Fuel Pump Issues

[SoCalManche]

1 minute ago, Jeep Driver said:

I suspect he's got a problem with all his grounds. 

Could the dipstick stud grounds be causing these issues? That is an overly important grounding spot, correct?

[Ωhm]

10 hours ago, SoCalManche said:

As far as how I've measured it, the ignition is OFF, I disconnect the two three-pin connectors, one coming from the truck cab, and the other being the fuel pump itself. Once the fuel pump is disconnected, I take the other connector and back-probe the middle pin, and ground out to the chassis. That's how I get 40 ohms.

 

Sounds like this ohms measurement is through the fuel gauge in the cluster (C139_B). Reading could be normal for measurement taken.

[SoCalManche]

Is there anyway someone can provide me assistance on what to look for as far as problems are concerned? If that's the correct ohms reading,then how to I measure to see what's incorrect?

[Ωhm]

Does the starter engage and turn the engine over when the IGN SW is in the CRANK position?

[SoCalManche]

Just now, Ωhm said:

Does the starter engage and turn the engine over when the IGN SW is in the CRANK position?

Yes, if fuel is put in the throttle body.

[Ωhm]

3 minutes ago, SoCalManche said:

if fuel is put in the throttle body.

So engine will START and RUN when fuel is added until added fuel is gone?

[SoCalManche]

Just now, Ωhm said:

So engine will START and RUN when fuel is added until added fuel is gone?

Correct. Starts up easily, and dies once fuel is burned off from TBI.

[Ωhm]

Need to take some voltage measurements. Use the following connectors callout. D1 and D2 are located under the hood, right side of engine compartment. Should have yellow covers on them.

 

 

D1_5 Battery Voltage (B+) Hot at all times.
D1_2 Battery Voltage (B+) Hot with KEY in RUN or CRANK position.
D1_6 Battery Voltage (B+) Hot with KEY in RUN position (only 2-3 seconds). This ones tricky, because of time limited.
Hope you can do these voltage measurements by yourself.

 

Forgot to mention, use battery negative terminal as DVOM ground.
 

[SoCalManche]

17 minutes ago, Ωhm said:

Need to take some voltage measurements. Use the following connectors callout. D1 and D2 are located under the hood, right side of engine compartment. Should have yellow covers on them.

 

 

D1_5 Battery Voltage (B+) Hot at all times.
D1_2 Battery Voltage (B+) Hot with KEY in RUN or CRANK position.
D1_6 Battery Voltage (B+) Hot with KEY in RUN position (only 2-3 seconds). This ones tricky, because of time limited.
Hope you can do these voltage measurements by yourself.

 

Forgot to mention, use battery negative terminal as DVOM ground.
 

D1_5: 12.5 volts

D1_2: 10.6-10.7 volts

D1_6: 1.8 volts

[Ωhm]

Remove Fuel Pump Relay and using a fused jumper wire, connect C216_1(30) to C216_4(87) at the fuel pump relay block. Retake voltage measurement at D1_6 again.

[Ωhm]

 

[Ωhm]

Also with fused jumper in place, fuel pump should be running (pumping).

[SoCalManche]

16 minutes ago, Ωhm said:

Also with fused jumper in place, fuel pump should be running (pumping).

Gotcha. I have to run and grab a jumper.

 

[SoCalManche]

1 hour ago, Ωhm said:

Also with fused jumper in place, fuel pump should be running (pumping).

Does it matter what size fuse to put in the jump wire?

[Ωhm]

1 hour ago, SoCalManche said:

Does it matter what size fuse to put in the jump wire?

 

If you have a choice, start with 15A fuse.

[SoCalManche]

14 minutes ago, Ωhm said:

 

If you have a choice, start with 15A fuse.

That worked to engage fuel pump via 15A fused jumper wire. Too much fuel entered the intake, so waiting a few minutes before trying to start again. Will come back with reading.

 

What does this mean for now?

[Ωhm]

Fused jumper wire is doing what the Fuel Pump Relay should do. Suspect Fuel Pump Relay. You said you've try a few different relay, but that jumper wire is doing the same thing. Hope engine starts.

[SoCalManche]

13 minutes ago, Ωhm said:

Fused jumper wire is doing what the Fuel Pump Relay should do. Suspect Fuel Pump Relay. You said you've try a few different relay, but that jumper wire is doing the same thing. Hope engine starts.

Would there be a reason as to why the original relay clicks repeatedly when a new relay won't? 

[Ωhm]

Relays can fail in many different ways. Clicking means the relay coil can't hold the switching contact down on the other terminal. Does engine start with a new fuel pump relay installed?

[SoCalManche]

1 hour ago, Ωhm said:

Relays can fail in many different ways. Clicking means the relay coil can't hold the switching contact down on the other terminal. Does engine start with a new fuel pump relay installed?

No.

 

With jumper wire connected, fuel pump constantly primes but no start.

 

With original relay connected, no priming but will start with fuel added to TBI.

 

Help...lol...

[Ωhm]

Does engine start with jumper and adding fuel to TBI?

[SoCalManche]

Also, now when I try to start with the original relay connected, the engine struggles to start with fuel added to TBI, and when it does, a popping noise occurs around the intake/TBI and it shuts off abruptly.

[SoCalManche]

Just now, Ωhm said:

Does engine start with jumper and adding fuel to TBI?

No, it didn't.

[Jeep Driver]

OK, well clearly it's not moving any fuel. 

 

Has it occurred to anyone that you have a bad pump????

 

It maybe that the pump has gone to ground and therefore the relay stammers. 

 

Time for a pump.......and go through ALL your grounds and cables and fused links...........ect.........

[SoCalManche]

2 minutes ago, Jeep Driver said:

OK, well clearly it's not moving any fuel. 

 

Has it occurred to anyone that you have a bad pump????

 

It maybe that the pump has gone to ground and therefore the relay stammers. 

 

Time for a pump.......and go through ALL your grounds and cables and fused links...........ect.........

I got a new pump orginally, which by the way isn't properly spec'd out for these trucks. But regardless, I took the original pump out, tested it at the battery, and it immediately started. Whenever I connect the jumper wire in the fuel pump relay, it immediate comes on. And it is definitely pushing fuel, because one of my fuel line retainer clips broke, and the new ones you buy need o-rings. I didn't know that, and so as soon as the jumper wire engaged between 30 and 87, fuel started coming out of the fuel lines at the connectors underneath the intake.