Lambda System Woes

[jchris]

Hello all, I have been helping a neighbor with his 82 SC. I have an 83 that I have mostly sorted out so he asked me give it a shot. He told me it began running rough suddenly and he stopped driving it. Here is what I have found.

The frequency valve is not working. So I began the chain of investigation as is well travelled on this board.

Test were conducted with the fuel pump relay jumped.

The O2 sensor relay gets power, powering 85 and 86 causes 30 and 87-87b to close. 30 gets 12v. We tried a new bosch unit with the same results. (it is a good one at least)

I cleaned the jetronic connections and inspected for cold joints on it's circuit board. Nothing obvious. I will be swapping in my box next to see if that does it.

In the engine bay.

On the 12 pin harness connector pin 4 gets 11.38v with the o2 relay in, and with connector jumped.

The F.V. has a resistance of about 3 ohms (2.7)
The F.V. wiring has continuity to the firewall connection. (pin 1 and 4)
The F.V. clicks when 12v is momentarily applied.

If it is not the jetronic box, what else can I check? I understand that the controller pulses the ground for the F.V. where can I check that the controller has a good ground?

Thanks for your thoughts!!

Chris

[jeffs9146]

Originally Posted by jchris

Hello all, I have been helping a neighbor with his 82 SC. I have an 83 that I have mostly sorted out so he asked me give it a shot. He told me it began running rough suddenly and he stopped driving it. Here is what I have found.

The frequency valve is not working. So I began the chain of investigation as is well travelled on this board.

Test were conducted with the fuel pump relay jumped.

The O2 sensor relay gets power, powering 85 and 86 causes 30 and 87-87b to close. 30 gets 12v. We tried a new bosch unit with the same results. (it is a good one at least)

I cleaned the jetronic connections and inspected for cold joints on it's circuit board. Nothing obvious. I will be swapping in my box next to see if that does it.

In the engine bay.

On the 12 pin harness connector pin 4 gets 11.38v with the o2 relay in, and with connector jumped.

The F.V. has a resistance of about 3 ohms (2.7)
The F.V. wiring has continuity to the firewall connection. (pin 1 and 4)
The F.V. clicks when 12v is momentarily applied.

If it is not the jetronic box, what else can I check? I understand that the controller pulses the ground for the F.V. where can I check that the controller has a good ground?

Thanks for your thoughts!!

Chris

Vacuume Leaks!!

Cracked air box
Leaky injector seals
Leaky vacuume lines

Fix all vacuume leaks first before attempting to adjust anything!!

[schumicat]

i would try to swap in a known good ecu from someone local or buy one on classifieds (around $100 and you can sell for same price if not the problem). vacuum leaks wouldn't cause fv to stop working (AFAIK). when my FV was dead it turned out to be a bad connection. i opened and cleaned all the connectors.

[jchris]

OK, well I finally got back to it (back in town) and tried placing the suspect oxs control unit (jetronic) into a known working system. After verifying that the good one worked (nice loud vibe from FV) while the FP is jumped, I swapped in the unknown box. No more vibe from FV.

Can I ask anyone who fixed this what solder joints were bad? Or maybe how to proceed to test it? They look good to my eye (albeit untrained!) I really don't want to shotgun it and do them all!

Thanks!