3B engine wont start. Fuel Injectors wont open

[vism]

Hi,

Have a Audi 90q that needs a upgrade in the engine dep, and the 7A engine is being replaced by a 3b engine. The 3b engine with wiring and such was taken out from a running S2, and everything was working well before the engine and wiring was removed. Now, in the 90, it wont start. We have located the problem to be the fuel injectors that dont open for any fuel. Our theory is that this is because the ECU wont send the trigger signal that is needed for the fuel pump relay to open properly.

By looking at this schematic from S2central, it looks like the fuel pump relay needs a trigger signal from ECU pin #3. We belive that this seems to be the problem, as nothing changes at that pin when we turn the ignition on or try to start it..

http://s2central.net/images/3B_ECU_Schematic.jpg

Does anyone have a clue why the ECU wont trigger it? Everything is lined up properly, and we have sparks at all plugs. The relay is tested and seems to be okay..

[terrybullwon]

When you turn the key to the ignition point just before it turns over, can you here the fuel pump?

[UrS4boy]

Hi,

By looking at this schematic from S2central, it looks like the fuel pump relay needs a trigger signal from ECU pin #3. We belive that this seems to be the problem, as nothing changes at that pin when we turn the ignition on or try to start it..

http://s2central.net/images/3B_ECU_Schematic.jpg

Does anyone have a clue why the ECU wont trigger it? Everything is lined up properly, and we have sparks at all plugs. The relay is tested and seems to be okay..

The ECU controls the fuel pump relay through pin 3/55 of the ECU.

AAN ECU pin-out (just for comparison, also has Pin 3/55 = J17 Fuel pump relay trigger)

http://forums.audiworld.com/s4s6/msgs/149829.phtml

Link to how a J17 works in an AAN car (for comparison):

http://forums.audiworld.com/s4s6/msgs/149827.phtml

So I can only think that your hall sender is not working properly to allow the ECU to trigger the fuel pump. For testing purposes only, you could jumper the fuel pump from the + post in the engine bay to the right hand side of the FP fuse (pull the fuse out) with switched wire and a spade connector. This should prove something. Better yet, you might want to check whether the fuel pump is working using a modification of this procedure (to fit your car):

http://forums.audiworld.com/s4s6/msgs/161382.phtml

HTH

Dave F.

[vism]

Thanks for the quick and very good replies

When you turn the key to the ignition point just before it turns over, can you here the fuel pump?

Nope.

Something that came to my attention now is that the distributor is from the 7A engine.. Could that have something to do with the problem?

[vism]

So I can only think that your hall sender is not working properly to allow the ECU to trigger the fuel pump. For testing purposes only, you could jumper the fuel pump from the + post in the engine bay to the right hand side of the FP fuse (pull the fuse out) with switched wire and a spade connector. This should prove something. Better yet, you might want to check whether the fuel pump is working using a modification of this procedure (to fit your car):

http://forums.audiworld.com/s4s6/msgs/161382.phtml

HTH

Dave F.

Could it be that the hall sender in the 7a distributor is different from the 3b? We tested the hall sensor and it was looking okay, but if the output is different form the 3b..

We jump-tested the fuel pump, and it functioned properly..

[terrybullwon]

Could it be that the hall sender in the 7a distributor is different from the 3b? We tested the hall sensor and it was looking okay, but if the output is different form the 3b..

We jump-tested the fuel pump, and it functioned properly..

I had a similar problem, The timing pin came out of the fly wheel and this caused the ecu to cut the fuel pump as it could not get a TDC signal. Like you when i bridged the fuel pump with 12V it would run.

I guess that this would also point to the dizzy as you sugested. I know the 3B engine its self had to versions of dizzys fitted. Maybe it is worth checking which one you should have

[UrS4boy]

Could it be that the hall sender in the 7a distributor is different from the 3b? We tested the hall sensor and it was looking okay, but if the output is different form the 3b..

We jump-tested the fuel pump, and it functioned properly..

Have you got the 7A hall sender connected to the ECU? (just asking).

Did you stay with the 7A flywheel? (The TDC sender pin might be missing on a 7A?)

If you looked at the J17 info, you should note that the J17 relay also powers the injectors. No Hall sender signal to the ECU = no fuel pump and no power to the injectors (its a safety thing re: engine operation during a front end accident).

You need to track these things down one at a time.

Good luck.

Dave F.

[kwlw]

Did you stay with the 7A flywheel? (The TDC sender pin might be missing on a 7A?)

It should be on correct place on 7A flywheel.

You need to track these things down one at a time.

Is dizzy oriented correctly? Don't know if it affect fuel however. Maybe flywheel sensor connector are mixed? That also gives nice non starting situation.

Sau

[Pirvu Eugen]

Sorry for asking! But you have the dizzi aligned with the flywheel mark when the gear mark is on top ,or you have the crankshaft 1 turn off?

[newsh]

This is what I'm thinking, 180 deg out?

[org:s2 limosine]

How strong should the outgoing signal from the G4 (TDC) be?

We tested the hall sensor.... and it had about 5Volt....
And we tested the G4, but we are not quite sure if we had strong signal.... 2-3Volt

Btw, the 90 quattro is my car
I could`t remember my username, so VISM started this tread

[Pirvu Eugen]

5 volts is ok for the hall sensor.
Check that you have all 3 marks aligned. Flywheel, camshaft and distributor!
Hope this helps!
Eugen

[org:s2 limosine]

Tryed another ECU today, same problem

I`m gonna check the 3 marks one more time
If it still won`t start, i`m mounting the 3B flywheel

[Pirvu Eugen]

You can check the pin by removing the starter and look throu the hole.
All the best!
I hope that the dizzy is 180 degrees out!

[org:s2 limosine]

After some hours in the garage to day, we found out that the distributor was 2-3cm wrong

I got the 3 marks aligned. Flywheel, camshaft and distributor!
Then i adjusted the distributor to the correkt place....

WOW.... is it really gonna start ........ ehh no, no life signs
But know i hear the fuelpump going

But there was no spark at the sparkplugg`s
It was spark last time i checked(3days ago)

After at quick check in the fusebox, i found out that one fuse had no 12v....
This is the white one,with 15amp fuse.(motor/motuer)

So no its back under the dasj, and see if there any fault

Anybody that knows what it can be?

Thanks for great help

(my english sucks, i know )