Heavy Duty Fuel Pump Relay

[Chris Hawes]

DMCH's part's store is still offline so I cannot illustrate which relay but the one that is causing me a problem turns on the fuel pump at the first turn of the key. It played up a month ago and then settled down, but this morning it wasn't having any of it so I had to bypass it by plugging the socket which has the purple/white wire onto a spare pin located near the locking module which continuously turns the fuel pump on.

I don't want to really order another from a vendor because it will be a 25+ year old part. Any ideas if there is a 21st century Bosch replacement?

Thanks in advance.

[NickT]

Do you mean the 'fuel pump relay' (also refered to as the "RPM" relay) ?

http://www.specialtauto.com/delorean-pa ... rical.html
http://www.specialtauto.com/delorean-pa ... jumper.jpg

If it is, the fix is usualy to install a new NEC555 timer chip in.
About £2 from maplins including a DIL socket so if it fails, you can replace the chip by levering it out of the socket with a screwdriver.

I personaly prefer the oem relay as it primes the fuel system for a second longer than the new bosch one.

New relay:
http://www.deloreans.co.uk/forum/viewtopic.php?t=1372
RPM (12V/30A) - Volvo: 898160-3523639

NickT.

[Chris Hawes]

YES! That's the bunny.

£2? This link shows it at just 53p:-
http://www.maplin.co.uk/module.aspx?ITA ... =8m10#spec

The new Volvo part is here:
http://www.partsforvolvosonline.com/pro ... ts_id=3688

I'll go with repairing the existing one I think...

Can the relay be opened without damaging it?

[bozzzydmc]

Chris Hawes Wrote:YES! That's the bunny.

£2? This link shows it at just 53p:-
http://www.maplin.co.uk/module.aspx?ITA ... =8m10#spec

Can the relay be opened without damaging it?

OK Its about £1 including a new 'DIL socket' to plug the chip into matey. Makes changing it in future a doddle ....

http://www.maplin.co.uk/Search.aspx?cri ... ce=15&SD=Y

Yes the cover just 'unclips' and pulled off.

[Chris Hawes]

Thanks guys, I have a local Maplin, so I'll jump on this tonight hopefully.

[Chris Hawes]

I popped out to the car over lunch and unclipped the cover and saw the 8-pin chip.

I have decided agains the DIL socket as chips in these kind of sockets can 'creep' and therefore overtime come loose. So I'll definitely solder the new chip in place.

By the way, the other components looked fine, is the failure with these relays always down to the chip?

[NickT]

Not heard of this chip 'creep' before.

I have had no problems with using DIL sockets in my years of experience !

I use them in ecu repairs as well as a couple of fuel pump relays I have fixed so if the chips are spiked/ fail then they are easier to change.

Good luck with the repair.

NickT.

[Rich H]

Quote:By the way, the other components looked fine, is the failure with these relays always down to the chip?

No, I've had ones with an open circuit capacitor, one transistor, two 555s and a burnt out track.

[Chris Hawes]

Visually I could not see any dry joints or burnt out components. I de-soldered the old chip and soldered the new one in place. At 10pm I went to the garage plugged it up......... turned the key one turn and ........ nothing happened. Bugger!

I have just this second realised, have I been a muppet, is it the second turn of the key that activates the fuel pump, if so I didn't try that?

[bozzzydmc]

Mine primes first time if I turn the key to position 2.

Could be something to do with the make of relay you have.

[Rich H]

Chris Hawes Wrote:I have just this second realised, have I been a muppet, is it the second turn of the key that activates the fuel pump, if so I didn't try that?

Err....yes, you're a muppet :wink: Second ignition position for the fuel pump...

[bozzzydmc]

Oh ...i took it as second turn of the key, not the turn the key to position 2

[Chris Hawes]

Bugger, that means it might work after all! I'll retry it this evening! Doh!

[Chris Hawes]

I have just got home went out to the car with the repaired relay and turned the ignition to postion 2 and the car fired up. It has since started a further five or so times flawlessly! Before the chip was replaced it stopped working only twice before. If it fails again, having seen the list of bits that Rich Has seen fail on them then I will change it out for a new Volvo one hoping that it will supply the same amount of prime time as the OEM version opposed to the 1 second shorter time that results with the Bosch RPM relay.

Thanks for the assistance guys, UIJ is now running properly again! :wink:

[Rich H]

If it fails again, stick it in the post and I'll swap out everything