2004 XC70 no start - faulty fuel pump and/or electrical connections? Topic is solved

[enotslim]

Sudden failure to start. Strong starter crank. No hint of firing. No fuel smell and no fuel leak when opening the Schrader valve at the rail after cranking. Similar symptoms ~18 months ago resolved without any real intervention on my part (except a new battery that was probably a red herring). At that time I determined the car does not have a PEM (see photo documentation of empty possible locations here: viewtopic.php?t=97929). Also looks like the car lacks a fuel pressure sensor (photo below)

The fuel pump fuse is OK visually and the fuel pump relay passes the multimeter tests (1. "Clicks" when 12V applied across switch 1/2. 2. Resistance across 3/5 and 3/4 go from infinite to "very low" and the reverse, respectively, when 12V is applied across 1/2). That's assuming I'm testing the correct relay (tested third position from the right on the board below the driver's kneewell guided by these instructions in the video below. Did not retest after swapping relays.


Removed the left rear seat to access the fuel pump and found some "corrosion"on the underside of the backing plate in register with some degradation of the underlying electrical lines (photo below). (Looks like the electrical supply goes directly to the pump instead of snaking over from the driver-side as I believe is the case for (slightly) newer models. Is this correct?)

I would like to determine if the electrical system is actually functioning before deciding to replace the fuel pump.

My questions:

Based on appearance is this electrical line likely dysfunctional? How can I test it before moving on to replacing the pump.?

Can the harness be replaced or does this require patching/repair of the existing wires?

How can I protect against future electrical issues? I will thoroughly clean the area and replace the gasket on both sides before considering any further disassembly, but might there may be more going on than a simple leak? Electrolysis/shorting through degraded insulation? Rodents?

I am a little concerned about connecting the battery to test delivery of voltage to the fuel pump with the rear seat electrically disconnected. Don't want any unresolvable codes, recreational air bag deployment, etc. Should the seat wiring be reconnected before reconnecting the battery and testing the pump wiring?

Any suggestions and advice, no matter how basic, is very appreciated.

Thanks.

[abscate]

You’ve got critter damage on that wiring, Dave. Look at the nuts they gathered up too.

[jonesg]

if you connect the battery with the rear seat out you'll get the SRS code and that requires a decent code reader to erase.
Vida would probably show signal missing at the pump, those are chewed wires.
I would get some heat shrink and patch the wiring up.

Maybe theres something you can paint on the harness to repel mice. Maybe this stuff.

[enotslim]

Thanks for tip about "NH Mouse Out" - new to me.

The tachometer does not move at all when cranking during attempted start. Is this normal? Could this indicate a faulty cam shaft position sensor (and is a simple replacement, I believe) or something else related that is preventing starting ?

Found this guide to testing the electrical components:

Swapped relays without change in no-start. Verified continuity of the fuel pump fuse and that 12V present on both sides of the fuse.

Disassembled wiring harness at the pump and tested leads. (Did not yet repair the harness.) I don't get 12V across any pair of leads with the ignition key in positions 1 or 2. I get 5V across several pairs as in the attached image. Text color is wire color. 5 and 6 are heavier gauge than all others.

1 and 3 show 5V if connected to any other lead. With key in position 1 and the connection placed on lead 4, the 5V voltage fades to zero after several seconds. With key in position 2 and the connection placed on lead 4, the 5V voltage is stable. All other voltages are stable at 5V with either key position.

On the pump side there is no continuity across any pair of leads. There is a drop to very low resistance across any pair of leads 1, 2 and 3. The resistance across 1/3 is twice that across 1/3 or 2/3. Resistance across 1/2 and 2/3 is equal.

Is this normal? Is it worthwhile and safe to directly apply 12V to the pump? I assumed that heavier gauge leads would be power. Is that correct?

[abscate]

Don’t guess in that plug pins there please. You are applying current to a pump immersed in gasoline.

Let’s find the 2004 wiring in VIDA and get those pins labeled.

You could buy a $30 alldata for a month and get it there , too

[jonesg]

maybe this,
https://cardiagn.com/2004-volvo-models- ... grams-pdf/

[cn90]

I think the 2004 models have PEM.

[enotslim]

I think the 2004 models have PEM.

I thought so too but was not able to find a PEM in any of the advertised sites: not next to the spare tire, behind the right rear fender liner, next to the fuel filter, or above the plastic fuel tank. Images showing these empty spaces are in this thread: viewtopic.php?t=97929.

Should I look somewhere else? I would love to find a PEM if it is causing the current yes crank/no start condition.

I also think I read that the PEM was introduced to the XC70 sometime during the 2004 model year. Maybe my 2004 XC70 is pre-PEM? Would a VIN lookup provide that info? How about a scan tool?

Thanks.

[jonesg]

It seems you're reaping the downside of not having Vida to test these circuits.

[scot850]

I would call a dealer with your Vin# and engine number and see if they can tell you. From what you said you have covered all the usual haunts for the PEM

Neil.