924 points ignition

[vitesse]

Have posted here as the problems are (or could be engine wide)

Have a friend who has an early 924 which he has had resprayed over a couple of years-it hasn't run for 4/5 years so he's had it delivered to his home garage here in Formby & has asked me to get it going(he knows little about cars & engines & has also had a brain tumour a few years ago but is in remission ,but not able to crawl around cars too easily)
I went to look at it whilst it was in the sprayshop & the sprayer(allegedly a friend of my friend )said he had tried to start it but on each occasion petrol had flooded the engine causing a hydraulic lock in the cylinders-his conclusion was that the CIS was faulty & it needed a new fuel distributor.
The battery was low but I got 12 volts at the distributor & noted that it had points & capacitor,decided to leave it until at my friends house.
Have got the Haynes manual ,also my friend has the full Porsche w/shop manual & note that the very early 924's had points ignition with no ECU module,using ballast resistors with the coil.

At his house,I have found HT at the plugs,the fuel pump runs but haven't tried to start it as battery was low.
Suspicious about the hydraulic lock,I checked the oil level,was about 2 litres over level-smelt strongly of petrol so drained the oil which seemed to be 50/50 oil-petrol,removed the newly fitted filter again same contents-these actions 2 weeks apart to let any petrol remaining evaporate,refilled with flushing oil & fitted new filter.
Having removed all spark plugs(new) but heavily sooted,engine turned over several times with now charged battery but had removed king lead & fuel pump relay.

As I don't wish to risk repeating the flooding episode,my next job is to check over the electrics of the CIS-& this is where I need some advice or pointer to a better treatise of checking the fuel distributor/pressure regulator system/cold start system than the Haynes manual.

a)Can the fuel distributor be jammed internally such that it overfuels & floods the engine?
b)Is it more likely to be say electrical-like the thermotime switch/pressure control valve etc?
c)A combination of both?

Any pointers to a easier diagnosis without stripping the fuel unit would help-I haven't got a fuel pressure testing gauge-although most other things like multimeter,test lamp,strobe etc.

He also has a spare 924 donor car but electronic ignition with ECU module,so a spare CIS set could be stripped,reworked if necessary-I know the manual suggests using all new seals etc but as I am doing this in 1.5/2 hr visits I need a short cut approach.

Car refs:-1977 model chassis no 9247107220-engine-XJ000490

Spare car;-1983 VIN-WPOZZZ92ZDN402227-engine-XJ007592

Incidentally,the spare car remnants will be available to anyone interested.

 

[vincematthews]

The Bosch Jetronic system, on these early cars, is a mechanical injection system. I like to think of it as a pump, fuel distributor and injectors plus some other components that correct this or that operating condition - fault finding can be frustrating. . There are several things that could contribute to your problems but I would start with the simple things first.

If you have a Haynes manual, do the fuel injector test listed on page 78 (Section 4.13 of Chapter 3).
This confirms whether the injectors are delivering the right amount of fuel and more importantly - in your case - are shutting off properly and not leaking fuel into the inlet manifold.
This test checks the fuel distributor too.

Don't forget the 5th injector (cold start) on the rear of the inlet manifold.

For other tests on the system, I made myself the equivalent of Porsche pressure test tool P378. It did cost me £50 but saves a lot of chasing around between the various components.

BTW should you need it, I have a brand new fuel pump which I believe will fit a pre 1979 model - bought in error.

 

[jwindwood]

Easiest fuel test is to:

Remove all 4 injectors and place in separate glass jars.

Remove fuel pump relay and bridge connectors so that it's live as soon as the ignition key is turned

Turn on ignition. If the injectors are firing, turn fuel screw until they just stop

Remove air filter and lift fuel metering plate-this should make injectors fire.

If so, the car should now start (Roughly) if its a fuel issue. You then need to fine-tune the mixture with a gastester.

 

[vitesse]

Vince,John,
Thanks for your assistance.I presume that once the sensor plate is lifted by induction airflow as one cranks the engine,unless the engine fires,then fuel continues to be pumped through the injectors until you switch off again-John ,your tip to adjust the fuel screw presumably minimises the fuel flow & is somewhere close to how the car should run.I have got a Gunson gas tester so can adjust mixture strength subsequently.

Regards,
Colin.

 

[mcscrew]

This link explains how the system works: -

http://www.auto-solve.com/mech_inj.htm

And this link, from the Mk1 Golf Owners Club, might be of some help for diagnosing your problem.

http://www.vwgolfmk1.org.uk/modules.php?name=Content&pa=showpage&pid=42

My Mk1 had sat for 11 years, and the old fuel in the system had turned sticky and jammed the sliding pin in the metering head - it's possible that you've got the same problem here.

If you can remove the metering head assembly you'll be able to see if the pin has jammed easily.

Hope this helps

Rich

 

[vitesse]

Rich,
Thank you for that information-there is no resistance to lifting or depressing the sensor plate,but I guess that is because the fuel pump needs to be run to pressurise the fuel distributor or the pin as you indicate is stuck.
Last weekend ,even with an LED spotlamp,I couldn't identify the Thermotime switch-I presume it is under the inlet manifold somewhere-this was part of initially checking out the resistances of the various sensors prior to using the glass jar process as in the earlier posts by Vince & John.
Hopefully ,this weekends visit will address that problem -plus checking the injectors & the plunger.
Thanks again ,everybody.

Cheers ,
Colin.

 

[vitesse]

Extracted all injectors plus the cold start 5th injector last weekend-don't half need a sharp action upwards to "plip" them free of the housing.Made up a fused jumper lead & this weekend checked the fuel flow.
Even with the airflow plate closed,a total of 400cc's of petrol flowed in 35 secs,1st try-followed by 210 cc's in 30 secs the 2nd-& that's without the CSV,so Rich,it looks certain that the valve is as you suggest,stuck fully open-that flow equates to 5 gallons an hour or so which wouild be distressing at say 30 mph,never mind tickover..

As it's difficult to observe the engine ,check the effect of the sensor plate whilst being ready to remove one of the the jumper lead connectors,this week I am going to make up an extension lead including the fuse & a switch so I can be at the front or side of the car when do more this coming weekend.

Need to get new washers & "O" ring this week-is there a trick to save the valve dropping out & getting damaged if I avoid the extra work of removing the entire airflow assembly?

Again,thanks for the assistance-learning all the time.

 

[mcscrew]

I think you're right - that flow rate sounds really high, and a stuck valve would match the lack of resistance from the metering plate, and the flooding you first experienced.

I dug out a pic of my metering head - I tried to tease the central pin out for ages and was really gently with it, but that didn't work. Even when I'd soaked it for a few days in fresh petrol and fuel system cleaner it still wouldn't budge.

In the end, I used some water pump pliers (ahem) and twisted the central pin around its axis - that broke the pin free of the fuel gum, and then I could tease it out a bit more gently. The steel it's made of was so hard that I didn't even mark it with the pliers - I had to use quite a lot of brute force but I got away with it. In theory it should be simliar on the 924.

There's no need to remove the nut and washer on the underside of the metering head either. I thought it might help with clearance for gripping the central pin, but it makes no difference.

Hope this helps

Rich

 

[vitesse]

Removed the fuel distributor top this last weekend-removed the whole unit 1st so could invert to prevent plunger dropping out if loose.Wasn't loose-completely stuck right in with only the tapered end of the plunger showing so nothing to grip at all to help break the stiction.
Have initially sprayed with teflon penetrating fluid-no effect-then brake cleaner (isopropyl alcohol)-no effect-now left soaking in 2-stroke garden equipment fuel-will now try effect of hot soldering iron to try & break the grip-once petrol vapour evaporated-also used my compressor to pressurise the pressure control inlet union-no effect.#
Spoke to a guy in Bedford I found on the web-he reckoned it can take 10 bar to break a stuck plunger but would need a threaded adaptor to apply that pressure which I don't have & my compressor doesn't do 10 bar,anyway.

When I asked him about stripping the 2 blocks of the head unit,this is the normal solution but reckoned I would not be able to get them to seal properly again afterwards.Anyone any idea whether it is a metal to metal seal using a joint sealant or is there a thin gasket in the joint?

Anyway,thanks to you ,now know the problem & solution-will leave to soak more but am likely to attempt the split.

Solved another problem on the e-bay track day car(red)-the lefthand rear sunroof drain pipe wasn't connected at the metal drain outlet -hence a continually wet rear footwell & steamed up windows when used in the winter..
The roof lining here was split when I bought it-clearly the seller had tried to replace himself without success-does anyone know whether you can buy a suitable material to repair it perhaps using a glue or black tape?

 

[vitesse]

Got 10 off the 3 sizes of copper washers & 2 new o-rings(1 as a )spare today -cost £2.50 at local fluid power distributors & separated the 2 blocks tonight with very little difficulty.Had to tap out the control plunger which stuck again when reinserted so will need to fully clean out the housing bore more later.As it's a waisted rod with 2 separate cylindrical ground sections above & below the waisted part,I suppose it is to be expected & needs to be flooded with fuel to lubricate it.

There is a thin metal shim at the joint (to answer my own question) & 3 small & 2 large O-rings on the outside of the sleeve the plunger fits into which make a seal within the top block.
It may be a case of a gentle rub with jewellers' rouge or silver polish to regain the correct sliding fit.

 

[mcscrew]

Mine cleaned up nicely just using petrol and a rag - the fit is unbelievably tight even when it's working properly.

All the advice I had from the Mk1 forum said don't split the metering head apart as it won't seal properly again, so I'm really interested to find out whether it will. When you get into things that not that many people have experience of (as I did when mine was stuck) people often quote what they've heard so you can never be sure it's accurate advice.

Hope all goes well anyway

Rich

 

[vitesse]

Rich,I know ,I know-having been told that,I have been considering the best way to get it leak free-thoughts include ;smear of petroleum jelly on the open face of the shim/gasket-pressing blocks together in a vice as screws are tightened,alt using clamps-it can't be rocket science-after all,some of the petrol pipes are only a cone contact fitting at the same pressure-I intend putting petroil mix in a spray bottle & well irrigate the parts as I assemble them.Hopefully,my wife won't hear the expletives!-she might hear the explosion though if the petrol vapour ignites[&o]

 

[vitesse]

First attempt,everything worked but weep at the block joint,despite clamping & tightening screws diagonally in rotation.
Since then,had it confirmed that steel shim gasket is a 1 shot job & impossible to get ,although have seen them in a kit with the O-rings on e-bay on the continent for £45 or so.

Also seen a post on American site showing rebuild of a 928 distributor re-using the shim with the use of a joint sealant called Indian Red Lacquer-so I am not giving up without a fight,have purchased a fuel resistant joint sealant & will FIGHT.

There seems to a school of thought that at the factory they used a jig drilled pressure assembly plate allowing the screws to be inserted by multiple driving head whilst under a press of some sort.

Last resort will be to send it to KMI in Bedford who rebuild them --for £216 + VAT.

 

[mcscrew]

That's interesting about the shim - if you don't have any luck with the sealant let me know, as I think I kept the fuel distributor from my 924, which did work ok last time I ran the car (2010 I think).

I can't quite remember where I put it but there's only a certain number of places it can be

Rich

 

[vitesse]

Rich, that's a kind offer-it would have to be the very early version with steel braided fuel lines right up to the banjo fittings that fit onto the outlet ports-year 1978 on did away with the electrical sensors & the pipes became steel at the distributor.

 

[jwindwood]

ORIGINAL: VITESSE

Rich, that's a kind offer-it would have to be the very early version with steel braided fuel lines right up to the banjo fittings that fit onto the outlet ports-year 1978 on did away with the electrical sensors & the pipes became steel at the distributor.

Braided fuel pipes remained until 1980 MY, so that gives you more chance......[]

 

[vitesse]

Are you sure ,John,I am sure the workshop manual shows the change in 78/79 although the remaining fuel line after the steel section may have still been braided-will have to check-the main change is the removal of the electrical sensors & also the injectors changed to an inline connection as well as the change to a DME & Hall effect ignition-there again I'm learning all the time.[8|]

 

[jwindwood]

Absolutely. The 1979 MY car I'm restoring at the moment has fully braided fuel hoses from fuel distributor to injectors etc, but has points ignition.
My previous project car was a 1980 MY and that had braided hoses, but electronic ignition.
My 1982 car has steel pipes.

 

[vitesse]

John,
The spare 924 my friend has unfortunately is the later version so can't swap bits easily.-However,the distributor plate is stamped-0 438 100 039,then underneath-060 82398 722.

 

[mcscrew]

My 924 was a 1983 model, with the steel pipes attached to the metering head, so I'm fairly sure it won't work.

It'll still be knocking around somewhere if you get really stuck

Rich