Reverse Polarity - What did it do to my car?

[erikv11]

Here's another good, older thread.

https://www.matthewsvolvosite.com/forums ... hp?t=61639

I am pretty sure I found out which relays were bad by testing for resistance, or maybe I applied 2 volts to listen for the click. I don;t think I would go the paperclip route on the main relays. When this happened to my 850 two of the three J relays were blown as well as some fuses.

[jonl]

A few days have passed and I accepted that, at best, I have a weak fuel pump and after 16 years it needs to be replaced. The deed must be done!

So, I got up the courage and my dremmel and asked a good friend with more experience than I to cut a big access hole next to the fuel lines. Many thank yous to Reese and to all who have written about their experiences with this procedure, we couldn’t have done it without you.

I then replaced the old pump with a new Volvo unit and spliced/soldered the old wire harness to the new pump. I was so excited to test the wiring that I forgot to reconnect the fuel lines Well, the wiring seems solid, the pump is pumping and I only needed to clean up a little bit of fuel.

Now here’s the weird part: Initially, I got fuel to the rail but it would not start. There was about 20 psi of pressure and it was holding it. The engine was so close to turning over. It made all the right sounds but it just wasn’t happening. I checked the fuel at the rail’s Schrader valve and got fuel and air. Maybe an ounce of fuel came out but now I can’t get any fuel at the rail.

The next logical step was to try and bleed the air out of the system. I tried two methods:
1) Turning on ignition for 3 seconds 3 times and then checking the valve on the fuel rail to see if any fuel came out. Then repeated the key cycles and fuel rail checks until I got some fuel. No success.
2) Next I jumpered the fuel relay, pressed in the Schrader valve and let the pump run until it pushed all the air out and I saw fuel. I let it run for 5 minutes. Could hear the pump pushing air through the valve but no fuel. Just some residual moisture.

I know that there is fuel in the tank. I could see it when the old pump was removed and the fuel gauge shows 6 gallons.

I’m guessing that the new pump was originally moving some fuel that was left in the lines but is now only pumping air because it’s not currently immersed in any fuel. Seems unlikely. The pump is right side up but, hey, I can’t see into the fuel tank right now.

Anyone have any thoughts?

Thanks,

[scot850]

The fuel tank in the AWD V70 versions is a saddle type and uses pressure to pump fluid from one side to the other where the pump is. This is done using an ejector 'pump'/ Reason for quotes is it is not actually a pump but a fuel level sensor and uses return pressure to equalise the fuel level in both sides.

I would suggest that you re0check the fuel lines at the pump and make sure you did not connect the fuel lines in reverse to the RH side pump.

Check the lines which is very hard to do to ensure the pipes have not failed as best you can. The links below may help you identify the pipes, but is all honesty you may find you have a failed pipe that cannot be seen on the top of the tank. The second link is from when I rebuilt the rear end of my 2000R which will be similar/identical from a fuel/emissions lines perspective. Check the 5th page for pipes.

https://www.matthewsvolvosite.com/forums/vie ... 66e36453f1

https://www.matthewsvolvosite.com/forums/vie ... 1&start=40

Neil.

[jonl]

Reese and I have been troubleshooting this problem for a couple of weeks now. It felt like this project was almost done when we got current to the new pump but that apparently wasn’t enough. We narrowed it down to two possibilities. 1) It could be Scott850’s idea about a fuel line failure of some sort or; 2) the pump was not sitting in whatever gasoline was left in the tank. So we added 4 gallons of fuel and it started right up. What a wacko car.

I really need your collective imaginations for this one. Anyone have an idea(s) as to how the fuel gauge could be working reliably before the fuel pump failed and then show that there’s 6 gallons in the tank but need 4 gallons in order to start at the end? FYI: the fuel gauge is now showing about 10 gallons since we added the 4.

Happy Labor Day

[cn90]

Maybe your fuel gauge is inaccurate, i.e., sticky.
Google "sticky fuel gauge Techron".
Many people have good luck with Techron.

[scot850]

Make sure the pump was re-fitted the correct way up. Also check the connecting pipe from the LH side and that the 2 pipes are orientated correctly. Check my links if you need to verify the correct connections.

The fuel gauge takes and average of the 2 sides of the tank to give a fuel level.

Did you replace the large plastic ring and rubber seal on the new pump? The seal doesn't always like to be re-used and the plastic seal ring is prone to cracking with re-use. People here claim to re-use them but it is not worth the hassle if it cracks and you may not notice it on tightening. There is also a specific tool for orientating the fuel pump to ensure it is fitted correctly. If you don't have access to it, look at my pictures to try to figure it out. Unfortunately I don't have a close up of the RH fuel pump from straight on, this is the best I have:

http://www.vivaperformance.com/awd-angl ... ardware-7/

Neil.

[scot850]

Don't know where that link came from! I was helping someone a while back on angle gear issues?

joni, I saw your note elsewhere about the fuel pressure you were seeing. Fuel pressure at the Schraeder valve should be 43psi at least. 20 psi is way too low for these engines. Still makes me think you have a pipework/leak issue.

Neil.

[jonl]

I need to close the loop on this project. Sorry it’s taken so long. The bottom line?

• 1) We were successful. No harm was done to the car from the putting the jumper cables on backwards. I feel very lucky.
  2) For me, cutting a hole under the back seat to access the old pump was the way to go. The new pump is doing its job, fuel pressure is being maintained when the car is off and we’ve driven several hundred miles. We’re most happy. It even seems to be running smoother than before the old pump died.

The most puzzling part about this job came after installing the new pump. I turned on the ignition and heard the new pump humming but the car would not start. Everything seemed fine but something was missing. From our point of view, either the pump was defective or there was no fuel for the pump to pump. How could I be out of gas? The gauge was reading about 6 gal. and it’s always been trustworthy. Well, since the idea of getting another replacement pump was very unappealing, I went out and bought two gallons of gas and put it in the car. Hooray!!! Intense feeling of accomplishment! We beat the Swedish engineers yet again! Time to crack open a beer!!

So what happened?
Remember, I started out with 12+ gallons of gas at the beginning of this adventure and, unbeknownst to me, when I pumped out 6+ gals. of gas through the Schrader valve/fuel rail, I was only pumping gas out of the passenger side tank where the pump is. Since the car was not running, no fuel was being transferred from the driver’s side tank. Hence the 6 gals. that the fuel gauge read. Even though I could see some fuel in the bottom of the tank after removing the pump, it wasn’t deep enough for the pump to suck it up. I was effectively out of gas.

Lesson learned: if you’re using this method to drain your fuel tank, keep a couple of gallons in a container for when the job is done. Happy motoring and have a nice day.