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Finally left me stranded

Sorry just got lost in the 'how you did it post'.

I assume you pull power from the OPS to trigger the relay then ground the relay coil. Then the relay powers the LP from +12v and LP wire through it's contacts.

Where is the relay getting it's +12v for the lift pump? Hopefully from a 12v source not the same OPS wire that triggers the relay.

Now here is the important part and IMO your issue: The relay coil when turned off is like an ignition coil. It will develop 300 volts and arc the OPS contacts unless there is a surge suppressor diode across the relay coil. Over time this will ruin the contacts and sometimes weld them together.

To install the diode across the coil you literally put it in backwards. Note put this diode directly on the relay coil wires as any switches in the way will render it useless. That would be with the diode band toward the positive connection so the diode doesn't flow any current with the engine on and OPS supplying power. Install wrong and the OPS or diode will instantly smoke off. So it's pretty easy to make sure it is correct and they are generally sold in packs of 2 at Radio Shack. :p

Flyback diode Explained here with diagrams for the coil side of the relay only (you got the LP contacts fine I assume):
https://en.wikipedia.org/wiki/Flyback_diode
 
THEFERMANATOR said:
Been a long time since I've seen a relay without the diode built into it.
Click to expand...

Well OEM relays would have this built in for sure.

Aftermarket: Never assume. Unless the relay specifies what coil connection is grounded and even then one has to look at the relay spec to see if it's included. Most generic off the shelf relays for headlight/fog light add on kits don't have built in diodes.
 
Interesting to learn this about relays. Guessing if the power source, controlling the relay, is a decent quality switch, may not matter as much?

Next thought - I've relocated my truck's large B&M stacked plate oil cooler & it will have a 10" fan to ensure/supplement adequate cooling airflow. Will have manual switch override, but planning to use this Derale fan control thermostat ( http://www.amazon.com/gp/product/B004XOQIBE/?tag=jhuntlink-20 ), to automatically regulate the fan on/off.

Guess I should check & see if the relay that came with fan has built in diode, in case that's needed to keep the fan control thermostatic switch alive.
 
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The schematic from Buddy should be here someplace. I posted it myself more than once.

There should be notations made to Buddy's schematic about not cutting or splicing anything. Make the upgrade plug and play like Leroy does his.

Cutting and splicing is a bad idea
 
Mine was a full plug-in harness once completed. I can remove it and all goes back to a factory look. Much the way my lift pump is with Leroy's fittings on the fuel lines and plug he has coming off the LP, itself.

I'll have to look at my relays, but I don't believe they had a diode. Anyone have a link for a suggested retailer? Our Radio Shacks were some of those that closed up a year or two back. Would the diode show up in the schematic that is printed on the side of the relay? I don't recall seeing this on by new ones, nor the OEM ones
 
Try digikey I bought a dozen relatively cheap from them. Most have a schematic that will show the diode printed in the relay. Mine didn't look like it had the diode so I destroyed one looking for it. Turned out it was cast into the plastic base.
 
Diode part number common as dirt 1N4007 is all you need.
 
I bought the complete relay from them with built in diode. IIRC you should search for relay and then narrow the results down by parameters
 
If I can remember I'll get the part number off mine when I get home. IIRC they were only $3-4 each. I bought a dozen of the and some prewired pigtails
 
Thanks, AK. I'll hunt that one up to see if I can find it.

LP not working, again today, on its own. had to jump it again to get it to operate after the engine was running. Thankfully, the Walbro is so loud that I can hear it over the engine, otherwise, I'd not have known it wasn't operating.
 
The diode goes across the relay coil wires. Note the positive "+" and the diode doesn't conduct when the relay is "on". It only conducts when the relay shuts off. This is why it looks to be in backwards.

relaydiode.jpg
 
Is there anything on the OPS, itself, that I can check to verify whether it's good or bad? I removed my relay harness tonight, so I can check it out to see if something is wrong with it, since I seem to have smoked my new OPS. New one on order.
 
Yeah, you're right on the fuse. I've removed the harness and couldn't find anything that looked different than the day I first installed it, so I'll probably put it back on and run the jumper for now. As time permits, I'll look into this further and will probably add the diode WarWagon suggested, at least.
 
The relay harness is back on. LP runs on WTS and engine run. I didn't change a thing, but suspect maybe the ground wasn't grounding well and allowed it to not work, there for a while. All seems well now. Fingers crossed...

I picked up an inline fuse for the power wire, today.
 
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