Technical Cinquecento 900 does not Start (Ingition ok, fuel injection not), starts with Brake-Cleaner!!!

[Roachdale]

Dear all,

i´m new to the forum and searching for some help as my Cinque is driving me mad.

i´m spannering since 30y, but mainly on carburated historic cars.

around 1y ago i purchased a Cinque 900 for my mothers caregiver ...i wanted a simple car without too much electronic, no electric windows, no power-steering , no aircon, no cambelt to change etc.... so i deciced for the "oldschool" pushrod engined 900. the car has original 40.000km, is rustfree and besides some dents in really good condition.

so far so good until recently:
one morning the car did not start anymore, it was running faultless b4:

starter motor turns over the engine as fast as usual, i have spark, i have fuel up to the throttle-body ( & each time you switch igntion to ON, you can hear the fuel-pump running / priming). but the injector does not inject any fuel during engine-cranking.
thats easy i thought...i will buy a new injector and thats it.

Nope it wasn´t, the new injector, as well as 2 used ones (from collegues) show the same problem.
on one PIN of the injector i can measure constant Voltage, once the ignition is ON. so the injector must be triggered by the Minus i guess?

if i spray brake-cleaner into the thottle-body the car starts straight away...sometimes it only runs until the brake-cleaner has burnt away , sometimes it keeps running and the injector works as it should.....but after 1 or 2 minutes, the engine dies again...sometimes it restarts...sometimes not.
if it runs and i move / bent / wiggle on the wiring-loom it remains running...the loom is original, not messed around with, no sings of marten damage / bites.

with brake-cleaner it ALWAYS starts straight away.

i can simulate this fault with 2 ECU´s (1 with immobilizer, 1 without)
for peace in mind i also changed the crank-sensor....obviously the problem remained (as i always had spark)
i also used a starter cable to connect battery minus with the engine-block...just to exclude an earth problem....problem remained.
meanwhile i´m lost. it looks like my injector sometimes get tiggered and sometimes not. but as far as i understand this basic-injection system , during start all the other sensors are not responsible for the injector to open at all?


do you have any ideas?

 

[loucifer]

Injector operating during engine running, makes a distinctive ticking noise. So I believe no ticking noise means that the injector is not opening and closing. Also you can see the liquidation of the fuel mist on the throttle body butterfly when the engine is running. Maybe there is some fuel starvation due to a blockage in the fuel line or a intermittent fuel pump problem.

Edit. You are right, the injector is triggered by minus from the ECU.

 

[Roachdale]

you misunderstood me: the injector seems not to get tiggered...in most cases...but in some cases he properly gets the trigger signal and you can also see and hear it working...i can even drive the car for 1km or so until it dies again.
sometimes it starts straight away, without help of brake-cleaner, most times not. (and i need bake cleaner)
sometimes it keeps running after the brake-cleaner start, often it dies after brake-cleaner is burned away.

my problem is: why the injector gets sometimes triggered and in most cases not.

it doesnt matter if its a cold start or a hot-start....if this helps.
it doesnt matter if i use ECU 1 or ECU2

 

[loucifer]

you misunderstood me: the injector seems not to get tiggered...in most cases...but in some cases he properly gets the trigger signal and you can also see and hear it working...i can even drive the car for 1km or so until it dies again.
sometimes it starts straight away, without help of brake-cleaner, most times not. (and i need bake cleaner)
sometimes it keeps running after the brake-cleaner start, often it dies after brake-cleaner is burned away.

my problem is: why the injector gets sometimes triggered and in most cases not.

it doesnt matter if its a cold start or a hot-start....if this helps.
it doesnt matter if i use ECU 1 or ECU2

According to Haynes, injector gets 12 volts from the one of the 87 contacts of the fuel pump relay (the other 87 contact powers the fuel pump itself) and minus from the 18 pin of the ECU. My approach would be to check continuity of the wires to eliminate broken wire fault.

 

[Roachdale]

This has been already checked and is fine

 

[Ralf S.]

The problem seems to be that the injector is okay but it's not being asked to fire (which includes the signal doesn't reach the injector). Either the fuel relay or connection around it is faulty or the wiring to the injector connecter plug is broken up and only works intermittently.

I suspect it's the injector connector block. If you remove the connecter plug from the injector you can fit a voltmeter into the pin claws... (or use a glass bottomed T20 bulb with the metal tangs folded out.. they'll fit into the connector block pin claws). When you crank the engine, the volts or the bulb should "flash".


Ralf S.

 

[Roachdale]

all this has been tested and is fine.

relais been swapped, relais been changed, wiring checked and measured.


every morning i can start the engine in 80% of the cases without problem....after 1 minute or so it dies...it can be restarted multiple times.....always dies after 1 minute or so.....than after a certain amount of starts it ONLY Starts by using brake-cleaner into the throttle body....with brake-cleaner, in most cases, it keeps running when the trottle is opened during start.

when it dies you can still hear the fuel-pump running a few milliseconds after, and in the moment it dies you can see that the fuel-spray from the injector just stopped b4 it dies.

 

[Ralf S.]

When it dies, does the injector have a signal? It fires up with brake-cleaner, so I guess the sparks are always working.. but if the injector is working but just not giving the car enough fuel, then that's a different problem to if there's no signal for the injector to work at all.

My thought is that there is a fuel starvation.. or low fuel pressure that only becomes insufficient to keep the engine running after a few minutes. You can test that by turning the ignition on and off a few times to prime the system after it's died... so that it can build up pressure again (if that's the problem).

A weird fault I had once (not on a Cinq) was that the fuel pump suffered from a split pipe, from the lifter to the outlet connector. So, the pump worked, the fuel was getting pushed up the pump and into the fuel lines but at higher revs, the split in the fuel pump was leaking fuel out of the pump/pipe back into the fuel tank. It took ages to track down.. but when we took the pump out the split pipe (it was a rubber "in-tank" spec' hose) had an obvious split in it.

Yours could be doing something similar.. but it fires with brake-cleaner, so it's a fuel problem for sure.

Ralf S.

 

[Ms402]

Put a gauge on and check the fuel pressure, you should have around 1bar of pressure. Check that the fuel filter is not clogged.

 

[Roachdale]

car is in the lokal garage since 5 days....they checked the error codes in the ECU....none....interestingwise they could not connect anymore to the ECU after several failed starting attempts. very strange.

the garage was telling me that the fuel-pressure on those injection systems are usually never a problem.

 

[purf]

Sounds like perhaps weak fuel pump or fuel filter which is under the car?

Will full throttle help at all when it stalls?

 

[Roachdale]

the ECU was damaged / playing mad.....it turns out that an ECU from an early NON-Immobilizer car, will fail after acertain time of usage (6 Months) when installed in a Immobilizer car (1998 model).

as an unlucky conicidence 1 pin was bent on my original (Immo-) ECU, showing simlar starting symthoms....after the Pin was straigtend the car fired-up straight away.

my garage told me "those single point injection system usaully never have problems with fuel-pressure, clocked fuel-filters, non-working injectors" "those systems work reliable and troublefree" "the only IMORTANT sensor that the car starts and runs is the crank-sensor...all the rest are non-important sensors, that the car runs properly....but it will always run, even with a map or temperatur sensor giving up"

 

[Ralf S.]

my garage told me "those single point injection system usaully never have problems with fuel-pressure, clocked fuel-filters, non-working injectors" "those systems work reliable and troublefree" "the only IMORTANT sensor that the car starts and runs is the crank-sensor...all the rest are non-important sensors, that the car runs properly....but it will always run, even with a map or temperatur sensor giving up"

Yes... that's why this was a weird one. But great that you sorted it.


Ralf S.