Any Ideas?

[geoff Ives]

Last week I added a 924 Series 2 Turbo to my stable. Picked it up on Thursday and drove 150 miles home, no problem. Friday and Saturday drove another 90 mile, brilliant. Sunday drove to Brands Hatch (109 miles) fine. Six miles out of Brands hatch on the return trip it stopped. On leaving it a while it would start but not run for long. Next morning ( haveing been rescued by the AA) I changed the coil and fuel pump relay as I had those in my workshop and all seemed fine FOR SIX MILES and guess what? Same as before. There is one clue that could be a red herring. The fuel rump relay does seem to get quite hot.
The first member who gives me the answer to this problem will get a free entry to next years Cotswold Rally.

 

[924nutter]

The fuel pump relay will get a bit hot as the pump probably draws 10 or 11 amps, otherwise the circuit would not be protected by a 16 amp fuse. I did experience misfiring with my 924 lux which I traced back to an old and knackered fuel pump, that whilst apparently sound was running slow and making the mixture too lean. Check the connectors on the fuse board. Mine had got so bad that it had melted the plastic block that the terminals clip into, and the feed wire insualtion for about an inch. Put an ammeter inline with the pump to see what current it draws to satisfy yourself that the pump is sound. Check the overboost switch connection on the R H S of the pressure duct ( it looks like an oil pressure switch) and check the central earthing point where a bunch of earths, including one from the igniton module, meet, on the L H S of the pressure duct adjacent to the M8 bolt that secures the duct to the throttle body. Check the integrety of the vacuum hose in that area, just below the blue plug on the fifth injector, that connects to the vacuum/pressure transducer on the igntion module, and make sure the banjo bolt is tight. Inside check the plug on the module is dry and that a water leak from the heater matrix is not making the electrics wet. Try those first, thats a bit to be getting on with.

Did you see the red 924 turbo on the anniversary laps at about 10:20? We were allowed to overtake slower cars on the Monday, providing certain conditions were met, so that was me going past the 924S and the white 912.

Come back soon if you get stumped.

 

[Guest]

Reminds me of a problem I had with an MGTD! That was due to a rusty fuel tank that was sending debris to the filter in the fuel pump. It would work for a while but then stagger to a halt. Had to whip off the filter on the pump and then replace it. In the end the solution was a new fuel tank.

But then again these German cars aren't built like MGs are they!

 

[937carrera]

I'll assume the car will start and run when cold, but not run when warm. I suspect a problem with the control pressure regulator / warm up regulator. This adjusts contol pressure based on the temperature of the WUR which is driven by the heat from a bimetallic strip within the WUR and conducted heat from the inlet manifold. An increase in temperature causes a change in the deflection of the bimetallic strip which increases the control pressure as the car warms up and thereby reduces the amount of fuel injected per time period.

A non operating / not electrically connected WUR will dump too much fuel into the engine causing flooding. Control pressure when cold will be about 2 bar, rising to 3.5 bar after 5 minutes if my memory serves me correctly.

Can you give some more info about how the car actually stops running ? Suddenly / gradual loss of power / increasing reluctance to rev etc

ps Fuel pump relays are always warm [8|]

 

[924nutter]

Obviously I have contracted the same disease through osmosis from my keyboard. having got the car looking nice for the festival, I took it to work today. On the way back much banging of unburnt fuel in the exhaust, no power, wouldn't rev, would barely idle, with the rev counter pithcing wildly between 200 and 4000 rpm indidcating an intermittent ignition problem. Well one of these three things cured it.
A) I switched the radio off.
B) I rotated all but the four extreme left fuses ( headlight main and dip beams) in the fuseholders to help make better connection.
C) pulled the plug off the igniton module and pushed it back on again.
Purred like a kitten all the way home. You pays your money you takes your choice.

 

[red924]

re

Did you see the red 924 turbo on the anniversary laps at about 10:20? We were allowed to overtake slower cars on the Monday, providing certain conditions were met, so that was me going past the 924S and the white 912

.

That was me in the 924S you overtook.
You seemed to have a slight speed advantage over my auto box.
Had a great weekend

 

[geoff Ives]

Hi Guys.
I haven't had time to check the suggestions made by JB yesterday but have done the following. Removed the filler cap (in case of a breathing problem caused by thre tank not venting) Rotated all fuses changing one that looked somewhat second hand. Unpluged and refitted ignition module. By chance the radio was not switched on.

Started prefectly. Ticked over smoothly at about 750rpm. Drove superbly 2 miles then detected the slightest hesitentcy. 5 - 6 miles loss of power arrived in my drive at 7.8 miles and let it tick over. After 2 minutes the tickover deteriorated and some popping in bexhaust stysem. Switched off.
Any further ideas.
Geoff

 

[924nutter]

By ignition module, I suppose I really mean what everyone calls an E.C.U. which is under the heater matrix in the cabin. I have found moisture on multi-pin plug and socket which doesn't help. The popping is from unburnt fuel that accumulates in the exhaust when the plug doesn't fire, then explodes when a charge of hot gas or a fragment of incandescant carbon comes along the pipe. This is (horses not zebras) an ignition problem on a percentage basis. Don't forget the earth cluster by the throttle body. Also try running the engine up in the dark, as you will be able to see if any of the plug leads are arcing out. In point of fact, for the cost of a set of leads you could replace them and take them out of the equation. There is one dreaded solution which I am loathe to suggest, and that is the breakdown of the speed reference sensor, a small magnetic transducer gives the ECU information about engine speed. The sensors are made from unobtanium, and getting hold of a good second hand one is a nightmare. Word is out that the turbo wont run without it and breakers on ebay are looking at a starting bid of £65 for a known good one.

 

[924nutter]

For those who are interested I was bedding in a rebuilt head, which I ran up for the first time Saturday afternoon, and was gradually building up the rpm, which was why I was going slightly faster each lap.

 

[924nutter]

Not that this will affect the misfire, but tickover for the turbo should be 900 rpm +/- 50. Set this with the 12 or so mm dia screw in the lhs of the throttle body.

 

[geoff Ives]

John.
You will now be known, to me at least, as '924 Genius'.
After you last post I found the unit under the heater matrix and pulled out all the plugs and re fitted them. I drove the car 15 miles. All Ok. Then I took it out (with my AA card clenched between my teeth) for 40 more miles. Perfect.
As promised I would like you to be my guest on next years 'Carole Nash Cotswold Rally'.
We will need as many 924's to try to regain the Best Register Trophy.
Thanks again,
Geoff

 

[924nutter]

Count me in. You must bring the new steed to the Anniversary celebration at Reading, where we be able to put faces to names.

 

[geoff Ives]

You shouldn't have a lot of trouble placing my face. It has been with me for 60 odd years and around PCGB quit a bit. As 911 2.7 Register Sec, Heritage Group Sec. Cotswold Rally Organiser, Manx, Irish and Isle of Wight Tour Organiser. Register Director and Cotswold Regional Organiser.
See you all at Reading.
Geoff

 

[924nutter]

Not you, me!