RRC Fuel Pump no Power.

[Dougal]

I've got a 1993 V8 RRC that's refusing to leave the garage. It ran fine 3 years ago.
No power to the in-tank fuel pump.
Wiring checks out fine.
Relay under the seat isn't powering up.
Relay checks out fine disconnected.
Relay socket has live feed and is getting power when ignition is switched on.
Relay socket earth is pulling up from 0V to 12V so there's no voltage difference to activate the relay.

This relay earth wire goes directly to pin #16 on the ECU.
I've borrowed a spare ECU and got exactly the same behaviour with no change.

Has anyone struck this before? It's like there's some input that's wrong to the ECU so it's not connecting earth to the pump relay.

 

[elbekko]

Does it have an inertia switch?

 

[SLOWPOKE693]

Have you checked continuity from pin 16 to the end of the wire? If you ground pin 16 manually does the relay activate and run the pump?

Is the pump just frozen?

 

[Dougal]

No inertia switch that I've found. Wiring for the pump checks out fine. But......

I dug out my old laptop with Rovergauge on it yesterday and plugged that in.
Engine temperature is wrong (-23C when it's more lik 10C)
Vehicle speed is wrong (194km/h when it's 0).
TPS isn't reading.
Voltage isn't reading.

I was able to borrow a spare ECU from a neighbour and have the same readings on both. So it's time for some more wiring investigation.
The vehicle has been stored in a clean dry garage for 3 years and everything worked when it was parked.

 

[M92PV4U]

Some have an inertia switch in different places to others. It can be A) next to the steering column, b) next to or close to the ECU Drivers kickpanel at the top. C) next to the fuse box under steering column.

 

[M92PV4U]

From some rr forum talking about early 90s rr.

 

[Dougal]

I found the inertia switch. They hid it well. It's in the correct position though and clicks in/out. It's not the problem.
It was under the LHF seat tucked right in against the rail and only visible with a torch from laying down in the rear footwell.

I've got some quality time to spend chasing wires and sensor voltages.

Fuel pump draws ~10A when jumped. Is that somewhat normal? I haven't pulled the fuel filter yet to check delivery because the EAS is slammed down and there ain't much room.

 

[elbekko]

10A doesn't seem ludicrous.
With those readings from Rovergauge it's definitely worth chasing down some grounds.

 

[Dougal]

So it turns out if you plug the EAS diagnostic cable into the ECU port it works. Which lead me to believe the other port was the ECU diagnostic port. But it wasn't and Rovergauge would just get enough signal to confuse every reading.

Swap the leads around and I now have Roverguage reading everything correctly. It's no longer doing 194km/h while standing still. Battery voltage, TPS reading, cranking rpm, coolant temp etc are all correct. Fuel pump priming button seems to work too.

Still no start and no fuel at the exhaust or plugs so I'm going for old standard problems of old fuel gumming up filters and injectors.

 

[Bebop]

Still no start and no fuel at the exhaust or plugs so I'm going for old standard problems of old fuel gumming up filters and injectors.

How can it be mechanical if your previous diagnostic showed an electrical problem :

No power to the in-tank fuel pump.
[...]
Relay under the seat isn't powering up.

 

[Dougal]

How can it be mechanical if your previous diagnostic showed an electrical problem :

I have since found and read the 14cux docs. The pump only runs for 2 seconds on key and it appears to be doing that.

I'll know more about the state if fuel flow when I get the injectors out.

 

[Bebop]

I have since found and read the 14cux docs. The pump only runs for 2 seconds on key and it appears to be doing that.

I'll know more about the state if fuel flow when I get the injectors out.

Before getting there, why don't you check fuel pressure and injector signal?

 

[Dougal]

Before getting there, why don't you check fuel pressure and injector signal?

I have got injector signals. I haven't run an oscilloscope on them but it's got a 12v ripple.

There is no easy way to check fuel pressure without getting better access to the fuel rail so it's all headed in the same direction right now.

 

[Dougal]

Plenum off, fuel rail out. Injectors seem to be working fine, fuel flow to the rail is minimal.
I'll change the filter before I go back to the pump.

Now I need to replace the injector o-rings. Viton (FKM) or HNBR (green)?

 

[Dougal]

Pump out. It's dead jim.

Everything looks good but it's jammed solid. Motor/pump unit is crimped together too. Can you buy replacement motor/pump units or do I need to replace the whole pump/sender assembly?

 

[elbekko]

Did they have the plastic tank yet in '93? If so, the pump assembly should be fairly easy to take apart. Can't remember exactly how the earlier ones went together, but not impossible they're not easily serviced.

 

[Dougal]

Did they have the plastic tank yet in '93? If so, the pump assembly should be fairly easy to take apart. Can't remember exactly how the earlier ones went together, but not impossible they're not easily serviced.

Yeah plastic tank. The fuel pump is an AC Delco (GM) unit that crosses over to a lot of other cars including Holden Commodores sold in NZ/Australia.

Original part number: AC 6443228
Alternative AC part numbers, 6442435, 6443327.
Bosch BFP772 (for NV-VR Commodore)
Aeroflow AF49-1021 (for VN-VS commodore).

It's a 37mm pump, around 230 litres/hour max and about half that at 3 bar: AEROFLOW EFI IN TANK PUMP COMMODORE VN TO VS STANDARD REPLACEMENT - AF49-1021 - everythingaeroflow

 

[elbekko]

Should be easy enough to get it out of the assembly and replace just the pump then. It's been a decade or so, but IIRC the pump assembly is easily taken apart. First take the floating pickup off the guides, then everything should be able to come apart?

 

[Dougal]

Should be easy enough to get it out of the assembly and replace just the pump then. It's been a decade or so, but IIRC the pump assembly is easily taken apart. First take the floating pickup off the guides, then everything should be able to come apart?

The assembly is already apart. It's just clips. That's how I got the pump unit part numbers. It's the pump unit that's crimped together.

Aeroflow pump ordered as above. I'll autopsy the old when the new is in.

EAS is working too. Turns out it can't get enough power through a USB-Serial converter to wake up the ECU, plugging it directly into the serial port it all came alive and I was able to run the pump and get ride height. I pulled the drain bung out of the tank and it's pristine inside. Amazing for 31 years old.

 

[Dougal]

New pump is in and buzzes like it should, perfect fit, old pump has been autopsied.

The motor on the old pump was fine. It's simply a lump of crud in the pump sections that solidified in the ~3 years it's been sitting there. If it had been kept in use it would likely have passed the same stuff through to the filters and I'd never have known.

But a new pump is peice of mind. I'll get pics up soon.

 

[elbekko]

Good news And agree on the new pump being piece of mind... sort of. With parts quality these days, you never know.

 

[Dougal]

Lots of pics to help out the next guy.

At this point I'm going to go ahead and recommend anyone with a fuelling problem to simply replace the internal tank pump first. Because the chance of your pump unit being partially blocked with crud like this is almost 100% due to the vehicles age.
You can't see or check this without destroying the pump.

About 10 years ago when I got this vehicle I had to retune the ECU to get it running right (overfuelling down low, underfuelling up top). I suspect I'm going to have to do this again now I'll hve correct fuel flow and pressure.

 

[Dougal]

And everything now works great.
Cranked and started within about 10 seconds (fuel rail was completely empty).
With a new battery it's got enough volts that the ABS pump and EAS (air suspension) compressors are all working exactly as they should.