature of your idle roughness? If the engine speed is hunting at idle that is a sure sign that the throttle switch has not been set up properly. The procedure for setting the throttle stop screw, adjusting the throttle switch and setting idle speed is set out in the fuel injection trouble shooting manual. Owners frequently use the throttle stop screw to adjust idle speed which causes all kinds of problems for the D jet system.

[VolvoRoyS]

Originally Posted by Laird Scooby

If memory serves you should have an AAV - Auxiliary Air Valve - for cold start idle speed increase.

I'm familiar with AAVs and think I tried blowing through it when the engine was cold - seemed to be open - and removed the air filter side when the engine was warm to no effect, so think the AAV is working but will check again.

[VolvoRoyS]

Originally Posted by c1800

The vacuum retard, apparently an attempt to improve emission performance. Most leave it disconnected and the port in the intake manifold plugged. Purportedly runs better without it.

The thermo time sensor in the block adjacent to the oil filter is what triggers the cold start injector. You appear to have that missing, hence the switch under the dash. It can suffice but don’t leave it “on” too long, I recall the time is something only about 10-15 secs. The hole in the block where the thermo time sensor resides is a blind hole, no need to seal or block that.

I trust your setting on the trigger points is as per published spec. They don’t require any filing like ignition points, in fact that may damage them. A simple swipe through with some clean brown paper or thin cardboard is all that is needed. A little distributor grease on the rubbing block is helpful.

In terms of your rough idle, go through the fuel injection fault tracing manual step by step to iron out problems.

To set your TPS I found this link most helpful.

https://vcoa.org/forum/9-P1800-1800S...onic-FI-system

Also check and clean the ground wires that attach to the rear of the intake manifold

Good luck and do report back your progress.

Looks like I'm going to be leaving the vacuum retard disconnected and good to know that the hole for the thermo timer is blind - thought it must be otherwise coolant would come out!

Trigger contacts in the bottom of the distributor are a new one for me. The only check I did was for alternate phases of continuity as I rotated the spindle - didn't check angles.

It will be Wednesday before I work on the TPS. The link you quote I have stumbled across and it told me where the idle adjustment screw was - I had tried turning a nearby 11mm bolt head! What does the bolt do?
Will report back on progress later in the week. Many thanks for the replies.

Roy

[142 Guy]

Originally Posted by VolvoRoyS

Trigger contacts in the bottom of the distributor are a new one for me. The only check I did was for alternate phases of continuity as I rotated the spindle - didn't check angles.

It will be Wednesday before I work on the TPS. The link you quote I have stumbled across and it told me where the idle adjustment screw was - I had tried turning a nearby 11mm bolt head! What does the bolt do?
Will report back on progress later in the week. Many thanks for the replies.

Roy

Don't worry about the phasing / timing / angle of the contacts in the base of the distributor that control the D jet system. The angles are not critical because the D jet is an untimed batch fire fuel injection system. What is important is that both contacts are opening and closing as the distributor rotates. Cleaning the contacts with a degreaser and applying a little of the proper grease to the rubbing blocks is OK. The current flowing through the contacts is in the order of milliamperes so there should be no need to file the contacts because of pitting.

I can't think of any 11 mm bolt heads in the vicinity. There are two ports for vacuum lines around the throttle body. One at 12 o clock and the other at about 7 o clock when facing the intake. These would normally have fittings for 1/8" vacuum lines on them; but, if somebody has removed the vacuum lines then there may be a blanking plug inserted in the port. The ports are typically NPT thread so the head is actually 7/16" not 11 mm; but, an 11mm wrench fits. If the bolts are brass that is a sure give-away that they are blanking plugs.

The aux air valve should be close to fully open when the engine is cold and completely closed when the engine is up to normal operating temperature. Fully closed at normal engine operating temperature is critical. How far open it is when cold is somewhat subjective being temperature dependent and its not exactly a precision device. If it is fully closed when hot and not closed when cold that is probably as close as you are going to get to a test for 'is it working'.

[VolvoRoyS]

Reporting back: today I set the throttle valve and then moved on to the throttle valve switch. Turns out that some previous owner has been active here as well; the boot was non-standard and underneath I found wire labelled 17 disconnected. An attempt had been made to re-solder it on. The plastic surrounding the wire had melted a bit and not really knowing how to get the connector out for re-soldering, cut the plastic away a little. Once I had it free I could see a barb on the connector which I should have somehow depressed- how is this done?- I'll need to know when a replace the connector. For the time being I have managed to re-solder wire 17 and refit the connector to the switch. Engine now idles quite well even with the vacuum retard attached - previously it would stall.

Took it on a short drive for the first time and noticed a vibration - prop shaft?

Still a bit annoyed at the way the PO butchered the cold start wiring; surely the best way to have done this would have been to fit the switch between the wires to the thermo timer?

[142 Guy]

Originally Posted by VolvoRoyS

Reporting back: today I set the throttle valve and then moved on to the throttle valve switch. Turns out that some previous owner has been active here as well; the boot was non-standard and underneath I found wire labelled 17 disconnected. An attempt had been made to re-solder it on. The plastic surrounding the wire had melted a bit and not really knowing how to get the connector out for re-soldering, cut the plastic away a little. Once I had it free I could see a barb on the connector which I should have somehow depressed- how is this done?- I'll need to know when a replace the connector. For the time being I have managed to re-solder wire 17 and refit the connector to the switch. Engine now idles quite well even with the vacuum retard attached - previously it would stall.

Terminal 17 is the contact for the idle control in the throttle switch. It goes to a contact in the switch which closes when the throttle is closed and sends a signal to the D jet controller to go into idle control mode. If the D jet controller does not get that signal the engine does not idle well (as you discovered) or at all.

As you seem to be discovering, butchered wiring and electrical connections are probably right at the top of the list of things that can kill the D jet system. Good sleuthing.

[VolvoRoyS]

Originally Posted by 142 Guy

Terminal 17 is the contact for the idle control in the throttle switch. It goes to a contact in the switch which closes when the throttle is closed and sends a signal to the D jet controller to go into idle control mode. If the D jet controller does not get that signal the engine does not idle well (as you discovered) or at all.

As you seem to be discovering, butchered wiring and electrical connections are probably right at the top of the list of things that can kill the D jet system. Good sleuthing.

Just noticed that there are numbers on the TPS BUT they don't correspond to the numbers on the wires in the plug. Looks like someone has had the wires out and put them in reverse order so now 17 is at the top as there's only one way that the plug can be fitted. Can you confirm that wire 17, for example, should go next to the number 17 on the TPS?

[142 Guy]

I drafted a long reply with attachments, went to submit the reply and it evaporated into the ether, so now I am a little cranky and the reply is going to be short.

First off, I am not able to confirm switch numbering because I converted my D jet to Megasquirt 6 years ago and no longer have the switch. I did check my 1971 service manual (green book) and the Volvo Fuel Injection Fault Tracing manual and confusion reins supreme as they show mirrored numbering arrangements at the switch (see attachments). Perhaps somebody screwed up royally during the design process and the switch and wire numbers got transposed and one document is referencing the switch numbers and the other referencing the wire numbers (which don't match up)????

Perhaps another owner with a D jet can pull back the wire harness and advise whether the wire numbers match up with the switch numbers and whether 17 is in the top or bottom position. Failing that, about the only way to confirm what is going on would be to do a functional test on the switch. Using a continuity tester connect between what you think are 14 and 17 which are the connections to the idle switch (based upon the wire numbers). With the throttle closed the idle switch should be closed (0 ohms) and once the throttle comes off the stop the switch should go open (infinite ohms). If that is correct then the switch is probably wired up as it should be. You can check the 14 - 9 and 14 - 20 contact operations if you want to - these should go alternately open and closed as you open the throttle.

For reference

https://volvo1800pictures.com/docume...lt_tracing.pdf

[c1800]

Here’s a pic of the TPS, As shown in the wiring diagram and the picture below, the 4 numbered leads on the TPS, from top to bottom are:

17, 14, 20, 9.

Edit, picture somehow loaded turned 90* to the right, the right side of the picture is the top.

[VolvoRoyS]

Once again many thanks for a prompt reply. The diagram seems pretty clear, so it is wired correctly. I have yet to check out the operation of the TPS. Although the engine idles quite well now it has poor response to the accelerator making it prone to stalling. I'm hoping I can fix that with attention to the TPS.
I'm also trying to work what new plugs and boots to order from that D-jet site you suggested as I would like to re-instate the wiring to the cold start valve, replacing the thermo timer with a switch that completes the circuit. I can find 3 white wires that have been messed with that might have originally led to the TTS, one of which is earthed; is this likely to be it?