Alfa Romeo Forums banner

21 - 40 of 44 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter · #21 ·
Just jumped the ignition switch and it doesn't appear to have powered 88a or AFM pin 39 by extension. Movement of the AFM flap doesn't appear to have worked either.

What's confusing to me is the fact that power is reaching the ignition coil with the key to run, and also to the distributor, but just not 88a at the relay, even though continuity checks out between the termination points.
 

·
Registered
Joined
·
3,249 Posts
Just jumped the ignition switch and it doesn't appear to have powered 88a or AFM pin 39 by extension. Movement of the AFM flap doesn't appear to have worked either.

What's confusing to me is the fact that power is reaching the ignition coil with the key to run, and also to the distributor, but just not 88a at the relay, even though continuity checks out between the termination points.
That is a head scratcher, alright. Somewhere in there you're losing 12 volt power...
 

·
Moderator
2015 Chevy (Holden) SS, 1989 Milano (Shankle Sport), 1991 164S
Joined
·
16,944 Posts
I might try to run temporary jumper wires from, say, the ignition coil, to 88a, etc, since the coil is getting power when you turn the key?
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #24 ·
I just tried jumping 88a off the coil. The result was power to pin 39 of AFM, and static 12v to the injector connecters. Fuel pump would still not turn on by movement of the AFM flap, so I jumped that too. With pressure at the rail, the engine will start for 2 seconds and die, but injectors have pulse with the power jumped to 88a.

I'm convinced my Alfa is haunted.
 

·
Registered
Joined
·
3,249 Posts
I just tried jumping 88a off the coil. The result was power to pin 39 of AFM, and static 12v to the injector connecters. Fuel pump would still not turn on by movement of the AFM flap, so I jumped that too. With pressure at the rail, the engine will start for 2 seconds and die, but injectors have pulse with the power jumped to 88a.

I'm convinced my Alfa is haunted.
Maybe not the entire GTV 6, but perhaps the ECU??? Is it time to check by substitution??

Or, at least disconnect the ECU plug, spray clean the connector and pins with electronics cleaner, and reconnect.
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #26 ·
I've got another unit on the way now, I got a spare with the car but it doesn't seem that either make a difference. One of the units had a burnt spot on the backside of the board underneath the metal casing but the other looked fine.
 

·
Premium Member
Joined
·
1,738 Posts
With the key on do you have power on 86c? Is your ecu chassis grounded?
Two bad ecu’s seem unlikely.
 

·
Registered
Joined
·
176 Posts
I believe the 88s's (including 88a) should be energized (at 12v) by the double relay. The big red wire should be a direct connection to the battery. I think if the injectors or seeing 12v, but 88a isn't, then the double relay is bad.
 

·
Moderator
2015 Chevy (Holden) SS, 1989 Milano (Shankle Sport), 1991 164S
Joined
·
16,944 Posts
It sure sounds like the symptoms we had with our Milano and a bad double relay.

Someone has come up with a wiring diagram for using two ordinary relays wired together to duplicate this unreliable Bosch relay. Unfortunately, it is very hard to read the schematic, with my old eyes, because of the colors he used in the graphic. I wish he had used better colors so I could then make a inexpensive version of this expensive product.
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #31 ·
With the key on do you have power on 86c? Is your ecu chassis grounded?
Two bad ecu’s seem unlikely.
Update:

I swiped a fresh set of injectors and installed them while I'm waiting for my ECU since I all of them were clicking very softly under the screwdriver test. I decided to jump the fuel pump and 88a to the injection harness and success, fired right up.

Still no pump or power to injectors/AFM without the jump leads though.

Does the ECU itself ground to chassis? I've checked the 3 connector ground pins and all seem well. I do also have power to 86c at the relay.
 

·
Premium Member
Joined
·
455 Posts
EDITED and corrected:

If you study the factory wiring diagrams and the "Double Relay Demystified" link that I posted above (which is good at explaining how the relay works but shows a slightly different configuration from the GTV6), you will see that 88a supplies +12V to pin 10 of the ECU, as well as pin 39 of the AFM (microswitch). 86b (relay coil input) is only energized when there is sufficient airflow to move the vane far enough to close the microswitch, which does not occur while the engine is cranking. For this, there is a separate input from terminal 50 of the starter, which goes to terminal 86a of the double relay. This closes the relay and energizes the fuel pump while the ignition key is in the "start" position. Once the engine fires, airflow should be sufficient to close the AFM microswitch and keep the fuel pump running.

So, you should check the 86a circuit and see if it gets power while cranking the engine. If it doesn't get power (or very low voltage, like below 9.5V while cranking, the the circuit should be checked back to the ignition switch (violet wire, goes to a connector just off the ignition switch).

Good luck.
 
  • Like
Reactions: alfaloco

·
Moderator
2015 Chevy (Holden) SS, 1989 Milano (Shankle Sport), 1991 164S
Joined
·
16,944 Posts
The diagrams you show are much better than the one for using two ordinary relays that I have, which is almost unreadable because of it being a poorly colored diagram. Thanks.

BTW, I don't know why the relays used in that expensive Bosch double setup are unreliable. Ordinary relays can work for many years, yet these seem to have a poor reliability record.
 

·
Premium Member
Joined
·
1,738 Posts
With the ecu plug disconnected, do you have continuity from double relay pin 85 to ecu plug socket 28?
I guess you must since it ran with power on 86a.
 

·
Premium Member
Joined
·
455 Posts
I edited my post above, the VW configuration of the double relay wiring is slightly different as shown the "Double Relay Demystified."

Have you checked the relay outputs directly while cranking the engine? If you get battery voltage at terminal 88d of the relay (output to fuel pump) while cranking, then you know that the inputs and ground of the fuel pump side of the relay are good, and the problem lies in the wiring between the relay and fuel pump (the inertia switch of the earlier GTV6s is wired between 88d and the fuel pump). If you don't have battery voltage at 88d while cranking or closing the AFM microswitch, then you have an input or ground issue.

Same thing with the outputs for the fuel injectors: the double relay supplies direct power to one side of each injector, one pair each via terminals 88f, 88e, and 88b. With the key on, each of these terminals should have battery voltage. Again, if not, then you have an input or ground problem. Ground unlikely since everything worked with power jumped to 88a.

It is entirely possible that someone has hacked into the wiring to add some sort of aftermarket alarm or kill switch---this was very common in the 1980s/1990s!
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #36 · (Edited)
I edited my post above, the VW configuration of the double relay wiring is slightly different as shown the "Double Relay Demystified."

Have you checked the relay outputs directly while cranking the engine? If you get battery voltage at terminal 88d of the relay (output to fuel pump) while cranking, then you know that the inputs and ground of the fuel pump side of the relay are good, and the problem lies in the wiring between the relay and fuel pump (the inertia switch of the earlier GTV6s is wired between 88d and the fuel pump). If you don't have battery voltage at 88d while cranking or closing the AFM microswitch, then you have an input or ground issue.

Same thing with the outputs for the fuel injectors: the double relay supplies direct power to one side of each injector, one pair each via terminals 88f, 88e, and 88b. With the key on, each of these terminals should have battery voltage. Again, if not, then you have an input or ground problem. Ground unlikely since everything worked with power jumped to 88a.

It is entirely possible that someone has hacked into the wiring to add some sort of aftermarket alarm or kill switch---this was very common in the 1980s/1990s!
Did another quick test of the relay pins under cranking. I tested 88d and the 3 pairs of injector wires 88f, 88e, and 88b as you described. All 4 pins read out at around 0.45v when cranking the engine. I'm going to poke around a tad and see if there might be a kill switch somewhere, it would certainly explain a lot.

Edit: not to do with the above, but I did spot a bit of fray on the wires going into the hall effect sensor on the distributor.
 

·
Premium Member
Joined
·
455 Posts
Did another quick test of the relay pins under cranking. I tested 88d and the 3 pairs of injector wires 88f, 88e, and 88b as you described. All 4 pins read out at around 0.45v when cranking the engine. I'm going to poke around a tad and see if there might be a kill switch somewhere, it would certainly explain a lot.

Edit: not to do with the above, but I did spot a bit of fray on the wires going into the hall effect sensor on the distributor.
Do any of the above output terminals have battery voltage with the key on/engine off?

As I mentioned in post #32 above, check the terminal 86a starter input to the relay, should have battery voltage while cranking (this should be around 10 volts due to the load/voltage drop across the battery while cranking).
 

·
Registered
Joined
·
53 Posts
I know this is basic, but are we certain the battery is fully charged? The ECU does not work properly when charge drops to 10.5 volts or less.
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #39 ·
Did another quick test of the relay pins under cranking. I tested 88d and the 3 pairs of injector wires 88f, 88e, and 88b as you described. All 4 pins read out at around 0.45v when cranking the engine. I'm going to poke around a tad and see if there might be a kill switch somewhere, it would certainly explain a lot.
I know this is basic, but are we certain the battery is fully charged? The ECU does not work properly when charge drops to 10.5 volts or less.
Battery is fully charged, I grabbed a new one from my local parts store to rule it out right away.
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #40 ·
Do any of the above output terminals have battery voltage with the key on/engine off?

As I mentioned in post #32 above, check the terminal 86a starter input to the relay, should have battery voltage while cranking (this should be around 10 volts due to the load/voltage drop across the battery while cranking).
Pin 86a is getting about 9.5v when cranking, but none of the other 4 are getting voltage with key on/engine off
 
21 - 40 of 44 Posts
Top