205 GTI 1984 Startup problem

[Lexa 0]

Hi!

 

Fresh 205 GTI 1.6 Jetronic project owner here bothering you and seeking your wisdom for these brilliant vehicles. I'm a proud owner of 1 ex 106 gti and currently have my second 106 gti project nearly finished!

 

But now for my first 205 GTI which I got my hands on fairly decent price because it wont run and is quite beaten up.

 

Here is the list I have already done following your forums:

 

1. Changed the ECU temp sensor for brand new one

2. Changed spark plugs for brand new one

3. Changed fuel filter for brand new one

4. Checked that the TPS sensor works properly

5. Checked the Tachymetric relay which was located in the black box besides the battery. I think it's very original one because of the humongous size of it compared the pics I see here and google. And it should work properly as you may read below

6. Contact sprayed and checked a hell of amount of pins /clips and wires like AFM etc. and tested them with multimeter

 

SO

 

When I crank the engine this is what happens:

 

The motor will fire up and then shut down immediately. It will run without any help like MAX two seconds.

 

Here is what I tested so far:

 

Just sprayed a whole lot of start spray into air filter and when I got the engine running I could spray the whole can down there and it wouldn't shut down. It runs very smoothly with all cylinders for laying around 20 years without driving it.

 

I have checked that fuel pump makes noise and when I take hose out of the filter there is nice burst of fuel coming when cranking. I also took out fuel injectors and cranked the engine they all sprayed fuel.

I checked that the the AMF opens when cranking the engine and it did. I also tried to run the engine without the AMF see if it does anything but it's the same.

 

By now I figured out that it may still be a fuel injection problem and to confirm that I left the fuel injectors out, poured gas right into cylinder and cranked the engine. SOON as it starts up it cuts down the fuel supply. Injectors completely stops spraying more fuel. Engine stops and after that the injectors will again spray 3 or 4 times when cranking and the motor fire ups following again immediate shut down.

 

This is just beyond me there must be some sensor left that I haven't checked or bad wiring etc. Somehow something tells or is not telling the ECU to supply any more fuel. Maybe it doesn't recognize that the motor is running and need fuel? I have no idea.

 

I have not yet tested SAD and I consider replacing of ignition amplifier (contact sprayed it though) and the Tachymetric relay for just to be sure. Or now when I writing this down I'm thinking maybe it's just a coil problem?

 

I SEEK YOUR GUIDANCE O WISE ONES

 

Thanks in advance!

 

[welshpug 1,661]

If you've  never seen it run/drive for long and it has been sat for some  time I would start by getting the injectors  sent away for testing/servicing.

 

if you had an inline spark  indicator you would be able to see if you are losing  spark or its a fuel problem  (if its  still running on easy start spray  then this confirms  you have spark fine however)

 

The ecu fires the injectors dependent on getting a signal from the ignition  amplifier which is triggered by the low tension side  of the distributor.

Edited November 3, 2022 by welshpug

[stewal 8]

If I remember correctly doesn't the tachy relay supply the fuel pump during cranking then the oil pressure signal from a running engine supplies a signal to the tachy relay to run the fuel pump?

 

The idea being the fuel pump stops with the engine.

 

If that's the case, assuming you have oil pressure, I would suspect the oil pressure switch, wiring or tachy relay.

[welshpug 1,661]

no connection from oil senders to the tachy relay.

[Tom Fenton 1,542]

7 hours ago, stewal said:

If I remember correctly doesn't the tachy relay supply the fuel pump during cranking then the oil pressure signal from a running engine supplies a signal to the tachy relay to run the fuel pump?

 

The idea being the fuel pump stops with the engine.

 

If that's the case, assuming you have oil pressure, I would suspect the oil pressure switch, wiring or tachy relay.

I have come across cars that work like that, but the 205 GTI does not.

[Rob_the_Sparky 9]

Well given that it runs on start spray then it suggests that there is a fuel problem (too much, to0o little or none at all.

 

Stuff I can think of that will impact it running if there is spark present:

 

Air leaks into the inlet after the AFM (A classic being the bolt in the inlet manifold that hold the distributer being missing but I have done that and it will run on throttle like that but not long at all on idle)

Fuel pump, injectors, pressure regulator, filters (I think there is one in line but not 100%), crap fuel, distributer wire to ignition amp and the amp itself (the ECU gets its rev input from here), water temp sender (the ECU one, not the two for the dash gauge and light) and of course the ECU itself.

 

Note: ECU is fuel only, spark is distributer driven (distributer, wire to ignition amp, ignition amp, coil, HT leads, spark plugs)

[Lexa 0]

Thank you all for your replies! Appreciate it!

 

As for weekend and today:

 

I tested out other coil, no luck.

I did override tachymetric relay that the fuel pump and injectors get constant power, no luck, ALTHOUGH it did run sometimes few seconds longer than usually

I took out the pressure regulator and tested it, it releases pressure around 2.8 bar and holds it around 2.5 bar.

I took out fuel pump. I put it in a bowl and connected it straight into 12v and it burst liquid around 1 meter off the ground constantly

 

I'm starting to believe it's the ignition amplifier or the wiring of it.

 

Tomorrow I will get my hands on for a fresh one, I'll keep you updated!

 

 

 

[welshpug 1,661]

If it runs on easy start it will not be the coil.

[Lexa 0]

Hello again!

 

I got the part today morning and switched the ignition amplifier and well it definitely did something. With each crank it almost starts but not quite, so not a total waste of money to switch that. (with the old one it might take few seconds it to sound like its starting)

 

I read from this post that this guy Gavin got the car running when disconnecting the connectors of AFM and ECU temp sensor (CTS?) out. And oh boy it worked for me too! It runs rich but engine sounds good and healthy. (For record I tried many times starting without the AFM but never disconnected the temp sensor for ECU).

 

 

Roundup: This guy had swapped old fuel pump to a cheap Chinese version and after that the car wouldn't work and had very similar problem with me. From may to august this guy battled with the car testing everything but in the end, he did swap the old fuel pump back and boom it was working again.

 

The first thing I did with this car was that I bought the new CTS sensor and replaced it. So that should sort that one out. I will test the values of AFM  and CTS but if they seem alright I think I'm going to invest fuel pressure indicator to check the whole fuel system if my fuel pump is in its end of the road. They were rather expensive ones when I did research.

 

Getting there little by little!

 

 

 

[DamirGTI 342]

If it's been sitting unused/non runner for that long , with the fuel still in the tank , expect to find all kinds of crap inside the fuel tank as well as inside the entire fuel system (steel lines , injector rail , injectors ..) and damage done to the fuel pump (roller cell mechanism) .

 

Modern unleaded fuel goes "sour" in about 3 months (firstly mainly loses octane rating) .. pushing 6 months or full +1 year and especially more/longer it'll start to degrade badly and eventually it'll solidify/crystalize .

If that's the case , need to clean up the fuel tank , fuel lines , rail , injectors . And check the fuel pump .

 

Try to "feed it" with the fuel pump arrangement in external tank and supply hose/system  .. find suitable container , fill it with fresh fuel (add/mix in some acetone and xylene to break the fuel deposits in the fuel rail and injectors) , connect with hoses , wire up and dip the pump inside - have a fire extinguisher near !!

And try like that , see what happens .

 

Chinese fuel pumps - don't even bother ... Only new Bosch pump or old used/second hand one (they do last for very long time , unless they've been left sitting inside the tank full of old stale fuel)

 

D

[Lexa 0]

Hi and thanks for answer!

 

I have pretty much cleared the fueling system and when I took out the fuel pump out I saw there was close amount of fuel that I have put in it! I don't believe it's the issue.

 

Today I tried to crank it up and the car wont start.... again! The starter motor is rotating the engine but It doesn't even promise now when till yesterday it did try to run and fired up after I disconnected the AFM and CTS. I checked that there is still spark (though it looked much weaker to me) and fuel coming. The spark plugs were pretty moist and tips were covered with carbon so I gave them a good clean. Still no luck.

 

I then tried to switch back old coil and ignition amplifier, no luck.

 

Cleaned plugs, dizzy cap and leads.

 

Is there some sort of fuse or relay that can do this problem? (Counting out the tachymetric relay) Or maybe it's just the wiring if I have accidentally done something when reaching  the CTS sensor as it's below the dizzy cap and there are all sorts of wires and plugs etc in that area.

 

Note that I changed nothing after yesterday, absolutely nothing.

 

Thanks!

 

 

 

 

[DamirGTI 342]

Yes , the SAD and CTS both have 2pin connectors ... blue should go on CTS , black on SAD .

You might've mixed them other way round ...

 

 

Tachymetric relay on very early cars (such as yours) is (should be) different than the usual ones on later cars .. burnt diode inside the tachymetric relay can cause similar problem , i've had those on a few occasions .

Try to open up the relay and inspect the internals with magnifying glass .

 

D

[DamirGTI 342]

.. also , thinking about this , could be something simple like eroded/dirty sticky contacts on the tachymetric relay .

 

Try cranking the engine (needs two obviously) while taping the relay with a screwdriver handle , if it makes any difference .

 

If not pop the relay cover off , leave it connected and press-and-hold relay contacts with you're fingers (if the wiring and relay are good you'll hear fuel pump buzzing ..) and again try to start it up like so ... if it starts and continues to run as long as you're holding the relay contacts , it'll be that .

 

Then , clean up the contact tips .. diamond file would be ideal but , fine grt sandpaper will do the job too .. wash off with contact cleaner or similar , and see what happens .. does it start and runs afterwards by itself or not .

 

http://www.dethomaso.fr/article-verification-du-relais-tachymetrique-65914473.html

 

D

 

Stolen pictures for demonstration purposes :

Edited November 10, 2022 by DamirGTI

[Lexa 0]

Thanks very much for reply!

 

Haven't tested that one yet but will give it a go if needed!

 

Little late update!

 

I left the car for a weekend ( 11-13.11) battery off and let it recharge. I also plugged everything back on as they should be.

Then on Monday 14th I decided well what a hell lets just put the battery on and crank it (I have read many posts that suddenly everything is fine) and well it happened to me also! (Kinda) Car fired up nicely and it did run very smoothly idle. But there was a choking problem if I gave it throttle it would shut down. It was choking. But with little bit of throttle tipping it would rev so I guess there is a mixture problem of air and gas that needs to be sorted. I let it run idle for 5-10mins and shut it down from the key.

 

I tried to fire it up again but it didn't want to start. It sounded the same as I did describe 10th of November reply.

 

Then few days past, same thing and it would fire up nicely. Gave it a small spin and it moves back and forth. Positive! But yet again it wont start warm.

 

Getting there little by little!

[Lexa 0]

SOLUTION

 

So I started the car again yesterday, it fired up really nice then after 2 minutes it shut down itself. Then it hit me.

 

Why is that when I leave car for a while and start it, it fires ups so nicely and all works well for a few minutes then it dies? It must be air! problem because of multiple times checking that injectors fire, fuel pump primes, pressure regulator works, etc.

 

So after the car died yesterday again, I took out the fuel cap, luckily I had spare hands available so I asked my girlfriend to seal  the cap and fill it with compressed air and after few seconds it did fire up.

 

Conclusion: The make-up-air of fuel tank was clogged. It must be that the air flows just enough that it runs after a while of waiting.

 

Note! In the past I did try several times starting without the fuel cap on and it didn't work! When we got it started with compressed air I left it running for 5-10minutes THEN put the fuel cap back on when it was still running and BOOM, Almost immediately shut down.

 

So I did "waste" around 100 euros for parts which I probably didn't necessarily need, but I think sooner or later they should have been swapped anyways, so whatever. It fires up so nicely now.

 

Hope this one helps someone out in the future!