[AKCub]

Chasing down a spark/no fuel issue on a 1993 RRC LWB with the 4.2l. No power to the fuel pump at this point. Starting to work my way through the diagnostics for the fuel injection system and want to ensure I'm following what the test procedure is telling me to do.

If you look at test procedure 3 for checking operation of the main relay it shows measuring the voltage on pin 87 of the main relay. My question(s) is/are- Am I checking voltage with the relay installed and reaching in to the desired pin for the voltage or am I going from the relay base? The other question is- is it acceptable to use the grounds on the 40 pin connector to the ECU for the voltage measurements?

Sorry if these have been answered already...

Thanks,

Scott

 

[Mikieman]

First thing I would do is confirm no spark by spraying starter fluid into the intake
To try and start it

 

[95classiclwb]

pin 87 is an output thus relay needs to be installed, ecu receives injector pulse from coil thru timing spark. as suggested above verify you have spark before moving to the next diagnosis. it is important you must have spark for fuel pump relay to activate.

 

[AKCub]

We have spark and it will fire on starting fluid. No power to fuel pump so chasing down where the electrons stop. It rolled off idle at a stop light and wouldn't restart. Fuel pump will run with external power and fuel filter has been replaced.

Will run the RAVE diagnostics to see if I can find the fail point.

Thanks for the info on voltage measurement.

 

[AKCub]

I have spark and engine will fire on starting fluid. No power to fuel pump at this point.

I will dig into the RAVE diagnostics now.

Thanks

 

[Mikieman]

I would check the ground at the fuel pump
It is connected to the frame on drivers side rear wheel well
It could also be as simple as unplugging the fuel pump and reconnecting it
Also you can power the fuel pump directly
As a test to see if it’s working
I’d check the fuel filter also
The fuel pump relay is number 22
Under passenger seat

 

[AKCub]

Yep, pump runs with another power source. Ground on front of right rear wheel
well checked, and then removed and cleaned and reconnected and checked for continuity again. Fuel filter replaced. Original relays swapped EFI/main with no affect and then replaced with new. Relays making noise appropriately after key on. Checked for power at connector in right rear wheel well and at fuel pump and nothing.

That’s why I’m headed into the RAVE diagnostics to see where the break in power is.

Thanks

I would check the ground at the fuel pump
It is connected to the frame on drivers side rear wheel well
It could also be as simple as unplugging the fuel pump and reconnecting it
Also you can power the fuel pump directly
As a test to see if it’s working
I’d check the fuel filter also
The fuel pump relay is number 22
Under passenger seat

 

[Mikieman]

When you powered the fuel pump and it came on
Did you try to start it
Just wondering
Another thing to check is the vacuum line at the pressure regulator
And keep a fire extinguisher close by when
Messing with theses things
I burned all the wireing on the back side of my motor a few years ago
Changing the injectors
So be careful
Just sayin

 

[AKCub]

I did not try to start it with the fuel pump powered. In hindsight I should have. Ill try today.

I had time to check the power in to to the ecu and both the battery and ignition leads are good. The pin from the coil (pin 39) is low (think the min was 9.5 and i was seeing more like 8.8 or 9. Gonna check that wire today including the inline resistor and connection at coil end. It still has the spade style connector on there. Since I’m getting spark i think the low voltage is probably ok but not ideal.
after that i hope to have time to check power to the fuel pump out of the ecu. Checking power from the relay should be quick. If that has power the open has to be between the relay out and the connector in wheel well since i have continuity from there to pump.
I will look at vacuum line to regulator as well today. If the regulator has failed, will the pump still go through the initial key on cycle? Or does that only affect the pump via ecu after engine is running?

When you powered the fuel pump and it came on
Did you try to start it
Just wondering
Another thing to check is the vacuum line at the pressure regulator
And keep a fire extinguisher close by when
Messing with theses things
I burned all the wireing on the back side of my motor a few years ago
Changing the injectors
So be careful
Just sayin

 

[reccerover]

Another test is to jump the fuel pump relay, simple double male wire, and see if you get power to the pump...I had an issue on my '90RRC where the "trigger" wire from the fuel cut-off was shorting giving me intermittent power to the relay....At least with this test you will know if power from the fuel pump relay to the pump is consistent...Then the only other places would be the ECU or the fuel cut-off switch....

 

[95classiclwb]

your fuel pump trigger and injector pulse wire is the one white black stripe next to mass airflow sensor.

 

[AKCub]

Thanks. That’s one of the wires that is on me list to look at closely

your fuel pump trigger and injector pulse wire is the one white black stripe next to mass airflow sensor.

 

[AKCub]

Thanks. That’s one of the wires that is on me list to look at closely

your fuel pump trigger and injector pulse wire is the one white black stripe next to mass airflow sensor.

 

[NormalEar]

There is a fuse under the passenger seat that you should check (if you have not already). I had a similar situation and it took me forever to figure it out. I followed the wire diagram in the back of the manual (not rave) to find it.


Sent from my iPad using Tapatalk

 

[95classiclwb]

I have found that once in while the inertia switch looses contact but it is not fully tripped, I knock on the side with the handle of a screw driver to fully trip and then reset. it has helped in the past. don't know why it happens, I guess the quirkiness and eccentricity of a british vehicle.

 

[AKCub]

If im reading my schematic correctly, that jumper should be from pin 30 to pin 87 on the relay base to run power to the pump directly. Does that make sense with your jumper? Looks like 30 is power and 87 is the normally open that powers the fuel pump.

Another test is to jump the fuel pump relay, simple double male wire, and see if you get power to the pump...I had an issue on my '90RRC where the "trigger" wire from the fuel cut-off was shorting giving me intermittent power to the relay....At least with this test you will know if power from the fuel pump relay to the pump is consistent...Then the only other places would be the ECU or the fuel cut-off switch....

 

[AKCub]

This may be a stretch but there is a white wire that comes off the positive side of the coil that splits and one side goes to a spade connector that attaches to the engine harness and the other side goes to a chassis ground on the fender just below the coil. There is a diode in series with the ground and it seems to have failed open. I don’t have a dedicated diode check mode on my multimeter but it is open both directions using the ohm mode.
Does this wire ring any bells associated with this fail mode for you with experience on these classics? I can’t find the diode on my schematic.

 

[RRLondon]

If you want to check and see if will run before definitively finding the fault, you can make a small jumper to go from (in the fuse box) the supply side of the cigarette lighter fuse, to the supply side of the fuel pump fuse.

This will bypass all of the pump/ecu/inertia switching protocols, but will give you a ignition key controlled supply to direct to the pump.

I've used this as a "get going" status while then working through to what is wrong and correcting it to reinstate the standard setup and safety measures.

It'll at least tell you with confirmation that the fault is within the switching logic and hardware.

 

[AKCub]

Thanks. Thats a slick idea for troubleshooting.

If you want to check and see if will run before definitively finding the fault, you can make a small jumper to go from (in the fuse box) the supply side of the cigarette lighter fuse, to the supply side of the fuel pump fuse.

This will bypass all of the pump/ecu/inertia switching protocols, but will give you a ignition key controlled supply to direct to the pump.

I've used this as a "get going" status while then working through to what is wrong and correcting it to reinstate the standard setup and safety measures.

It'll at least tell you with confirmation that the fault is within the switching logic and hardware.

 

[AKCub]

I missed the time window to edit-

Thanks. That's a slick idea for troubleshooting. Like an old phone exchange. Gotta love the interwebs.
It looks like on mine ('92) those fuses are under the passenger seat. Ill poke around there tomorrow as time allows.

If you want to check and see if will run before definitively finding the fault, you can make a small jumper to go from (in the fuse box) the supply side of the cigarette lighter fuse, to the supply side of the fuel pump fuse.

This will bypass all of the pump/ecu/inertia switching protocols, but will give you a ignition key controlled supply to direct to the pump.

I've used this as a "get going" status while then working through to what is wrong and correcting it to reinstate the standard setup and safety measures.

It'll at least tell you with confirmation that the fault is within the switching logic and hardware.