Hi all, I have been trying to diagnose, my now, no start condition. I need to check the frequency valve and I have no idea what it looks like or where it is, any help would be appreciated. Lester
If standing at the back of the car, it's immediately to the left of the Bosch fuel meter distribution array. Image Unavailable, Please Login
Have you checked the overload protection relay located it he trunk passenger side? There is a metal panel under the carpet on the very far right. You have to uncrew the panel and lift out and you will see an ECU and the relay next to it. The relay will have a fuse attached to it on top.
No and thank you for giving me the description of the location. What does the overload protection relay do?
A faulty relay will cause difficult starting and if the car starts it will run very rough and poor. It is part of the frequency valve system. Steve Magnusson is the expert and can give you full description on how it works
My 328 would start barely and run very rough. Diagnosed it as the protection relay being bad and swapped it out and runs great.
It's actually the "Overvoltage Protection Relay", but F shortened this to just "Protection Relay" in their documentation. Its function is to protect the injection ECU from an overvoltage condition if the alternator fails and wrongly puts out a high voltage. If a failed alternator does put out a crazy high voltage = the Zener diode inside the Protection Relay goes into conduction = intentionally blows the 10A fuse (that is inside the Protection Relay on the early 5-pin version and on the outside of the later 4-pin Protection Relay) to disconnect (i.e., "protect") the injection ECU from that high voltage. jlc308 is correct that a non-working Protection Relay (if the fuse is blown or if it has failed for some other reason) will make starting and running the K-Jet with Lambda models difficult because the injection ECU uses the frequency valve to add extra enrichment during starting and a fixed average amount of enrichment during normal running. With a dead Protection Relay = FV is always closed = very lean condition. The FV should always be buzzing/vibrating whenever the fuel pump is running (i.e., during starter motor cranking, during engine running, or if you unplug the safety switch and turn the key "on" to run the fuel pump). If you can get the fuel pump running, you should be able to tell by touching the FV if it is buzzing/vibrating, or not.
That's the later 4-pin Protection Relay with the external 10A fuse. The US 1984-85 K-Jet with Lambda models (308QV and Mondial QV) came with the earlier 5-pin Protection Relay with the internal 10A fuse that isn't meant to be user-replaced. It is possible to update those systems from the older 5-pin to the later 4-pin Protection Relay (and many have been updated as the 4-pin style is all that is available now), but it takes moving the terminals in the Protection Relay socket around: Image Unavailable, Please Login
I have replaced many of both. The latter relay with external fuse I have never seen one with a blown fuse. There is typically a spot on internal board that looks like it has gotten hot. The early version with internal fuse it is always in my experience a blown fuse and not once found a charging system malfunction. After replacing many I just started soldering in a single strand of copper wire from a stripped piece of 14ga wire and never had an issue with that repair. Not sure how good an idea that may or may not be but its worked for me.
