1998 V70XC - New fuel pump, troubleshooted 9470674, new wiring, and odd fuel gauge behavior (problem resolved)

[abscate]

You can pass it ,of course, but you are removing a safety feature Volvo engineered in.

The fuel pump controller looks for a 40 Hz signal from the engine and shuts off if that stops. That’s a safety feature to turn off fuel in a crash that turns off the motor.

I’m comfortable bypassing that as it is an edge case but your risk tolerance may vary.

I would pursue the connector route and find that voltage drop ftom fuel pump relay to pump.

I think the 99 v70 fuel delivery is the same …her it is ..

There is only one wire between the fuel pump relay and pump connector going through big connector 24, right side under dash. I don’t remember what Swedish colour for P is but that’s the only one to test!

2/23 and 6/31 are the relay and pump, respectively

On edit…it’s pink! If you are measuring the voltage at the pump connector, make sure the ground at the rear crossmember is good too. Maybe check voltage on the plus pin with the meter on a different ground point

[rspi]

Are you testing voltage with the pump connected or unplugged. Over the past 2 years I have encountered about 50% of the DW200 pumps received were bad.

[VolvoOwl98]

You can pass it ,of course, but you are removing a safety feature Volvo engineered in.

The fuel pump controller looks for a 40 Hz signal from the engine and shuts off if that stops. That’s a safety feature to turn off fuel in a crash that turns off the motor.

I’m comfortable bypassing that as it is an edge case but your risk tolerance may vary.

I would pursue the connector route and find that voltage drop ftom fuel pump relay to pump.

I think the 99 v70 fuel delivery is the same …her it is ..

Good to know about that safety feature, that's a smart, simple way to get that done. Personally I'm okay with that feature being bypassed, especially since the upgraded wiring has its own fuse (25A) right by the battery and a relay in the back that has a wire that connects to a signal wire (which I don't know if that's the wire with the 40 Hz signal, but it could be?).

I do plan to pursuit where that voltage drop is coming from, but I may have to postpone that until after Saskia's running again (unless I'm forced to) because of other time constraints.

I think so too, I'm not entirely sure how much was changed between ME4.4 and ME7

Are you testing voltage with the pump connected or unplugged. Over the past 2 years I have encountered about 50% of the DW200 pumps received were bad.

With the pump unplugged from positive wiring. I hope I didn't get a bad DW200, I'm not sure if VAST checks them before they reterofit them into the assembly, but I'd imagine they would with the level of attention to detail they do. At least I could hear it humming with 8V, so it's alive to that point.


Also a reference photo of the ground connection from the back right side wiring harness. Access gained by unscrewing the T25 holding in the sill trim and prying it out, then lifting up some carpet.

(Photo before vacuuming and giving the ground a good dose of wire brushing and a bit of dielectric grease to help conductivity)

[abscate]

I think fuel delivery was unchanged on relay, pump, and wiring.

Ground looks fine. Find that 5 volts!

[VolvoOwl98]

DISCOVERY!

I believe I’ve found a source of the trouble! When comparing the photos in the DW guide for installing the wiring, I noted that the pink wire going into the gray connector is the positive (power) which (on Saskia at least) has the connector with a center ridge to keep from the wrong connector being put on. And it turns out, the positive and negative connectors on the VAST fuel pump are swapped!

I feel really silly just now noticing this even after I had compared the old and new fuel pump connectors side-by-side…
(I place a small blame on whatever current sickness I’ve got)

So hopefully a simple swap of connectors will do the trick

Connectors from the car (pink is positive from the fuel pump relay)

Note the difference in the ridge. New fuel pump connectors on the left, old on the right

Update: it also just dawned on me that if the ground was getting voltage instead of ground, one of the wires on the ground connector runs into a connector that plugs into wiring that comes from elsewhere by the fuel tank, which if my understanding of the system is correct, is the electrical line that comes from the sending unit on the left side.

Cable labelled MARWAL I think is from sending unit, note one cable from fuel pump ground goes into fuel pump connector that meets with sending unit

[abscate]

Lo and behold, it did make a difference. Still no start, still only getting 7.95V at the back when key turned to Pos. II, but now when the positive wire from the new pump is disconnected from the car, the gas gauge reads correctly!

I should have caught this earlier. That fits the above perfectly.

[VolvoOwl98]

!THERE IS SIGNS OF LIFE!

The new relay clicks with the key in position II, and the fuel pump makes a healthy (and much more audible) wirr sound for 2 seconds!

I can't test starting yet because there isn't enough fuel in the tank and I have to bounce to a social function, but I'm already very ecstatic about this nearly confirmed victory!

[abscate]

Home stretch!!

[Vova585]

Sorry, but dielectric grease will only make everything worse! It is not conductive. If you want to protect the connector and maintain the current flow- no-ox-id paste is your best bet.
https://www.amazon.com/NO-OX-ID-Special ... B00HDF9EXE

[VolvoOwl98]

Sorry, but dielectric grease will only make everything worse! It is not conductive. If you want to protect the connector and maintain the current flow- no-ox-id paste is your best bet.

Oh, well I'm very glad to know that now! I guess I've been misremembering what it's purpose is, then