I stopped to top up my half full tank on the motorhome and when I tried to start it the engine spun over freely but no sign of it firing. I waited about 5 minutes and tried again to no avail then called out the AA who arrived about 15 minutes later. First time he tried it same problem but second time it fired up and ran OK so I headed off to my destination. Stopped the engine when I got there and checked it would start again which at the time it did.

I left the van there for a couple of days and then decided to go for a bit of shopping, wouldn't start again so got the AA out and they diagnosed that the fuel pump in the tank wasn't running. They suggested getting a new fuel pump fitted by a local garage but at that stage we had no idea whether it was the pump, the relay or something else. I checked the voltage at the fuel pump connector and got just 11.33 volts, it held the voltage until the relay tripped out after the timed period. I also checked the inertia switch by tapping it to set it off then resetting it manually. During the period that the relay was energised there was a buzzing sound from somewhere under the bonnet?

I'm not sure whether the fuel pump relay is next to the 20 amp fuel pump fuse in the fuse box under the bonnet, or whether there is another relay involved; there seem to be a few listed on eBay for the 130 multijet that look totally different to the four pin plug in base type in the fuse box.

I've moved some of the relays of the same current rating around to see if that helps but nothing gets the pump running.

Got the van recovered to my house and set about getting the pump out of the tank, once out I connected it direct to a 12 volt battery and it ran fine. I put it back in the tank and ran a direct 12 volt feed to it from a spare battery and it pumped fuel and the engine started up straight away.

I'm at a loss as to what to do next; I can't drive it to a dealer to be checked over and don't know anybody in the area who does house calls to sort this sort of thing out.

Any ideas to prevent me from tearing what little remaining hair I have from my head????

I've had an identical issue with the fuel pump in an Opel/Vauxhall Frontera. On warm days the pump sometimes refused to start and once after two hours waiting and being towed to the dealer the engine started immediately.
The cause was a ceramic bearing in the pump that didn't have enough clearance. In cold fuel the pump rotated freely, with warm fuel the pump temporarily seized.
Fuel fed back to the tank by the return line can be quite hot!

I bought another pump on Ebay, fitted it in the tank unit and never had problems anymore.

I'm hoping that this might cure mine, found a brand new pump on evilbay for £50 so hoping that will turn up and sort the problem. Thanks for the reply!!

Replacement pump turned up today, plugged it in and no different so back to the drawing board! ARGHHHHHHHHHH

Any electric motor, such as the fuel pump, takes a high current briefly on start-up which then reduces when it is running. If you have a poor contact (= high resistance) somewhere in the pump supply or earth lines, it could be enough to sometimes reduce the voltage so much that it prevents the motor from starting. The 11.3 volt reading sounds rather low to me, and it might be even lower at the instant the pump is attempting to start up. Suggest you check all relays, fuses and connectors in the chain from the battery all the way to the pump and from the pump to earth.

I've just checked the earth side by connecting the earth supply from the pump connector to the pump using a jumper cable, then using another jumper from the positive pump connection connected direct to battery + the pump ran fine so that has eliminated bad earth IMHO.

Then connected the positive pump connection to the positive of the pump connector using a jumper and connected the earth direct and nothing (as would be expected)

I conclude from this that the power feed to the positive side of the pump is failing.

Looking at the wiring diagram the pump relay (T10) is powered from the battery via 15A fuse (F21). The ground side of the relay is connected via the inertia switch to pin 85 (coil) pin 86 goes to pin 20 of the Engine Management Control so I guess the next step is to check the Inertia switch for continuity then if that is OK the output from the Engine Management Control.

I've already checked the fuse and transposed relay T10 with one of the others in the fuse box on the basis that it is unlikely that two relays would go tits up at the same time.

Tried bridging the inertia switch connections 1 and 3 to simulate a closed circuit and nothing.

Just tried connecting pin 87 to pin 30 of pump relay T10 which should give a direct positive supply to the pump and still nothing????

I'm wondering if the immobiliser chops into this circuit and is the possible cause of the problem???

When I turn the ignition to the first position there is a hum from somewhere in the engine compartment and a slight whistling sound.

Either that or I'm slowly going round the twist!!!

The pump relay is only activated for a few seconds when you turn the key.
Once the engine has reached a minimum rpm the firmware in the MMU restores power to the relay. This prevents a catastrophe in certain accident situations.

Correct, the pump relay is energised for around 10 seconds, I've counted roughly 12 seconds on mine, during that time there is a faint humming sound, which seems to be coming from the area behind the steering wheel, in the engine compartment. When that time out ends I can hear a relay click and I then get a faint high pitched hum for around 10 seconds after that.

What I can't make out is how the pump won't run if I bridge the feed terminals of the relay momentarily? The fuse is OK so doing that should connect the positive side of the pump direct to the battery via a 150A battery fuse that is also OK.

The only thing I can think is that the immobiliser has been cut into the fuel pump positive supply between the relay and the battery and is open circuit. I've contacted the alarm manufacturers and they feel it is unlikely as the only pair of wires from the immobiliser that could have been used are rated at 6A max continuous.

Borrowed a basic fault code reader and got the engine running by connecting the fuel pump direct to the battery, it started first turn!

When I stopped the engine and did a diagnostic check I got error code "P0089 Pressure Regulator 1 Performance"

The low pressure fuel pump has a return line to the tank so I'm not sure if the error code relates to incorrect pressure in the low pressure side (as the fuel pump was running direct from the battery) or perhaps it refers to the high pressure regulator which may be faulty and holding off the fuel pump circuit??

Thinking a bit further on this......................maybe the error code occurred because I removed the power from the fuel pump before stopping the engine? It might have seen low fuel pressure as the supply failed.

Took out the main fuse/relay panel from under the bonnet to check for corrosion of connectors, which I've heard some mention previously. all looked clean and I got continuity from the pins expected so it isn't in there.

Interestingly I did another check on the voltage at the pump connector and it has dropped from the initial 11.33 volts to just over 9 volts during the 12 second energised phase after turning the ignition key to position 1.

I'm thinking there must be a high resistance connection somewhere or possibly a short?

The case continues!! :bang::bang:

EUREKA!!!!!

Found the problem. Grey wire from pin 16 on the brown connector had a high resistance to the positive terminal on the fuel pump so I bridged it with another bit of wire and hey presto the pump whirred up when the relay energised, ran for about 10 seconds then dropped out when the relay opened again.

Rather than chasing the fault down the hard to trace grey wire I will just chop it both ends and run a new bit of wire.

Hope this might help anybody else who has a similar problem.

WELL DONE..!!

your electrical knowledge ( and persistence) paid off there,

could you add a few photo's as you do the job?,
somebody is bound to have this again in the future

EDIT - be interesting to see if the @11.3 volts improves once the repair is effected also..,

Charlie - Oxford

varesecrazy said:

WELL DONE..!!

your electrical knowledge ( and persistence) paid off there,

could you add a few photo's as you do the job?,
somebody is bound to have this again in the future

EDIT - be interesting to see if the @11.3 volts improves once the repair is effected also..,

Charlie - Oxford

Click to expand...

Just finished putting it all back together so didn't see this post until all was sorted, sorry, didn't take any photos. It was just a case of chopping out the bad bit of wire between pin 16 of the brown connector and pin 1 of the fuel pump connector and fitting a new bit of wire between the two cut ends. No way I was going to trace the original wiring under the glued down flooring.

Didn't check the voltage as the desired effect (pump running!) had been achieved.

Took it for a test drive and all seems fine..................fingers crossed!!!!

Ducatiman said:

Rather than chasing the fault down the hard to trace grey wire I will just chop it both ends and run a new bit of wire.

Click to expand...

I would definitely chase it down, could be water ingress, chaffing, pinching, strain etc. I would want to see as there are bound to be other wires in the same danger.

corcai said:

I would definitely chase it down, could be water ingress, chaffing, pinching, strain etc. I would want to see as there are bound to be other wires in the same danger.

Click to expand...

Agree to some extent but I'm applying the "if it ain't broke don't fix it" approach. There are 4 wires running to the pump; 2 for the pump and 2 for the gauge, if I get more problems it is likeliest to be the earth to the pump which runs separately from the live feed (which I've replaced)