Another car won't start - fuel pump or controllers? Topic is solved

enotslim · Post by **enotslim** » 10 Aug 2021, 17:26

One day last week my 2004 XC70 failed to start in the early am. Strong crank but no sound of the fuel pump engaging and no ignition at all. Used an external battery jumper with the same result although perhaps stronger cranking. I had been driving regularly short distances without any indication of a problem. This was a surprise.

Assuming the fuel pump was not activating this could be no/faulty electrical signal to the pump or or a dead pump. Fuel pump fuses looked OK (#21 15A in the engine compartment fuses and #33 15A in the driver side column fuses). Do not have spares to swap for a functional test.

Let car sit in driveway several days. Tried again and started normally. Drove around the neighborhood. Felt normal. Did not try high speed or high fuel demand driving. Started several more times seemingly normally. I might have heard the fuel pump activate before the first start but I didn't hear it on subsequent starts.

Being an optimist I drove this car to work today. Everything normal. Left work 10 hours later and car would not start with identical symptoms tp previous failure.

Any thoughts about the most likely problem? Intermittently failing fuel pump? Fuses should not cause this (although I did not examine the fuses after the second failure). Can relays or some other electrical part cause this? Relay? CEM? PEM?

What is the simplest definitive way to determine if the fuel pump is/is not dead or failing or if something else is responsible?

Thanks.

Post by **abscate** » 10 Aug 2021, 20:01

You can try a PEM swap but VIDA will let you turn the pump on amd off in software amd confirm fuel pressure

Post by **cn90** » 10 Aug 2021, 21:30

Agree,

Find a used PEM on ebay (about $40-$50) or at local junk yard.

If your XC70 happens to have the PEM mounted above the fuel tank, look for my post showing the tricks:
- Basically 7-mm socket for that small bolt.
- Slide the metal plate out.
- Then slide the PEM out.
- Then use a small screwdriver and gently lift the tab on the connector to disconnect it.

Post by **abscate** » 11 Aug 2021, 03:10

Dave .it might be worth opening up your PEM and seeing how much aluminum oxide has fallen on the circuit board from the heat sink, cleaning it off wit contact cleaner,and trying it. I got mine to work reliably again , until my new one from FCP came. I went new because that car travels long amd far away to places like Boston

viewtopic.php?f=9&t=84169

Post by **Blacklab467** » 11 Aug 2021, 14:21

Going back to basics, check the Schrader valve on the fuel rail to see if there's pressure when it won't start. My car had an intermittent fuel pump failure a few years ago, this was before I knew anything about PEM's and Vida and such. The car would intermittantly get "dead pedal" once or twice a week or wouldn't start, then it got much more frequent. New pump was about $200.

Post by **Blacklab467** » 11 Aug 2021, 14:23

I would add that it's almost impossible to reliably tell if the fuel pump is operating by listening, even with the back seat removed.

enotslim · Post by **enotslim** » 03 Oct 2021, 16:23

Sorry for the length but I'm now quite confused about this whole thing. Due to "life" this car sat for ~1 month while I searched for the PEM. Didn’t find it. More about that after the end, but ...

After all that the battery was pretty low at 5.4V (that may indication irretrievable battery). No luck jumping with an portable jumper so I jumped using a good battery from another car. Engine started easily. Ran engine ~ 1 hour to charge battery and it then started daily for seven days. Resting battery voltage was 12.5V. With cables connected the voltage slowly decreased over days/weeks. With cables disconnected the voltage is stable ~12.03V for at least four days.

Detected a parasitic battery leak of 3.7 A with rear rear hatch door closed/light off and 4.0 A with rear hatch open/light on. Now need to ID source but the car starts and runs as long as the battery doesn’t discharge too far.

Could this all be due to a parasitic leak that discharged the battery so it was sufficient to run the starter but insufficient to activate the fuel pump, perhaps due to failing to activate a relay? (Eventually the starter also stopped activating.) I haven't (yet) found a fuel pump relay. Maybe it ran away with the PEM to hide somewhere? This explanation (failed battery) would be fine with me except for the fact that the car initially wouldn't start only 10 hours after being driven (battery should have been charged) and AAA was not able to start the car using their mobile jumper expressly designed for this purpose. (AAA-man said he charged it daily.) The fact is I never tried jumping with a battery I knew was good until what I described above.

So now I have a car that starts and runs fine but I'm wary of stopping anywhere. OK for touring but not for transportation. Time will tell if this is stable but I would like some assurance that it is before venturing very far. And I will track down the parasitic leak. And carry a good portable jumper.

Suggestions please? What am I missing?

Thanks.
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Saga of the missing PEM - PEM is not on top of the gas tank. The tank does not look like the metal tanks with the PEM on top and the too clearance seems too small. Plastic tank? Also did not find a PEM next to the fuel pump, in the spare wheel well or behind the right rear fender liner. Please see pics (the jack is secondary to a jack stand also in place out of view). The spare wheel well does have what looks like the PEM connector shown in other threads (obviously not connected to a PEM). Could the modification have been done to move the PEM to the spare tire area but the PEM no longer be present (or required)? Or is this connector intended for something else (that is missing)?

Post by **abscate** » 04 Oct 2021, 04:49

The early P2s don’t have a PEM but I thought by 2004 PEM was used. Vida would tell you of course

A low or marginal battery will give all sorts of bizarre behaviors. Cranking is not a good diagnostic for a battery being sufficient to run the car well.

See my 1999 thread on a battery down to its last 5%

viewtopic.php?f=1&t=92161

darylrobert · Post by **darylrobert** » 04 Oct 2021, 05:26

thats the tow bar connector near the spare tyre. when was your fuel filter changed or is that rust normal?

enotslim · Post by **enotslim** » 18 Oct 2021, 07:59

Thanks regarding the toe bar connector. It is time for a fuel filter change but the rust may also be "normal" given New England's salt covered winter roads.