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

[enotslim]

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

I tried setting up VIDA multiple times without success. Instructions I found were so fragmented and confusing I just gave up. I'm a Python programer. I run virtual machines. And I gave up. Can you (please) point me to instructions that even I call follow? I'm Mac-based with Windows access when forced. How about using a Microsoft Surface 3 (I know it's old) running Windows 10? Might be able to change to Windows 7 if needed. PM if necessary? Thanks!!!

[jonesg]

We do have a vida forum, those guys are the experts.
I bought vida on a thumb drive that has its own operating system, no need to fiddle around , once its set up you just plug it in and boot up.

Boot&go
https://diaglaptops.com/wp/dice-units/

[enotslim]

Pretty sure this car does not have a PEM. Found statements that if a car doesn't have a FPR then it also won’t have a PEM. I can’t find either, and the FPR should be obvious on the end of the fuel rail.

When the car would not start I used an Autel scanner and found numerous codes (some of which were about fuel issues - I can list them if it will be useful but there were a lot). After clearing all codes only a few recurred on rescan:

ECM-928C ECU, comm error; Faulty signal, Cruise Control Lever, Signal Faulty/Missing
REM-8F10 Position sensor xenon lamp; Signal too high
SWM-000A Permanent fault; Comm with SW buttons; Faulty signal (detected 3 times in succession)
SWM 0008 Intermittent fault; Comm with SW buttons ; Signal too low
SWM 0009 Intermittent fault; Comm with SW buttons ; Signal too high

At this point I fully recharged the battery (it had declined to ~11.8V) and the car started normally for the next week. Not sure if this reflects clearing codes, recharging the battery, both or neither. Could be coincidence.

After several days of test starts to make sure everything was stable I drove the front end onto ramps to wrap the exhaust until I can perform a proper fix of the noisy flex pipe. I then checked the voltage drop across a few fuses, rechecked the codes (no change) and attempted to "burn in” the muffler wrap. However, the car would not start. It caught briefly (a few combustion cycles) but then failed. Still failed even after another full battery recharge (sitting on the ramps). I disconnected the battery and left it that way for several days.

Yesterday I reconnected the battery, tested the voltage drop across a few fuses, scanned and found the same above codes, and "cleared all codes” without a change in the codes displayed. Then, almost magically, the car started. Codes remained the same. Disconnected battery to prevent parasitic leak. Reconnected and started again this morning. Installed a quick disconnect switch to protect the battery more easily.

I am confused. Sounds like the fuel delivery stopped between start attempts while the car sat on ramp. None of the remaining codes seem obviously related to starting. I’m assuming the initial legacy codes are not interpretable due their uncertain relationship to the current status of the car. I can provide them if it might help.

I suspected that the parasitic leak could have lead to several problems due to low battery, but fully recharging bears no consistent relationship to starting or not.

Suggestions? Did the prolonged battery disconnect time lead to resetting something important? I’ve read about that - or removing specific fuses - doing the same thing. If so the path to stable starting must require fixing the underlying problem (whatever it is).

Would VIDA/DICE provide more precise diagnosis?

Currently I can’t rely on the car to start even though it started 5 minutes previously and nothing obvious changed in the interim.

[Vova585]

I think that your fuel pump is likely done. Those 2 big wires on the connector to the plastic cap are 12v supply to the pump. I would spray a contact cleaner there and take a bulb from the headlight (any 2-4 amp light for load would do) and carefully connect it to the corresponding big wires. Make sure bulb is not touching anything that can be melted by its work. Attempt to start. If you see bright light consistently while you are cranking..your pump is dead. You can try an occasionally working "BMW trick" -car is not starting. You verified electricity is coming and bulb is bright. Reconnect the plug and with rubber mallet hit a couple times on top of the fuel pump plastic cap(without much force,it's plastic) if your car starts after that-your pump is dead.
In case you will decide to go for pump you will need: pump, fuel filter, fuel pump ring key(sometimes can be rented from advance) and a new rubber gasket for fuel pump unit.
Hope helps a little.

[abscate]

The metal pump is isolated from the top cap by rubber hose, so that trick won’t tell you much. Visual here

[enotslim]

Thanks. And starting after thumping could simply be coincidence.

I would be happy to replace the fuel pump. I just have no confidence that will solve this intermittent problem. Currently I have no objective evidence identifying a fault that can explain the intermittent failure to start. And no way to know if pump replacement does solve it. If I replace the pump and the car starts until I die, I guess that could be considered a success? I want to follow some objective data that reflects the cause, not the effect.

Assuming there is no PEM or FPR does that mean that all "regulation" of fuel delivery depends solely on the pump itself, or does another component operate in this configuration? Perhaps the ECM/ECU that are throwing codes?

I am figuring out the best way for me to access VIDA/DICE or something equivalent. VIDA installation is stalled due to Microsoft SQL Server issues that I will eventually resolve - or I will purchase from the link given earlier in this thread.

[enotslim]

I put a lot of stock in the fact that I did not get 12V by multimeter at the fuel pump power leads when the car would not start. But I probably didn't measure soon enough after switching the key to the "on" position. If the car does not start, does the voltage decrease from 12V after a few seconds (for safety reasons)?

[Vova585]

Let's do this- let's locate the fuel pump relay. My guess it will be under the hood to the left of the car next to the air cleaner box. The positive cable from trunk will be entering that box. Hopefully the owners manual book or the reverse of the plastic cover of that fuse/relay box will help us identify the correct one(sorry I am too lazy to go to my own car to look it up). Remove the relay. There should be markings on the relay pins or the plastic sitting place of the relay. Look for numbers 30 and 87. Number 30 is commonly will have 12v(battery voltage hot at all times. Passway here battery-fuel pump relay fuse-fuel pump relay). Confirm you have 12v at pin 30. Then create an electrical bypass between 30 and 87(wire that will deliver 12v to the pump itself).
I would use 2 male connectors of this type Dorman Conduct Tite Blue 1/4in 16-14 Gauge Male Disconnect(copy paste from autozone so don't judge). They will fit pin sitting places perfectly and will provide you with reliable connection at the same time will not damage the fuse box. After you connected 30 and 87 go to the fuel pump cap area and listen for any sounds of life. If all quite-remove the connector from the cap and with multimeter check which one of big wires is your 12v from relay. Then check ground. If you have both, don't rely in multimeter to tell you 12v. Do that setup with headlight bulb as I was talking about before(reason-you might measure 12v on the connector delivered by 1 small section of the damaged wire, but when you will apply the load equal to the load of the pump the amperage will not be enough to do the job). If your test bulb is bright and glowing and pump is not working, then most likely your pump is dead. Low possibility that inside of the tank some electrical connector dislocated. I would order one from fcp with a fuel pump key and fuel cap new o ring and then open the tank as in my post above. If you will find disconnected wire-ypur luck pay for return shipping and get your money back,if not-replace the pump.

[Vova585]

In regards to the fuel pressure regulator. I think there are 3 types of regulators possible. Newer cars control the fuel pressure through the electronic feedback- pressure sensor signal to the ecm- fuel pump control module which will increase or decrease voltage and this regulate the pressure.
Option 2- inside of the tank there is a pressure regulator
Option 3- pressure regulator installed on fuel injector rail, usually closer to the driver side of the car at the very end of the rail or below it.
I would take a vin from your car and go to some "volvo oem parts" volvo dealer website and under fuel system would be able to narrow down what type you have. However I doubt that fuel pressure regulator fault would result in no start. You would still be hearing the pump working trying to push against the resistance of the regulator.
Back to the previous post. Wanted to add that ground can be at fault as well and you can have that same effect of seeing 12v with multimeter but not enough current to do the job due to damaged or corroded ground wire. You can run a short section of test wire to battery negative and test the load bulb this way to exclude issues with ground wire.

Answer about 12v at the pump: you would expect to see 12v at the pump briefly when you move the key into 2 position (1 is ac, 2 is on, 3 start) it is necessary to prime fuel system and bring the fuel pressure to necessary psi to assure start. Such will be seen only for 1-2 sec maks.
Then you would expect to see 12v at the pump when car is cranking(it is necessary to provide fuel as above) and 12v is seen when car is idling/driving.
Try the trick with fuel pump relay bypass and it will help you narrow your problem. Please keep us posted.

[Vova585]

Also update about "tapping" method. Fuel pump cap is connected to the fuel pump assembly inside of the tank by 2 metal pieces. By creating vibration on top of the cap the force might be enough to "unstuck " the fuel pump and it will work for some time. Rationale here- fuel pump is basically an electric motor which turns the star shape "fan" on the bottom. Bottom part can differ from model to model and might include additional rollers(look up audi 100 fuel pump if interested). But nevertheless it is the electric motor with bearings in it. Fuel pump is a delicate creature and relying on fuel to cool itself and provide lubrication. Those people that like to drive with less than 20% of fuel in their tank or better letting the tank go dry are doing themselves a disservice (think about fish on the ground and that would be your pump without fuel). Overtime internal components wore down and either bearing or "fan" or brushes will say enough. Sometimes prior to that happening the pump will be "sticking" so that's were the "tapping" method might be of help, but not a solution.