|Fuel Pump Relay Mods
| Updated: April 10,
M A I N S
Adding a Secondary Relay to take the High Load off your 240 Fuel Pump Relay<<< The fuel pump relay in your 240 takes a lot of abuse and it's expected to run your fuel pumps for years and years without fail. They do fail, but usually not because they wear out. Most fail because of unwanted heat after years of use. They often run hot because; 1. They handle a heavy load. 2. The heat causes their plug connections to develop higher resistance, which then causes more heat, which then makes a failure begin like the melted terminal in this photo.
This is not for everyone, but it seemed to help for me for many years.
Below I have outlined how I added a standard inexpensive 4-pin cube relay (or 5-pin will work too) to handle the pump load, giving the original expensive fuel pump relay a much welcomed rest. The new added relay can be any standard 4 or 5 pin type relay with a load rating of 15 amps or higher.
| <<< Here's a pic of what that heat can do to the relay plug. This is extreme. Most of the time the melt damage to the plug is minor, but it can get bad.
But even if you do NOT feel this mod is right for your car, please read the info BELOW on using Anti-Corrosize Zinc Paste on your electrical connections. I strongly believe this paste would have prevented the damage in these photos.
|What this extra relay mod does is take
the heavy load off of the expensive Volvo relay and
puts it on the inexpensive standard relay. This allows the Volvo relay to be used as a low current switch
to activate the standard relay, which will handle the load instead.
The new extra standard relay is triggered by pin 87 from the original fuel pump relay and receives its main battery power from pin 30 of the original relay circuit. As an option, you may instead run a dedicated battery wire to pin 30 on the new relay. I suggest 12 gauge wire. This should provide a bit more voltage to your pumps. If you do this, then the wire should always contain a fuse between the battery and relay.
|K-Jetronic (Mechanical Injection) Relay
|LH-Jetronic (EFI) Relay
If we can just just keep our electrical connections clean and tight, almost all of the electrical issues would be gone forever. That would be nice, right?
I have owned a number of Volvos over the last 30 years and my current 240 is way over 30 years old. It almost never has electrical problems. Nothing like the endless numbers of other 240s out there that I hear about so often. What's the difference you ask? The difference is that my 240 has been always garaged all of its life. Why is that important? Because leaving any car out in the open elements for years and years slowly introduces corrosion to grounds and power connections until things begin to go wrong.
So if you own one of those cars that has been outside forever, it's not too late. You can still clean as many grounds and electrical connections as possible.
And while you're at it, I recommend that you smear a little anti-corrosive zinc paste on those connections.
Many people in the Volvo community gravitate toward Ox-Gard, which does a similar job.
The below information was contributed by Ron Kwas and should come in very handy to old Volvo owners:
Anti-Corrosive Zinc Paste (a generic name for zinc dust contained in a grease) was originally developed for and later required by electrical codes for use on alumunum to copper electrical connections (or other dissimilar metal connections). No, it's not the same as Dielectric Grease, which is often incorrectly recommended. Dielectric Grease can offer some protection in the form of encapsulation from moisture, but it also carries with it the potential disadvantage of locking in moisture or corrosion which may have already begun. Anti-Corrosive Zinc Paste (or ACZP) is the next evolution of the encapsulation principle, because zinc (the lowest on the Galvanic nobility chart) neutralizes corrosion on a micro-scale to truly protect connections on a long-term basis during the encapsulation, INCLUDING an added protection from corrosion which may otherwise begin to form in that connection.
Ron uses and recommends Penetrox A (by Burndy). Many Volvo fans are familiar with Ox-Gard, which is a similar zinc compound. Ron and I are huge advocates of treating ALL electrical connections on our cars (except of course High Voltage Ignition connections) with a suitable version of this material.
You can learn more about this stuff at Ron's page here:
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