Suspected fuel pump/filter problem with 1990 240DL

[Walking_Cube]

Hi everyone!

I'm glad to have found this forum because I'm baffled by the following situation.

My dad owns a 1990 240DL that has only 20K(!) on it. He drives it only in the summer time. My dad doesn't believe in tune-ups because he has had numerous bad experiences with sleezy mechanics - both at 3rd party garages and at the dealer.

Last summer, it started making a strange noise near the driver's side rear wheel, a faint buzzing noise coming from what I thought is the fuel pump, a noise that wasn't there before. We ignored it because that's what can be expected from a 19-year-old car.

This summer, we drove it a few times and the car was happily fine, except that the noise is still there. Then suddenly one day, the car won't start. We suspect that it's a fuel problem because when we removed the spark plugs, there isn't even a whiff of gas on it. Since the car won't start, we can't really hear if the fuel pumps are working or not.

After an appointment with Dr. Google and reading many posts on this forum, I have the following questions (and pardon me, but some of these questions are incredibly noobs):

1 - Is there a way to tell whether it is problem with a blocked fuel filter, or a busted fuel pump(s)?
2 - The external fuel filter is just in front of the driver's side rear wheel, but there are two cylinders at that location. Which one is the filter?
3 - Where is the fuel pump relay? How do we test whether it is functioning?
4 - I check fuses #4 and #6, and the fuses themselves are ok. How should I test to see if there is actually power going through them when I start the ignition?
5 - Are there other things that I should look into?


Thanks a lot!


Bob

[GeorgeKL]

There are 2 fuel pumps, one in the tank (low pressure) and one underneath the car (high pressure). The LP pump lifts the fuel from the tank and feeds the HP pump. There is also a fuel reservoir next to the HP pump which is the other "cylinder" you can see. The noise your HP pump is making sounds like mine just before it gave up the ghost. The fuel filter is bolted to the bulkhead (firewall) on the left hand side as you stand at the front.

In my case, the LP pump packed up and the HP pump was doing all the work which lead to overheating (not difficult in KL!) and bearing failure. I replaced both pumps and all's OK. If you open the fuel filler, you should be able to hear the LP pump running - or not.

Given the cost though, I'd replace both pumps and the filter at the same time.

[billofdurham]

Walking_Cube, welcome to Matthew's Volvo Site.

If the car stands for a period of time and the ignition is switched on you should be able to hear the pumps kick in, albeit momentarily. The easiest way to hear the in-tank pump is to remove the filler cap and get your ear as near as possible to the filler. You could also try inserting a piece of hose in the filler neck and using it as a stethoscope. The main pump can be heard by lying down at the side of the car and listening. Also put your hand on the pump and you should be able to feel it working. Obviously, unless you have very long arms, you will need an assistant to switch on the ignition whilst you do the listening. Better still, adopting the lazy approach, you switch on the ignition and let the assistant do the listening.

To answer your questions:
1. Not really without changing one or the other.
2. The filter is the unit which has the fuel line from the tank attached to it. Apologies to GeorgeKL but the main filter on the US models is next to the fuel pump and not on the bulkhead. My 240 did have a filter in that location but it was a carb model.
3. The attachment shows the locations of the relays on your car.
4. To test power flow through the fuses you need a voltmeter or a multimeter. Touch the + probe to the out end of the fuse and the - probe to earth (ground). You should read 12 volts.
5. There is another fuse for the fuel injection system detailed in the attachment.

I agree with GeorgeKL about changing both pumps if you find one is faulty. There is always a knock on effect with these pumps which causes failure in both eventually.

Do a search for Fuel Pump in the RWD section using author Kmaniac in California USA. Chris had problems and has done a good write up.

240 relays.pdf

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Bill.