1990 740GLE rough idle in tank fuel pump

[Digger65]

Hi forum
just wanted to see if i can get a few pointers on this issue
not getting the quiet reassuring hum relating to an operational in tank fuel pump
also whiny main fuel pump -presumably drawing vapor through, a "gassy" odour (not from me) and rough idle
in addition an occasional blip in power loss under load, car full uphill

before i purchase a replacement pump i wanted to check whether a faulty relay might be the issue here?
Would the main pump be working at all if a fault with the relay?

many thanks
D

[AllHailKingVolvo]

When the in-tank pump is weak or has failed, in my experience you’ll get a whooshing, cavitating noise from the in-line (main) pump and the car will exhibit some hesitation when the tank is 1/4 full or slightly below.

My old 740 Estate did this, I fully intended to change the in-tank pump and gauge sender unit but my mother in law offered me silly money for the car and has since changed the unit herself. Up until then, i just filled it up every time it was around halfway full, which headed off the problem.

[TonyS9]

If you are worried about relay, check the voltage at the pump connector in the rear cubby hole (at least thats where it is on the 940).

Normally the relays fail completely/intermittently rather than cause a volt drop. Can be crack joints or coils.

Pumps will wear out because they used brushed DC motors and the brushes are not serviceable. My experience (single in-tank pump) was a grinding noise on priming and occassionally and increasing frequency of total power loss or non-starting. Might be hard to differentiate the 2 pumps.

[Digger65]

Originally Posted by TonyS9

If you are worried about relay, check the voltage at the pump connector in the rear cubby hole (at least thats where it is on the 940).

Normally the relays fail completely/intermittently rather than cause a volt drop. Can be crack joints or coils.

Pumps will wear out because they used brushed DC motors and the brushes are not serviceable. My experience (single in-tank pump) was a grinding noise on priming and occassionally and increasing frequency of total power loss or non-starting. Might be hard to differentiate the 2 pumps.

thanks
will look tomorrow if possible
am i looking for 12V ignition on at in-tank pump?

think i have located the pump just in front of boot area where spare tyre is located

thinking on i did have some starting issues relating to a arcing king lead in damp conditions i guess it could have gone bad while it was proving difficult to start
D

[Laird Scooby]

Originally Posted by Digger65

thanks
will look tomorrow if possible
am i looking for 12V ignition on at in-tank pump?

think i have located the pump just in front of boot area where spare tyre is located

thinking on i did have some starting issues relating to a arcing king lead in damp conditions i guess it could have gone bad while it was proving difficult to start
D

You'll only get 12v at the pump if the engine is running - it primes for a second or two when the ignition is first switched on then remains off unless the engine is being cranked or is actually running.

Is yours a saloon or estate?

[Digger65]

Originally Posted by Laird Scooby

You'll only get 12v at the pump if the engine is running - it primes for a second or two when the ignition is first switched on then remains off unless the engine is being cranked or is actually running.

Is yours a saloon or estate?

..that would explain why i wasn't getting voltage at the block connector
mine is an estate and have located the pump hatch
i have two block connectors running to the pump

green/white stripe- brown/white stripe to same

and
Red -red
Brown-brown
Grey-grey
which connector should i be measuring voltage at pls?
thanks again
D

[Laird Scooby]

According to this diagram :

http://www.myvolvolibrary.info/Tech_...Y89_wiring.pdf

the wires should be Pink, Black and the third one will be the fuel gauge.

With the engine running, you should have 12v+ on the pink, 0v on the black and double check the black wire has a good earth by using another earth point, rechecking the +12v on the pink and then check the voltage on the black - should still be 0v.

I don't recognise the green/white and brown/white as being part of the fuel gauge/pump circuit - i may have missed something but something in the back of my mind says electric aerial.

[Digger65]

Originally Posted by Laird Scooby

According to this diagram :

http://www.myvolvolibrary.info/Tech_...Y89_wiring.pdf

the wires should be Pink, Black and the third one will be the fuel gauge.

With the engine running, you should have 12v+ on the pink, 0v on the black and double check the black wire has a good earth by using another earth point, rechecking the +12v on the pink and then check the voltage on the black - should still be 0v.

I don't recognise the green/white and brown/white as being part of the fuel gauge/pump circuit - i may have missed something but something in the back of my mind says electric aerial.

ok have run the meter between the pink and the brown getting 13.74 Volts
pink to grey the same reading
despite the discrepancy between colour coding on wires i can assume that the pump is getting enough voltage and the pump is in fact bad?
the green/white brown/white does run through to the pump so a little confused by that one too

[Digger65]

image of green/white
weirdly enough car starts fine and runs ok apart from the highlighted issues mentioned
just the whine on main fuel pump
blip in power loss under load
vapour smell
rough idle

[Laird Scooby]

It's just crossed my mind what the green/white and brown/white cables are and they're not running to the tank! Just looks that way!

If you unplug the green/white and brown/whitee plug from the connector, take it for a test-drive you'll find the speedo no longer works and (if you have it) the ABS warning light will come up.

It goes to the speed sensor in the diff which not only gives road speed signals to the speedo but also to the ABS system.

From what you're saying, the symptoms don't change when you unplug the in-tank pump so it's a fair bet it's probably FUBAR.

If you have to renew the pump, renew the tank seal as well, the part number is 1367623 and it looks like this :



If you can smell petrol vapour, chances are it's past its best, also inspect the flow and return rubber hoses as they perish on the ends. If the two that come directly off the tank are perished, the tank has to come out for access to where they connect to the rigid nylon pipes that continue towards the front of the car and then change to rubber again!

One rubber hose is 12mm bore, the other is 8mm bore, if you need to renew one length you'll almost certainly need to renew all of them as they are all 28 years old! Mine needed doing about 18 months ago when mine was about 28 years old - had to do the whole lot!