1.6 Gti Injection/ Ecu Questions

[Astra Dan 0]

Having recently aquired a 1989 1.6 GTi, I'm trying to familiarize myself with how it works before I tackle it.

 

Firstly, I'd like to understand the fuel injection system. From reading other posts and searching, I get the impression these cars don't have a full blown electronic injection, rather a basic circuit that controls fuel and spark timing. It doesn't refer to a pre-programmed map, and it's doesn't have any facility for 'learning'? It also appears to have no way of indicating a fault? I can see no 'ECU' light on the dash when the ignition is on. I'm used to Vauxhalls and their handy ECU light that lights up when there's a problem, and you can flash out the codes relating to faults by shorting 2 wires on the diagnostic socket. Is there an equivalent on this engine? I'm lucky in that my 205 did start, but I'd like to keep it happy. Is there anyway to detect a fault, other than the engine behaving erractically?

I know there's a water temperature sender for the dash guage, and a switch for the STOP light, is there one for the ECU as well? I've read the engine has a TDC sensor, but it's not connected and is for reference, is this correct?

I also see there's a throttle position sensor and a obvious flap-type airflow meter. Are there any other sensors the ECU uses? Where is the ECU itself?

 

Sorry for the long post. Many thanks for any answers!

Edited November 19, 2007 by Astra Dan

[pug_ham 240 3 Cars]

Hi Dan,

 

The jetronic ecu is a very simple one, it only really controls the fuelling & the spark timing is still mechanically controlled by the dizzy. (Its often considered a clockwork ecu).

 

You are right saying that the 205 doesn't usually have an ecu MIL on the dash unless its a late cat equipped 1.9 model.

 

Not many engine sensors have an input to the ecu, in fact only the coolant temp sensor (not the dash guage) has. None of the engine other oil pressure or water temperature sensors send a signal to the ecu.

 

You are also correct saying it has a TDC sensor but its not used by the management system, its purely for diagnostics when plugged in at a dealers (to get an true rpm signal).

 

The throttle position sensor is just an open closed switch with no signal for its actual position except closed at idle or WOT.

 

The ecu on your car should be up under the dash in the drivers footwell. There is a hole by your irght knee as you drive, its in there along with the tachymetric relay.

 

When something is wrong you have to try to figure out what & replace those bits.

 

Graham.

[Astra Dan 0]

Excellent, thanks very much for the reply.

 

So is there 3 coolant temp senders? 2 under the inlet, one near the dizzy? Gauge, switch and ECU?

Edited November 19, 2007 by Astra Dan

[Astra Dan 0]

Another thought.

 

If the TDC sensor is not connected, how is the fuel pump triggered? From the coil in the same way the rev counter works presumably?

Edited November 19, 2007 by Astra Dan

[pug_ham 240 3 Cars]

Yes, there are three coolant sensor, one for the ecu & the other two are in the thermostat housing, usually behind it towards the bulkhead. One for the temperature guage & the other the temp warning switch.

 

The fuel pump is triggered by the ignition momentarily for starting & then the relay is held closed by a wire that branches off from the coil feed (wire 32a) once running. The relay then opens again when it looses its spark.

 

Graham.

[Rob_the_Sparky 9]

FYI the closest that Jetronic gets to a map is a laser trimmed variable resistor in the AFM, hence a Jetronic AFM is specific to a particular engine type.

[Astra Dan 0]

Thanks for the replies. Much appreciated.