All,

So before I begin my quest for knowledge, a quick update on the transmission issue after engine mount replacements.

Its been about a month of driving and the car all of sudden now goes into drive like it used too. I have not looked at anything as I have not had the time, but I drove it last night and well, it now goes into gear without me have to shift slightly into 3. We'll see if this continues.

Now onto the problem at hand.

The car yesterday, once, and then again today, almost left my wife stranded.

While driving the car, according to my wife it appears to just die lose power and die. So much so today that she had to stop the car and put it in park to restart. The car did restart right away and she was able to make it home without further incident.

So the question is where to start looking? My first thought as of now is the fuel pump relay. I've replaced it with a used one, but have no history on this one as it came from the PNP.

So where else might I look? Might the transmission thing that used to be happening be an issue as well and that this is now biting me in the ass?

Thoughts???

Thanks in advance,

Matt

Pull the transmission fluid dipstick and check the level and condition of the
fluid. It should be clean, if it's old, burned/brown then it's important to
flush the tranny ASAP. You can find several DIY video's about how to flush it.

Bill

There are two relays that can kill the fuel pump.
one is in the lower level of the main fuse block, the other is
above the radiator.

You can listen for the pump when you first turn on the ignition, it will
make some noise for several seconds. If you hear the noise, then the relays
are working. The fuel pump noise does NOT mean that the pump is pumping!

Then you simply go to the fuel injection rail on top of the engine and look for a Schraeder valve. It's the same style valve as in your tires.
Take the cap off and press the center valve pin being careful to hold a rag so you don't get gas on you. There's about 80 PSI with a healthy fuel pump.
If no gas comes out then the fuel pump has probably failed.

Don't forget there's an in-line gas filter too.

Bill

Bill,

Thanks for the insight. Did not know that there is a second relay. That is good to know!

Do the fuel pumps usually give any type of indication that they might be failing?

Thanks in advance,

Matt

Any fuel pump that is failing can make the engine cough or sputter (at least a little) before it totally dies. Good idea from Bill about checking fuel pressure at the rail! How many miles on the car? Doubt the main pump is going unless the car has many miles on it. My 850's pump is original with over 250k on it. Volvo main fuel pumps are very robust and usually last a very long time before crapping out..

At least with 850's it is much more likely to be one of the fuel pump relays than a main pump failure. I gather you replaced the other one. I suggest checking the one under the hood. That one is probably more likely to go because of greater exposure to the elements.

Well, I ordered a pump today and it will be here next week.

I plan to purchase or rent a pressure tester and see what is going on. If the value is lower than it should be, I believe 80 PSI, then the pump comes out and I'll put the new one in when it shows up.

The wife drove the car again today with the new to me main fuel relay and on the one part of the trip she had a hesitation, but coming home she said it ran fine.

It has to be one of these three components. I can't think of anything else that it could be.

Thanks for all the suggestions. I keep you all posted on this as I move through the diagnostics.

Matt

Maybe I didn't read carefully but:

Can this also be spark related? Would there be a code that can be read that might help? Could there be some kind of electrical connection that goes faulty when the car hits a bump? TO me the puzzle is how it can it restart right away.On my old 940 the impulse sender would quit but I could re-start after an imagined 'cool down' - maybe the contracting contact worked when it got cool. Dunno. Is there something that controls fuel pressure so that when the car is off the pressure lessens to the point that the pump can again start to work? But what force is occasionally hi or lo and then after some time returns to normal? Pressure, heat, electrical charge (capacitor somewhere). If you do seem to locate the faulty part it would be interesting to keep testing to see what the problem actually is with the part and also to prove that it is definitely the cause.

Horatio,

Since I'm not 100% sure that it is the fuel pump at this time my plan is as follows:

Tomorrow I'm going to take the original fuel pump relay to work and take it apart. I plan to look for cold solder joints and capacitors that are failing open.

Next I plan to rent a fuel pressure tester and hook it up to the fuel rail and start the car. I want to see what the pressure is and if it fluctuates at all. It it does, then I'm really leaning that the fuel pump is failing.

Finally, I plan to take the new fuel pump when it comes in and take it to work and find out how much current a brand new fuel pump is drawing. Then once the old is out and replaced I plan to take that one to work as well and measure its current draw and then compare the two. I also plan to measure the fuel pressure of the new one so that I can compare it to the old one.

If the problem persists after this, I've at least eliminated the fuel pump and now have a spare. I will have to investigate both fuel relays then so as to determine which one or both are causing the problem.

Don't worry, I'll keep everyone posted here. It might be sporadic, but I will post.

Matt

http://www.ebay.com/itm/Volvo-Fuel-Pump-Relay-4-Prong-850-C70-V70-KAEHLER-New-/253198661165?hash=item3af3d0f62d:g:ujIAAOSwjTlZg8nL&vxp=mtr

Cheap. To jump, pull the relay and insert large paper clip in 15 and 87. The pump will run as soon as the key is in position II.

To verify fuel pressure after the engine dies, just uncap the schrader valve and push on the pin.
--
Keeping it running is better than buying new

Don't waste time on old relays- You can replace both relays with new for short money Boneyard relays are old and maybe the reason the car is there.

Don't bother with checking the exact pressure either, follow the original
suggestion. If it doesn't start press the fuel rail Schraeder valve- if gas comes out then the pump is OK.

Did you find the Wiring diagram?

Bill

I really don't think it is the pump. I believe it is most likely an electrical issue. Reason I say this is your wife was able to restart the car numerous times after it stopped running. Normally if the main pump dies the car will stop running and not restart. It should also sputter and cough as the fuel supply is cut-off. That is what happened when the fuel pump died in my VW years ago.

Personally, I would consider replacing the relays (cheap) and/or testing the electrical flow at the pump first before replacing the pump. Those Bosch main pumps are robust but also very expensive...:)

Also (if my memory serves me correctly), if the electrical flow at the camshaft sensor (also cheap) is skittish the car can stop running randomly. Much like when the crankshaft position sensor dies in the RWD cars.

Bill,

I have found the wiring diagram, however I do not see where a second relay is mentioned, so I'm somewhat confused on that one.

I will check the pressure tonight as you suggested and get back to you.

I will also see how I need to jumper the relay in the event that it dies again while driving it and then start driving it to work starting tomorrow.

As far as new relays, I can repair them for cheaper than what it will cost me to buy a new one.

Again, if you have pictures of the second relay, I'd greatly appreciate it.

Thanks in advance,

Matt

No you can't repair relay points !

The points go to hell, and you simply need to buy new ones for abt $25 each.

I'm working from a 1995 850 schematic here:

get the page for Fuel injection 64 for me

The Fuel Pump relay is 2/23

The other Main Fuel relay 2/32 enables +12VDC to the injectors.

Look at the wiring diagram, The pump needs to pump gas,
the injectors need: +12VDC, and the ground side is switched by the CPU
to run them.

Don't get hoodwinked by hearing the pump and assuming it's pumping.
The pump can make noise without pumping...Ask me how I know.
The impeller can disappear or fail to spin, whatever.

BUT, If it's making noise, chances are that the 12V and ground, are there
If it doesn't start AND there's gas at the rail, you can look at the relay
over the radiator. These two relays are legendary for crapping out with old age.
They often get funky before outright quitting.