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

[VolvoOwl98]

SASKIA LIVES ONCE AGAIN!

Just have to get some of the suspension stuff that I unbolted back into place and make it down to the gas station for the first fill-up on a good pump

[VolvoOwl98]

Update, was able to drive and get some fuel. She purrs much smoother now

Tested fuel pressure at the rail, it now climbs to about 48-50 psi, which is higher than the previous 40 psi. However, upon engine off it still pretty quickly loses pressure. I know that's often attributed to a check valve, but I feel the odds of a new pump and assembly shipping in with a bad valve isn't super likely, and the old pump was exhibiting the same behavior too... any chance it's the fuel pressure regulator?

Very happy to have (eventually) successfully gotten stuff worked out so Saskia's driveable now and I don't have to stress about the fuel pump now. I do still need to investigate where the voltage drop from the fuel pump relay to rear wiring is, especially since that wire acts as the signal wire for the new relay put in the back as a part of the wiring kit.

One step closer to getting things resolved, but not quite yet. Progress is a positive, though

[VolvoOwl98]

Currently reading some fuel gauge inconsistencies.

Filling up the tank last night, gauge worked fine. This morning, seemed just fine, maybe a smidgen higher (I had chocked that up to fuel settling overnight, potentially an incorrect assumption).

After driving in the morning, came back in the afternoon and gauge had risen more. Driving home it increased relatively quick, nearly up to full. Also CEL came on after small pull (getting up to speed after making a 100° right hand turn onto a 55 MPH road, RPM’s at max 4300), probably from EVAP code.

Read with VOL-FCR when home, many thanks to the creator(s) of the software, huge help!

Current codes are as follows:

From ECU
EFI-611 Fuel tank system large leak

From Transmission ECU
AT-143 Kickdown switch, signal too low

From combined instrument readout
CI-221 Vehicle speed signal missing
CI-113 Fuel Level Sensor Signal too high
CI-131 12 pulse vehicle speed signal too high
CI-222 Vehicle speed signal faulty
CI-211 D+ signal to low

Any code deciphering and/or electrical wizards have some insight? (Especially for the fuel level sensor signal, ECU and Transmission codes I’m not very worried about at the moment)

[abscate]

Wipe out those codes and see what comes back. A low battery will throw spurious codes on the v70 platform , the evap code is probably an aged hose somewhere. Look in the front for good karma

[VolvoOwl98]

Wipe out those codes and see what comes back. A low battery will throw spurious codes on the v70 platform , the evap code is probably an aged hose somewhere. Look in the front for good karma

All the codes are back. EVAP I have a few sections of hoses in the front I have yet to replace (the main one being p/n: 1270480 (IPD link: https://www.ipdusa.com/products/16668/E ... vo-1270480)).

Over the course of the fuel gauge acting funny, it has gone down, seemingly in proportion to the amount of fuel burned (just at the wrong position amount on the gauge).

I'm currently working on the assumption that there's an electrical fault leading to the incorrect gauge

Diagram of the system for my emissions code with fuel pressure sensor highlighted (p/n: 9155870)

23 - Fuel tank and connecting parts AWD -1998 For cars with emission code 4, see product sign., AW42 AWD.png (92.74 KiB) Viewed 763 times

Wondering about something being up with the fuel pressure sensor/how it connects to the fuel pump wiriing

[abscate]

If the !998 is the same as later awd it just takes 12 volts to two series wipers , one on each side. If either one fails the system rails to full I think. If you don’t have full 12 volts to the sensors, you will get wierd things happening

That circuit is in a thread here somewhere

[abscate]

Correction to above. The fuel gauge is wired to the CEM with a supply voltage and a return voltage drop ftom the two wipers in the tanks. The supply voltage is probably a regulated 5c dc input. If I can get to mine today I’ll check

[VolvoOwl98]

Back at this again, this time with a much less rushed timeline for having wheels to go places

First started by reading resistance values of the old pump, then figured out how to read the resistances for the stuff in the car. The old pump read from a range of 5.5 ohms for full to 160 ohms for empty. As I understand things these numbers can have some small variation within the fuel level full range, but not exceeding a few ohms.

Resistance measured of the old pump (and how to measure)

Then went to check the fuel pump resistance and the passive sending pump resistance:

Resistance measured of new pump and passive sending unit

The variation between the pump and passive sender was a curious thing to note, but seemingly to be expected per my reading at this Swedespeed thread here (relevant comments quoted below): https://www.swedespeed.com/threads/volv ... on.695943/

To quote,
"That ejector has a rating for 2.5-7.5 ohms for full, and 165-170 ohms for empty. The fuel pump sending unit has a rating of 2.5-7.5 ohms for full and a rating of 157.5-162.5 ohms for empty. These added together gives up the fuel level sensor ohm rating of 5-15 ohms for full and 322.5-332.5 ohms for empty"

And

"Don’t mirror the RH curve 1:1. The two cards aren’t perfectly identical slopes and the saddle tank isn’t symmetric"


So this leads to my current readings and adventure. Both the left and right side senders are giving values indicating that the tank is full, and that may partially explain my slow fuel fill and only being able to put in about 4 gallons as discussed here: (viewtopic.php?t=108179). Of course there's still the EVAP system to deal with on that, but that can likely wait.

So does this mean in the quasi-fuzzyheaded state from being very under the weather yet motivated by adrenaline and stress, my count for how much fuel is in the tank is incorrect... which if so I won't hide, but oi
(Also raises the question of how to check... short of running the car until she drinks it all from the tank... I know it's tricky on these cars but would siphoning the gas be a viable route?)

That doesn't explain the odd behavior where the gas gauge went up and pinned itself at full or why the instrument cluster is giving a reading for the fuel gauge voltage being too high, but at least I have some more pieces to the puzzle. Voltage anomalies are next on my list of things to investigate

Edit: Devised a plan for checking if fuel resistance levels are working right, going to drive around some and re-check with the multi-meter to see if/how far the values change

[abscate]

It’s really hard to siphon from the AWD tank. There is an anti siphon valve at the bottom of the long fill, which stops North American Tank Opportunists from stealing gas. The railed full behavior is just the wipers being old amd going to open circuit.

[VolvoOwl98]

The railed full behavior is just the wipers being old amd going to open circuit.

Unfortunately, I have learned that this is partly the situation I'm in (though not with the old wiper on the passive sending unit)

I drove around some and re-checked the resistance at both, the passive sender is now reading 38 ohms after 27 miles of driving from my previous check, and the new fuel pump is still reading 4.3 ohms... which does explain why the gauge is still going down (currently reading just a hair above the first tick mark down from full), but much slower than it should...

Which means dropping the tank (again), which while not hard, is annoying to have to do again