Help! Wiring diagram for fuel pump relay?

[1996 850 T5]

Hi guys, not been on for a while as working offshore now, and my old man now drives the ovlov in my absense

Im a bit lost on this one, and really hoping you guys can help.

My T5 has been running sweet as a nut for the last year or so, but my old man went to start it the other day, the engine span over healthily, but it just wouldnt fire?

I was away at the time (work offshore), so when I got back, I tried starting it, but just no luck.

Opened the bonnet, and when the ignition is turned on the grey fuel pump relay thats located under the cover at the back of the rad is chattering away randomly? Also the coil was buzzing away continuously (so being constantly energised)

I had spares for both, so first swapped the fuel pump relay over, same symptoms, then swapped the coil, same symptoms...

You can hear the fuel pump is wurring away when you turn the key, and I checked the fuel rail was being pressurised by bleeding it whilst the ignition was on, and plenty of fuel gushed out into the jar, so im adamant its not the fuel pump thats faulty?

I noticed though that when I disconnect the grey fuel pump relay, the coil stops buzzing, so they are def linked somehow?

Put everything back, and tried to figure out what could be causing all this.

Unluckily, haynes doesnt have a single wiring diagram for the grey fuel pump relay, dug out my copy of VADIS, and no luck on their either (unless Im missing something?)

Anyway last week, I resorted to calling out a autoelectric engineer who went through all the connections and joints for:

crank sensor
cam sensor
fuel pump relay
coil
fuel pump

all seemed ok, and had very little of no resistance across the joints

he also tested all the connections to the ecu mouth organ from each item, again all came back ok/acceptable?

So he couldnt really determine what was causing the problem?

Then, bizarrely enough, we pulled a plug to check it was still sparking and the bloody thing started on 4 cylinders!

put the plug back in, and problem seemingly solved, the thing purred away brilliantly. I started/stopped it about 6 times to make sure it wasnt a fluke, and had no problems at all, so put it down to a dodgy connection on one of the above that we had fixed while messing about.

But....the very next day and back to square one, cylinders not firing and the fuel relay crackling away?!!!



From a search on here last week for starting problems, one thread stated that when you span the engine over, the tacho should move? And If it doesnt, then the crank sensor might be dodgy/dead? Is this true?

Well mine doesnt even twitch when you spin the engine over, so that might be a clue?

Before I go changing over other components willy nilly though, Id really like to track down a wiring diagram that shows how the grey fuel pump relay is wired in? can anyone help?

There are no ovlov dealerships over here anymore, so Im knackered in that respect


Sorry for the epic whinge, just trying to give as much info as poss! And need to get the car running for my old pa ASAP

Thanks all

Joe

[roryscott30]

Hi there,

did you read my thread i posted last week with exactly the same problem and it was an intermittent fault with the fuel pump. I would take it out and try it on the battery to eliminate it

cheers

Rory

[t5 stealth]

u say the fuel pump relay is behind the rad.........
afaik the fuel pump relay is below the windscreen...under the plastic cover in the fuse box....
also if u hear the pump buzzing then its working.

[NorthlandDave]

Wiring diagrams for the relay: http://www.volvoclub.org.uk/tech/ser...ngDiagrams.pdf (pages 12-13)

The relay is the top left of the first diagram, Fuel System Main Relay (Front Of Eng Compt). As t5 stealth said fuel pump relay is in the fuse box, it's on the second diagram top right Fuel Pump Relay (In Central Electrical Unit).

I had a similar sounding problem after replacing the radiator, was the connection at the bottom of the grey fuel system relay. In the plug the insulation breaks down that holds the connectors in place and after plugging it into the relay the connectors push out the bottom of the plug or the broken bits of rubber stop a good connection. Had to blow out the bits of broken rubber insulation and push the 4 connectors from the bottom of the plug when reconnecting the relay to get a good connection.

Had the same chattering when wiggling the wires or bumping the area around the relay, as the relay clicked on and off from the intermittent connection. I could still get a good connection from the relay connector back to the ecu with a multimeter as i was testing on the metal connector and the broken rubber pieces weren't in the way.

Hopefully this might be a cheap fix, have you tried reading the codes? I wasn't able to read the codes with the relay not connected, could be another symptom to check.

Dave

[1996 850 T5]

Sorry, yes, your right its the Fuel System Main Relay im on about, rather than the pump relay near the fuses.

Ive hard wired the pump direct and that chirps away nicely, so I can hopefully rule that out Rory

Dave, your a dreamboat for that link, Ive been pulliung my hair out trying to find those! Hero!

[nobananas]

That grey relay tucked up behind the rad top cover also kills the cam pulse if it's playing up and kills the spark (but not the coil feed, trust me on this one !) . Chances are the wiring to it is rotten where it's bent back double as it enters the multiplug. I would check this very carefully. Took me a day or so in a campsite in Keswick last year trying to diagnose that little problem when the car failed to start one morning !

[1996 850 T5]

Cheers guys, got dragged off to Tenerife for 2 weeks, so not been able to do much, but my auto spark friend is meeting me at 10am tomorrow and by hook or by crook we are going to get the damn thing moving again, even if we have to rewire the whole dam car!

Cheers for all the input so far