Fass Fuel pump install help

[Lloyd T]

Hi, Lloyd here. I have a 2000 Monaco Diplomat ISC 315 HP 8.3L CAPS pump Cummings diesel. I have lost my references to the instructions from a member that had posted very good instructions on installing Fass fuel pump.
He was a mechanic, race car builder, machine shop, and was from western states like Montana, or Idaho. maybe. He have very good pictures, part numbers, with lots of helpful tips. I had a computer failure and lost all notes. I want to thank all of you for you help. This site has helped countless times. Lloyd Thornburg.

[groveln]

Originally Posted by Lloyd T

Hi, Lloyd here. I have a 2000 Monaco Diplomat ISC 315 HP 8.3L CAPS pump Cummings diesel. I have lost my references to the instructions from a member that had posted very good instructions on installing Fass fuel pump.
He was a mechanic, race car builder, machine shop, and was from western states like Montana, or Idaho. maybe. He have very good pictures, part numbers, with lots of helpful tips. I had a computer failure and lost all notes. I want to thank all of you for you help. This site has helped countless times. Lloyd Thornburg.

Just put Fass system in the search window & you'll see many of the installs

[shootist]

You want Mikes thread, zmotorsports. I want to bring up a critical point, make sure and use the bosche relay with the diode. Relays can generate really high (as much as 170 volts) voltage when they open. It's for protecting your ecm etc.

[jacwjames]

Originally Posted by shootist

You want Mikes thread, zmotorsports. I want to bring up a critical point, make sure and use the bosche relay with the diode. Relays can generate really high (as much as 170 volts) voltage when they open. It's for protecting your ecm etc.

X2, Zmotorsport but he also has video's on Youtube.


Shootist
I've read about the relays/diode issue and a question came up on how to hook it up
There are 2 wires for the fuel pump, is there a way to know which one goes to which post??????

I'm not sure it was ever explained.

[shootist]

Originally Posted by jacwjames

X2, Zmotorsport but he also has video's on Youtube.


Shootist
I've read about the relays/diode issue and a question came up on how to hook it up
There are 2 wires for the fuel pump, is there a way to know which one goes to which post??????

I'm not sure it was ever explained.

I explained it in one of my threads iirc. Just can't remember it all now. Seems you just hook up the relay pos and neg as designed. They will work either way, but the diode won't.

[shootist]

Originally Posted by jacwjames

X2, Zmotorsport but he also has video's on Youtube.


Shootist
I've read about the relays/diode issue and a question came up on how to hook it up
There are 2 wires for the fuel pump, is there a way to know which one goes to which post??????

I'm not sure it was ever explained.

Here's a picture of how to wire it

[Alpine36]

The two lift pump wires attach one to terminal 85 and one to 86. Polarity makes no difference, as the ECM is simply looking for internal resistance, and the relay coil has approximately the same resistance as a running lift pump.
If you do not do this the ecu will throw a code 278.

FWIW here’s my install from five years ago. It’s run flawless for the last 20k miles, knock on wood…

https://www.irv2.com/forums/f104/fas...ne-484540.html

[shootist]

Originally Posted by Alpine36

The two lift pump wires attach one to terminal 85 and one to 86. Polarity makes no difference, as the ECM is simply looking for internal resistance, and the relay coil has approximately the same resistance as a running lift pump.
If you do not do this the ecu will throw a code 278.

FWIW here’s my install from five years ago. It’s run flawless for the last 20k miles, knock on wood…

https://www.irv2.com/forums/f104/fas...ne-484540.html

Polarity makes a difference when it comes to the diode in your relay. If you don't have a diode equipped relay you are chancing burning out your ecm and your tcm as well as the electronics in your fuel pump accumulator.

[Alpine36]

Originally Posted by shootist

Polarity makes a difference when it comes to the diode in your relay. If you don't have a diode equipped relay you are chancing burning out your ecm and your tcm as well as the electronics in your fuel pump accumulator.

Really? Care to share where you got this information?
I understand coil fields collapsing sending potential back feed voltage spikes, but these relays are already diode protected, and there is no “load” being applied to the relay. The ecu is simply monitoring resistance thru the relay coil, mimicking a operating lift pump.

Maybe if what you are saying is correct you could share with the rest of us the correct polarity wiring procedure…

[shootist]

Originally Posted by Alpine36

Really? Care to share where you got this information?
I understand coil fields collapsing sending potential back feed voltage spikes, but these relays are already diode protected, and there is no “load” being applied to the relay. The ecu is simply monitoring resistance thru the relay coil, mimicking a operating lift pump.

Maybe if what you are saying is correct you could share with the rest of us the correct polarity wiring procedure…

If you want to look it up go ahead. Tired of getting hit with this prove it baloney. If you read the thread I posted a picture of the wiring on mine. When coil voltage collapses it can generate high voltages. The diode is put in to protect from it. Look at the picture.

[shootist]

Originally Posted by Alpine36

Your picture does not help anyone trying to determine proper polarity to terminals 85/86. The relay in your picture does not show diode polarity orientation btw. I believe these relays are equipped with a zener diode, thus making polarity a moot point.
Sorry, sounds like I offended you, but the rest of the class may like to know since, apparently, it could do thousands in damage if done incorrectly. We’re all here to learn, not get offended, tired or call baloney on asking a simple question.

FWIW, all Bosch relay wiring diagrams show terminal 85 as ground, 86 as trigger (B+) but in reality it doesn’t make any difference on a diode protected relay such as the one you pictured.

The picture shows clearly the red tape on the wire and what side its on, and it was meant for one person in particular. Diodes are absolutely one way. It's not a zener, which is still biased one way.

[Alpine36]

85 ground, 86 positive. It’s all you needed to say.
Yes, it’s a one way diode shown on the schematic you posted, however your relay pictured didn’t show that, nor did it show which wire went where. I believe that’s all the OP was asking.

[shootist]

Originally Posted by Alpine36

85 ground, 86 positive. It’s all you needed to say.
Yes, it’s a one way diode shown on the schematic you posted, however your relay pictured didn’t show that, nor did it show which wire went where. I believe that’s all the OP was asking.

I want the person doing his own installation to understand what he is doing. Put this here and that there doesn't help a person to learn anything. (By the way, they make these relays with the poles reversed on the diode.) They call them transient suppression diodes, you have a large one connected to your ecm wiring to keep transient voltage from the caps hitting it. Diodes do go bad with weather so replacing it on an old caps system is a good idea. It's required by Cummins on an ecm change for the warranty.

[Alpine36]

Yes, I already replaced the transient suppressor as a precautionary pm.
Good advice.
So I suppose I’ll eat a little crow and admit that these diode equipped Bosch style relays are technically polarity sensitive on the contact pull in coil, however many online resources show them wired either way.
My take on it is, that since the coil is not shedding any sort of load when opening the likelihood of any damaging voltage spike is extremely low. The main takeaway is use a quality diode equipped relay and wire the contact coil to the manufacturers recommendation on terminals 85/86.