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Full Version: Fuel pump not running, but it works when relay is jumped
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Hi,

Im trying to track down an issue with my cars fuel pump not starting when the ignition is switched on. I know that the pump itself works, as I jumped pins 30 and 87 on the rpm relay and the pump immediately primed. So I got a new rpm (green) relay from Delorean.eu but after connecting that the pump still doesn't prime. Sad Maybe I got a broken one? Is there a way of testing the relay itself? I assume the wiring from the relay to the pump must be ok, since the pump works when the rpm relay is jumped... Is there anything else I can check?


Thanks,

Simon
Fuel cut out switch in drivers footwell, and/or earth to pump. Perhaps try a temporary earth to the pump this by-passes the kill switch.
Chris
Thanks, I'll give that a try next! I did find the cut out in the footwell earlier, but cycling the switch didn't seem to do anything. I will see if I can do as you suggest!

Thanks,

Simon
Actually scrub what I wrote, wrote it without thinking and is incorrect. I have got a spare RPM relay if you wish to borrow it to check yours. Mine does not always prime, does it run though?
Chris
My fuel pump has always primed when turning the ignition on. It suddenly stopped a few weeks ago and I was unable to start the car. I gave the battery a good charge and managed to eventually get the car started, however it ran roughly and cut out as soon as I applied any throttle. I suspected the battery and got my local garage to test mine, which was showing as running only 6 volts and it wasn't holding a charge.

So I got a new battery and I also cleaned all the contacts to the fuelpump. The prime primed once after doing this, then stopped again. I then got a brand new rpm relay to replace the Volvo branded one in the fuse box. That didnt fix the problem, so I then tried jumping the pins and the pump immediately started to prime (it made the usual noise anyway). So I know that power is getting to the pump. I also know that lights etc all work fine as does the starter motor. I have not tried starting the car with the pins jumped - doing that sort of thing worries me! However this does confirm that the pump is doing something.

It's certainly possible that both rpm relays I have are damaged in some way. If I could borrow a known working one it would be a great help. It is possible that there is a problem between the ignition barrel and the fuse box? I do hear relays clicking when I turn the ignition on though, and the starter motor does turn, so I assume that wiring is ok.

Not really sure what to try next!
Simon,

I'm no electrician, so can't help directly, but on a general note, I always keep my battery in tip-top nick. I use an isolating switch all the time and keep it trickle charged over the winter. Ive found in the past that a dodgy battery can cause all sorts of problems.

The mechanic who has been maintaining Delores for the last 9 years told me it had had 3 batteries in that time….and that's using an isolator switch and starting it once per month! Mind you it only did 230 miles in that time! ( I've already added another 1000 in the last month and its running much better now.)

in similar circumstances in the past…..I get a friend around with his car and try swapping various bits until you identify the dodgy item. Not very scientific but its always sorted me out.

.
My car hasn't has much use this year (probably only a couple of hundred miles) but over winter I remove the battery and I have recently fitted a cut off switch which I hope will help preserve the battery charge. Again, any advice is greatly appreciated!

Thanks,

Simon
Quote: Ive found in the past that a dodgy battery can cause all sorts of problems.
Applies even more to modern cars!
If you wish to borrow an RPM relay I'm happy to lend you the one out of my car I also have a new spare from SpecialT auto, But have not tested it. There does appear to be a lot of faulty ones of these kicking around from comments over on DMCTalk, indeed I had a faulty one from SpecialT auto the one I have now is a replacement but have not checked it out.
Chris
That's very generous of you Chris, thank you. Everything else on my car has always worked well, so hopefully it is a simple issue of a batch of faulty relays.

Simon
<RANT>

Aaaarrrrrrrrrrrghhh!

This fuel pump priming thing is a myth.

The stock RPM relay is specifically DESIGNED NOT to prime the fuel pump.

Any priming effect you are experiencing is caused an erroneous spike coming from the ignition ECU, NOT the RPM relay.

My D has never primed it's fuel pump. I have fixed over a dozen of these RPM relays, most from cars
which 'prime' the fuel pump. Every single one tested on my own car, and not a single one has ever primed my fuel pump...EVER.

If your fuel pump doesn't 'prime' when you turn on the ignition, don't worry about it, it's perfectly OK!

</RANT>
Calm down dear :lol: That's why I wrote that mine does not always prime (though sometimes does) I think the problem Simon has is that it does not pump either when running.
Chris
On a slightly related matter…I have a hot start problem….ok if started with a few minutes, but not if left for 15 mins plus…..I have to play with the round flappy thing then!

I presume its a duff fuel accumulator ? I don't even know what it looks like…never mind where to buy one….any comments welcome. Sad



.
Hi Chris,
The Accumulator is tucked up in the middle of the frame so it's a bit difficult to get at unless you have a pit or a lift. I had LJH's replaced about 10 years ago. It is a Bosch item and the garage that did the job was a Bosch centre so they had no problems getting hold of one.

Some detail of what it looks like herehttp://www.ffp.fi/index.php?mid=2&pid=92

Special T Auto in the States have them for $122.00 I can't remember what I paid with fitting but it was less than £150.00.

Best Regards
Nick H
Thanks Nick,

I do have a lift so I will have a good look around ( some stuff was moved on the RHD's)




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Chris Williams Wrote:Calm down dear :lol: That's why I wrote that mine does not always prime (though sometimes does) I think the problem Simon has is that it does not pump either when running.
Chris

My car has always had the pump "prime" when switching the ignition on, i.e. it makes a buzzing noise for a few seconds and then stops. To me this makes perfect sense. (Every single other car I have ever owned also does this...). Regardless of whether the stock behaviour of the De's RPM Relay is to prime or not, what can I check from here? If I try to start the car, the starter just cranks the engine. I know the fuel pump works if I bypass the RMP relay. So is this now an ignition ecu issue? I'm rapidly running out of what I can self diagnose and test now. I checked a whole bunch of fuses last weekend and they looked ok, although I could have missed something... my fuse box suffers heavily from previous owner syndrome... Sad
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