problems with vacuum advance

[delorean12uk]

Hello everybody, I am after some technical assistance with the vacuum advance on 'UDW' or POS as I fondley call her. I have to own up, our very own club favourite, the very man who puts tourette syndrome sufferers to shame, Uncle Tony, together with Andy Carvosso changed the motor in the car for me to try and get me back into the enthusiam of having a Delorean, and all I had to do was finish it off. Which over the last couple of weeks I have been doing as I would like to take it to Eurotek, and use it as an Effigy and set fire to it!! No, as much as I have liked to have done that at times, i retract that statement because I don't mean it. Anyway, I have got the car running as per Volvo spec, she is running Volvo metering and air flow, and I have an auxillary air valve replacing the idle speed motor. As per the manual, she is ticking over at about 850/900 rpm and I have set the timing to 10 degrees. To do this the vacuum advance on the distributor has to be disconnected, but when I reconnect it the Rev's raise to about 1200, which is the vacuum advance pulling in. I then put a spark retard valve or a Vacuum delay valve in line from the inlet manifold to the dizzy, and all that does is the rev's increase at a slower rate rather than instantanously raising to about 1200. I know it's not right so i have disconnected the vac line to the dizzy. has anyone got any idea's as to what the problem might be??? I have already checked for vac leaks, and Tony reckons I should re-install the idle speed motor, but by doing that i am not resolving the problem. he also called me a c@#t as well, but thats a different story, so i am open to suggestions if any of you good people may have any idea's as to what the problem may be. Regards

[A Van]

Calling Nick T

[Rich H]

Then you must have continual vacuum to the dizzy from somewhere. If you put your finger over the end of the pipe have you got suction?

The supply to your dizzy should be coming via the vacuum solenoid in front of the fuel distributor. Do you have a vac solenoid?

If so, try disconnecting the electrical connection to it. Do you still get vacuum on the pipe?

If so, you either have the pipes on the solenoid the wrong way around or the solenoid is buggered.

If you don't have a vac solenoid in line with the feed to the dizzy, then you need to get one, otherwise you'll have vac advance to the dizzy all the time. The vac supply is at the front of the left hand inlet manifold. You should tee this to the vac solenoid (which then goes to the dizzy) and to the CPR

[Tourettes Tony]

get the idle motor back on lol, no seriously there is no vac selenoid as its running volvo gear, my car has never had a spark retarder ever (only on the de cpr)and has always ticked over at 750-800 even with a split vacuum hose ( with idle motor :wink: ) im gonna come over the weekend and sort you out mr monk TT

[NickT]

Sounds about right. Just re-install the vac advance solenoid in line between the inlet manifold vacuum and the vac advance of the distributor and all will be fine.

If you don't have a vac solenoid then just screw in all of the brass screws, reconnect vac advance to distributor and re-set the idle using the throttle screw.

Good luck,

NickT

ps Check your primary fuel pressure is 5.3 bar and the Co is 2% +/- 0.5%

[delorean12uk]

Cheers Nick for the info. what controls the vac solenoid then??? I do have one lying about somewhere. Tell me if I'm on the right track with this one; is it one of those limit switches on the throttle spole/ linkage that operates the vac solenoid, so when you put your foot right to the floor, the limit activites, operates the vac solenoid and the vac advance then works on the dizzy????

[NickT]

delorean12uk Wrote:Cheers Nick for the info. what controls the vac solenoid then??? I do have one lying about somewhere. Tell me if I'm on the right track with this one; is it one of those limit switches on the throttle spole/ linkage that operates the vac solenoid, so when you put your foot right to the floor, the limit activites, operates the vac solenoid and the vac advance then works on the dizzy????

The large throttle switch (between brass screws and fuel distributor) operates the vacuum solenoid.

When the throttle plate is closed, the switch is pressed closed.
With the switch closed, the solenoid gets 12v at the coil.
This energises the solenoid and blocks the vacuum from the engine to the vacuum advance and also admits air into the vacuum advance diaphragm so it returns fully to non advance (ie no residual vaccum left).
This retards the timing back to mechanical advance only so the base setting of 13 deg btdc is correct.
[10 deg btdc for volvo spark distributor]

As soon as the throttle is opened by a small amount the solenoid is de-energised (loses 12v at the solenoid plug) and the vacuum advance is re-instated.

NOTE: The vac pipes should be connected as per the diaphragm, if they are connected back to front then you will admit air into the inlet manifold causing slightly lean running.

If you have volvo gear on, don't bother with vac connections to the thermo vac switch, this was added to aid emissions and quick heat up of the cat and spark distributor has a different advance curve.

Re-plumb as follows:

Inlet manifold vac take off to T piece (T1)
Connect pipe between original Delorean CPR T piece to one side of T1
[or Volvo CPR vac point to one side of T1]
Connect Dist Vac solenoid centre section to other side of T1
Connect outer edge of Vac solenoid to Vac Gauge or use finger to detect vacuum.

With engine idling there should be no vacuum at the pipe that is to go to the distributor advance.
With engine just off throttle there should be vacuum at the pipe that is to go to the distributor advance.
This should be true regardless of engine temperature.

The switch at the throttle spool is the Wide Open Throttle (WOT) and is a switched signal input to the fuel computer to default the duty cycle on the bleed/ frequency valve to 60% causing a slightly richer mixture (assuming the base fuel setting is correct) ignoring the oxygen sensor feedback signal. [Not used with Volvo gear] NB. On Automatics, the second of the double switch is a switched signal input for kickdown purposes although kickdown will still work due to the circuit.

Hope this helps,

Nick.

ps Did you get that article I found on t'internet about overhauling the fuel distributor on a porsche?

pps I just bought volvo gear with 2 fuel distributors but the plungers are a bit stuck. I have been spraying them with WD40 but what did you use to free yours with? I remember something about soaking them in acetone.