Help Needed, 1.6 Wont Start

[RP1983 4]

Hi everyone,

 

I recently bought a 1600 gti non runner.

 

I was told by the previous owner that he has heard it run but he couldnt get it going for me. He seemed to think it was a fuel relay problem but after swapping that for a known good one it still wouldnt go.

 

The car turns fine on the key, I have good spark across all four leads and I have put power to the fuel pump myself and checked that the pump is spinning the correct way but still no joy.

 

Unfortunatly at some point in the cars life it has fallen into the hands of a diy electrician and most of the wiring appears to have been tampered with so I am facing great difficulty trying to trace the power problems and ideally need to just give everything power myself to make it fire.

 

Can someone please give me any direction to go from here as I really wanted to hear the engine run before I remove it. I also need to know how can I test for a pulse at the injector and what controls this?

I tried to test it earlier with a 12v light bulb but got nothing so suspect this could be the problem at the moment but was not sure wether the injectors even use 12v

 

Any help will be greatly appreciated.

[Anthony 1,003]

Injectors should have a +12v feed on one pin from the tachymetric (fuel pump) relay, and the ECU pulls the other pin to ground to fire the injector.

 

If the relay is suspect then it's probably worth temporarily bypassing it by using a couple of pieces of thickish wire from the constant 12v wire (brown usually) to the two thick white wires - this will provide constant 12v to both the fuel pump and injectors. This is purely for testing - don't leave it like that as you'll flatten the battery and could prove dangerous in an accident.

 

The 12v power feed for the tachymetric relay comes from the shunt box in the engine bay near the battery - worth checking that the wire is still connected, and that the fuse (under the black cover) for it hasn't popped. It's the single brown wire that disappears off under into the loom and underneath the inlet manifold.

[welshpug 1,657]

the injectors do use a 12v ignition switched live to one side, the ecu earth's the other side, due to the frequency a normal filament bulb or a multimeter wont react fast enough, an Auto/Power probe with its red/green LED does however.

[DamirGTI 342]

So it has spark , but check if it has fuel - unbolt the fuel rail from the inlet manifold , complete with the injectors , and crank the engine few times over looking @ the injector tips (ask a mate to help you out with starting the engine ..)

 

The injector pulse is controlled by the ECU , there's special "noid" test lights for this purpose testing injector operation .. but once running you can "test" them by "poor man's approach" with the screwdriver or stethoscope listening for clicks .. for testing injector on a non runner you'll need dwell meter

 

Damir

 

EDIT : beaten by the boys !

Edited February 26, 2010 by DamirGTI

[Rob Thomson 6]

Simple injector test is to listen to them through a long screwdriver or extension bar from your socket set, ie. press one end against the injector, the other against your ear and get someone to crank the engine. They make a very distinctive tap/click when they operate.

 

Can you hear fuel flowing when you operate the pump?

 

If you've got a spark, fuel flow and working injectors you're almost there.

[DamirGTI 342]

Worth checking if the ignition lead order is sound on the dizzy cap as well as cambelt ..

 

Damir

[RP1983 4]

That is some great information from all of you.

 

It sounds like I will have to try doing what you have suggested Anthony, the car will not be driven anyway as it has no Tax/Mot.

 

By the sounds of things it is lack of power to the fuel relay that will be stopping the injectors as this has had all the wires cut and messed with hence It gave no power to the pump either. I will have a check of all the connections on that shunt box first just to see if it is something simple there.

 

Just to confirm, are you referring to the two white wires under the steering cowling to do the bypass trick?

 

Thanks again

[Anthony 1,003]

Just to confirm, are you referring to the two white wires under the steering cowling to do the bypass trick?

No, the thick brown and two thick white wires on the back of the tachymetric relay - one white wire powers the pump, the other the injectors.

[DrSarty 90 1 Cars]

There's brilliant advice here, but I think you just need to re-order what you do.

 

What I mean is, we know there's spark, but you really ought to find out first if you are getting fuel. I wouldn't play with any wires until you know the answer to that. Fuel rail off, a tray or some plastic cups and get someone to crank it over. Then we'll know where we stand before moving on.

 

Then, if we DO have fuel and we know we have spark, it could be as Damir suggested that we either have the spark in the wrong order or no compression. This is why he suggested checking HT lead order and whether the cambelt is intact and the camshaft is turning. I'd do that next, before touching any wiring.

 

Did you say you had spark at the plugs, or only going between the coil and dizzy? It's possible if it's the latter that the rotor arm/dizzy cap are knackered, or the rotor arm's even missing.

 

What I'm saying is the engine needs simple things in the correct order to run. I wouldn't assume just yet, that the sight of some DIY electrical work means it doesn't work. Some of my first attempts at looms weren't pretty but they worked.

 

Only when we've established the above would I move onto the excellent tests and changes mentioned elsewhere in here.

Edited February 26, 2010 by DrSarty

[Daviewonder 533 3 Cars]

Has the car been stood for a while, could the fuel have gone off?

[RP1983 4]

No, the thick brown and two thick white wires on the back of the tachymetric relay - one white wire powers the pump, the other the injectors.

 

Ah i'm with you, thanks again for this info.

 

Dr Sarty, thanks for the extra ideas and advice. I should have been more clear when I said about spark, I meant that I have one on all four leads. I didnt actually remove the plugs as I figured the chance of all four failing was quite slim.

 

I can tell you the cambelt is definitly intact and the engine sounds like it has plenty of compression when cranking. It really is dead though when turning over, not a hint of a fire.

All the wires to the fuel pump relay have been cut and rejoined for some reason, I have no idea if they are on the correct pins etc hence me pointing the finger at this. The pump will not prime or run at all unless I put my own live to it so would I be right in thinking it will be the same for the injectors?

 

I'll be having a better look at it this afternoon so will hopefully have a bit more joy armed with all the info I now have, thanks again everyone

[DrSarty 90 1 Cars]

Even when you get your fuel pump running properly off the relay, it would still be worth pulling the fuel rail and check all of the injectors are firing. Then at least you know you are getting fuel and spark.

 

Then all we need is to make sure the spark's in the correct order and she should go.

[RP1983 4]

Update:

 

Thanks to the great info recieved by all the car will now run.

 

I still have not managed to identify the actual problem but it looks to be earthing related.

 

I followed what Anthony suggested and checked first that I had power through the thick brown wire. That was fine so proceeded to bridge it to the two white wires. When they were both connected the fuel pump was still not doing anything so I seperated them to double check I was getting a good connection. On the second attempt of connecting I noticed that the one white wire wasnt sparking as the ends touched. As I knew I had power at the brown wire I thought it must not be grounded so ran a wire from the earth wire on the pump to a good earth(door check strap) and straight away the pump started.

 

I cranked her over and up she fired, the engine sounds sweet as a nut albeit a little lumpy and a little smokey but no bad tapping, rattling or knocking. Now I just need to decide what to do with her.

 

Thanks once again for the help and info, this place is invaluable.