Trouble shooting a bad fuel pump

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sleeper850
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Trouble shooting a bad fuel pump

Postby sleeper850 » Fri Apr 09, 2010 3:40 am

1998 V70 AWD Turbo 158,000 miles
I recently ran the car out of gas. The car stalled of course and I attempted to restart the vehicle several times to try to move it off to the side of the road. I refueled with 1/4 tank and eventually got the car started. The idle was rough and the car hesitated and stalled while driving. I started the car and let it run but it would stall at idle several times. The car was driveable but not normal. I replaced the fuel filter and the car has the same symptoms. The code reader says MAF or VAF. When I start the car and rev the engine the rpms drop and then resume. It does this every time I press the gas pedal. The exhaust consistently smells like sulfur and when the car reaches normal temperature the car stalls more frequently. I would like to avoid chasing possible problems and buying unnecessary parts. I would appreciate some advice on troubleshooting this. Also, is the fuel pump located on the passengers side floor board in this vehicle. If so, I will follow the fuel pump repair posted here. Thank you for your time and advice.

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Ozark Lee
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Re: Trouble shooting a bad fuel pump

Postby Ozark Lee » Fri Apr 09, 2010 4:10 am

Thank you for a very complete post on what actually led up to your issue. It is usually about page three where it is revealed that the gas tank was run dry or that the spark plug wires were melted to the head after the car ran out of coolant.

The bummer about many fuel pump issues is that fuel pressure is not a monitored system hence it will post no codes on its own. Low fuel pressure or low fuel flow will, on the other hand, post other codes such as fuel trim limit errors or MAF errors.

What you need to do is check the fuel pressure both at idle and under load. You can buy a fuel pressure gauge for cheap at either Harbor Freight of even O'Reilly Auto Parts for around $35.00.

I am normally in Fairway and I have a gauge in the tool chest in the garage but I am out of town on a job at the moment, were I at home I would loan it to you or help you check it out.

What were your specific P codes?

My only Volvos at present are 850s and yanking the fuel pump and checking the filter sock is a snap. On the XC's things are way different and you either need to drop the tank or cut a hole in the floorboard behind the rear seat to get to it. I don't have VADIS on my laptop so I can't tell what you need to do on a V70 AWD.

Inasmuch as you ran it out of gas immediately prior to the problems I think you are on the right path.

...Lee
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'99 V70XC - RIP - Wrecked Parts Car.
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jblackburn
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Re: Trouble shooting a bad fuel pump

Postby jblackburn » Fri Apr 09, 2010 4:36 am

The procedure, unfortunately, for your car is the same as one of the XC's. You'll have to cut a hole in the floorboard, or drop the rear suspension out and drop the tank. I'd start by checking the fuel pressure and see where that leads you. If you see problems there, I or someone else can direct you to the write-up someone did about replacing one on an AWD model.

The exhaust consistently smells like sulfur and when the car reaches normal temperature the car stalls more frequently.

This, to me, however, sounds like an air issue rather than fuel. It's way overcompensating for something, either an airhose is loose, or the MAF is dead. I did the exact same thing to my car last weekend when I neglected to clamp down hoses all the way, and it happened when my airflow sensor died before that. Can it run any better with the sensor unplugged entirely?
'98 S70 T5
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sleeper850
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Re: Trouble shooting a bad fuel pump

Postby sleeper850 » Fri Apr 09, 2010 4:43 am

After reading the post for the faulty coolant temperature sensor, these symptoms sound similar to the bad fuel pump. Now, I am looking at the faulty coolant temperature sensor as a possible culprit. I will gladly take your advice and check the fuel pressure first and go from there.

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Re: Trouble shooting a bad fuel pump

Postby sleeper850 » Fri Apr 09, 2010 4:48 am

I have "cleaned" the MAF and do not notice any difference. I have also disconnected the MAF and and started the car and did not notice any change in the idle. I have not attempted to drive the vehicle with these changes bc I don't want to get stranded again.

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Re: Trouble shooting a bad fuel pump

Postby jblackburn » Fri Apr 09, 2010 5:02 am

OK, possibly one thing eliminated then. One other thing to add to your list of checks would be the fuel pressure regulator just under the silver fuel rail cover. If you can take the cover off and pull off the vacuum line to the regulator (look away while you're doing this, don't ask how I know), gas shouldn't spurt out or the vacuum line is wet. A bad regulator can dump fuel into the vacuum system and cause rich-running conditions and hard starting.
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

sleeper850
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Re: Trouble shooting a bad fuel pump

Postby sleeper850 » Fri Apr 09, 2010 5:08 am

Is the fuel pressure regulator located at the end of the rail? Is it capped?

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Re: Trouble shooting a bad fuel pump

Postby jblackburn » Fri Apr 09, 2010 5:14 am

Nah, it's a silver frisbee-shaped thing sort of towards the passenger side of the car on the fuel rail. Take a look at the PDF misha posted in this thread:

viewtopic.php?f=1&t=25331
'98 S70 T5
2012 Chevy Cruze LT 6MT


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

sleeper850
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Re: Trouble shooting a bad fuel pump

Postby sleeper850 » Sun May 23, 2010 1:03 am

I replaced the fuel pump (using the cut the whole in the floor method) and the car ran better but the sulfur smell was still present. I then replaced the MAF with a Bosch replacement but the smell was still there. I decided to replace the coolant temp. sensor and the sulfur smell disappeared. Thanks for your help.

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Re: Trouble shooting a bad fuel pump

Postby whoa » Sun May 23, 2010 1:49 am

Wow; bad luck to have the ETC sensor go out just when you ran empty.
1996 850 Turbo Wagon


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