New electric fuel pump not working 90 GW

[InspectorB]

Hi all!

I removed the mechanical fuel pump and installed a Holley red pump and wasn’t able get the wagon to start. It cranks great but don’t think the pump is running. I’m not that experienced with car stuff so I’m sure I did something wrong. Any advice would be much appreciated.

I used a painless wiring harness but ended up installing a oil pressure safety switch and wired it based on the Holley diagram below.

Pump ground wire screwed to frame near pump
Pump hot wire ran to relay (as described in painless diagram)
Small yellow wire from relay (for ignition in painless diagram) ran to P on safety switch
Wire ran from S on safety switch to starter solenoid
Wire ran from I on safety switch to orange electric choke wire
Ground from relay ran to other ground wires near battery
Battery wire from relay ran to 30amp fuse then to battery



Cheers,
B


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[will e]

I think the way you have it wired up it 'should' work. Do you have a multi-meter or voltage tester?

I think the first thing to try is to make sure the relay and pump are working by manually bypassing the safety switch. This can be done by removing the P wire from the safety switch and connecting it directly to power from the battery (if it will reach or with a jumper). If the relay and pump are good and wired correctly the pump should turn on. You will be able to hear it run. If it doesn't run then you can further bypass the relay and attach the pump directly to the battery. This is only for a test purpose. You will hear the pump running. Don't leave it connected in either of the configurations for very long, just a few seconds, if you hear the pump running.

If you find the relay and pump to be working then you will want to verify the wiring for the safety switch.

The switch has two power inputs, one from the solenoid and one from an 'ignition on' source. The third is obviously the output. When cranking, the solenoid side will provide power to the output even if there is no oil pressure. When running the 'ignition on' side provides power but only if there is oil pressure.

Once you confirm that the relay and pump are working. Remove the wire from the solenoid and connect it directly to the battery, with a jumper if needed. The pump should turn on, even with the ignition in the off position. Again, only do this for a few seconds if you hear the pump running.

Does the truck start and then eventually die or will it not start at all?

Again, you should be able to easily hear the holley red pump running, they are not quiet.

[InspectorB]

You rock Will e! Thanks for the awesome response! I do have a multi meter and will try this out and report back. As of now it won’t start at all.

Cheers,
B







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[will e]

The multimeter will really help!

When you do get it working you might consider modifying it so that you have a hidden 'kill' switch in the cabin. This can be handy to avoid having your truck go too far if it is stolen. It will start and drive for about 100 yards and then die. When the thief cranks the motor, it will start again because the solenoid provides power while cranking. It will drive an even shorter distance and then die again. It almost certainly won't die in a good place. I'd get it working first before applying any modifications.

Mine will sit for a while so I am also adding a 'primer' switch so I can prime the carb without cranking. I am also adding a 'keyed' kill switch in the cabin so I can turn off the fuel pump with a locking key. This all in addition to the cabin hidden kill switch. It's not operational yet but will be in a couple of weeks. I can send you the diagrams on how to do this if you are interested.

[InspectorB]

Sounds like a great idea actually. I’d love to see them! I’ve actually herd of a few trucks disappearing in our area over the last year or so.


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[will e]

Sounds good. Let me get it actually working. I didn't have the oil pressure cut off switch, the primer or the key'd switch in the system before. Once I have it all working I'll post a write up with the wiring diagrams and pictures.

[InspectorB]

I was able to get some time with the Jeep today and followed those steps. The pump and relay worked when I bypassed the safety switch and hooked the p wire straight to the battery.

I got to the point of removing the wire from the solenoid. The relay and pump didn’t run when I hooked that wire to the battery. Does this mean the safety switch is bad? I did notice the p terminal on the safety switch was a bit loose. The others were not. Possible issue? Also the plug for carb choke switch near oil filter is super loose. Bad connection likely.

While doing this I happened to stumble on a frayed wire near the carb. It was sparking when I hooked the battery up and turned the ignition. I’m not sure what it is but it’s orange to black and went to some kind of throttle stop on the carb. There’s also a black rubber sleeve on the wire. The wire goes from orange to black here. Any idea what this Is? Can I just re run this wire or do I need to add another black sleeve thing? Picture below

Sorry for all of the rookie questions

Cheers, B




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[letank]

seems like the ignition power to throttle stop solenoid, it is positiv..... check w voltmeter!
usually the wiring loom is behind the thermostat housing

[will e]

All right, good job on bypassing the pressure switch and confirming the relay and pump are working. That pump is pretty easy to hear huh?

When I tested my safety switch with a multi-meter it was not installed and there were no 'wires' on it. I confirmed the solenoid side of the switch was connected to the power side (the circuit was complete). This makes sense because it is a 'Normally Closed' connection. The ignition side was not connected and this makes sense because it only should be connected if there is pressure.

What does this mean to you? The answer is yes, when you take the wire connected to the 'solenoid' wire of the safety switch (NC) and provide power to it from the battery the fuel pump should turn on. This assumes you have reconnected the power wire that you tested above. (And your switch operates the same as mine. I have the Holley switch).

If it does not there are a couple of possibilities. The first is you have the safety switch wired to the jeep incorrectly.


If you have the Solenoid and Ignition wires reversed the pump would power up when you turn the ignition 'on'. However, you used the choke wire which itself is regulated by a pressure switch. I think the next test is to take the wire that is connected to the ignition side of the safety switch and connect it to the battery power. The pump should NOT turn on if the safety switch is wired correctly to the Jeep. If the pump turns on then you need to double check your wiring. If the pump doesn't turn on then I suspect the safety switch is not working on the 'solenoid' side.

I assume the Jeep runs when you bypass the safety switch? You should get the jeep warmed up a bit with the safety switch bypassed and then reconnect the power wire to the safety switch. Be careful, it will be a bit warm. Then try starting the jeep. It should start, there is gas in the fuel bowl and listen if the pump is running. If it is running then the pressure side of the switch is working and you have it wired correctly. If it is not running you either have a bad switch, it is not wired correctly or the source you believe is 'ignition on' is not working or is not actually ignition on.


As Michel (letank) confirmed the other wire you are discussing is for the anti-diesel solenoid. This get's power when the ignition is on. If it is sparking then find where the wire has rubbed through and fix it. If you want a bit of information on how this system works let me know. The black part is the connector. The anti-diesel solenoid is a part common to many of the older cars which is why the wire color is not the same as the wire color on the Jeep. This circuit would be an excellent source for your electric fuel pump 'ignition' ' wiring. In my opinion it is better than the Choke wire since it is always powered when the ignition is in the 'on' position.

[will e]

Any updates?

[InspectorB]

Hey Will E!

Thanks for checking in but haven’t been out there to sort it out. My wife just had our first child and works been demanding. Hoping some time frees up this weekend. Will keep ya posted


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[InspectorB]

Hey Will e!

Was finally able to carve some time out and finally got the truck started! Ended up being a bad safety switch. In hindsight, I recall dropping it on my driveway,which is long and steep, and it rolled for a few feet.

It ran great for a mile or two but then started a violent jerk or shutter when accelerating at low speeds and only after several minutes for driving. It seemed to quit once you pushed through and pushed the pedal further. Any thoughts?

Ignition module, plugs and wires are new along with the new holly red pump.

And yes, that pump is very loud!! Wish I didn’t mount it below the drivers side

Cheers,
B


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