Hi Folks,

Long story but I saved a 1994 Volvo 850 Wagon from the auto crusher. The car was sitting for a good 2 years before I adopted it. Below is the laundry list of issues that I have observed. Many of which I noticed are termed "Popular Volvo Problems" and fun DIY projects.

My first order of business is to resolve the common Stalling / No Start issue.
From reading the many threads, the Fuel Pump Relay or Fuel Pump is the most likely culprit.

My question; is there any harm or danger with temporally removing the Fuel Pump Relay and installing a jumper between Pin 15 and Pin 87 to run the Fuel Pump continuously?

I want to drive the car while trying to diagnose the stalling issue.
In my diesel trucks, the Carter P4070 electric fuel pump (lift pump) runs continuously.
In the diesel trucks there is an Oil Pressure Switch (OPS) relay. The OPS (relay) keeps the fuel pump (lift pump) running as long as there is oil pressure. This is a safety feature in case of an accident so diesel fuel doesn't get pumped into a fire if there is one. I know the Carter fuel pumps can run continuously without any chance of creating too much pressure or overheating.

Will the Volvo in tank fuel pump cause problems if it is run continuously while the car is driven?

Thanks,

-Kevin


- Stalling / No Start.
- Stuck Caliper (manually un-stuck but still hear friction when car is rolling).
- Cracked Axel boots.
- Climate Fan speed Hi or Off only.
- Climate Fan squeaks.
- Tail Gate Struts not keeping tail gate up.
- Tail Gate Dome Light does not come on but has power.
- Tail Gate Washer Pump does not come on.
- Driver Electric Seat does not recline.
- Sun Roof shade fabric has fallen off.
- Odometer not working.
- AC not working.
- Radio needs Code.
- Driver Door Strap Broken.
- Whining Power Steering Pump.

- Check Engine Light (Successfully Reset)
- Service Light (Successfully Reset)
- Blinking Up Arrow (Successfully Reset)

 

I don't think so. The relay is there to help avoid flooding and fuel delivery when the car is not suppose to be running (cam sensor fault, etc.).

 

Thank you RSp007

I made the jumper last night and installed it in place of the Relay.
I was experiencing the stalling / starting problem once every few days.
I guess time will tell if the relay is the issue.
I watched your video. It was a great help.
Comparing my issues list to your Video list, it look like you have fixed most of my issues I will be watching a lot of your videos. Thank you for making all these videos.

Cheers,

-Kevin

 

You are welcome. I have more to do. LOL

 

Will the Volvo in tank fuel pump cause problems if it is run continuously while the car is driven?

The pumps on everything I know of run constantly while the engine is running so there shouldn't be a problem as it's normal to run full time.

The main purpose of the relay or almost any relay for that matter is to control a high amperage circuit with a low amperage circuit.
Think of the starter. You have a low current, small wire circuit leading to and from the ignition switch to send a signal to the solenoid to close the circuit from battery to starter through the "big" cables. If you chose to run that cable up the steering column it would need to be even bigger as the amount of resistance to flow increases with length. Then there is designing a switch that can carry that amount of current and cycle enough to give a satisfactory life.
Relays are used to keep the high current (amps) path as short as possible and to allow low current controls to switch it off and on. It's cheaper in materials, builds less heat and offers less resistance. The added advantage to relays is building in safety's in the low current side like Rspi mentioned. Running wires to roll over switches or to timers or the ECM is easier and cheaper in the fuel pump relays low current (amps) thinner wiring and the components don't need to be physically capable of handling the load the the fuel pump needs to operate. They just need to be able to handle the small current the relays electromagnet needs for switching.

 

Kiss4aFrog, RSPI,

Thank you for the explanation.
The Jumper is working great!
Two Days with no Stalling

Thanks,

-Kevin

 

Thank you for the help.

Jumper is Working Great!!
Six Days with no stalling.

I just ordered a replacement Fuel Pump Relay.

Thanks,

-Kevin

 

If you're handy you can always repair yours. It's common for the capacitors to go bad. Not always the problem but might be nice to have a spare if you're handy with a soldering iron and have a radio shack near by.

http://www.matthewsvolvosite.com/for...ic.php?t=13806