Volvo 760 2.3 turbo - power issue

[Laird Scooby]

Check the fuel pump relay and the fuses that feed the pumps.

Can't remember the fuse numbers off the top of my head but #30 rings a bell, i'll look them up later.

Also are you sure you got the connector into the ECU correctly? They can be a bit fiddly at times so worth double checking.

[lessertegasi]

Originally Posted by Laird Scooby

Check the fuel pump relay and the fuses that feed the pumps.

Can't remember the fuse numbers off the top of my head but #30 rings a bell, i'll look them up later.

Also are you sure you got the connector into the ECU correctly? They can be a bit fiddly at times so worth double checking.

Hi,
Thank you so much for the prompt response once again. It means a lot.

I am afraid I don't know how to check the fuel pump relay nor the fuses.
Where should I look at?

I will try the connection again for sure. You can't really tell to be honest as it is all covered and it's a bit tight down there.

Best

[Laird Scooby]

Originally Posted by lessertegasi

Hi,
Thank you so much for the prompt response once again. It means a lot.

I am afraid I don't know how to check the fuel pump relay nor the fuses.
Where should I look at?

I will try the connection again for sure. You can't really tell to be honest as it is all covered and it's a bit tight down there.

Best

Assuming that it's the facelift 760, the fusebox is in the end of the dashboard, visible only when the drivers door is open.

[lessertegasi]

Good morning.

I located the fuse boxes.
How can I test that they are working or not?

Also, last night I took the car on a ride (was waiting for the streets to be empty) and realised that the issue is getting worse.
Suddenly and as I was standing on a traffic light the RPM erratically decreased and within 2-3 seconds the power of the car cut off and obviously the engine switched off.
It is very bizarre but as more things are getting fixed or replaced the issue becomes worse.

[Laird Scooby]

Originally Posted by lessertegasi

Good morning.

I located the fuse boxes.
How can I test that they are working or not?

Also, last night I took the car on a ride (was waiting for the streets to be empty) and realised that the issue is getting worse.
Suddenly and as I was standing on a traffic light the RPM erratically decreased and within 2-3 seconds the power of the car cut off and obviously the engine switched off.
It is very bizarre but as more things are getting fixed or replaced the issue becomes worse.

Fuse boxes???? There's only one on a 1988/9 760! Locate fuse #30 and the orange tool to remove the fuses.



Remove the orange tool from its parking place by squeezing the top and bottom of it gently and pulling, keep your grip the same and push it on to fuse #30, release your grip and then pull the fuse out.

Hold it up to the light and you should see an unbroken link between the spades. Any suspicions, renew it. Then clean the spades on the fuse with a soft (brass is good) brush, some emery paper or fine sandpaper but ensure you remove any dust/grit afterwards and then refit, ensuring the fuse goes fully home.

Now repeat this procedure for fuse #31 which is your main fuel pump.

Fuse #30 is 10A (red) and fuse #31 is 25A (clear) - don't mix them up!

There are other possible causes but let's do this one thing at a time so we all know what stage we're at!

[lessertegasi]

Originally Posted by Laird Scooby

Fuse boxes???? There's only one on a 1988/9 760! Locate fuse #30 and the orange tool to remove the fuses.



Remove the orange tool from its parking place by squeezing the top and bottom of it gently and pulling, keep your grip the same and push it on to fuse #30, release your grip and then pull the fuse out.

Hold it up to the light and you should see an unbroken link between the spades. Any suspicions, renew it. Then clean the spades on the fuse with a soft (brass is good) brush, some emery paper or fine sandpaper but ensure you remove any dust/grit afterwards and then refit, ensuring the fuse goes fully home.

Now repeat this procedure for fuse #31 which is your main fuel pump.

Fuse #30 is 10A (red) and fuse #31 is 25A (clear) - don't mix them up!

There are other possible causes but let's do this one thing at a time so we all know what stage we're at!

I meant the fuse box and the relay box

I opened the fuse box and checked the fuses. Seem old but I can't tell if they are not working really.
Some of them were not put in properly and also numbers 5,16, 17, 24 are missing but I saw on an online diagram that these are spare.
I have a car parts place very close to mine. Shall I buy the fuses and replace them anyway?

Also I found this http://vi.raptor.ebaydesc.com/ws/eBa...=1596022187317 is it possible that changing it would make any difference?

Best

[Laird Scooby]

Originally Posted by lessertegasi

I meant the fuse box and the relay box

I opened the fuse box and checked the fuses. Seem old but I can't tell if they are not working really.
Some of them were not put in properly and also numbers 5,16, 17, 24 are missing but I saw on an online diagram that these are spare.
I have a car parts place very close to mine. Shall I buy the fuses and replace them anyway?

Also I found this http://vi.raptor.ebaydesc.com/ws/eBa...=1596022187317 is it possible that changing it would make any difference?

Best

If you follow what i said about checking the fuses above, you'll stand a good chance. There are some spare ways in the fusebox so don't worry about missing ones. It might pay to simply renew the fuses, then that eliminates them as a problem.

That looks like the right fuel pump relay, always handy to have a spare - it's fun changing it as well!

[lessertegasi]

Originally Posted by Laird Scooby

If you follow what i said about checking the fuses above, you'll stand a good chance. There are some spare ways in the fusebox so don't worry about missing ones. It might pay to simply renew the fuses, then that eliminates them as a problem.

That looks like the right fuel pump relay, always handy to have a spare - it's fun changing it as well!

The fuses have 32V on top but my local shop has 12-24V blade fuses for sale with the right amp though.
Does that make any difference?

Thank you

[lessertegasi]

Ok.
Found the right ones.

I will let you know how it goes.

I highly doubt though that this could be a fuse issue as I swapped them around in the past with ones that certainly worked and nothing changed.

[Laird Scooby]

Originally Posted by lessertegasi

The fuses have 32V on top but my local shop has 12-24V blade fuses for sale with the right amp though.
Does that make any difference?

Thank you

Originally Posted by lessertegasi

Ok.
Found the right ones.

I will let you know how it goes.

I highly doubt though that this could be a fuse issue as I swapped them around in the past with ones that certainly worked and nothing changed.

As long as the voltage is above 12V it's the current rating you're intrested in only. Not that it makes a lot of difference, it's only going to be the insulation has been tested to that level and 12 or 24 or even 32V isn't going to hurt you.

Are you sure you swapped fuses around in the past? You weren't aware of where the fusebox was or which fuses controlled the fuel pumps so if you had found it do you actually know which fuses you were swapping? Also you may have created problems if you did that by fitting dirty fuses into places where there isn't enough current to remove the oxidisation on the blades - hence the advice to clean the blades!

Just FYI, i've had exactly this symptom on my 760 V6 where the fuse holders got warm and wouldn't pass current through the fuses with oxidised/dirty blades on the fuses. Pulled the fuses, clened the blades, refitted and off i went. I've also had similar on a few of my 740s, one had previously been bypassed with a new, aftermarket fuseholder which had subsequently become dirty and oxidised and got hot and stopped the car. Ten minutes later it fired up and i finished my journey.
I later found the culprit and renewed the fuseholder again as it had simply cooled down and restarted.

This is step 1 in a process, we could jump about through the process trying this that and whatever but all we'd do is waste a lot of time. We might strike lucky and fix it by accident during that jumping about but then you wouldn't know the cause of the problem. Sometimes because of the age of the car, you'll find 2 or 3 (sometimes more) related things all fail within a close time to each other, you've had the fuel ECU problem, there could be others that helped push the ECU to failure, we don't know what caused the failure yet, whether it was simply age or another problem further down the line.