Testing vacuum advance unit.

[chano]

Hi,

Apologies for what must seem like a (another) very basic question.

I removed the distributor this morning before trawling the local scrappies here on Gran Canaria looking for a used one (no luck). Looks like i will have to order a Hall sender unit from the UK.

Before removing the distributor, i noticed that the vacuum advance unit only has one pipe attached. Is this normal on DJ engines? The pipe is attached to the hose connector that points towards the distributor. There is another connecter on the back/top of the vacuum unit without a hose attached and the connector isn't sealed/plugged. When i unscrewed the unit from the distributor and started twiddling withe the pullrod arm, i noticed quite a bit of oil coming out of this unplugged connector. Again, is this normal?

1990 2.1 petrol injection - DJ.

Is there a way to check the vacuum unit once it is removed from the distributor?

Thanks

Alan

[toomanytoys]

It should have 2 hoses connected.. but the one thats connected is the "retard" side.. which wont help performance and running... you need to see if the other hose is still about and if the the end on the throttle body has been plugged..

Testing vac unit... suck on either tube.. should be able to create vacuum on it, if you can keep sucking then its got a split diaphragm, replace the unit.. the arm should also move when you do suck..

[chano]

Thanks.

Where exactly does the missing hose attach? I assume when you say check to see if the throttle body has been plugged, it attaches there if it hasn't been plugged.


Alan

[Grun]

Thanks.

Where exactly does the missing hose attach? I assume when you say check to see if the throttle body has been plugged, it attaches there if it hasn't been plugged.


Alan

Alan,
Just had a look at mine (1986 2.1DJ), and there is a pipe from the throttle body to the forward (Cab) side of the vacuum unit. (Comprises a short length of hose, a plastic tube, then a short length of hose again).

From the opposite (rear of vehicle) side of the vacuum unit there is a hose with a 'Tee'. One hose from the 'Tee' goes to the fuel pressure regulator, the other to the centre part of the inlet manifold. (Black painted section).

Mike

[chano]

Thanks, Mike.

When i removed the distrinutor this morning there was definately only one hose attached: the one from
the rear of vehicle side of unit. I'll check later to see if there are any hoses without homes dangling from the engine. There is still oil
coming out of the unit from the connector nearest the cab when i move the pullrod arm on the vacuum unit. Is this normal?


Alan

[Grun]

chano said

There is still oil
coming out of the unit from the connector nearest the cab when i move the pullrod arm on the vacuum unit. Is this normal?

I would say, 'not normal' would expect there to be only air in the vacuum unit, but if it has been missing a hose from the cab side, then it has been open to contaminants sucked in as the diaphram moves to and fro......(I guess!).

P.S. Have a look at this thread.......http://forum.club8090.co.uk/viewtopic.php?f=2&t=57374....." onclick="window.open(this.href);return false;. especially the last couple of posts as davidvincent managed to find a cheap Hall Sender, (which needed a bit of modifying) to get over his problem. Perhaps a pm to him would help you.

Mike

[chano]

Just found the other hose. It was dangling from the throttle housing. Oil still dripping from the connector on the vacuum unit when
i move the pullrod!


Alan

[Grun]

Alan,
Re-read my previous post, I have made an 'E D I T' to it.
Mike

[chano]

Thanks, Mike.

Very interesting and informative thread.

The Bosch dealer here on Gran Canaria can order a Hall sender from Madrid - 170 Euros! Just Kampers advertize one for ₤57. Their
website says it will fit the 2.1, but when i emailed them the Bosch code number on my distrubtor, they said it wouldn't fit. Very strange.

I know Brikwerks have them in stock and Simon at Brikwerks has confirmed it will fit my dizzy. It will be cheaper to buy one from him at ₤85 and have it sent over.


Alan

[Grun]

Alan,
Before I spent £85, (leave alone 170 Euros), on anything I would want to follow 'bigherbs' advice and check out the rest of the ignition system, (minus the Hall sender). see below..........

Re: No Spark (The saga continues!)
by bigherb » Wed Sep 09, 2009 9:01 pm

The hall sender is simple to check just remove the centre HT lead from the distributor and hold it about 5mm away from a metal part of the engine or bodywork and away from the fuel system, remove the three pin plug from the distributor and probe a piece of wire into the centre pin of the plug, switch on the ignition and then scrape the other end of the wire along a metal part of the engine this should then produce sparks from the HT lead, if you get sparks then the rest of the ignition system is OK and the hall sensor is at fault. before you replace the sensor check there is more than 5 volt across the two outside pins of the three pin plug.

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bigherb

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Mike

[chano]

Mike,

I intend to try 'bigherbs' Hall sender test tomorrow. Wish i'd seen this post before i removed
the distributor.

Alan

[Grun]

Alan,
I have a couple of manuals which cover electronic / fuel injection systems, as it is rather new technology to me, (an old duffer).

According to what I have read, the Hall sender is a silicon chip through which is passed a small current from one edge to the opposite edge.
When a magnetic field passes through the major axis, (i.e. the face) of the chip, a (tiny) voltage is created across the other two edges.

(Think of it as a thin square) Current from left edge to right, voltage appears from top to bottom edge when magnetic field goes through the thin face.

The thing is that the sender needs a current feed and an earth return to provide its voltage output. So a perfectly serviceable hall sender will not work without the feed (and earth return) circuit.

This is what I believe 'bigherb' refers to when he says.......

before you replace the sensor check there is more than 5 volt across the two outside pins of the three pin plug.

I tend to stick to the old adage....... 'If it ain't broke..........' so having had (as yet) no problems with the distributor and associated gizmos, I can only tell you what the books say. They tend to be generalist, but feel free to ask and I will do my best to find what I can from them.

Mike

[chano]

Phew, Mike! Way over my non mechanical head. Sticking a cable into the sender connector... as described by 'bigherb
is about my limit. I'll report back with results of test (or crying for help).


Thanks

Alan

[chano]

Re: No Spark (The saga continues!)
by bigherb » Wed Sep 09, 2009 9:01 pm

The hall sender is simple to check just remove the centre HT lead from the distributor and hold it about 5mm away from a metal part of the engine or bodywork and away from the fuel system, remove the three pin plug from the distributor and probe a piece of wire into the centre pin of the plug, switch on the ignition and then scrape the other end of the wire along a metal part of the engine this should then produce sparks from the HT lead, if you get sparks then the rest of the ignition system is OK and the hall sensor is at fault. before you replace the sensor check there is more than 5 volt across the two outside pins of the three pin plug.

I assume you stick the wire into the plug that detaches from the distributor and not into the hall sender connector on the distributor? I tried this, with the coil HT lead resting on the engine with the connector about 5mm from metal, but when i scrape the bare wire on the chasis all i get is a mild tingle and no spark.

I'm struggling to find any bare, clean metal in my engine bay, will making contact with painted bodywork still produce a spark?. Is it safe to hold the HT lead when running the test?

Apologies again for what must seem like pretty basic questions.


Alan

[toomanytoys]

Wire brush a clean patch on the engine.. No a painted area will not give you an earth..
Not advisable to hold an HT lead with your bare hand.. lots of volts are possible... clamp/wedge it in a sutable postion..