[SOLVED] Inline fuel pump – Am I doing something wrong with wiring?

[Kia.]

I need a second brain to look as what I'm doing to see if I'm missing something.

I have an 1989 K5 that I have installed an LPG system with original tank. All working perfectly. However, I needed a bigger tank, so have removed the original petrol tank, installed a larger LPG tank, and installed a backup custom petrol tank with an in inline fuel pump.

I want to use the original cable for the original pump, it has two wires...

PINK and a TAN and WHITE. PINK is power (12v) TAN and WHITE is the fuel gauge.

...from what I have managed to find out via the wiring diagrams.

So have connected the PINK to the POSITIVE on the new inline pump, and grounded the NEGATIVE to the chassis.

However, the pump doesn't do anything. The pump is good, as a test I've put direct power to it and pumps fine.

I have power coming into the PINK cable, and also have measured all cables to make sure there isn't any issues with broken cables etc.

So the question is...

Am I actually missing anything for the new inline pump not to to work? Is there a cable or sensor I need to check?

I'd really appreciate is someone could point me in the right direction.

Some random images of new parts etc... Original pump connector / new LPG tank / Making room for LPG tank / New auxiliary petrol tank

 

[Fastereddie]

My first though is check the ground.

 

[Kia.]

My first though is check the ground.

Yeah me too. I've moved that sucker about 5 times already, and to different locations.

I was wondering if there was something else I could have missed, like a sensor, or maybe no power to the pump if the gauge wasn't connected?

 

[Fastereddie]

Well, 89 was tbi originally so it will only send voltage to the pump for two seconds when you first turn the key for a prime pulse. Then you have to be cranking or have oil pressure to turn it on.

 

[ktmoutfront]

Let me get this straight. Are you running dual fuel? I have not seen that in anything but my dads 1973 2500 that he installed back in 1973.

 

[Kia.]

Well, 89 was tbi originally so it will only send voltage to the pump for two seconds when you first turn the key for a prime pulse. Then you have to be cranking or have oil pressure to turn it on.

That's the thing, I'm not getting the prime pulse.

Key turn, no pump action.
Cranking fine, not starting.

The issue I have is that the LPG system needs petrol to start the car, hence needing the aux petrol tank. But it can run on both fine.

The car was totally fine with the old tank etc.

It does look like it may very well be a cabling issue, but I can't fathom where the problem is. I might have to have a new look at it tomorrow and double check it all, although I've done that a gazillion time already :-(

 

[Kia.]

Let me get this straight. Are you running dual fuel? I have not seen that in anything but my dads 1973 2500 that he installed back in 1973.

Yup. LPG and Petrol

LPG is WAY cheaper that petrol here in the EU.

I get about 380 miles with both tanks. About 300 on LPG.

 

[Blue85]

Verify those color codes! Power should be tan/white. If you measure the fuel sender line (pink), there will be voltage there from the cluster - until you connect a load to it.

PINK and a TAN and WHITE. PINK is power (12v) TAN and WHITE is the fuel gauge.

...from what I have managed to find out via the wiring diagrams.

So have connected the PINK to the POSITIVE on the new inline pump, and grounded the NEGATIVE to the chassis.

If I'm wrong about that:
The TBI system uses a relay for the fuel pump (mounted on the firewall). I think there is a test point for it there. There's also a backup source of pump power, which is an oil pressure switch. That way, the vehicle can run with a bad relay, you just have to crank for a while. https://ck5.com/forums/threads/tbi-wont-fire-up.346311/page-2#post-4261591.

It's possible you have an intermittent problem or also just a bad connection. You want to measure the voltage to the pump while it is powered. A bad connection (ground bolt, relay contact, connector contact) can give you 12V with no load, then fall to almost nothing when the load is connected. Then you can trace backwards from there.

 

[Blue85]

Also from the 1989 manual:

 

[Blue85]

I have an 1989 K5

Oh, no, it's the:

 

[Wes Harden]

Also be sure to check your ecm fuses, if one them popped then the computer may not turn on the fuel pump. ECM A & B, and instrument fuses.

 

[Kia.]

Verify those color codes! Power should be tan/white. If you measure the fuel sender line (pink), there will be voltage there from the cluster - until you connect a load to it.


View attachment 472277

If I'm wrong about that:
The TBI system uses a relay for the fuel pump (mounted on the firewall). I think there is a test point for it there. There's also a backup source of pump power, which is an oil pressure switch. That way, the vehicle can run with a bad relay, you just have to crank for a while. https://ck5.com/forums/threads/tbi-wont-fire-up.346311/page-2#post-4261591.

It's possible you have an intermittent problem or also just a bad connection. You want to measure the voltage to the pump while it is powered. A bad connection (ground bolt, relay contact, connector contact) can give you 12V with no load, then fall to almost nothing when the load is connected. Then you can trace backwards from there.

You're absolutely correct. The TAN/WHITE is the power. Thanks for that!

 

[Kia.]

Also be sure to check your ecm fuses, if one them popped then the computer may not turn on the fuel pump. ECM A & B, and instrument fuses.

This was what I missed. Even though I did check them, I think something must have tripped the ECM B fuse when trying to diagnose the pump issue with the power.

The truck now works on both LPG and Petrol now I can leave the workshop and make my family happy!

Thanks to all for pointing me in the right direction!

I'll be posting pics of the build soon!

 

[Kia.]

Oh, no, it's the:
View attachment 472280

LOL!!