Tecchie Question time!

[PaulHere]

A 924 Lux technical question for the 924 forum boffins here from member Liz []

SYMPTOMS
1. One of three things: a. Initially the car will simply "cough" the engine will briefly stall and immediately restart with an audible backfire. b. On other occasions the car will stall completely. The car will neither restart through "rolling" in gear with the ignition on or, having pulled to a halt, nor will it start immediately with the starter motor. The Fuel Pump Relay is found to be very hot to the touch. If the car is left for approximately 5 minutes, the car will restart. c. Finally, having stalled as described above, occasionally, the car will not restart even having been left for a considerable time (60 plus minutes). In these circumstances, the Fuel Pump Relay will be found to have burned out. If the relevant terminal positions of the Fuel Pump Relay are bridged with a spaded wire, the car will immediately start (regardless of how long since the stalling event).
d. On one occasion, the car stalled, and would not restart. The AA was summoned and, having found that the Fuel Pump Relay had burned out, the mechanic bridged the relay terminals with a spaded wire with a 15 Amp fuse rigged in line (as described above). The car started immediately and was driven for approximately 60 miles. The car then stalled once again (typically, after the attendant Patrol Van had departed). The fuse in the wire fitted by the AA had not blown. After approximately 5 minutes of regular trying, the car started. Obviously, in this instance, the Fuel Pump Relay was not the symptomatic point of failure despite the other symptoms being identical.

2. There are no common circumstances when failure occurs. Failure will happen in any gear, at any speed, at any engine loading (including tick-over). Failure has never happened when the engine is cold and tends to happen on trips of more than 30 miles. The frequency of failure is increasing.

ACTION TAKEN
3. My local OPC (Glenvarigill of Glasgow (who have serviced the car for the last 5 years)) has checked out all the wiring. Initially they found a broken earth terminal in the fuse box. The problem re-occurred. The second attempt was to replace the Fuel Pump "" once again the problem has re- occurred. The car is back with Glenvarigill "" who are attempting to find the root cause.

OTHER FACTORS
4. The car is very much a fair weather car and covers only 2,000 miles a year.
5. Whenever the car stalls, the Fuel Pump Relay is found to be hot, to the point of being uncomfortable but not impossible to touch.
6. Possibly related factors: a. When being driven, most particularly over rough road, "chattering" can be heard from the area of the Relay panel (Yet failure leading to a stall most frequently happens on smooth surfaces when the relays are "silent"). b. Occasionally, the car's windscreen wipers will sweep, as if the stalk has been pushed briefly up to request a single sweep.

Liz

 

[924nutter]

If a new pump hasn't cured the burning out of the relay then something else must be drawing excess current. Whether it be an early 924 with a single fuel pump, or the later models with a secondary pump in the tank, teminal 87 on the fuel pump relay also supplies current to the warn-up regulator (red and white wire) and the auxilliary air-valve (black and green wire) Check first to see if either of these wires have been chafed through and are shorting out either where they come through the bulkhead (though this is unlikely as the wires are in a loom) or between where they exit the loom and their electrical conection. The insulation goes brittle with age and due to the underbonnet heat could crack off and expose bare wire. The 924's wiring is a bit of a bird's nest at the best of times. If you can't find anything amiss there then suspect the heating element in the air-valve, as the construction of the warm-up regulator is such that the likelyhood of a short there is minimised.

 

[924nutter]

Re: Single sweep of the windscreen wipers.
Is it accompanied by the screen jets working?
I have an as yet untested theory that as muck and old grease accumulate around the contacts in the self parking mechanism in the wiper motor, coupled with the wear that takes place over what could be as long as 28 years in the U.K., sometimes the self park contacts close momentarily, initiating a single wipe. Once the wiper has moved through 60 degrees of arc the cam in the motor lets the contacts close anyway and continue the single wipe. My 83 lux did it, my 79 lux doesn't. My 80 turbo did it once but my 82 turbo never has.
If it bugs you take out the relay, but be aware that the wipers will not self park or operate automatically when you wash the screen. In simple tems, when you pull the lever to wash, the relay shorts out the contacts in the self park and a built in timer controlls how long they stay bypassed.

 

[924nutter]

Do we have any feedback WRT accuracy of diagnosis on this one yet?

 

[PaulHere]

I posted the original enquiry on behalf of Liz who now posts here as 'lizhayle'

Hopefully Glenvarigill of Glasgow OPC have sorted something out.

 

[Guest]

[8D] 924 Nutter - thanks for the info on my fuel pump relay issue. The car goes into Glenvarigill tommorrow (4/6) hopefully they will fix it.

With regard to the wipers - no the washer jets do not work when the wipers sweep "unbidded". I have found that pushing the wiper switch arm forward (the reverse of pulling for a wash/wipe) sometimes helps.

Sorry that it has taken so long to come back to you but I had a problem with my log in.

Liz

 

[924nutter]

WRT the wiper sweep, if the screen jets do not operate then it is probably the interval wipe circuit which is being intiated. Next time it happens, listen for the relay clicking just before the wipe. This will confirm it is an interval wipe.

Once I have that info I can explore the wiring diagrams further

 

[danmason]

I have an associated issue with my 924 - when I pull on the wiper stalk my wipers work fine but I am getting no spray. This is despite the brand new motor, which seems to be working fine - it powers up okay, precisely the same as it does when plugged into my 951. However, there's just no water. Sometimes if I keep pumping the stalk for a loooong time (maybe 3 mins) I'll get a few trickles and then one of the jets will make a dispirited attempt to squirt. What's going on? [&:]

 

[Guest]

I had the same problem and after ruling out the washer motor I found it was the contacts on the wash/wipe stalk. Had to take off the steering wheel to get to everything,cleaned the contacts and now washers are working as normal.

 

[danmason]

hmmm, i've even gone so far as changing the stalks but still no joy unfortunately.

 

[924nutter]

The system on a 924 has, at the reservoir end, a tee in the feed pipe to the jets, which feed back into the reservoir. If the non-return valve rubbers perish, the jets block with rubber fragments, and the water just recirculates. Take the pipe off the non-return valve and see if you get water out. If you don't, then the pump is either drawing in air around the drive shaft, or the foot filter is blocked with slimy residue. If you do get water, renew the jets and the non-return valves. I wouldn't recommend using second hand parts, unless new are unavailable, for obvious reasons.

These are the part numbers:
Jets, UP TO '84 914 628 203 11 or 944 628 911 00 (heated)
Jets, '85 on, Right, 944 628 077 00 or 944 628 077 01c (heated)
Jets, '85 on, Left, 928 628 077 00 or 928 628 077 70b (heated)

Non-return valves, all: Right, (has tee piece) 914 628 433 00
Left, 477 955 481

 

[Guest]

924nutter - Thanks for your reply. I can confirm that the relay does chatter just before the wipers swipe.

 

[danmason]

ORIGINAL: 924nutter

Thanks, I'll try and check this out at the weekend.

 

[924nutter]

Terminal S1 on the relay earths, via the brown/black wire internally through the switch, on terminal S1. When the intermittent action is selected this connection is switched off. What I assume happens then is this starts an internal timer on a chip within the relay which pulses the self park circuit long enough for the s/p contacts in the motor to close and allow a single wipe. If the wipers go intermittent then this part of the circuit must operational, so it follows that somewhere between S1 on the relay, and earth, the continuity is being lost. Over to your qualified or competent auto-electrician to find out where.

 

[Guest]

[] Thanks for that I will check it out.

 

[Guest]

Wipers!
I don't know if the 924 system is the same in the 924S but by the sound of it they suffer in similar ways. I have a chattering relay and the spontaneous wipe. I cured the relay quite easily by pulling the damn thing out! That sorted the spontaneous wipe too, but it has the downside that the auto park no longer works and neither does the intermittent wipe mode (which isn't a surprise). Now I operate in two modes. In wet wintry weather I put the relay back in, on dry summer days I leave it out. Life's a real pain in spring and autumn. I was advised that this fault is caused by poor contacts in the stalk, but that putting a new one in wasn't always a cure because the Brazilian part now on offer, even from OPC is no where near as good as the original from Germany.

 

[924nutter]

This is certainly an option, and something I have done myself in the past. It could well be at the contacts inside the switch where the earth drops out. The only thing to do is wait till the fault recurs , perhaps with a jumper lead at the ready, and earth out terminal S1 on the switch to see if the wipe stops. Another place to investigate is pin e7 on the back of the fuseboard, to which the brown/black wire connects. If this is loose or corroded then the same thing will happen.

 

[Guest]

[&:] Sorry that it has been so long since I have posted on this item - especially as I was the originator!

Well - the car went into Glenvarigill, along with the technical advice from 924Nutter (thanks again for your help). They tried fitting alternative supplies to the relay without success.

Their next suggestion was a replacement Coil and Ignition amplifier (the silver box on the top of the front passenger side wheel arch). Cost £40 for the coil and £275 for the amplifier. Both fitted in mid-August.

That seemed to have cured the problem - BUT - still chattering from the relays and the old intermittent wipe without request issue - solution - remove the wiper relay. Having removed the wiper relay, there was still a "strange" noise from the area of the relay "holder". The noise sounds like my old model railway when the connections were a little corroded - a sort of fizzing noise.

I drove the car from Glasgow to Southampton with an overnight in Cumbria when my husband and I moved house. Unfortunately during the journey the car cut out, and then immediately restarted a couple of times on the rough and very bumpy back roads at the begining of the trip - with the annoying fizzing noise described above. When we reached the smooth motorway the problem ceased and the car performed faultlessly for over 350 miles.

I conclude from this that the original fault was a complex issue of more than one problem. I think that at least one of the parts replaced (fuel pump, fuel pump relay, ignition coil and amplifier) was faulty - I have often suspected the amplifier had an intermittent fault. I also conclude that there must still be an issue with the wiring.

The next step is to replace the relay holder and the wiring loom to the holder.

DOES THIS MAKE SENSE?

Liz

 

[PaulHere]

I've heard that the relay/fusebox holder can often be the cause of some strange electrical occurences - so I would investigate there next.

Hopefully that should cure the cutting out as well

Let us know how it goes []